Ten things you don't know about black holes

By Phil Plait | October 30, 2008 8:48 pm

Well, they’re black, and they’re like bottomless holes. What would you call them?
-Me, when a friend asked me why they’re named what they are

Ah, black holes. The ultimate shiver-inducer of the cosmos, out-jawing sharks, out-ooking spiders, out-scaring… um, something scary. But we’re fascinated by ‘em, have no doubt — even if we don’t understand a whole lot about them.

But then, that’s why I’m here. Allow me to be your tour guide to infinity. Or the inverse of it, I suppose. Since it’s Halloween this seems appropriate… and my book Death from the Skies! just came out, and there’s lots of ways a black hole can destroy the Earth. Mwuhahahaha.

So below I present ten facts about black holes — the third in my series of Ten Things You Don’t Know (the first was on the Milky Way; the second about the Earth). Regular readers will know a few of these since I’ve talked about them before, but I’m hoping you don’t know all of these. And if you do, then feel free to leave a comment preening about your superior intellect. Mind you, this list is nowhere near complete: I could have picked probably 50 things that are weird about black holes. But I like these.


1) It’s not their mass, it’s their size that makes them so strong.

OK, first, a really quick primer on black holes. Bear with me!

The most common way for a black hole to form is in the core of a massive star. The core runs out of fuel, and collapses. This sets off a shockwave, blowing up outer layers of the star, causing a supernova. So the star’s heart collapses while the rest of it explodes outwards (this is the Cliff’s notes version; for more details on the process — which is way cool, so you should read it — check out my description of it).

As the core collapses, its gravity increases. At some point, if the core is massive enough (about 3 times the mass of the Sun), the gravity gets so strong that right at the surface of the collapsing core the escape velocity increases to the speed of light. That means that nothing can escape the gravity of this object, not even light. So it’s black. And since nothing can escape, well, read the quotation at the top of the page.

The region around the black hole itself where the escape velocity equals the speed of light is called the event horizon. Any event that happens inside it is forever invisible.

OK, so now you know what one is, and how they form. Now, I could explain why they have such strong gravity, but you know what? I’d rather let this guy do it. I hear he’s good.

So there you go. Sure, the mass is important, but sometimes it’s the little things that count.


2) They’re not infinitely small.

So OK, they’re small, but how small are they?

I was writing about black holes in my previous job, and we got in a fun discussion over just what we meant by black hole: did we mean the object itself that collapses down to a mathematical point, or the event horizon surrounding it? I said the event horizon, but my boss said it was the object. I decided she had a point (HAHAHAHAHA! A "point"! Man, I kill me), and made sure that when I wrote about the event horizon versus the black hole itself I was making myself clear.

Like I said above, to the collapsing core, its clock keeps ticking, so it sees itself collapsing all the way down to a point, even if the event horizon has some finite size.

What happens to the core? The actual mass that collapsed?

Out here, we’ll never know for sure. We can’t see in, and it sure enough isn’t gonna send any info out. But our math in these situations is pretty good, and we can at least apply them to the collapsing core, even when it’s smaller than the event horizon.

It will continue to collapse, and the gravity increases. Smaller, smaller… and when I was a kid I always read that it collapses all the way down to a geometric dot, an object with no dimensions at all. That really bugged me, as you can imagine… as well it should. Because it’s wrong.

At some point, the collapsing core will be smaller than an atom, smaller than a nucleus, smaller than an electron. It’ll eventually reach a size called the Planck Length, a unit so small that quantum mechanics rules it with an iron fist. A Planck Length is a kind of quantum size limit: if an object gets smaller than this, we literally cannot know much about it with any certainty. The actual physics is complicated, but pretty much when the collapsing core hits this size, even if we could somehow pierce the event horizon, we couldn’t measure its real size. In fact, the term "real size" doesn’t really mean anything at this kind of scale. If the Universe itself prevents you from measuring it, you might as well say the term has no meaning.

And how small is a Planck Length? Teeny tiny: about 10-35 meters. That’s one one-hundred quintillionth the size of a proton.

So if someone says a black hole has zero size, you can be all geeky and technical and say, not really, but meh. Close enough.


3) They’re spheres. And they’re definitely not funnel shaped.

The gravity you feel from an object depends on two things: the object’s mass, and your distance from that object. This means that anyone at a given distance from a massive object — say, a million kilometers — would feel the same force of gravity from it. That distance defines a sphere around an object: anyone on that sphere’s surface would feel the same gravity from the object at the center.

The size of an event horizon of a black hole depends on the gravity, so really the event horizon is a sphere surrounding the black hole. From the outside, if you could figure out how to see the event horizon in the first place, it would look like a pitch black sphere.

Some people think of black holes as being circles, or worse, funnel-shaped. The funnel thing is a misconception from people trying to explain gravity as a bending in space, and they simplify things by collapsing 3D space into 2D; they say the space is like a bed sheet, and objects with mass bend space the same way that a massive object (a bowling ball, say) will warp a bed sheet. But space is not 2D, it’s 3D (even 4D if you include time) and so this explanation can confuse people about the actual shape of a black hole event horizon.

I’ve had kids ask me what happens if you approach a black hole from underneath! They sometimes don’t get that black holes are spheres, and there is no underneath. I blame the funnel story. Sadly, it’s the best analogy I’ve seen, so we’re stuck with it. Use it with care.


4) Black holes spin!

It’s kind of an odd thought, but black holes can spin. Stars rotate, and when the core collapses the rotation speeds way, way up (the usual analogy is that of an ice skater who brings in his arms, increasing his rotation rate). As the core of the star gets smaller it rotates more rapidly. If it doesn’t quite have enough mass to become a black hole, the matter gets squeezed together to form a neutron star, a ball of neutrons a few kilometers across. We have detected hundreds of these objects, and they tend to spin very rapidly, sometimes hundreds of times a second!

The same is true for a black hole. Even as the matter shrinks down smaller than the event horizon and is lost to the outside Universe forever, the matter is still spinning. It’s not entirely clear what this means if you’re trying to calculate what happens to the matter once it’s inside the event horizon. Does centrifugal force keep it from collapsing all the way down to the Planck length? The math is fiendish, but do-able, and implies that matter falling in will hit matter inside the event horizon trying to fall further but unable to due to rotation, This causes a massive pile up and some pretty spectacular fireworks… that we’ll never see, because its on the other side of infinity. Bummer.


5) Near a black hole, things get weird

The spin of the black hole throws a monkey in the wrench of the event horizon. Black holes distort the fabric of space itself, and if they spin that distortion itself gets distorted. Space can get wrapped around a black hole — kind of like the fabric of a sheet getting caught up in a rotating drill bit.

This creates a region of space outside the event horizon called the ergosphere. It’s an oblate spheroid, a flattened ball shape, and if you’re outside the event horizon but inside the ergosphere, you’ll find you can’t sit still. Literally. Space is being dragged past you, and carries you along with it. You can easily move in the direction of the rotation of the black hole, but if you try to hover, you can’t. In fact, inside the ergosphere space is moving faster than light! Matter cannot move that fast, but it turns out, according to Einstein, space itself can. So if you want to hover over a black hole, you’d have to move faster than light in the direction opposite the spin. You can’t do that, so you have to move with the spin, fly away, or fall in. Those are your choices.

I suggest flying away. Fast. Because…


6) Approaching a black hole can kill you in fun ways. And by fun, I mean gruesome, horrifying, and really really ookie.

Sure, if you get too close, plop! You fall in. But even if you keep your distance you’re still in trouble…

Black hole, down the drain

Gravity depends on distance. The farther you are from an object, the weaker its gravity. So if you have a long object near a massive one, the long object will feel a stronger gravitational force on the near end versus a weaker force on the far end! This change in gravity over distance is called the tidal force (which is a bit of a misnomer, it’s not really a force, it’s a differential force, and yes, it’s related to why we have ocean tides on Earth from the Moon).

The thing is, black holes can be small — a BH with a mass of about three times the Sun has an event horizon just a few kilometers across — and that means you can get close to them. And that in turn means that the tidal force you feel from one can get distressingly big.

Praying to this guy won’t help.

Let’s say you fall feet first into a stellar-mass BH. It turns out that as you approach, the difference in gravity between your head and your feet can get huge. HUGE. The force can be so strong that your feet get yanked away from your head with hundreds of millions of times the force of Earth’s gravity. You’d be stretched into a long, thin strand and then shredded.

Astronomers call this spaghettification. Ewwww.

So getting near a black hole is dangerous even if you don’t fall in. Evidently, there really is a tide in the affairs of men.


7) Black holes aren’t always dark

The thing is, black holes can kill from a long way off.

Disk of DOOOOOM!
Image credit: NASA/CXC

Matter falling into a black hole would rarely if ever just fall straight in and disappear. If it has a little bit of sideways motion it’ll go around the black hole. As more matter falls in, all this junk can pile up around the hole. Because of the way rotating objects behave, this matter will create a disk of material whirling madly around the hole, and because the gravity of the hole changes so rapidly with distance, matter close in will be orbiting much faster than stuff farther out. This matter literally rubs together, generating heat through friction. This stuff can get really hot, like millions of degrees hot. Matter that hot glows with intense brightness… which means that near the black hole, this matter can be seriously luminous.

Worse, magnetic and other forces can focus two beams of energy that go plowing out of the poles of the disk. The beams start just outside the black hole, but can be seen for millions or even billions of light years distant.

They’re bright.

In fact, black holes that are eating matter in this way can glow so brightly that they become the brightest continuously-emitting objects in the Universe! We call these active black holes.

And as if black holes aren’t dangerous enough, the matter gets so hot right before it makes the final plunge that it can furiously emit X-rays, high-energy forms of light (and the beams can emit even higher energy light than that). So even if you park your spaceship well outside the event horizon of a black hole, if something else falls in and gets shredded, you get rewarded by being fried by the equivalent of a gazillion dental exams.

I may have mentioned this: black holes are dangerous. Best to stay away from them.


8) Black holes aren’t always dangerous.

I’m right there with you, dude.

Having said that, let me ask you a question: if I were to take the Sun and replace it with Folgers crystals a black hole of the exact same mass, what would happen? Would the Earth fall in, be flung away, or just orbit like it always does?

Most people think the Earth would fall in, sucked inexorably down by the black hole’s powerful gravity. But remember, the gravity you feel from an object depends on the mass of the object and your distance from it. I said the black hole has the same mass as the Sun, remember? And the Earth’s distance hasn’t changed. So the gravity we’d feel from here, 150 million kilometers away, would be exactly the same! So the Earth would orbit the solar black hole just as nicely as it orbits the Sun now.

Of course, we’d freeze to death. You can’t have everything.


9) Black holes can get big.

Q: What happens if two stellar-mass black holes collide?

A: You get one bigger black hole.

You can extrapolate from there. Black holes can eat other objects, including other black holes, so they can grow. We think that early on in the Universe, when galaxies were just forming, matter collecting in the center of the nascent galaxy can collapse to form a very massive black hole. As more matter falls in, the hole greedily consumes it, and grows. Eventually you get a supermassive black hole, one with millions or even billions of times the mass of the Sun.

However, remember that as matter falls in it can get hot. It can be so hot that the pressure from light itself can blow off material that’s farther out, a bit like the solar wind but on a much grander scale. The strength of the wind depends on many things, including the mass of the black hole; the heftier the hole, the windier the, uh, wind. This wind prevents more matter from falling in, so it acts like a cutoff valve for the ever-increasingly girthy hole.

Not only that, but over time the gas and dust around the black hole (well, pretty far out, but still near the center of the galaxy) gets turned into stars. Gas can fall into a black hole more easily than stars (if gas clouds collide head-on their motion relative to the black hole can stop, allowing them to fall in; stars are too small and too far apart for this to happen). So eventually the black hole stops consuming matter because nothing more is falling into it. It stops growing, the galaxy becomes stable, and everyone is happy.

Don’t panic!
OK, maybe a little.

In fact, when we look into the Universe today, we see that pretty much every large galaxy has a supermassive black hole in its heart. Even the Milky Way has a black hole at its core with a mass of four millions times that of the Sun. Before you start running around in circles and screaming, remember this: 1) it’s a long way off, 26,000 light years (260 quadrillion kilometers), 2) its mass is still very small compared to the 200 billion solar masses of our galaxy, and therefore 3) it can’t really harm us. Unless it starts actively feeding. Which it isn’t. But it might start sometime, if something falls into it. Though we don’t know of anything that can fall into it soon. But we might miss cold gas.

Hmmm.

Anyway, remember this as well: even though black holes can cause death and destruction on a major scale, they also help galaxies themselves form! So we owe our existence to them.


10) Black holes can be low density.

Of all the weirdnesses about black holes, this one is the weirdest to me.

As you might expect, the event horizon of a black hole gets bigger as the mass gets bigger. That’s because if you add mass, the gravity gets stronger, which means the event horizon will grow.

If you do the math carefully, you find that the event horizon grows linearly with the mass. In other words, if you double the black hole’s mass, the event horizon radius doubles as well.

That’s weird! Why?

The volume of a sphere depends on the cube of the radius (think way back to high school: volume = 4/3 x π x radius3). Double the radius, and the volume goes up by 2 x 2 x 2 = 8 times. Make the radius of a sphere 10 times bigger and the volume goes up by a factor of 10 x 10 x 10 = 1000.

So volume goes up really quickly as you increase the size of a sphere.

Now imagine you have two spheres of clay that are the same size. Lump them together. Is the resulting sphere twice as big?

No! You’ve doubled the mass, but the radius only increases a little bit. Because volume goes as radius cubed, to double the radius of your final clay ball, you’d need to lump together eight of them.

But that’s different than a black hole. Double the mass, double the size of the event horizon. That has an odd implication…

Density is how much mass is packed into a given volume. Keep the size the same and add mass, and the density goes up. Increase the volume, but keep the mass the same, and the density goes down. Got it?

So now let’s look at the average density of matter inside the event horizon of the black hole. If I take two identical black holes and collide them, the event horizon size doubles, and the mass doubles too. But volume has gone up by eight times! So the density actually decreases, and is 1/4 what I started with (twice the mass and eight times the volume gives you 1/4 the density). Keep doing that, and the density decreases.

A regular black hole — that is, one with three times the Sun’s mass — with have an event horizon radius of about 9 km. That means it has a huge density, about two quadrillion grams per cubic cm (2 x 1015). But double the mass, and the density drops by a factor of four. Put in 10 times the mass and the density drops by a factor of 100. A billion solar mass black hole (big, but we see them this big in galaxy centers) would drop that density by a factor of 1 x 1018. That would give it a density of roughly 1/1000 of a gram per cc… and that’s the density of air!

A billion solar mass black hole would have an event horizon 3 billion km in radius — roughly the distance of Neptune to the Sun.

See where I’m going here? If you were to rope off the solar system out past Neptune, enclose it in a giant sphere, and fill it with air, it would be a black hole!

That, to me, is by far the oddest thing about black holes. Sure, they warp space, distort time, play with our sense of what’s real and isn’t… but when they touch on the everyday and screw with that, well, that’s what gets me.

I first thought of this at a black hole conference at Stanford a few years back. I was walking with noted black hole expert Roger Blandford when it hit me. I did a quick mental calculation to make sure I had the numbers right, and related to Roger that a solar system full of air would be a black hole. He thought about it for a moment and said, "Yes, that sounds about right."

And that, me droogs, was one of the coolest moments of my hole life. But thinking about it still makes my brain hurt.


Conclusion:

Well, what can I say? Black holes are weird.

As it so happens, there was a lot more that could be said about them, of course. What about wormholes? What about how they form? what about Hawking radiation? Can black holes totally evaporate?

You can find answers to these and other questions elsewhere on the web (and even on this very blog); I couldn’t cover everything in just ten sections! But I’ll note (shocker) that chapter 5 of my book Death from the Skies! talks in detail about how they form, and what they can do if you get too close to them. Later chapters also talk about the black hole in the core of the Milky Way, and what will happen to black holes a long time from now… literally, 1060, 1070, even a googol years from now.

But even then, that’s not the scariest thing about black holes. I almost didn’t put this in the post, it’s so over the top mind-numbingly horrifying. But I’m a scientist, and we’re skeptics here, so we can take it. So I present to you, the worst thing about black holes of all:

"If there’s any justice at all, the black hole will be your grave!"

Comments (318)

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  1. Phil, I’m disappointed. You took all day to write this, and you neglected the obvious “they suck” joke?

    Tsk, tsk.

    (Great article, btw. I’m about 2/3 of the way through DFTS and enjoying every minute of it.)

  2. Radwaste

    Hey, if the FSM’s noodly appendage doesnt save you, it’s because you are supposed to die that way.

    And… Hi, Teddi!

  3. Kurtis W.

    My first astronomy professor told me to remember that black holes don’t suck, physics does.

  4. I knew that.

    Some of these can be added to the list of weird things in general. Like if you thrust to go forward in orbit, you slow down (your orbit gets higher, which is a slower orbit). And when a star runs out of fuel, it gets hotter (due to gravitational collapse).

    Is this a more modern graphic for the Milky Way? (I need a new T-Shirt).

    http://www.spitzer.caltech.edu/Media/releases/ssc2008-10/release.shtml

  5. I actually love that film for some inexplicable reason – it’s one of my guiltiest pleasures…

  6. Dan

    I love the notion that we could all get sucked into a black hole and have out individual atoms mingling around with one another like socks and underwear in a clothes dryer.

    So, you know, we’ll meet someday, Phil. I hope you’ll sign my book.

  7. Gary

    Any information about string theory and BHs? That we can understand?

  8. Tony

    The low density black hole thing blows my mind too! In intro to astrophysics last year I did a quick calculation and seemed to find that a black hole with the mass of the observable universe would be smaller than the observable universe…

  9. Is it really accurate to consider the density of a black hole to be the total mass within the event horizon, since all of the matter exists in the singularity (save that which is in the process of getting sucked between the event horizon and the singularity). It’s a bit like, say, considering the density of the earth and the moon to be mass(earth) + mass(moon) / volume(sphere of 300,000 km radius). Except that the event horizon is perhaps an even more arbitrary distance than the orbit of the moon!

  10. Pete

    Point #10 was referred to in Heechee novels – where (IIRC) it was postulated the aliens jumped into a mega-large BH to escape the heat death of the universe. I have not checked the math ( hell, I probably can’t DO the math), but the gravity gradient might be slight enoutgh to avoid spaghettification as you entered….

  11. Daniel

    Point 11…Your bank account. I KID!!!! :) cool info.

  12. Bill

    The other wild thing about a solar system full of air is that it would have the mass of A BILLION SUNS! That’s 0.5% the mass of the GALAXY. We really do live in a nearly perfect vacuum.

  13. Ian

    With #1:

    I sat through a talk by Lawrence Krauss recently at an undergrad physics conference titled “Our Miserable Future.” One point he brought up (I’m hoping I get this right), is that a black hole of the mass of this universe would oddly enough have the density and size of this universe! This means we could essentially be on the *inside* of the largest observable black hole. And that’s what really blows my mind.

  14. IBY

    Well, I guess you managed to put one thing I didn’t know about black holes, which was the last point. Does that still allow me to have bragging rights? :)

  15. I knew a lot of this from your book of course, but a thought just occurred to me: So wait…If black holes rotate, and are spherical, then they have poles? I mean if it shrinks, to that itty-bitty size, then the spin must be HUGE, right? Interesting to think about.

    As for never seeing past the event horizon, you may have heard- we’ve replicated it in the lab with lasers. I’m always hopeful we can pull off the mathematically improbable, even if there’s little to support that hope.

  16. Black holes always leave me with more questions, the more answers I get, so maybe I’m too dense:

    How would we know if we (right now on Earth) were already within the event horizon of some ultra-hyper-super-massive, yet extremely non-dense “black hole?”

    Does the empty space within chemical bonds and the huge empty space between sub-atomic particles decrease as mass is ‘falling into’ a black hole?

  17. Reid

    In Michio Kaku’s Parallel Worlds, he makes the point that a black hole with the mass of the universe . . . has about the same density as the universe.

    I had to put the book down.

  18. J. D. Mack

    Phil, you and I are roughly the same age – hence the loud laugh that came out of my mouth when I read the Folgers Crystals joke!

    J. D.

  19. My brain won’t stop going over the last point!

    My worst thing about black holes: insomnia!!

  20. timur

    I knew 1-9, and the basic behind 10, but I never thought of 10. This is cool. So the Universe is a black hole?

  21. dkary

    Point 10 leads to another interesting fact about black hole feeding habits.
    As “Pete” points out, if you fall into a really big black hole, you don’t go through spaghettification (at least, not until you’re well inside the event horizon). But think about what this means for “bright” black holes.

    For a relatively small black hole (less than a billion solar masses) you can’t really get a star into it without the tidal affects tearing it apart into a disk. It is the energy loss in these accretion disks that are slowly spiraling to the black hole that makes quasars so bright.

    However, a big enough black hole doesn’t have to do that. It can start swallowing stars whole (hole?). As a result, a really big black hole may not be a luminous as a smaller one, just because it’s not ripping apart passing stars and making nice bright disks and jets out of them.

  22. Rich

    You mentioned the Plank length in the second point but referenced the Fermi length in the fourth point. I only hazily remember the Plank length, but haven’t heard of the Fermi length.
    Could you clarify

  23. Rich, nice catch. That’s a typo. I was thinking about the Fermi Paradox earlier today, and must have written that instead of Planck! I fixed it, thanks.

  24. I came close to talking about SMBHs not having big tides, but ran out of topics. This was a tough one to write, and a tough one to narrow down to these topics. I wanted to cover stuff not necessarily in the book, or easy to find on the web.

    To make it more fun, my calculator batteries died, so I was using one I downloaded on my Mac, which freaked out over numbers with big exponents. I was taking inverses and getting 0. Grrrr.

  25. hale-bopp

    But Phil, as a loved one of yours pointed out to me once upon a time, air does not have a constant density so you cannot do that calculation :)

  26. Rowan Bulpit

    This is Science. This is Interesting.

  27. Debs

    Folger’s Crystals. Bwahahaha…hee.

    And as for the Disney flick- Dangit, Phil! You’ve probably kicked off another round of the recurring nightmare that movie caused me to have…

  28. DarthCaitSith

    You know the thing that makes me the most curious about this post is: What are the beers on the bookshelf in the background of the video from #1

  29. FrankZA

    “So volume goes up really quickly as you increase the size of a sphere. ”

    Um, is the size of a sphere not measured by its volume? The volume increases very quickly with an increase in radius/diameter…

    Pedantic perhaps…

  30. ad

    11) Black holes evaporate. See Hawking Radiation.

  31. khoavuong

    I’ve read that black holes eventually evaporate (for the lack of a better word) but later saw a BBC documentary claim they can only get bigger.

  32. tdhowe

    3) My first thought was — “The enemy’s door is down!”

    Seriously this is the one thing that gets me in almost every space sci-fi movie, why people assume that there is some fixed point that should be up or down for everyone everywhere in space is beyond me. (and yes I do realize that you are talking about a 3-d object being assumed to exist in a 2-d space, but it is a similar mistake to assume everyone will always have the same reference frame and coordinate system; and one I believe contributes to this misunderstanding.)

  33. Umm, Phil, You’re pulling my leg(s) when you said this, right?

    “Astronomers call this spaghettification. Ewwww.”

  34. Mark

    re: Your point #1 – ouch!
    While there is a certain consensus about that film sucking so hard it’s DVD might be called an accretion disk (SCNR), it was quite effective in giving me nightmares when I was a child. And ignoring the vapid science of it all, it works quite well as a “horror house” story. The scene with the book (+anthony-perkins-) shredding – urgh. To this day, I don’t know how that film managed to get its age rating – maybe someone didn’t watch further than “Disney” in the titles.
    Of course, thanks to the wonders of modern digital distribution, we can marvel at the plainly visible “zero gravity” wire-fu of moviemaking days gone by… :)

  35. Knight of L-sama

    Okay, 2 questions.

    1) What happens to the matter entering the region of the ergosphere where spatial warping exceeds the speed of light?

    2) This one’s been bugging me for a while. What happens when the expansion of the universe meets the event horizon of a black hole?

  36. jokergirl

    “Of course, we’d freeze to death. You can’t have everything.”

    Wouldn’t we be fried by the radiation first?

    ;)

  37. Bozothedeathmachine

    I’ve read that theories that a black hole can spin quickly enough that the event horizon forms torus shape with the event horizon still in the middle of the torus. In such a case, one not need to pass the event horizon to reach singularity. What up with that?

  38. slw

    I always thought the core of a black hole collapses down to Planck density, not length. Would be slightly more intuitive(as far as there can be anything intuitive about black holes), as collapsing down to Planck length would mean every black hole core is the exact same size, regardless of it’s mass. Even more weirder would be if you had a hypothetical black hole with mass equal to Planck mass, the size of the core in that case would be equal to the size of it’s event horizon.

    Could you provide a reference to some math that shows why black hole core collapse is limited at Planck length instead of density?

  39. Nigel Depledge
  40. tai

    I was waiting for number 10 the whole time I was reading this. It was easily the craziest thing I remember learning about black holes back in college. Great list!

  41. Wouter Lievens

    The “hole life” pun made me giggle.

  42. Ade

    I have quite a soft spot for The Black Hole, as I saw it at the cinema when I was 10. And, seriously, how trippy is that Reinhardt-trapped-in-Maximilian’s-body finale in (presumably) hell?

  43. Grebion

    Wow, the detail in point 5. that space could be dragged around the black hole at more than the speed of light…quite amazing, and new to me.

    But regarding point 10…for the “would be a black hole” calculation, you’re only considering whether the concentration of matter would have an event horizon. This ignores entirely what would happen inside the event horizon, which I think is relevant for a meaningful definition of “density”.

    The first question is, is it possible to have something with sufficient gravity to have an event horizon outside its surface without at least part of what’s “left inside” inevitably collapsing into a singularity?

    A quick intuitive guess would be maybe, if it’s sufficiently large. Has anyone done any calculations on how large that would be?

    The second question is, if such a structure would be stable, could something like that actually form in nature, and if so, how?

  44. Phil, that was masterful! Thanks so much. (runs off to make Useful Notes) :)

    Best! — DD

  45. You also forgot that referring to the term “Blackhole” in a council meeting is classed as being racially offensive, as happened earlier this year.

  46. GQ

    The knowledge! IT BURNS!

    Lots to think about there. Great article. I’m dead thick and that so pretty much all of this was news to me and I don’t pretened to understand all of it but damn, that was good readin’!

  47. Awesome article! :D
    I knew a few, but most were new to me. The plank length thing and the density thing were the most insightful (read: confusing).
    Might be worth pointing out pamela’s recent post http://www.starstryder.com/2008/10/20/black-holes-only-grow-so-big/ about black holes. That they have a theoretical limit to their size would make a good #11 :)

  48. redx

    That low density bit is fairly cool. I didn’t know that. I’m annoyed at myself for applying what’s been ground into me in physics classes.

    You see the thing derived for you. You see all the variables cancel out, and you still need to have rather obvious implications pointed out. I so don’t grok physics.

  49. Paul A

    That was a fantastic read, I feel like my brain capacity has doubled since I finished it :)

    Can’t wait till I can afford your book, it’s next on my reading list.

  50. Regarding your last point, if you *really* want to bake your noodle then make it a double feature. First watch “The Black Hole” and then follow it up with “Event Horizon”. They’re fundamentally the same story but told in very different ways.

    Which one is scarier? Well, one has people tearing each other apart with their bare hands and clawing their own eyes out after literally traveling to Hell, and the other has Ernest Borgnine. You make the call… ;-)

  51. Numbers one through nine I knew;
    but number ten, ah that was new.

  52. Great article. For regular readers of your blog and books, I’m sure many had a grasp of most of these, however, I am making links to this post like crazy! This is great stuff, and more people need to be exposed to this! Thanks again Dr. Plait!

  53. RL

    This is an excellent article.

  54. James

    Phil,
    Would it be ok for me to run off a copy of that section for my kids to read in Physics when we cover gravity later on in the year, and for astronomy for next year?

    Secondly, regarding the funnel analogy we use to describe warped space….Its a 2D model to explain something 3D (or 4D with time…). When I use this in class every year with a big piece of spandex representing space, a large mass in the middle for the sun, and marbles of various masses for planets. Every year a student will say: Ok, what is the planet is “over here” or “down here” (somewhere not on the plane of the spandex). I tell then it acts as though the “spandex” plane is at that spot as well. This got some students and to talking about this and thinking:

    Is there any way to create a 3D model of all of these “funnels” around the mass in the center, and if you could what would it look like? In short, is there a way to create a 3D visual representation of curved space? I don’t have the expertise to know if it could be done, but I am willing to bet that the person who created that 3D nearby stars program could. Thoughts on this?

  55. Something that’s been bothering me about black holes lately is “how long does it take stuff to reach the middle of a black hole?” Clearly the answer requires a “that depends” the size of the moon.
    Yes, from the perspective of the falling thing the answer is not long at all. From the point of view of those of us on the outside time slows as it gets closer and closer until it pretty much just stops right there on the event horizon, right? The object passes through and keeps falling. How long does it take to get from there to the core? Does the gravitational well of the black hole become lopsided? Would there be layers of attracted matter falling inwards for eternity? I can see how there could be billions of tons of low density matter slowly falling toward a high density core for eternity.
    But I could be visualizing it all wrong.

  56. James

    Sorry for all the typos in my post there, my coffee hasn’t kicked in this morning: Eliminate When in the second paragraph, change to OK, what if the planet if “over here…, and change to I tell them…..

    I need a spell check on this thing….

  57. American Voyager

    Phil, don’t put Disney’s movie down too much. The concept was good. The exdcution was terrible. I was lucky enough to have read the book before watching the film. It was fantastic! I think Disney was attempting to dumb it down to the kiddie level and sadly, they succeeded. Read the book. You’ll love it!

  58. a simon

    Ibid: rom the perspective of the falling thing the answer is not long at all
    No, from the perspective of the falling thing you will see the event horizon to glow from hawking radiation and shrink faster than you can fall towards it till it implodes just before your eyes, and you will find yourself in distant ( like 10^1500 years ) future without having to fall in any singularity at all

  59. DrFlimmer

    Your “hole life”, Phil?
    Well, welcome back from the stone-age :-D We don’t need to live in holes anymore….

    But: This was an awesome article, even if I knew many of these things AND that you already mentioned some of the points in the very first (in the video…). Thanks a lot!!

  60. kuhnigget

    re: The Black Hole

    I just started as a lowly intern at the Disney studio when that film was wrapping. Everyone on the production was unhappy with it. The studio head (son in law of Walt Disney, Ron Miller) was still pissed because he had passed on Star Wars. The director, Gary Nelson, thought the special effects guys had taken over. The special effects guys (great old-timer Peter Ellenshaw, among many others) thought the story sucked worse than a black hole and that their effects were the only thing anyone would be interested in. Actors didn’t like it because those zero-g wire rigs were probably making them sterile (“ball busters,” in the words of Anthony Perkins…not that he’d care about being sterile). And the hard-core Disneyphiles were upset that it was going to get a PG rating…the first in Disney history.

    Nonetheless, the publicity department did a huge campaign on the film, only to see it land with a big ol’ clunk at the box office.

    One more BTW…the guy who designed the robots, including the most annoying mechanical man in the history of the world, Old Bob, was a Disney imagineer whom I worked with later, and who was also a serious Christian fundie. I mean, serious. Who knows what he thought about that “heaven and hell” ending!

  61. shaurz

    If black holes evaportate… then will the universe also evaporate?

  62. anotherDan

    If black holes emit so much energy (point 7), if we replace the sun with a black hole, wouldn’t we all fry instead of freezing to death?

    also, I was always told that the universe sucks, not blows (I guess it’s all relative, though, right?)

  63. anotherDan

    check that, Blows not sucks
    …I blow (or do I suck?) for typos

  64. Gary Ansorge

    James: Try a Klein bottle, ie, a 2D representation of a 3D bottle with an entry but no exit,,,
    ,,,always loved those mathematical inventions,,,

    There are a number of characterizations of black holes that produce paradox.
    The only identifying characteristics of a black hole we can know are the mass, charge and radius. All other qualities disappear, therefore,,,
    1) Charge: how can it exhibit a charge, if the force transfer particle(photon) cannot exceed light speed?
    2) How can we even feel a G-field from gravitons(the force carrying particle) since C is the escape velocity of the hole and presumably everything must succumb to that force??? Note: we have yet to detect gravitons,,,

    Me thinks we must either rework our standard model of physics, which proposes force carrying particles,(to include force carrying particles that exceed C) or accept that those forces (electric field, gravity field) generate their effects without the mediation of force transfer particles at all,,,

    Black holes: one paradox piled atop another

    If space/time can expand, it must also be able to contract. If the space/time in which our matter is imbedded contracts, we would not know we were falling into a singularity, because as with Zenos paradox, we just keep getting closer, but the space/time between us and it keeps getting smaller and the particles of which we’re made also get smaller.
    Woo-Hoo,,,and the ride goes on forever,,,

    GAry 7

  65. Gary Ansorge

    Thanks for the BH posting, Phil.

    Been wanting to get those paradoxes off my chest for a loooong time,,,

    GAry 7

  66. Mu

    One question, if two black holes collide and unify their event horizons – do the actual singularities unify too? Or does the preservation of momentum mean that they circle each other for eternity?

  67. Phil, I always love the “ten things you don’t know” posts. Keep ‘em up!.

  68. Phil, this is a great article. I particularly like #10, which I didn’t know at all. The others were all pretty familiar. ;)

    Oh, and, uh… I like The Black Hole! It was one of those movies I saw as a little kid that made me go: SPACE EXPLORATION IS AWESOME. I know it has lots of wrong stuff in it, but just like all the movie mistakes in Total Recall, somehow they just help me enjoy the movie all the more. (This is not usually the case with me: normally I’m the first one to suffer intense pain when confronted with Treknobabble or ScriptScience.) And, really, Roddy McDowall as a wise-cracking robot? Priceless.

    “Vincent, were you programmed to bug me?”
    “No, sir; to educate you.”

  69. if black holes eat eat each other why not 1 big black hole eats everything in the iniverse and then it is to big to hold all the matter and it blows up like the first big bang and we start all over again

  70. Nigel Depledge

    Ibid said:

    Something that’s been bothering me about black holes lately is “how long does it take stuff to reach the middle of a black hole?” Clearly the answer requires a “that depends” the size of the moon.
    Yes, from the perspective of the falling thing the answer is not long at all. From the point of view of those of us on the outside time slows as it gets closer and closer until it pretty much just stops right there on the event horizon, right? The object passes through and keeps falling. How long does it take to get from there to the core? Does the gravitational well of the black hole become lopsided? Would there be layers of attracted matter falling inwards for eternity? I can see how there could be billions of tons of low density matter slowly falling toward a high density core for eternity.
    But I could be visualizing it all wrong.

    If I understand correctly, an observer outside the event horizon would see an infalling object gradually slow down, then stop at the event horizon, where its light gradually redshifts and fades into invisibility (how long this takes depends on the gradient in the gravitational field).

    An infalling observer does not notice the event horizon (assuming a large BH and hence a relatively gentle gradient in the local graviational field at that point). However, as the infalling observer gets closer to the singularity, the gravitational gradient increases, to the point where tidal forces (or, OK, Phil, differential gravitational forces) cause spaghettification. How long it takes to reach the singularity depends on the radius of the event horizon and the strength of the gravitational acceleration. And, potentially, on the local density and orbital velocities of other infalling matter.

  71. Cheyenne

    So beyond cool. My second favorite post from Phil (I also agree the “10 Things you Don’t Know” ones are some of my faves).

    If you like that one he wrote this one is fun to read (or re-read) as well.
    -blogs.discovermagazine.com/badastronomy/2008/09/08/ten-things-you-dont-know-about-the-earth/

  72. Rodney

    Great posts,

    You guys give me a headache (and in a good way).

    My heads full, for the day, but I will come back and re-read some of these posts again.

    Thanks,

    rod

  73. Chris A.

    Re: #10
    Okay, but wouldn’t a solar system full of air (I’m presuming you assumed sea level density) quickly collapse due to the mutual gravitation of all that mass?

    Which begs the next question: What would the pressure of all that air have to be to prevent collapse? (Probably not a trivial calculation–I’m getting Lane-Emden equation flashbacks right about now…)

    Followed by: What would the temperature (assuming the ideal gas law applies) be that corresponds to that pressure? I’m guessing (based on nothing more than gut intuition) that the temperature would have to be ginormous, as in “particles moving relativistically” big. And once that happens, the particles act like they have more mass ala Lorentz, so I’ll bet it collapses anyway.

    Fun to think about, though.

  74. Chris A.

    Re: #2
    Isn’t it likely that once we have a theory of quantum gravity, it might very well describe a state of matter that the black hole becomes, and stops collapsing at, well before it reaches the Planck scale? (I recall talk of “quark bags” some years ago…)

  75. Chris A.

    Re: #5
    Related to this is the fact that at the photon sphere, if you’re traveling in a circular orbit, as you thrust the engines to go faster, centrifugal force (yeah, I know, it’s a pseudo-force) actually shoves you _inward_, not outward because spacetime is sort of turned inside-out. (Scientific American had a nice article about this some years back.)

  76. IVAN3MAN

    Phil Plait:

    Of course, we’d freeze to death. You can’t have everything.

    Not necessarily, there is still geothermal energy that we could rely on, and let’s not forget all the hot air from politicians that could be channeled into gas turbines to drive electrical generators. :)

    @ kuhnigget

    You had better watch your language, kuhnigget, because I’ve already been told off twice by his Lordship, Phil Plait, for using “bad language”. :roll:

    Phil Plait: “… coolest moments of my hole life.” :P

  77. Chris A.

    Re: #6
    Personally, my favorite way a black hole can kill you is this:
    Even if you find a huge, low density black hole (like the monster in M87) and fall in, knowing that the tidal forces wont spaghettify you (Kip Thorne writes about this in “Black Holes & Time Warps), you will die in a spectacular way. As you approach the event horizon, time in the universe will appear to speed up due to relativistic effects. Just before you cross the event horizon, you’ll see stars winking out, going supernova, etc. Sounds like a great show, except that the photons’ “clocks” will be running hyperfast too (thanks to relativistic blue-shifting). Meaning that the frequency of every photon falling on you will be shifted to the shortest possible wavelengths (ultra-high energy gamma rays) and incinerate you. Ouch.

    Okay, I’ll shut up now. :)

  78. @BA “See where I’m going here? If you were to rope off the solar system out past Neptune, enclose it in a giant sphere, and fill it with air, it would be a black hole!”

    Hmmm, not according to my calculations. The basic equation is this:

    Rs = 2 * G * M / c^2

    Rs is the Schwarzschild radius in meters
    G is the gravitational constant (6.67E-11 m^3 per kg per sec^2)
    M is the mass within the event horizon in kilograms
    c is the speed of light (2.998E8 meters per second)

    So M = c^2 * Rs / (2*G)

    rho = M / V = M / ((4/3) * pi * Rs^3)

    rho is the average density in kilograms per cubic meter
    V is the volume in cubic meters
    pi is 3.14…

    So we have rho = 3 * c^2 / (8 * pi * G * Rs^2)

    And then Rs = c * Sqrt(3 / (8 * pi * G * rho)

    Plugging in the density of air at sea level for the standard atmosphere which is 1.225 grams per cubic centimeter = 1,225 kilograms per cubic meter we get:

    Rs = 3.62E11 meters = 2.4 A.U.s

    This is only out to the asteroid belt, not the entire solar system.

    If you wanted the entire solar system out to the orbit of Neptune (30.1 A.U.s) then the density should be 7.9 kilograms per cubic meter which is the density of air at an altitude of about 40 kilometers, not at sea level.

  79. @BA “Black holes can eat other objects, including other black holes, so they can grow. We think that early on in the Universe, when galaxies were just forming, matter collecting in the center of the nascent galaxy can collapse to form a very massive black hole. As more matter falls in, the hole greedily consumes it, and grows.”

    If you drop any object straight down into a black hole from and outside observer’s perspective it takes an infinite amount of time for the object to reach the event horizon. That should apply to other black holes falling towards the event horizon. Thus, from our perspective no merger of black holes should have ever occurred since they would take infinitely long to happen. This seems to be a contradiction in terms of the supposed supermassive black hole at the center of the Milky Way galaxy. Theoretically it should have taken an infinite amount of time for it to form from component black holes and yet we observe that it’s there. That seems to be a pretty big paradox that I’m trying to get my mind around, … unsuccessfully.

  80. Todd W.

    @Tom Marking

    Ahhh! Mathematics!

    *crickets*

  81. @BA “Worse, magnetic and other forces can focus two beams of energy that go plowing out of the poles of the disk. The beams start just outside the black hole, but can be seen for millions or even billions of light years distant.”

    Yeah, I’ve never quite understood the two jets coming out from quasars and how they relate to the black hole at the center. A couple of points:

    1.) Magnetic field lines CANNOT cross the event horizon boundary.

    2.) Therefore if the jets are aligned with the magnetic field then the magnetic field exists in the gas disk and has nothing to do with the black hole itself. If the black hole has a magnetic field inside the event horizon it has nothing to do with the magnetic field outside the event horizon.

    3.) The axis of the jets does NOT have to be the same as the angular momentum axis of the black hole’s rotation. They may be totally separate.

  82. @Todd “Ahhh! Mathematics!”

    Run away! Run away!

    ARTHUR: Right. How many did we lose?
    KNIGHT: Gawain.
    KNIGHT: Hector.
    ARTHUR: And Boris. That’s five.
    GALAHAD: Three, sir.
    ARTHUR: Three. Three. And we’d better not risk another frontal assault, that rabbit’s dynamite.
    ROBIN: Would it help to confuse it if we run away more?
    ARTHUR: Oh, shut up and go and change your armor.
    .
    .
    .

  83. zeb

    I got one that’s really weird. The other day, I was playing around with the equations and decided to see how big a black hole it would make if you squished all the known matter in the universe together.

    Accounting for all the dark matter as well, I found out that the black hole produced is actually LARGER than the co-moving distance to the cosmological horizon. In other words, all the matter currently known to exist is currently inside its own event horizon, meaning that it should immediately form a black hole. (Without accounting for dark matter, the size of the black hole is “only” about 20 billion light-years in diameter).

    Now dark energy/the expansion of the universe probably negates this in some way, but it is still kind of spooky.

    Also, a comment on #6. Interestingly, supermassive black holes don’t do this as much. They’re billions of kilometers across and the human body is only a very tiny fraction of the whole distance. You could orbit quite close without being shredded by tidal forces (though it will happen if you get sufficiently close to ANY black hole).

  84. Chris A.

    @Tom Marking
    Phil’s statement was correct: The Solar System filled with air would be a black hole. You just calculated the _minimum_ density needed, which turns out to be less.

    That being said, your calculation uses the formula V = 4/3 * pi * r^3, which only works in flat (Euclidean) spacetime, not the case with a black hole! All that warped space would increase (significantly) the volume contained within a given radius, bringing Phil’s air-filled solar system closer to the critical density. How much closer, I couldn’t say.

  85. sometimes it’s the little things that count.

    Exactly what I told my wife.

  86. @Myself “Rs = 3.62E11 meters = 2.4 A.U.s”

    Arrrggghhhh!!! Egad!!!! The equation is right but I plugged in the wrong number for rho. It should be just 1.225 kg/m^3 not 1225 kg/m^3. (Damn that conversion from grams per cubic centimeter to kilograms per cubic meter!!!) This makes the Schwarzschild radius for an average density of air equal to 76.6 A.U.s., not the 2.4 A.U. I previously stated. So it’s actually 2.5 times the size of Neptune’s orbit that has to be filled with air to make a black hole. Surprised no one caught that mistake before I did. But then, I guess they had already run away by that time. :)

    * crickets *

  87. Kory

    Hi all, first time posting here, though I’ve been reading for years.

    Anyway, I just wanted to point out something minor about #2. Typically (in general relativity) we call the event horizon the black hole, and the r=0 place the singularity. This is because it is possible to have a spacetime that has an event horizon with no singularity, they are weird and probably can’t exist in reality, but they do exist mathematically. The other way around, a singularity with no event horizon is impossible, cosmic censorship and all that.

    To summarize, Phil you win that argument with your boss, at least according to most any general relativist.

  88. It’s so nice to come here after reading the latest logical atrocities being perpetrated in the political world and read a science discussion…

    I remember sitting through that awful Black Hole movie and smirking every few minutes as another law of science went crashing down in flames…

    For some reason that movie was particularly egregious about it. Almost as bad as the “Kesla run in 12 parsecs” line from Star Wars IV.

  89. Oh, and about those beers behind Phil’s head… I wonder if he’s ever thought of brewing his own? Black Hole Brew maybe?

  90. Bill J.

    Re: #10
    Since the force of gravity by distance is reduced by the inverse square law, wouldn’t the mass of the black hole would have to increase by a factor of 4 to double the radius of the event horizon? The volume would still decrease as the black hole got larger, but only by a linear factor, not by a square.

  91. John Fleming

    Contrary to the title, I knew all ten already. I can has cookie?

  92. Disney’s “Black Hole” had the worst robot in high budget sci-fi, and that’s saying something.

    I think I understand the current thinking on the formation and effects of black holes, but nobody seems to answer my question: How can matter or energy pass through the event horizon from the greater universe. As matter falls toward the event horizon, it goes faster and faster, time for the matter passes more and more slowly, and the matter becomes shorter and shorter in the direction of travel. As the matter approaches the event horizon it is also approaching the speed of light, and relativistic effects become more and more pronounced. Taken to the speed of light wouldn’t an object becomes two dimensional in the direction of travel and virtually detached from the universe in time. The matter would never cross the event horizon.

    Now I’ve got a headache.

  93. Bill Nettles

    Ok, you got me on # 10…low density. Who’d ‘a’ thunk it, being fed all this stuff about neutron stars and a spoonful weighing a google of grams. But how does that jive with #2? Where did all that mass go?

    Can you answer # 11 for me? What the temperature of a black hole?

    If the temp is above 0 K, how can all that matter collapse to a Planck length, since Brownian motion keeps things apart?

  94. Bill Nettles

    Bert,
    Didn’t that happen on an episode of Stargate SG-1?

  95. Well, they’re black, and they’re like bottomless holes. What would you call them?
    -Me, when a friend asked me why they’re named what they are

    I remember hearing this line (or a very similar one) on either The Daily Show or The Colbert Report. So either great minds think alike, or else your friend is a certain director of the Hayden overhead projector planetarium and he stole your line.

  96. Chris A.

    @ccpetersen
    I think I’ve seen the Star Wars Faithful ™ argue Han Solo’s apparent conflation of time and distance units this way: By navigating along the shortest path, Solo could get to his destination faster, with his 12 parsec path taking him dangerously close to objects normally avoided by more cautious pilots choosing longer (and thus slower) routes.

  97. I suppose someone should also mention Greg Egan’s Java applet that shows what the view looks like as you get close to a black hole.

  98. Re. #9 —

    In the event that the black hole at the center of our solar system did start “feeding” and sucking stuff in, how long would it take us to find out?

  99. Cuz, it could have happened already. Just sayin’. Which would explain a lot about the current election and the last few years of high fashion.

  100. Xulxanrov

    BTW, the “Astronomy Fail” photo is of the Black Hole, a laboratory surplus store in Los Alamos, so called because “everything goes in and nothing comes out.” So the name does make some sense…

  101. Snath

    Dammit Dr. P, now I have to listen to Muse all day. I was really enjoying Lisa Hannigan, but now I have a hankering for Supermassive Black Hole.

  102. @Chris “All that warped space would increase (significantly) the volume contained within a given radius”

    I believe it goes the other way for positively warped space – the volume is less than you expect. For example, consider the following 2D case. You have a circle of radius S. The expected Euclidean area contained in the circle is pi * S^2.

    Now suppose S is really a curve on a sphere going half-way around the sphere so that S = pi * R where R is the radius of the sphere. Now the surface area enclosed by the “circle” is 4 * pi * R^2 or (4/pi) * S^2. This is only 40 percent of your Euclidean expectation. So I believe this effect goes in the reverse direction of what you stated.

  103. Eric H.

    Now, I have very little understanding of astronomy and cosmology, my knowledge is limited to one astronomy class I had in college and what I read here on this blog and a few others, but I have one question:

    How do you know that the density of a black hole is uniformly distributed? In order to say that a black hole has the density of air(assuming it is the size of our solar system) you would have to assume that the distribution of matter is uniform, would you not?. I thought that all the matter fell into an incredibly small point, the plank length, as you point out in point # 2. If this is true then sure you can say the average density of the black hole(the volume of space where the escape velocity is greater than the speed of light) is the same as air, but if all the matter is compressed into that one point, wouldn’t most of that space actually be a true vacuum, completely devoid of all matter?

    The other question I have with black holes deals with the idea that matter cannot move faster than the speed of light and that the escape velocity required to escape a black hole is greater than the speed of light. Now I could be completely wrong on this, but isn’t the escape velocity the inverse of the gravitational pull? For example, here on earth the acceleration due to gravity is about 9m/s so in order to escape the earth you need to be able to achieve greater than 9m/s acceleration? If this is true then wont a black hole’s gravity within the event horizon pull things at an acceleration rate greater than the speed of light towards the center of the black hole?

  104. @Bert “The matter would never cross the event horizon.”

    That’s true only from an outside observer’s perspective. If you were falling in with the matter you would cross the event horizon and smack into the singularity from your point of view. Before you crossed the event horizon you would observe the outside universe age an infinite amount of time so these are strange beasties all right.

  105. José

    Almost as bad as the “Kesla run in 12 parsecs

    Han Solo wasn’t wrong. He was just being polite. You see, a long time ago in a galaxy far far away, the word “parsecs” was simply slang for “pardon me for a second”. I hope that finally clears up the confusion. No need to thank me. Just knowing I made a difference is all the thanks I need.

  106. @Eric “How do you know that the density of a black hole is uniformly distributed?”

    Yes, of course we know that the density within the event horizon is not uniform. All Phil is saying is that if you started out with a sphere with a radius 2.5 times Neptune’s distance from the sun and composed of uniformly distributed air at 1.225 kilograms per cubic meter then that would be enough mass to create a black hole. Of course, all of the air would rush inward and form a singularity.

    “I thought that all the matter fell into an incredibly small point, the plank length”

    I suspect that eventually it will be found out that the true radius of the black hole is determined by quark degeneracy pressure or string degeneracy pressure and is much bigger than the Planck length. When we get a true quantum theory of gravity worked out then we’ll know for sure.

    “Now I could be completely wrong on this, but isn’t the escape velocity the inverse of the gravitational pull? For example, here on earth the acceleration due to gravity is about 9m/s so in order to escape the earth you need to be able to achieve greater than 9m/s acceleration?”

    Yep, you’re completely wrong on that. You’re confusing gravitational acceleration which is 9.8 meters per second per second at the surface of the earth with escape velocity which is 11,200 meters per second. Notice how they have different units? The correct formula for escape velocity is:

    Ve = sqrt(2 * G * M / R)

    Ve is escape velocity in meters per second
    G is the gravitational constant (m^3 per kg per s^2)
    M is the mass in kilograms
    R is the radius in meters

    Now, set Ve equal to c (speed of light in a vacuum = 2.998E8 meters per second) and solve for R. There’s your Schwarzschild radius (i.e., radius of the event horizon).

  107. My-Name-is-Kenneth

    Disney’s The Black Hole was not the worst thing ever made. In fact, it had potential and felt like something they might have done from the 1950s.

    TBH had its good moments, including the music, the special effects, the starship Cygnus, and the daring (for Disney) plot piece that the mad scientist had lobotomized the rest of the crew to be his slaves (organic robots?). Somebody even swore a couple of times.

    On the other hand, the robot VINCENT and his Cygnus buddy – well, the less said, the better.

    As for that film cover you have: The ship was NEVER above any planet; in fact, they never visited an actual world once in the whole film, and the accretion disk around the black hole in The Black Hole was a much brighter red-orange with a lot more accretion debris. Somebody who didn’t see the film or didn’t care took some license with this. Why didn’t they just keep the original cover?

  108. Actually, Disney’s The Black Hole wasn’t all that bad. You said BHs are spheres. But later you acknowledged that they spin. Glowing hot gas swirls around them, orbiting in the plane of rotation, then falling in. That means that most black holes really do look like a “cosmic drain”, and I have seem pictures showing just such appearance. Check out this real (if processed, but not distorted) image:
    http://static.howstuffworks.com/gif/black-hole-ngc4261.jpg

  109. Some more things you didn’t know:

    11.) The photon sphere is a spherical region of space surrounding the black hole where light photons travel in orbits. For a non-rotating black hole its radius is 1.5 times the Schwarzschild radius (i.e., radius of the event horizon).

  110. BMcP

    Awww.. I liked that movie, sure it was silly and the science was awful, but I was seven when it came out and when you are seven, movies about Black Holes are just awesome! :)

    Thanks though for all the fascinating facts on Black holes, just reading it, my initial thought is “whoa…”. They are indeed among the most mysterious objects in existence.

  111. bjn

    Stephen Hawking proposes that information does exit a black hole (an extension to the concept of Hawking Radiation):

    http://news.bbc.co.uk/2/hi/science/nature/3913145.stm

    He goes into it in detail (layman’s detail) in “The Universe in a Nutshell.”

    “Big” implies physical size so unless you’re talking event horizon, that’s a poor description. It’s not big, it’s massive.

  112. Black holes have no inside. Since it takes forever for an observer to reach the surface…
    Oh, yes, from the point of view of the falling observer there is an inside. Sure, also from the point of view of a dead person Heaven exists. What cannot be observed does not exist in science. In science, neither Heaven nor the black hole inside exists.

    Oh, but there is a solution of general relativity for the inside. No, there is not. This solution is not valid. Reason: the singularity at the center.

  113. 12.) A black hole contains only 3 physical properties:

    A.) mass
    B.) electric charge
    C.) angular momentum

    Since the collapsing star contains much more state information than this, it means that information is lost when a black hole forms. This violates most notions of physical processes in which information can change form but is never destroyed. This conundrum is known as the black hole information paradox.

  114. Chris A.

    @Tom Marking:
    You’re right about the volume/radius relationship in positively curved space (mea culpa). However, black holes have a fourth property besides mass, charge, and angular momentum: temperature (ala Stephen Hawking). Admittedly, in macroscopic black holes the temperature is essentially negligible, but there it is. :)

  115. Yup. Knew all of that. Does that make me a certifiable Black Hole Nut or something?

  116. Creptic

    Nr 10 hit me too, but wouldn’t this sphere of air collapse? Or already been collapsed? Is the bending spacetime an issue here, to the outside a dot, to the inside not-so-dense and wide?

  117. @Tom
    “That’s true only from an outside observer’s perspective.” That’s where I live. From my perspective a Black hole is a shell of relativistic matter encasing a singularity. The universe’s greatest jawbreaker.

  118. Connor

    Love the Soundgarden reference :)

  119. > 4) Black holes spin!

    Phil, you needed to make this section a bit longer.

    “What happens as the rate of spin approaches the speed of light?”
    “Things get really interesting!”

  120. Wow,

    What an exiting run on black holes for Halloween. Pretty scary. Trick or treat! What are you supposed to be little one with your black close and make-up? A black hole mam. I’ve come to your door to suck up all your candy! If it is not forthcoming, suffer the dire consequences!

    I was trying to explain the principle above to those that had a concern that CERN might create a black hole. I assured them that it could not, but if it did how much mass could a theoretical black hole the mass of a couple of protons “suck up”? Answer: zero. Yeah, it would quickly sink to the center of the earth if it did not dissipate first. But what could it do there? Answer: zero.

    Also back holes do not have to be a vacuous point as most popular mathematical theories assert. They could be just another form of condensed matter, much denser than a neutron star, comprised of elementary, yet undiscovered field particles, like highly compressed dark matter or fundamental Higg’s type particles. The zpf could be evidence of these particles generally random field energy of motion excited in part by neutrinos — prior to their progressive compression by a pre-existing, slow spinning black hole in an adolescent growth spurt.

    your friend forrest

  121. @Aranoff “What cannot be observed does not exist in science. In science, neither Heaven nor the black hole inside exists.”

    You’re forgetting that relativity tells us that the observations of all reference frames in the universe are equally valid. Thus, the reference frame of the observer who is falling into a black hole is equally valid as our own. Thus, the inside of black holes do indeed exist just as much as any other observation that one might make.

  122. Andrew

    @Chris A.

    This isn’t quite as reaching as it sounds – the Kessel run actually involves going past a cluster of black holes (okay, don’t ask me how /that/ works), so saying he did it in under 12 parsecs is really implying that the Millennium Falcon has so much thrust that you can get that deep into their gravity wells and still get back out. Of course, we all know this isn’t what Lucas had in mind, but it’s a nice coincidence that the explanation makes complete sense even though it’s a retrofit. (Aaaand that’s my geek moment for the evening.)

  123. Winslow Morgan

    Hi Phil,
    That Photo of “The Black Hole” Is up in Los Alamos NM, Ed Grothus runs the salvage or our prolific nuclear bomb program and sells the stuff on the cheap. STUFF is the operative word.
    Ed’s also an anti nuclear activist in the city that made the bomb! Wants to erect a set of peace polls in the town, but they won’t let him. Imagine?

  124. engineer

    Phil,

    I’m with Kory. Your boss was wrong.

    The event horizon and the mass are the black hole’s primary descriptors. That gravity concept is a nonsense because it relates to gravity at the surface of a notional sphere of matter which is the physical black hole. However, the radius of this sphere of matter is essentially unknowable and incapable of being calculated or measured – only hypothesised. So the event horizon is the knowable and demonstrable “size” of a BH.

  125. Rudy

    okay… in your elaborative explanation, i conclude therefore that the universe itself is a Black Hole, and in layman’s understanding no matter, even our thought could escape within. Even astronomers can’t give us concrete explanation what is beyond since space exploration begun, because they too and their unmanned space craft can’t escape this vast universe (BH as I recently known). Haha! in observance of the Halloween, I add up this weird explanation related in your column. Since no matter can scape the Black Hole, only Ghost or Spirits will do. Did you know that most of the person undergone Near Death Experience had seen a tunnel of Light? Because their spirit tend to scape this Black Hole. We are dealing different spectrum of light here because of different matters colliding each other, but when we departed their is only one spectrum of light we see – the Light of Peace, as I myself experience it. Take it or leave it! Science (as pure matterialism) itself can’t give us infinite knowledge. Try to add a little bit of Spiritualism because it will bring you to a definite conclusion of all unanswered explanation.

  126. Rudy

    okay… in your elaborative explanation, i conclude therefore that the universe itself is a Black Hole, and in layman’s understanding no matter, even our thought could escape within. Even astronomers can’t give us concrete explanation what is beyond since space exploration begun, because they too and their unmanned space craft can’t escape this vast universe (BH as I recently known). Haha! in observance of the Halloween, I add up this weird explanation related in your column. Since no matter can scape the Black Hole, only Ghost or Spirits will do. Did you know that most of the person undergone Near Death Experience had seen a tunnel of Light? Because their spirit tend to scape this Black Hole. We are dealing different spectrum of light here because of different matters colliding each other, but when we depart their is only one spectrum of light we see – the Light of Peace, as I myself experience it. Take it or leave it! Science (as pure matterialism) itself can’t give us infinite knowledge. Try to add a little bit of Spiritualism because it will bring you to a definite conclusion of all unanswered explanation.

  127. Bart

    Phil,
    #10 got my brains all messed up for a few hours! You did say that:

    “If you were to rope off the solar system out past Neptune, enclose it in a giant sphere, and fill it with air, it would be a black hole!”

    It would BE a black hole? Or would it just have the same average density required of a black hole of that particular mass, whilst occupying the predicted event horizon volume, but without the singularity in the middle?

    According to my calculations (which may be wrong, of course; I normally deal with molecules and negative exponents), a sphere with a Sun-to-Neptune radius filled with air at sea-level pressure would be about 230 million times the mass of the Sun. Which, if it all somehow DID collapse into a black hole, would certainly make a humongous one to be reckoned with, but, would it ACTUALLY collapse into itself of its own? Just like that?

    I guess my question is, if you had a sphere of that size with a uniform distribution of air at ambient pressure in it, would it BE a black hole? Or are you saying that IF that amount of gas WERE somehow to collapse on its centre of gravity, it WOULD create a black hole with an event horizon radius equivalent to the Sun-to-Neptune distance? (and if it didn’t, it would just be a rather opaque region of space to look into with [some] telescopes, but not otherwise noteworthy)

    Cheers,
    Bart

  128. Chris A.

    @Bart
    It’s not the singularity that defines a black hole, it’s the event horizon (light can’t escape, thus “black”), which Phil’s construct would definitely have.

  129. Judy & Gar Reeves-Stevens

    Fascinating stuff! Anyone remember “Kyrie,” a short story by Poul Anderson? A woman and an alien are telepathically linked. The alien falls into a black hole (or hits the event horizon) — and to his frame of reference dies in an instant. But in the woman’s frame of reference, she telepathically experiences his death *forever.* Definitely Hallowe’en spooky.

  130. rub

    May I know what is the lifespan of a black hole?

  131. Arlo

    The sun as Folgers crystals… lol, nice reference. I love that commercial. Ha-cha-cha-cha…

    I haven’t read the massive amounts of comments here, but I was reading recently about quantum gravity and “space atoms”. ie: The idea that the origin of the universe wasn’t a singularity. That all the matter in the universe was compressed as small as it could be, but that because only a certain amount of matter can be packed into any of these minimum units of space, that it had a definite volume. It may have been a recent Scientific American article.

    Does this factor into the size of the matter in a black hole at all, or does this kind of “volume” only show up when you are talking about the entire universe compressed into the smallest possible space? If it’s 3x solar mass or a billion times solar mass, does it still crunch down to Planck length? Is 1 Planck length considered a singularity? Are black holes considered a singularity in the same way that the origin of the universe is considered a singularity. Don’t singularities imply infinity and therefore the idea that we need to check our math? So many questions!!! :)

  132. Joe Cicak

    What if a black hole grew so large that it’s density was equal to our present Universe? If that’s possible, then, perhaps our universe actually is an enormous black hole. As its mass continually increases, its event horizon expands outward, and its density decreases. Distance increases between galaxies inside the event horizon. The view from inside our black hole would look exactly like the expanding universe we see around us.

  133. Wow. I never understood why black holes were black until today. Thanks for posting the video in the middle of this blog post so I could finally understand.

  134. Well done! Great article!

  135. Bart

    @Chris
    “It’s not the singularity that defines a black hole, it’s the event horizon (light can’t escape, thus “black”), which Phil’s construct would definitely have.”

    But that’s the part I’m having trouble with. You always hear that things “collapse into black holes under their own gravity” so hearing that merely (ok, understatement) filling the mother of all balloons with air would make a black hole (without any collapsing going on), is a bit counter-intuitive. Not that I would expect these things to be easy to visualize.

    So is Phil saying that having that particular mass of air spread throughout that particular volume would create a body with a gravitational pull sufficient to prevent light from leaving (hence a black hole)?

    Cheers,
    Bart (having cold pizza with garlic sauce for breakfast, munch, munch…)

  136. Brad

    I’m pretty sure you neglected to mention hawking radiation… Black holes don’t just suck up matter and never spit anything back out again. Recent calculations suggest that black holes emit streams of energy (radiation) out from them. Steven Hawking had a long standing bet with another physicist about this topic (he was on the side that black holes never emit anything), he lost after he did the math himself and figured out that they must and paid his debt by buying the guy a complete encyclopedia.

  137. Gary Ansorge

    Arlo:
    There’s a statement that goes ” MAthematics doesn’t break down at the singularity,,,mathematicians break down,,,”Snark!

    Bart: Yes!!!

    GAry 7

  138. darklooshkin

    a question: what would have to happen to make a black hole explode?

  139. Osakaguy

    Wait, isn’t Simon (#comment-130255) above right? As you fall past the event horizon (assuming the black hole is large enough to allow safe passage at this point) time will pass normally relative to yourself, but the future history of the entire universe will start to flash by outside. Since time is practically stopped at the event horizon relative to the outside world, the outside world will end up in its heat death phase which will allow the Hawking radiation to give out more than the black hole receives from the microwave background.

    Before you can even get much past the event horizon, the black hole will evaporate. Probably killing you in the process though…(?)

  140. Bart

    @Gary

    Ok, this black hole business is weirding me out (but is way cool of course).

    Question: if at one end of the spectrum you have “small” black holes with a singularity at the centre, and at the other end something like the mother of all balloons, with an event horizon but no singularity, what happens in the intermediate range? If you keep adding matter to a “small” black hole, does the singularity (presumably the size of a Planck length?) slowly “grow” in size and “expand” back into electrons and nucleons, and eventually recombine into “normal” matter when it reaches the size of Phil’s balloon? What would the nature of that matter be? Hydrogen? Hydrogen and helium? Other elements?

    Boy this is weird. :-)

    Cheers,
    Bart

  141. Andrew D.

    I’m having trouble understanding #2. Does the singularity continue to decrease in size, or does it stop decreasing in size once it reaches a Planck length? If it stops, then yes, it has an actual size. If it continues to decrease then I would say it has an infinitesimal size. Since the concept of infinity is magnitude increasing without bound, the concept of “infinitely small” is approaching zero without bound. That is, there is an asymptote at zero.

  142. gnostic 23-7

    you forgot the most important fact– Black holes do not exist!
    Einstein and Schwarzchild both proved this mathematically, and in fact there is NO observational proof that “black holes ” are anything other than imaginary constructions of faulty mathematical reasoning. Not one concrete piece of evidence exists that supports “black hole” theory, beyond math, on paper, that was explicitly judged to be impossible by Einstein himself. Look to the electric universe hypothesis to see the inherent silliness of the idea. The physicists are lost in the contortions neccessary to keep their “standard model” viable, creating an entire bestiary of magical, invisible constructs like “dark energy”, “dark matter”, “black holes”, etc. which become required to keep their boat afloat in the face of contradictory evidence. I don’t pretend to know the truth, but that is exactly what orthodox scientists are doing when their models require that over 90% of everything that exists is in a form which cannot be observed, detected, measured or experimentally demonstrated, “dark” energies and substances and reigions beyond the “event horizon” that remain unrevealed forever save for the omniscience of math.

  143. David

    I don’t know. For some reason I like the quivering membrane theory over string theory. Seems to give better credence to how other dimensions can exist and how the bang banged.

  144. The next stage after the total “contraction” or “Planck-ing” would have to be the Big Bang. This would presume the coalescense of all the black holes
    and then the renewed formation of the Universe……………I assume that we will not be around to “see” this!!!!

  145. Gerry G.

    If I were to live on the inside of the event horizon, could I see outside into the universe, or would the universe look to me like our universe does, like it has some boundary limit. If the boundary of our universe is “expanding” and our iniverse is a black hole which we live inside, this would meed our invivese is feeding on something beyond our event horizon.

    Loved the article, thanks, will read the book soon as a result.

  146. blaah coal

    About the density thing, if the solar system were filled with air, I don’t think that would be a bh. Standing on the earth I feel the combined gravity of all the mass of the sphere, but much of that mass which is not directly below my feet is pulling left or right. If it shrank to a singularity, all the gravity would be pulling in the same direction, and be much greater. So a solar system of gas would not have the same impact as a singularity of the same mass.

    And since all the equations for bh result in paradoxes, how does anyone know where equation and reality part company? The math might seem to work right up to the moment it becomes paradoxical, but if there’s any solution to the paradox, it might be that the math was wrong from the start. And if there’s no solution to the paradoxes, then our whole reality is illogical and there’s no reason to trust any logical or mathematical model. Maybe scientists should admit that anything beyond actual observation is just a guess.

  147. 13.) The black hole theory may be the WRONG theory. We may be dealing with gravastars here, not black holes. A gravastar has a spherical shell of superdense matter called Einstein-Bose condensate and vacuum contained in it so no singularity at the center.

    http://www.space.com/scienceastronomy/astronomy/gravastars_020423.html

  148. gnostic: We see stars near the center of the Milky Way orbiting the exact center as if there were a 4 million solar mass object there that is emitting no light at all. if you have any other ideas of what this object may be other then a black hole, I’m listening.

  149. So is Phil saying that having that particular mass of air spread throughout that particular volume would create a body with a gravitational pull sufficient to prevent light from leaving (hence a black hole)?

    Yes, exactly. The matter does collapse down to the central singularity inside the event horizon, but it wouldn’t have to for the horizon to appear.

  150. Jochen Bedersdorfer

    Nice article. Thanks.

    But I actually liked BLACK HOLE from Disney. I love the music and the effects.
    And if you look at simulated photos of black holes, the one we saw in the movie doesn’t look completely out of place.

    Still waiting for the sequel! RETURN FROM THE BLACK HOLE :)

  151. Interesting to see the argument about the event horizon vs. the singularity (“I said the event horizon, but my boss said it was the object.”)

    I’m with Phil’s boss, myself.

    It gets down to a bias in defining what things are, I guess… essential properties vs impact on the physical universe :)

    So, for those who consider a black hole to be primarily defined by its event horizon… what about naked singularities? Are they a subset of black holes, or an entirely different object? Or are black holes a subset of naked singularities? Which class contains the other?

  152. gnostic 23-7 said “Look to the electric universe hypothesis to see the inherent silliness of the idea”

    I was wondering where the EU people had gone. Plasma v Gas discussion starting in 5… 4… 3…

  153. kuhnigget

    @ Brad:

    I think the bet between Hawking and Kip Thorne was paid off by a subscription to Penthouse magazine, not an encyclopedia. Hawking, apparently, is a bit of a horndog.

  154. @Tom Marking “This makes the Schwarzschild radius for an average density of air equal to 76.6 A.U.s.”

    A quick and dirty formula for the average density is as follows:

    rho-avg = 7.187 / R^2

    where rho-avg is in grams per cubic centimeter and R is in astronomical units. Thus, plugging in some different values for R:

    R = 0.723 A.U. (Venus); rho-avg = 13.7 gm/cm^3 (about the density of the element mercury)

    R = 1.000 A.U. (Earth): rho-avg = 7.1 gm/cm^3 (about the density of iron)

    R = 1.523 A.U. (Mars): rho-avg = 3.1 gm/cm^3 (about the density of basaltic rock)

    R = 2.68 A.U. (asteroid belt): rho-avg = 1.0 gm/cm^3 (the density of water)

    R = 5.204 A.U. (Jupiter): rho-avg = 0.26 gm/cm^3 (about the density of cork)

    R = 9.582 A.U. (Saturn): rho-avg = 0.08 gm/cm^3 (about the density of styrofoam)

    R = 30.104 A.U. (Neptune): rho-avg = 0.008 gm/cm^3 (6.5 times density of air at sea level on earth)

    R = 76.6 A.U. (2.54 times Neptune’s distance): rho-avg = 0.001225 gm/cm^3 (density of air at sea level on earth)

  155. munktae

    This article was simply amazing.

    You broke everything down very well for someone like myself who had no prior knowledge of black holes and their nature.

  156. kuhnigget

    @Jochen Bedersdorfer”

    “I actually liked BLACK HOLE from Disney. I love the music and the effects. And if you look at simulated photos of black holes, the one we saw in the movie doesn’t look completely out of place.”

    Ha! When the movie first came out, Chicago film critic Roger Ebert carped that, “…the black hole (in the movie) doesn’t look like any black hole I’ve ever seen.”

    I was always curious as when and where he’d seen other black holes.

    Insert joke about the South Side of Chicago.

  157. @BA “if you have any other ideas of what this object may be other then a black hole, I’m listening”

    How about a gravastar?

  158. @gnostic “The physicists are lost in the contortions neccessary to keep their “standard model” viable”

    There was a very good episode of the show Nova on PBS the other night called something like the “Ghost Particle” talking about neutrinos. The results of several experiments blow the doors off the standard model which predicted that neutrinos are massless and travel at the speed of light. It seems that’s all wrong. Neutrinos have mass, travel slower than the speed of light, and STRANGEST OF ALL, they switch back and forth between three flavors. How weird is that? It would be like a proton travelling on its way from the sun to the earth, all of a sudden becomes a neutron, then later switches back. I’m not sure if this lends credence to the Electric Universe theories but it does mean that the Standard Model is dead as a doornail.

  159. gary

    So I start reading the article and within 3 sentences there is a plug for your book. I notice also an ad for your book in the right column of the web page. I check out the video and there is a plug for your book. I see a spaghetti monster picture and guess what the fsm is holding in his hand? Then finally, of course, you could not resist adding another shameless plug for your book in the conclusion. This could have been a decent article if only your obsession to sell your book hadn’t clouded your writing so bad.

  160. @Bart “I guess my question is, if you had a sphere of that size with a uniform distribution of air at ambient pressure in it, would it BE a black hole? Or are you saying that IF that amount of gas WERE somehow to collapse on its centre of gravity, it WOULD create a black hole with an event horizon radius equivalent to the Sun-to-Neptune distance?”

    It’s actually 2.5 times the sun-to-Neptune distance. If you just had air at 0.001225 grams per cubic centimeter in a 30 A.U. radius sphere it would NOT be a black hole. But that point aside, if you could assemble a 76.6 A.U. radius sphere of air at 0.001225 grams per cubic centimeter it WOULD BE A BLACK HOLE instantly and an event horizon at 76.6 A.U.s would be established.

    Of course, the escape velocity of all of the air molecules inside such a radius would be the speed of light meaning that none of the air molecules could ever escape. And since they must be travelling at less then the speed of light the mutual gravity will collapse them into a singularity. According to classical general relativity theory all world lines within the event horizon must interest the singularity in the future so all of the air molecules are doomed to fall into the singularity.

    When we add quantum mechanics into the picture then things become stranger still. The event horizon is no longer a perpetual boundary. Particles can tunnel through it and reach the outside, thus Hawking radiation. So some of the air molecules may be able to escape via quantum tunneling.

  161. “all world lines within the event horizon must interest the singularity in the future”

    Damn those fingers. They didn’t type what the brain commanded of them. Of course, I meant INTERSECT, not INTEREST. You can probably figure out the intent of my other typos which seem to be frequent.

  162. tom.cat

    8. The fact that black holes are not dangerous *to you* if you’re far enough away doesn’t mean they’re not dagerous *at all times*.

  163. @ Brad, Kuhnigget

    Not sure that Kip Thorne paid off his share, but Hawking paid off Preskill with a baseball encyclopedia.

    Interestingly, John Preskill isn’t sure that Hawking is conceding for the right reasons, which just goes to show you that in the realm of theoretical physics, the argument is sometimes regarded as more interesting than the answer (physics is a lot like mathematics, that way).

    http://www.theory.caltech.edu/~preskill/jp_24jul04.html

    There is some evidence to support Kuhnigget’s proposal that Hawking is a bit of a horn dog, however, since the current wager’s terms are here:

    http://www.theory.caltech.edu/people/preskill/bets.html

    “The loser will reward the winner with clothing to cover the winner’s nakedness. The clothing is to be embroidered with a suitable, truly concessionary message. “

  164. Tom Marking, Phil

    “A gravastar has a spherical shell of superdense matter called Einstein-Bose condensate and vacuum contained in it so no singularity at the center.”

    Gravastar nice word. Yeah Tom, It’s similar to a large asteroid or Earth sized sphere made up of nothing but Bose-Einstein condensate but there in no vacuum or shell. The related theory would assert that it is made of compacted very solid (individually not spinning like a proton) field material, something like dark matter or non-spinning Higg’s particles. Its surface could be considered fuzzy and would consist of strings of non-spinning field particles and possibly some Bose-Einstein condensate (which do spin). As you would move out from this dense central spinning area you would be in a very dense vortex area primarily comprised of strings of field particles. Moving outward toward the event horizon this vortex speed could be close to speed of light for the fastest spinning black holes.

    At the event horizon of a galactic black hole, only plasmoidal material exists, primarily electrons and atomic nuclei swiftly orbiting sometimes close to the speed of light. Outside the event horizon. because of the speed and density of the vortex, molecular mater would be first ionized then desintigrated into atomic particle mater. As it goes down the drain of a black hole it’s further reduced to nothing but stings of field particles which are even further broken down into small strings or even single field particles, roughly a millionth the diameter of an electron, then compacted in the central spinning black hole.

    All Black holes have a two dimensional character to them since they spin on an axis which is perpendicular to the plane of a spiraling galaxy, surrounding them would be some form of spiraling cloud or ring of incoming, eventually to be recycled mater.

    The biggist totally unknown thing about black holes is that besides being gobblers, they created maybe 90% of the mater of the galaxy in the first place. In its formative stage, inside the event horizon long strings of field material are bent into loops becoming self engaged. At this point they begin to spin. Only three configurations remain stable, protons, electrons, and positrons (contrary to conventional theory anti-protons are not stable particles). When the pressure inside the event horizon becomes great enough these newly created particles are ejected in gigantic jets of particles jettisoned from both poles of the spinning black hole area. This is why there is a direct correlation between the size of the galaxy and the central black hole. No Big Bang was needed to create the universe.

    Black holes and stars would accordingly create mater from field particles. The first galactic black holes created 100% of the mater of the resultant galaxy. The universe would be much older than we presently imagine.

    To see the whole theory go to pantheory.org

  165. 14.) The Penrose Process is a process whereby an advanced technical civilization may extract energy from a rotating black hole.

    http://en.wikipedia.org/wiki/Penrose_process

    You send a particle into the ergoregion of the black hole and you get back a particle with higher kinetic energy. So far I have not seen this particular scheme used in any science fiction story including Star Trek, etc. The scheme was first described by Roger Penrose (yes, that same kooky guy who wrote “The Emperor’s New Brain” a few years back), a British physicist.

  166. gary, when you write your own book and have your own blog, then you can write what you want.

  167. Phil

    last part of tenth thing we dont know…

    “I first thought of this at a black hole conference at Stanford a few years back. I was walking with noted black hole expert Roger Blandford when it hit me. I did a quick mental calculation to make sure I had the numbers right, and related to Roger that a solar system full of air would be a black hole. He thought about it for a moment and said, ‘Yes, that sounds about right.'”…

    wouldn’t it just act like a black hole to something outside the event horizon (i.e., the edge of the “solar system”), because gravity would decrease as soon as something got inside it (and eventually be at zero by the time it got to the middle of this air filled “solar system”?

  168. Phil

    continued from above comment…

    instead of becoming ever closer to the mass which has the diameter of a Planck length, and increasing its gravitational attraction?

    the singularity of this large black hole would be more dense the singularity of a smaller black hole, because it is still a Planck length across, but the relative density (and the mass) of the of the area within the event horizon would be the same as the “air filled solar system”.

  169. The results of several experiments blow the doors off the standard model which predicted that neutrinos are massless and travel at the speed of light.

    I was reading about the possibility that neutrinos had mass years before it was demonstrated experimentally. I don’t recall it killing the Standard Model either way. In fact, my impression was physicists were delighted with the discovery, since it helped explain the apparent deficit in the number of neutrinos being produced by the sun. (Older experiments only detected one type of neutrino.)

  170. Phil, what you said in comment directly above is pretty much gospel! I believe it should be that way. A little extra income, extra time to contemplate, teach and discuss. There is a lot of time wrapped up in creating and producing this web site, resulting in learning, contemplation, and recreation for thousands. Thank You.

    Forgot to say that black holes create protons and electrons, their jets fuse a lot of plasma into alpha particles (helium nuclei), stars and supernovae create all the other atomic material.

    IN ESSENCE, A VERY SIMPLE UNIVERSE

    footnote: stellar size black holes probably do more taking apart than creation.

  171. IVAN3MAN

    gnostic:

    […] Not one concrete piece of evidence exists that supports “black hole” theory, beyond math, on paper, that was explicitly judged to be impossible by Einstein himself. […]

    GRO J1655-40* is a binary star consisting of an evolved F5 primary star and a massive, unseen companion, which orbit each other once every 2.6 days in the constellation of Scorpius. Gas from the surface of the visible star is accreted onto the dark companion, which appears to be a stellar black hole with several times the mass of the Sun. The optical companion of this low-mass X-ray binary is a sub-giant F star. Studies of the bright light emitted by the swirling gas frequently indicate not only that a black hole is present, but also likely attributes, e.g., the gas surrounding GRO J1655-40 has recently been found to display an unusual flickering at a rate of 450 times a second. Given a previous mass estimate for the central object of seven times the mass of our Sun, the rate of the fast flickering can be explained by a black hole that is rotating very rapidly.

    GRS 1915+105* or V1487 Aquilae is an X-ray binary star system which features a regular star and a black hole. It was discovered on August 15, 1992 by “GRANAT” — International Astrophysical Observatory space telescope. The binary system lies ~40,000 light years away in Aquila. GRS 1915+105 is the heaviest of the stellar black holes so far known in the Milky Way Galaxy. It is also a micro-quasar, and it appears that the black hole may rotate at 1,150 times per second.

    So there!

    *Source: Wikipedia; NASA — APOD

  172. that was explicitly judged to be impossible by Einstein himself.

    Well, golly, if Einstein said it was impossible, then it obviously must be. That guy was smarter than everyone ever and was never blinded by his preconceptions.

  173. kuhnigget

    @ Pat Cahalan:

    You are right about the Hawking/Thorne evaporating black holes bet. The Penthouse subscription was for an earlier bet, regarding the nature of Cygnus x-1, the first “discovered” black hole.

    And I can vouch for Hawking’s horndoggedness…of an entirely healthy sort. When he’s here in Pasadena at Cal Tech, he frequents the Burger Continental restaurant, which features belly dancing on weekends. I’ve seen him there several times. The owner of the restaurant told me a story about one visit, during which he’d strapped a video camera to his wheelchair and secretly taped the dancer doing a rather, um, personal belly dance for Dr. Hawking. All in good fun, so I was told.

    Healthy libido = healthy mind = cosmic thinking.

  174. Osakaguy

    Hey guys, I don’t mean to be a pain, but I’d really like to get some feedback on my comment above. (#comment-130510). Maybe Phil, or one of the other black hole experts could take a look. Am I missing something obvious? It seems like you could never reach the center of the black hole before it evaporated…? Thank you!

  175. IVAN3MAN,

    Based upon that speed of rotation you can calculate its diameter assuming its surface is traveling at close to the speed of light, 1,150 times per second. If the rotation speed were one revolution per second at the speed of light, a point on the equatorial circumference would be traveling 186,000 miles in one second. At 1,15o revelotions per second, at the speed of light, the circumference would be 186,000/ 1,150 or about 162 miles. Its diameter would be 162/pi or about 51.5 miles, about the size of Thebe one of the small inner moons of Jupiter.

    Naked Bunny,

    Neutrinos are theorized to have spin by both conventional and most alternative theories. According to an alternative theory for this reason they would create a small surrounding field vortex that would give them an almost infinitesimal mass. As electron neutrinos age, again according to this alternative theory, they would slow down because of ages of traveling through the zpf. As they slow down their spin would increase, increasing the size of their field vortex which would increase there reaction to gravity, therefore there mass would also increase. At this time they, and their momentum, could be absorbed by ordinary matter, becoming one of the major components of pushing gravity which today might be called a graviton.

    for the entire theory see pantheory.org

  176. Glacial Spain

    It seems like I saw a documentary on black holes years and years ago that showed a guy (hypothetically) flying a spaceship close to the event horizon and then returning home to find that several hundred years had passed on earth, while in his own experience only a few months had passed.

    Is that correct – time passes more slowly near the event horizon?

  177. kuhnigget,

    nice equation! Healthy libido = healthy mind = cosmic thinking. I would like to think that it suits me well.

    Osakaguy,

    Many black hole theorists agree with Hawking radiation in one form or another. The rate of dissipation for most black holes would accordingly be much less than its gobbling rate so that many could be as old as anything in the observable universe. According to most theories no observer could ever come anywhere near a black hole without first being spaghettiized.

  178. Glacial Spain,

    If the event horizon were moving at close to the speed of light and if you flew in a contrary motion to maintain your relative position to the surrounding galaxies, you would be traveling close to the speed of light relative to the field that surrounds you. In this case time for you would slow down or be dilated relative to the outside world if you were not spaghetiized first which you probably would be. The related non-standard theory asserts that first ionization and then spaghetiization would be complete at about 1/10 the speed of light relative to the motion of the field that surrounds you. To overcome this dissintegration a ship would need a gravity shield, something that today is only discussed in science fiction or obtuse theory.

    for the entire theory see pantheory.org

  179. Its amazing what we know about black holes.
    There is a fun idea that they are doorways.
    It would be great if used as doorways one day.
    Science fiction tends to be science fact.

    thanks from tony

  180. Charles Boyer

    Forever is a long time, Phil.

    Wouldn’t matter that passed the event horizon eventually evaporate out again?

  181. Nigel Depledge

    Tom Marking said:

    Plugging in the density of air at sea level for the standard atmosphere which is 1.225 grams per cubic centimeter = 1,225 kilograms per cubic meter we get: . . .

    Nuh-uh. The density of air at sea level is rather less than 1 g per cc (this being the density of water at STP). Perhaps you meant 1.225 g per dm3? But this sounds like a very small figure.

  182. pccitizen

    Fascinating stuff!!
    If the universe is a black hole (who woulda thunk it), then does this mean the observable universe, or does it also include that part of the universe which expanded out of our knowledge (no light has reached us yet…) because of inflation? How do we have any idea what the size of the inflated universe is?
    John

  183. @Nigel “Nuh-uh. The density of air at sea level is rather less than 1 g per cc”

    Already been corrected. Please read the posts. The standard atmospheric density at sea level is 0.001225 grams per cubic centimeter = 1.225 kilograms per cubic meter.

  184. 15.) And now for the coup de grace. How far away is the closest black hole to the earth? Bet y’all want to know that number. I notice the BA didn’t tell ya so I’m gonna do it. We can estimate it. How? Bear with me…

    First we’ll need a few parameters:
    Let Mbh equal the mass limit for main sequence stars above which they eventually form black holes. Let’s set Mbh equal to 10 solar masses.

    Now, the distribution of stars in our galaxy (and presumably the universe as a whole) follows a power law:

    dN = K * dM / (M ^ alpha)

    where dN is the differential number of stars, K is a constant, M is the mass of the star in solar masses, and alpha is a constant. From observations of nearby stars alpha seems to be ~2.5. So we have:

    dN = K * (M ^ -2.5) * dM

    Integrating between the lower limit for mass M1 and the upper limit for mass M2 we have:

    N = (K / (1 – 2.5)) * (M2 ^ (1 – 2.5) – M1 ^ (1 – 2.5))

    If we let M2 be the maximum mass of stars (= ~100 solar masses) and M1 be the minimum mass of stars (= ~0.1 solar masses) we can solve for K. Also, setting N = 1 so we normalize for fractions we get:

    K = 0.0474

    Now the fraction of stars in the galaxy which will eventually form into a black hole is this:

    Fbh = (K / (1 – 2.5)) * (Mmax^(1 – 2.5) – Mbh^(1 – 2.5))

    Plugging in all the number we get Fbh = 9.68E-4 which means that slightly less than 1 in 1,000 stars will become black holes. So far, so good.

    Now we compute the rate of black hole formation in the galaxy per year which we represent by Rbh:

    Rbh = Rs * Fbh

    where Rs is the rate of star formation in the galaxy (usually taken to be ~10 stars per year and incidentally, this is the first factor in the Drake equation). So we have:

    Rbh = 9.68E-3 stars that will eventually turn into black holes created per year

    Since the lifetimes of massive stars (greater than 10 solar masses) is relatively short compared to the lifetime of the galaxy we can also take this number to equal the number of black holes formed per year. So one black hole is formed in the Milky Way galaxy every ~100 years. I’ll leave it for Phil to calculate the odds of its axis being aimed right at us and being close enough to fry us via GRB (gamma ray burst). Hopefully he does some of those calculations in his new book.

    So, how many black holes are there now in the Milky Way galaxy? It’s a simple rate multiplied by time equation:

    Nbh = Rbh * Tgal

    where Tgal is the age of the galaxy in years (let’s set it to 8 billion years since estimates range from 6.5 billion years to more than 11 billion years). Nbh is the current number of black holes in the galaxy.

    So Nbh = 7.7E7 or 77 million black holes currently somewhere in our galaxy. Of course, this does not take into account the merger of black holes to form larger black holes which will reduce this number but let’s ignore that effect for now.

    Now, how close is the nearest one of those dudes? Well, the galaxy is roughly a disk 50,000 light-years in radius and 1,000 light-years thick with a central bulge of 5,000 light-years in radius. Throwing all this into the mix I get the following value for the volume of the Milky Way galaxy:

    Vgal = 8.3E12 cubic light-years

    So on average, each black hole should have the following volume all to itself:

    Vbh = Vgal / Nbh = 1.1E5 cubic light-years

    Taking the cube root of this value, we get:

    Dbh = 48 light-years which is the average distance between nearest black holes and roughly the same as the average distance from us to the nearest black hole.

    So, only 50 light-years. That’s less than the distance to many of the brighter stars such as Canopus, Rigel, Aldebaran, etc.). If we consider the fact that the rate of star formation Rs was much higher in the past than now, then this number may be even less. So, somewhere out there only 50 light-years away from us (or more likely closer) a black hole is lurking. I wonder how long it will take us to find it. I also wonder if there are any techniques developed for exoplanet searches that would help us detect these guys.

    So the bottom line is, they might be closer than you think.

    Enjoy!!!

  185. @IVAN3MAN “GRO J1655-40* is a binary star consisting of an evolved F5 primary star and a massive, unseen companion… GRS 1915+105* or V1487 Aquilae is an X-ray binary star system…”

    And the evidence for a singularity at the center of these two objects would be exactly what? Also, what is the evidence for an event horizon surrounding these objects?

  186. @Naked… “I was reading about the possibility that neutrinos had mass years before it was demonstrated experimentally. I don’t recall it killing the Standard Model either way.”

    http://hitoshi.berkeley.edu/neutrino/neutrino2.html

    “…This picture also explains why neutrinos are massless. If a left-handed neutrino tried to collide with the Higgs boson, it would have to become right-handed. Since no such state exists, the left-handed neutrino is unable to interact with the Higgs boson and therefore does not acquire any mass. In this way, massless neutrinos go hand in hand with the absence of right-handed neutrinos in the Standard Model.

    .
    .
    .

    Now that neutrinos do appear to have mass, we have to solve two problems. The first is to overcome the contradiction between left-handedness and mass. The second is to understand why the neutrino mass is so small compared with other particle masses — indeed, direct measurements indicate that electrons are at least 500 000 times more massive than neutrinos. When we thought that neutrinos did not have mass, these problems were not an issue. But the tiny mass is a puzzle, and there must be some deep reason why this is the case.

    Basically, there are two ways to extend the Standard Model in order to make neutrinos massive. One approach involves new particles called Dirac neutrinos, while the other approach involves a completely different type of particle called the Majorana neutrino.
    .
    .
    .

  187. @forrest noble “Gravastar nice word. Yeah Tom, It’s similar to a large asteroid or Earth sized sphere made up of nothing but Bose-Einstein condensate but there in no vacuum or shell.”

    Is this guy for real or yet another graduate of EUU (Electric Universe University)? A large asteroid, eh? No shell, eh?

    http://www.sciencedaily.com/releases/2002/04/020423075643.htm

    “On Earth, a Bose-Einstein condensate forms when matter is plunged to very low temperatures approaching Absolute Zero, the theoretical temperature at which all atomic motion – the motion of electrons, protons and all other subatomic particles within an individual atom – is believed to cease. When matter is cooled sufficiently to become a Bose-Einstein condensate, the atoms that make up the matter enter a strange new phase. The atoms all reach the same energy state, or quantum state, and they coalesce into a blob of material called a “super atom.” The properties of Bose-Einstein condensates are the subject of intense study and many physicists are working to understand them.

    Mottola and Mazur believe that dying stars collapse to the “Event Horizon” – in essence the point of no return for objects entering the gravitational field of a black hole. At this point, the matter in the dying star transforms to a new state of matter that forms a Gravastar. According to the two researchers, the dying star’s matter creates an ultra-thin, ultra-cold, ultra-dark shell of material that is virtually indestructible. The new form of gravitational energy in the interior is akin to a Bose-Einstien condensate, although it appears on the inside to be a bubble of vacuum, hence the term Gra (vitational) Va (cuum) Star, or Gravastar.

    .
    .
    .

    Although unconventional, Mottola and Mazur’s Gravastar explanation for black holes does solve at least one serious quandary created by black hole theory. Under a black-hole scenario, the amount of entropy created in a black hole would become nearly infinite. Physicists have struggled for years to account for the huge entropy of black holes, and largely have failed. Unlike their black hole counterparts, Gravastars would have a very low entropy.

    .
    .
    .

  188. @forest noble “contrary to conventional theory anti-protons are not stable particles”

    ROFLMAO. And your evidence for this would be what? Oh, I know, the anti-proton collided with a proton and both were annihilated. Therefore the anti-proton isn’t stable but the proton is.

  189. dat crazy bok

    Tom it sure seems I’ve read word for word a lot of what you’ve said. Do you simply spout from articles to make yourself feel better?

  190. dat crazy bok

    or have i read your article somewhere? lol

  191. Dan Sickles

    “Black Hole Brew” – I would like for some of that to cross my event horizon. Do they come in a sixularity?

  192. Tom Marking,

    Contrary to conventional theory anti-protons are not stable particles, ” And your evidence for this is what?”

    The evidence that I know of concerning the lack of stability of anti-protons is that the best containment to date requires a cyclotron to contain them which inadvertently would also reinforce their spin rate. To my knowledge, the greatest half life yet achieved to date for a single anti-proton is 18 days. There is no proof that this particle’s loss rate in a cyclotron, or or otherwise, is solely due to interaction with ordinary matter. This is only a theory. The alternative theory which I adhere to, which is supported by a whole universe of evidence, is that they are not stable particles. This is why we don’t see them!

    Interesting calculations above concerning the estimated distance to the closest black hole, certainly “sounds” reasonable.

    your friend forrest

  193. kitsune

    I am definitely a layperson in these matters, but cosmology fascinates me. I wanted to be an astronomer, but couldn’t quite get past the college calculus. Anyway, something occurred to me while reading these posts — I wonder if anyone has a comment? Assuming black holes exsist (which I see some scientists aren’t quite sure about), then if our universe IS a black hole, then would the black holes in our universe contain their own universes? And so on? You know, Men in Black style? Just a thought I had — I wonder about the implications.

  194. correction above:

    “the greatest half life yet achieved to date for a single anti-proton is 18 days.” should have read:
    the greatest half life ever achieved (to date) for a group of anti-protons was 18 days.

  195. Charlotte

    Hi I just happened to stumble in here and WOW…
    I’m amazed reading through the article and responses…such dedication!
    Personally, I bypassed physics for art, philosophy, and psychology studies – trying first to see clearly what was before me physically and then marvelling too at what lies beyond surface apearances in the deepest recesses of the human experience beyond …enthusiastically musing over the matter and meaning and mystery I’m accustomed too but then the MATH.
    Seems there’s significant frustration and excitement about the mystery and magic of the not quite understood black hole. I noticed most of you guys are guys I wonder about the impact of cross refferencing your studies to the world of relationship in a ‘wholistic’ way. For instance, I wonder if more guys study the black hole theories than women for instance and why? hee hee. How related are the black hole theories to co-dependent relationships. If we’re in a black hole now and the universe is having her way with us eventually things will really heat up, twist and turn and then Ka-Pow right? What a way to go- a little spagetazizing is worth it, no?
    Seriously, with all due respect, thanks for being smarty pants;-)

  196. Kitsume,

    Never heard a “serious definition” of a black hole that could contain ordinary matter like stars, planets, galaxies, life, etc. , or exotic matter (or vacuous points) like black holes. This kind of conjecture I’ve only heard of in science fiction.

    Charlotte,

    Black holes are only a small part of the entire fields of astronomy and cosmology. There is a lot of math/ physics involved in the technical parts of it and many theories. Many women have gone into the biological sciences, some into astronomy, but few choose advanced math and physics. Still fewer choose theoretical physics where most black hole theory/ hypothesis are developed. My guess is because these fields don’t appeal to most women when they are young. Also, to get a PhD in these fields is difficult and generally impractical because it’s hard to find a job, and if you do the pay is small compared to other scientific fields like biology, medicine, engineering, ecology, geology, etc. for the equivalent schooling.

    I presume it is interesting to everyone commenting here because black holes are one the biggest influences on reality that we still know little about, leaving a wide range for conjecture and speculation that men seem to be fond of. But if you are really interested in this stuff, Charlotte, beyond superficial conversation, a good start would be to start educating yourself in whatever you are interested in by reading about it on the web, where a general background, most recent news, theory, and conjecture can be found — like you found this web site.

  197. Phil, I think your initial inclination was correct and #10 above may be wrong.

    “10) Black holes can be low density. ”

    This of course may currently be the most popularly accepted theory/ hypothesis.
    Just because it is the current view, however, doesn’t mean you have to believe it or accept it. Remember, you are also a skeptic. I propose that skepticism should also include theories in science until there is a preponderance of evidence, and even then be Leary of the conclusions if they don’t make clear sense to you– at least that’s my opinion.

    It will be a long time before we are fairly certain what is inside a black hole. Some theory including my own (pantheory.org) would assert that a black hole itself has a solid surface, for a stellar black hole, as you suggested, it could be just a few kilometers across. For those black holes that radiate jets and spin rapidly the calculation for the diameter from where the jets originate (which I propose is at or close to the diameter of the event horizon at the poles) in the above example (my writings at 12:53 pm) was 51.5 miles. This would leave quite a distance from the black hole itself to the event horizon but inside the event horizon there does not have to be a void. To the contrary, beyond the event horizon moving inward I think you would find an increasingly dense soupy plasma vortex of dark matter. In this theory the density would progressively increase up to the surface of a black hole, the densest state of matter that exists outside a single field particle of dark matter. If this theory is true, all black holes from their center to the event horizon would all have a similar density.

    your friend forrest

  198. Chris A.

    @Osakaguy:

    No, the black hole whose event horizon you are hovering above would not evaporate before your eyes, because it’s subject to the same spacetime warping (slowing of time) as you are. Only the universe outside the black hole’s gravity well will appear to be aging at hyper-speed. Put another way, the black hole’s “clock” will be running just as slow as yours, relative to the rest of the universe.

  199. Gary Ansorge

    kitsune:
    The answer to your question:
    ,,,then if our universe IS a black hole, then would the black holes in our universe contain their own universes? And so on? You know, Men in Black style? Just a thought I had — I wonder about the implications.
    Is simply: we don’t know,,,

    The reason we assume matter collapses to the infinitely small w/in a black hole is because the force carrying particles that keep matter from collapsing are subject to the same velocity limitations as all other matter, ie, they can’t go “up hill” against the black hole gravity, thus there is nothing to prevent the matter from collapsing. So MAYBE all black holes have universes inside,,,maybe,,,

    As far as the math/calculus is concerned, its difficulty is directly proportional to the way it is taught. I was fortunate to have Dr Wolfgang Rindler as my teacher in Differential equations. He taught it as a “cook book course”, ignoring the theory and concentrating on the five techniques we use to solve those equations. The techniques include solving by parts, which is a brute force approach and is particularly amenable to solution by computer. It’s what we use when a more elegant approach seems non-productive. Dr Rindlers approach allowed us to merely “turn the crank” and produce solutions. So simple even an engineer(like me) could understand it,,,

    Gary 7

  200. @gary “Then finally, of course, you could not resist adding another shameless plug for your book in the conclusion. This could have been a decent article if only your obsession to sell your book hadn’t clouded your writing so bad.”

    So what you’re really saying is this. Let rho-t be the total information density of this blog in bits per cubic meter. Now let rho-b be the total information density relating to Phil’s new book (What was the name again? Death From the Clouds? Death From Something? Or something like that, right?) in bits per cubic meter. Then adjusting for relativistic time dilation you’re saying:

    rho-b / rho-t > 0.999

    Yeah, I’ve noticed the same thing and I got similar results.

    (Sorry, I couldn’t resist. I had to stick in the odd equation there. :) )

  201. @dat crazy bok “Tom it sure seems I’ve read word for word a lot of what you’ve said. Do you simply spout from articles to make yourself feel better?”

    And your contribution to this discussion would be exactly what? So glad you can read text word for word. That is what text is composed of.

  202. @forrest noble “The evidence that I know of concerning the lack of stability of anti-protons is that the best containment to date requires a cyclotron to contain them which inadvertently would also reinforce their spin rate. To my knowledge, the greatest half life yet achieved to date for a single anti-proton is 18 days. There is no proof that this particle’s loss rate in a cyclotron, or or otherwise, is solely due to interaction with ordinary matter.”

    Ooops, here I go again “spouting” off information from technical journals instead of pulling it from my posterior. I apologize to one and all.

    http://home.earthlink.net/~dckennedy/pubs/PASCOS99.pdf

    “Cosmic rays are high energy protons, antiprotons, nuclei, electrons, and positrons in interplanetary and insterstellar (IS) space. The dominant component consists of protons (Hydrogen H) with a smaller admixture of heavier nuclei, especially He (Figure 1). Antiprotons occur at an abundance of 1.0E-4 to 1.0E-5 times that of protons. These energetic particles with kinetic energies K greater than 10 MeV are galactic in origin
    .
    .
    .
    Laboratory limits have been obtained for the antiproton lifetime. Earlier limits include the LEAR Collaboration at the CERN antiproton storage ring (t-antiproton is greater than 0.08 years) and the antihydrogen Penning trap of Gabrielse et al. (t-antiproton is greater than 0.28 years). The best current laboratory limit is that of the APEX Collaboration at the Fermilab antiproton storage ring (t-antiproton is greater than 50 kiloyears for antiprotons and t-positron is greater than 300 kiloyears).”

    So a couple of points:

    1.) Antiprotons are stable enough to travel thousands of light-years through the galaxy and arrive at earth

    2.) As experiments have improved the storage time for antiprotons have increased. They are currently at least 50,000 years, not the 18 days being claimed and are likely to climb even higher as the experiments improve.

    Both of these facts suggest that antiprotons are extremely stable particles, perhaps as stable as protons.

  203. IVAN3MAN

    @ Tom Marking

    Man, you’ve been busy(!), judging by your posts above. As to your question:

    And the evidence for a singularity at the center of these two objects [GRO J1655-40 & GRS 1915+105] would be exactly what? Also, what is the evidence for an event horizon surrounding these objects?

    Here are the links to the “evidence” you requested:

    Black Hole Paradox Solved By NASA’s Chandra;

    Discovery of a 450 HZ Quasi-periodic Oscillation from the Micro-quasar GRO J1655-40;

    Optical Observations of GRO J1655-40 in Quiescence;

    The micro-quasar GRS 1915+105;

    Strange, Powerful Object in Milky Way Galaxy Shoots Out Material at Super Speeds;

    GRS 1915+105

    As Dr. Phil Plait said above, “if you have any other ideas of what this object may be other then a black hole, I’m listening.”

  204. IVAN3MAN

    @ Tom Marking

    ADDENDUM: Here’s another one on GRS 1915+105:

    A Very Massive Stellar Black Hole in the Milky Way Galaxy

  205. Osakaguy

    @ Chris A., and forrest noble

    Thanks for the response! I’m still not sure though, because looking at the “Future_of_an_expanding_universe” page at Wikipedia (and I guess making a lot of assumptions about that future) they say there is a black hole era around 10^40 to 10^100 years. It says: “A supermassive black hole with a mass of 10^11 (100 billion) solar masses will evaporate in around 2×10^99 years.”

    It’s been awhile since I studied physics, but I think that means 2*10^99 years of “outside” clock time. Since the observer (or any old atom, doesn’t matter) is passing through the event horizon where time is basically stopped compared to that outside clock, won’t those 2*10^99 years flash by in an instant? So it still seems to me that the black hole would evaporate just as you pass through the event horizon.

    I mean even if you cross the horizon at your local time = 0, and you get half way to the center of the black hole at time = 1, the outside universe has possibly sped through another 10^500 years or more, and the black hole shouldn’t even exist anymore! So how could you even get even a centimeter into the black hole?

    (Again assuming what Wikipedia says about Hawking radiation, and the future state of the universe is true…)

  206. Dale Locklin

    I just got the book today on sony e-book,will comment late

  207. Nice read. There is a lot that I don’t know or understand about black holes. For example: why would it be impossible to build a ladder once you’re inside the event horizon, and just climb out? Or why would it be impossible for someone just outside the event horizon to drop a really strong rope down to me, and simply pull me out?

  208. Gary Ansorge

    Frans van Otten:

    ,,,and I reiterate,,,
    The reason we assume matter collapses to the infinitely small w/in a black hole is because the force carrying particles that keep matter from collapsing are subject to the same velocity limitations as all other matter, ie, they can’t go “up hill” against the black hole gravity, thus there is nothing to prevent the matter from collapsing.

    ,,,thus, the ladder, whether inside or outside, cannot maintain its structure, because of that inability for the force carrying particles to go uphill against that G field. Thus there IS no repulsive or attractive force felt by the particles comprising the ladder and it spagettifies indefinitely.

    GAry 7

  209. Gary Ansorge

    Osakaguy:

    Even photons falling into a black hole would be stretched, because the G filed closer to the BH is more intense than the G field further away, so it “stretches:, ie, red shifts, the in-falling light and that makes the external space/time appear to slow down.

    GAry 7

  210. Frans van Otten, click on my name and the link will lead you to a list of Frequently Asked Questions on Black Holes, which should provide the answer that you’re looking for.

  211. Osakaguy

    @ Gary Ansorge

    Thanks for the reply, but that point wasn’t what my comment was addressing. I am claiming that matter actually can’t reach the center of a black hole. I’m hoping someone here can explain where I am misunderstanding something if my claim is incorrect.

    But regarding your point, that actually isn’t the case for large black holes. Here is what Wikipedia says on that topic: “The strength of the tidal force of a black hole depends on how gravitational attraction changes with distance, rather than on the absolute force being felt. This means that small black holes cause spaghettification while infalling objects are still outside their event horizons, whereas objects falling into large, supermassive black holes may not be deformed or otherwise feel excessively large forces before passing the event horizon.”

  212. Tom Marking,

    It is a good link that you posted but I think the key to it is in the last couple of sentences.

    “some of these isotopes are unstable, their populations must be continually replenished to
    maintain their observed abundances.”

    Cosmic Rays contain a large amount of alpha particles that interact with atmospheric and other isotopic material in the galactic plane. Secondary anti-protons can by created by the interaction of these two entities. I think their claim for observing primary cosmic anti-protons because of their energy levels is wrong. Fluxes of solar electrons and our magnetic field can accelerate these particles beyond their initial velocity after being created. After all, the solar wind is moving at roughly a million miles per hour. Just a few seconds of age could put the source of these anti-protons out a million miles.

    Although you have made statements concerning the present storage half life being greater than 18 days, which may be true, you have presented no evidence. Considering this to be true, I would say that they have just found a better way to reinforce their spin. Also, if this is the case, where are the brand new proposals for anti-matter rocket engines. There are many credible, sophisticated designs out there for positron propulsion drive. I hope you’re right on the longer storage time but I think you went too far when you stated “50,000 years”. At least your conclusion was qualified by “perhaps as stable as protons.” Closer to the truth that I would assert is “perhaps not.” What about the universe of evidence out there which backs my contentions?

    I would say that if they have found a better cyclotron storage system, they also have figured out a better way to re-enforce anti-proton spin to enhance their longevity beyond what is naturally achievable. Still it is a good link and science in general which makes contrary conclusions to what I believe are the facts. I will keep your link, thank you! (see pantheory.org — my theories, equations, and evidence).

    Osakaguy,

    What I have said is that matter disintegrates inside a black hole. What would be the meaning of time to non-fermionic, non-spinning dark matter? The word I like to use is spaghettiized. The ideas you have are related to the theoretical equations which I believe don’t really have a clue as to what is inside a black hole — none-the-less I agree that this conjecture is interesting.

  213. Matthew

    I think it would be interesting to work out how large other fillings would need to be to form a black hole, like a water filled blackhole, or an ice cream filled black hole. Who wouldn’t want an ice cream blackhole?

  214. Great article. What we know for sure about black holes is pretty small compared to what we want to find out about them. I have many astonomy documentaries on my site that offer opinions on black holes that don’t really conflict, but rather look at them from different positions. There is new evidence coming in all the time and I think we will be closer to the truth by the end of this century.

  215. Osakaguy,

    Just read your word “spaghettification” which I missed on the first read. I think that might have a better ring to it than my spaghettiization. I may have to “adopt” it from time to time. Thanks.

    forrest

  216. José

    Who wouldn’t want an ice cream blackhole?

    You obviously haven’t considered the massive brain freeze implications of black hole ice cream.

  217. @forrest noble “Although you have made statements concerning the present storage half life being greater than 18 days, which may be true, you have presented no evidence.”

    I did present evidence. The article I quoted had several specific time periods for anti-proton storage for several different experiments. It is you who have not given us your source for the 18 day number.

    “What about the universe of evidence out there which backs my contentions?”

    Forrest, I did visit your web site which is:

    http://www.pantheory.org

    I skimmed through it including your online book entitled “The Pan and Ipan Theories”. Funny thing is this. There are no mathematical equations anywhere to be found, either on the web site or in the online book in PDF format. Maybe they are there some place hiding but I wasn’t able to find them and I was looking. So is the Pan/Ipan theory completely non-mathematical? How can you overturn the world of particle physics and cosmology without any new equations to replace the old ones?

    I am completely down with the lone wolf thinker who comes up with new ideas that stand the existing theories on their heads. Indeed I applaud such folks. Einstein did it and so did many others. But especially in physics and cosmology some math is necessary. So I doubt very much that your “theory” will gain many adherents in the world of physics and cosmology. I also notice that your web site’s forum section has exactly 2 posts in it.

  218. Ian Osmond

    About your point #10 . . . if black holes can be low density, well, 1 hydrogen atom per cubic meter would be pretty low density.

    But if you chose a large enough radius . . . would it still be a black hole?

    Seems to me that that would place an upper bound on the size of the universe — once the universe is big enough for the entire thing to count as a black hole, then, well, we’re on THIS side of the event horizon, anyway, so that would be a practical upper bound, wouldn’t it?

  219. Dark

    Very illuminating article. I’m only 17, but I understood most of this well enough.

    Guys, science may be a confusing subject with many contrasting theories, but no need to argue like this. Tom, it’s far too easy to read a mocking attitude and a superior tone into your posts. I know you may not like his theory because of a lack of any mathematical evidence, but there is no need to use speech-marks around the word theory. A theory is simply an idea, whether it’s backed up or not. Solipsism is a theory. No mathematics there.

    Also, isn’t it low to comment on his forum? That has really nothing to do with either this discussion or whether his theory is correct or not.

    I shall definitely have to remember this site, it seems very interesting indeed.

  220. dave o

    You know, before you get a black hole,you get something that does funny things with time. In the case of a air bubble about the size of maybe the orbit of Mars, the sunlight coming out of the bubble would be red shifted. The average density of the universe is published at 5 x 10^-30 g/cm cubed. Not much, but if you go out from a star about 5 billion light years, the matter inside that 5 billion light year bubble would be red shifted a significant percentage of the “expansion of the universe” Hubble redshift. Which kind of makes dark matter a klutzy patch on the theory.

  221. @ Tom

    > Ooops, here I go again “spouting” off information from technical
    > journals instead of pulling it from my posterior. I apologize to
    > one and all.

    Nice.

  222. @dave o “The average density of the universe is published at 5 x 10^-30 g/cm cubed.”

    That’s approximately 1 hydrogen atom per cubic meter or 1.67E-27 kilograms per cubic meter. Plugging that density into the formula:

    Rs = c * sqrt(3 / (8 * pi * G * rho))

    So Rs the Schwarzschild radius is 3.1E26 meters or 33 billion light-years. From what I can find on Wikipedia the quasar with the highest redshift has a redshift value of 6.43 which corresponds with a distance of 28 billion light-years which is just within this Schwarzschild radius value. So maybe it’s just a coincidence or maybe it’s not.

  223. @Chris A.

    “Personally, my favorite way a black hole can kill you is this:
    Even if you find a huge, low density black hole (like the monster in M87) and fall in, knowing that the tidal forces wont spaghettify you (Kip Thorne writes about this in “Black Holes & Time Warps), you will die in a spectacular way. As you approach the event horizon, time in the universe will appear to speed up due to relativistic effects. Just before you cross the event horizon, you’ll see stars winking out, going supernova, etc. Sounds like a great show, except that the photons’ “clocks” will be running hyperfast too (thanks to relativistic blue-shifting). Meaning that the frequency of every photon falling on you will be shifted to the shortest possible wavelengths (ultra-high energy gamma rays) and incinerate you. Ouch.”

    I didn’t comment on this until now. It’s very interesting. I think you’re neglecting one important factor and that is the velocity induced Doppler effect from the point of view of the observer falling through the event horizon. There are two effects here:

    1.) The observer’s clock is slowed down relative to the outside universe or conversely the outside universe’s clock is sped up relative to the observer. Consequently photons are blue shifted and the energy flux per unit time is increased. This is the gravitational red shift effect. But there is also another important effect which is:

    2.) Velocity Doppler red shift. The observer is falling into the event horizon at an accelerating rate. The velocity is likely to be high relative to the speed of light and thus the stars, galaxies, etc. to the observer’s aft will appear red shifted. This will tend to compensate for the blue shifting due to the gravitational red shift effect. The only location where it won’t would be in a perpendicular direction to the observer’s montion towards the black hole. So it would be an interesting calculation to figure out which effect wins. Does the blue shift fry the observer or does the red shift save him for later spaghettification. I don’t think we can know the answer for sure unless we do some sophisticated numerical simulations.

  224. S.D.

    Of all I’ve read above and of what little I understood, the most striking thought of all was Ian’s post in which he shared, “A black hole of the mass of this universe would oddly enough have the density and size of this universe! This means we could essentially be on the *inside* of the largest observable black hole”.
    Much smaller than Planck’s Length and much larger than we can imagine this universe to be, is the mind we imagine it all though.
    Interestingly Walt Disney was mentioned at the end. It seems to me that his type of imagination will take us beyond to not only better understand but to be as one with the forces that define. After all, it was in and through our imagination that all of this started. I am certain the same will take us beyond what lies on the other side.

  225. Tom Marking,

    I found your source for the evidence you presented. Thanks.

    “How can you overturn the world of particle physics and cosmology without any new equations to replace the old ones?” Maybe they are there some place hiding but I wasn’t able to find them and I was looking.

    You are right Mark. They were hiding.

    http://www.pantheory.org/

    The “missing” mathematics and formulations that you couldn’t find are in the following book locations: Chapter 13, the Pan Gravity Theory, on pages 57D2 through 57E2; Pan-chain (coil-string) configuration mathematics can be found in Chapter 18, page 87. , Chapter 19, The Pan Theory of Relativity, can be found on pages 101A-102A.

    It’s intended to be a popular book so that too much mathematics, like Hawking’s books and others, don’t put in much math because publishers call it the kiss of death for a popular book. I have a higher percentage of mathematics and graphing in my technical papers, one of which I will put on my web site in a few days, maybe by Friday or sooner if you wish to review it.

    You or anyone else interested can contact me at the website or personally at forrest_forrest@netzero.net for any reason. Still have to add the Table of Contents and an index to the book so things will be easier to find. Maybe the most important part of the book, other than the mathematics, is the Prediction and Concept Section, pages 104 through 107.

    Dark,

    Keep on trucken. Thanks for the comments. Maybe you will go into a field of science as a profession. Many that do find it fascinating.

    Dave,

    I think within the next decade after the James Webb telescope is up, a lot of the present cosmological ideas, hypotheses, and theories will be in trouble, especially since no ages will be found where the universe is progressively becoming denser which in the Big Bang Theory is mandatory, i.e. galaxies are supposedly expanding away from a more dense past and into a less dense future. No such observations have been forthcoming. In fact the contrary has been observed– that the density of galaxies progressively decreases as you look back in time. The is predicted by alternative cosmology and contradicts the Big Bang Model. This prediction was made by me in 1959 and can be seen as prediction #1, page 104, and the related mathematics pg. 101A-102A, at the above noted website.

    your friend forrest

  226. correstion above: should have been Prediction #3 (instead of Prediction #1) pg. 104,

    http://www.pantheory.org/

  227. Tom Marking,

    Some quick math on the likelihood of an anti-proton getting hit by matter in an open field of space. The diameter of an anti-proton (same as a proton) is estimated to be 10^15 meters. The density of protons in intergalactic space is roughly the equivalent of one proton per cubic meter, much greater within the galactic plane. The number of (cubic) meters in a light year is about 10^16. Therefore an anti-proton could only travel roughly one light year (+ – 2 standard deviations, 95% probability) before it would likely be hit or run into intergalactic matter. If they are unstable particles like a neutron in open space (life expectancy 11 minutes), they wouldn’t last long. This is also because of the almost countless additional electron neutrino strikes that they would encounter. Within our part of the solar system (mostly produced by the sun) there are roughly a million electron neutrinos per cubic meter. Most of them traveling near the speed of light. This would be roughly one hit every nine thousand meters. If they are unstable, which I assert, they could only last a few seconds before annihilation. If they are really more stable they could last maybe a year before bang! So it appears statistically that there is no way any observed anti-proton could have had a source outside our solar system.

    Tom and all, always looking for critical minds to edit my book by making editorial comments. Contact me on site or at the above e-mail. There’s an editor’s page, page 2 in the text. The most recent upload will be completed this evening western standard time.

    cheers

  228. @forrest noble “Some quick math on the likelihood of an anti-proton getting hit by matter in an open field of space. The diameter of an anti-proton (same as a proton) is estimated to be 10^15 meters. The density of protons in intergalactic space is roughly the equivalent of one proton per cubic meter, much greater within the galactic plane. The number of (cubic) meters in a light year is about 10^16. Therefore an anti-proton could only travel roughly one light year (+ – 2 standard deviations, 95% probability) before it would likely be hit or run into intergalactic matter.”

    The equation to use is that for mean free path (MFP) which is as follows:

    L = 1 / (N * sigma)

    L is the mean free path in meters
    N is the particle density in particles per cubic meter
    sigma is the cross-sectional area of the travelling particle in square meters

    For spherical particles: sigma = 0.25 * pi * D^2
    where D is the diameter of the travelling particle in meters

    Combining equations yields:

    L = 4 / (pi * N * D^2)

    For a proton or antiproton let D = 1.6 femtometers (1.6E-15 meters). For intergalatic space let N = 1 hydrogen atoms per cubic meter, so L = 4.97E29 meters = 5.2E13 light-years. Perhaps you want to use the interplanetary particle density of 1.0E6 hydrogen atoms per cubic meter. Now L = 5.2E7 light-years. Of course, this calculation does not take into account the fact that the antiproton will spiral around the galactic magnetic field lines as well.

    “This is also because of the almost countless additional electron neutrino strikes that they would encounter. Within our part of the solar system (mostly produced by the sun) there are roughly a million electron neutrinos per cubic meter. Most of them traveling near the speed of light. This would be roughly one hit every nine thousand meters.”

    The interaction cross-section between protons or antiprotons and neutrinos should be extremely small. Neutrinos can pass clear through the earth without interacting with a single atom so they should not have much impact on travelling antiprotons.

  229. Hello !

    I have read about half of your book Death From the Skies ! (and fully read Bad Astronomy) and I have a question about black holes. I’m pretty sure of the answer but would like confirmation. I’d like to know if a mini black whole with gravity such that it could not affect significantly the moon’s orbit and the earth’s orbit could possibilty become a satellite of the Earth somehow. From what I know I’d think that it would be possible until it evaporates but as you said, logic and black holes don’t mix very well.

    Thanks and keep up the good work !

  230. Jumblepudding

    “spaghettification” needs to be in a horror movie set in space some time. That is just too awful and gruesome.

  231. There is no argument, and there should not be — you need to address my statistics directly.
    If not we’re talking apples and oranges. Do you want to know the “truth” or do you want to appear to be right. Anti-protons will be hit within one light year. Do you want to avoid these statistics.

    You don’t get it. It doesn’t matter how much matter (light years) neutrinos can pass through, there will be some hits. Those hits, however, would be meaningless if anti-protons are stable, if not that would be the end of them. No standard density in particular different from what I stated would make much difference . Regardless of what density you choose anti-protons don’t have a chance if they lack stability. If they have stability, one year is what the statistics indicate. That’s it. Re-examine my stats and tell me if I’m wrong.

    “Spiraling around a magnetic field” has nothing to do with their longevity. The faster they travel, the more likely they would be to get hit. Consider everything else constant, at an infinite speed they would immediately get hit. Reduce their speed and the probability per given time frame goes down. We’re far off topic anyway. Just throw this criticism at my theory on the web. You’ll do us both a big favor and we would stop burning the Bad Astronomer’s web space. You’re very smart. Use my website to vent your criticism. I think I need your help more than this web site does concerning off-topic matters.

    Demand recognition, I’m not shy.

    your friend forrest

  232. Spaghettification, that’s also very nice. I will have to sum up all of the alternative wording and give a prize.

    Mine, spaghettiization, looks like it won’t come in first, but still if were me, I would want to remembered as being spahettiized. Otherwise it’s an also ran as far as the other choices offered herein.

  233. Letraix

    Great post, but questions remain.

    What’s the life cycle of a black hole? The start of the story seems fairly fixed. Star explodes, yadda, yadda. Presumably this happens fairly often, and one (some? some to become one?) of the larger black holes end up milling around at the centre of a galaxy, occasionally wolfing down a star or gas cloud. Then the story gets really hazy. What happens between being a galactic mousetrap and actually consuming its host galaxy? (Assuming a quasar, etc. is a galaxy being eaten by a black hole?)

    What happens when the black hole runs out of stuff to eat? Assuming it only gives off radiation while it’s dining, I guess it could only be detected by its gravitational effect on other bodies? I’ve heard talk of “evaporation”, which sounds like a “we don’t know at all, but best guess is…” answer. Apparently it’s also a convenient answer for some questions around determinism? Vague and convenient answers make me think again.

    I suppose the event horizon will get larger as the black hole acquires more mass. How large can a black hole (event horizon) get? And finally, are there processes happening within a block hole that could change the nature of the body entirely? For example, is there a possibility that the thing could start expanding or doing odd things to space? Dr. Phil mentioned that there is no way to know what goes on in there, but is anyone working on determining how the internal workings may affect the surrounding area? Particles under as much stress as the universe can muster could presumably do something weird…

    Understandably I’m getting to this post rather late, but any advice on where to get these answers would be appreciated.

  234. Dr. Sanford Aranoff

    The commonly accepted approach to discussing a body falling into a black hole (BH) using General Relativity (GR) is this. A distant observer notes that the falling body never reaches the event horizon (EV), as relativistic time dilation slows the fall. However, there is a solution of GR from the point of view of the falling observer, which crosses the EV in finite time and continues falling to the center. At the center of the BH there is a singularity. When the observer falls past the EV, he sends out a light signal, which does not cross the EV, so that the external observer never sees this signal. This leads to the common expression, that a BH is an object which light cannot escape. Let us call this the standard explanation of a body falling into a BH.

    This approach is wrong and misleading. Physicists must refrain from using such language. Let us first clarify what physics is, and I will begin with mathematics.

    Mathematics is a collection of arbitrary self-consistent statements. We may have different collections, i.e., mathematical systems, but each system must be self-consistent, but do not have to agree with statements from other systems.

    Science, and in particular physics, is a collection of theories. A theory is a mathematical system along with observational and experimental agreement. If it is impossible in principle to perform an observation, the theory cannot speak about that situation. Science also includes guesses, research proposals, and hypotheses, not all of which are theories. Although a theory must be self-consistent in order to be a valid theory, complete agreement with observations are neither possible nor needed. All theories agree to only a partial extent with observations.

    When physicists are faced with observations that disagree with a theory, initially we must accept the theory and realize that there are unresolved issues. For example, the orbit of Mercury did not fully agree with Newtonian gravitation (NG). Until GR resolved the problem, we accepted NG and the Mercury puzzle.

    With this background, let us look at the situation of the body falling into a BH. There are three reasons why the standard explanation is wrong. The first is that since it cannot be observed in principle, the theory cannot speak about it. The counter argument, “since the falling observer can observe it, it is a valid observation,” is not a valid argument. If we accept the argument that something that a falling observer (someone who cannot return nor communicate with the rest of the world) can observe is considered as a valid scientific observation, we then lose our ability to criticize people for believing that the dead go to Heaven. The dead person (one who cannot return nor communicate with the rest of the world) observes Heaven. We scientists must be very careful about our scientific reasoning, and not give others the opportunity to twist it to make it sound as if we support religion.

    The second reason the standard explanation is wrong is that we can mathematically prove that a singularity exists at the center. This proof means that the mathematics of the path of the observer inside the BH is inconsistent. When we say that a future theory of quantum gravity (QG) will resolve the issue, we then are not speaking about the current theory, GR. We must simply say that GR does not describe the situation inside the BH. Leave it as a puzzle if you wish, as the orbit of Mercury was a puzzle.

    When we describe a BH as a place where light cannot escape, we are describing the situation inside the BH, and this is something we must not do. We must refrain from mentioning the inside of a BH. We must not confuse the public with our guesses what the inside of a BH is with our actual knowledge based upon the established theory GR. Let us say a BH is black as objects falling down the BH take forever to fall down and so are red-shifted out of existence.

    In summary, we have shown that the concept of the inside of a BH is not valid based upon fundamental principles of science: the need for observation, and the need for mathematical consistency.

    There is a third argument, which is weaker than the above two arguments, but still is interesting. Consider two observers A and B falling down the BH. Both start from the same point, but A started first with a higher initial speed than B. As B approaches the EV, he notes that A never reaches the EV, as B is an external observer, and all external observers note that it takes forever to reach the EV. Since B crossed the EV in finite time, B will note that he crossed the EV before A. The coordinate systems of A and B are time-like, as they can communicate. Time-like events preserve time ordering. A must always happen before B. Yet this is violated when B crossed the EV. The conclusion is that B did not cross the EV.

    The question people have on their minds is that how can we explain the fact of the existence of a solution of GR for an object crossing the EV in finite time? My answer is that we can use another fundamental principle of mathematics to reject this solution. This principle is boundary conditions (BC) or initial conditions. The classic example is that we reject all solutions of the wave equation for a vibrating string except those that satisfy the BC. The science of music is based upon this important principle. We can say that the singularity at the center is a BC that rejects the solution of crossing EV in finite time. The concept of BC can also be used to reject the advanced solution of Maxwell’s equations of electromagnetism, for this solution violates causality.

  235. The point has been previously brought up that a human being falling into a stellar-sized black hole will spaghettify (i.e., be torn to shreds) long before he or she reaches the event horizon. But for supermassive blackholes the tidal forces are weak enough to allow entry of human beings intact through the event horizon. I decided to quantify this effect assuming that the maximum force differential between head and toes that a human being can tolerate is 5 times body weight.

    Assuming this, then a minimum sized black hole of 3 solar masses has a spaghettification radius of more than 300 times the event horizon radius. A 100 solar mass black hole has this ratio at about 30. The cross-over mass appears to be a little less than 20,000 solar masses. For black holes of this intermediate mass the spaghettification point is right at the event horizon boundary. For supermassive blackholes like the one in the Milky Way galaxy core the ratio is less than 0.03 which means a human being can make it about 97 percent of the way from the event horizon down to the singularity before being killed.

    ***************************************************************************

    Spaghettification statistics for black holes

    The black hole is assumed to be nonrotating and with zero electric charge
    A human is assumed to be ripped apart when the differential force exceeds
    5.0 times body weight

    Mass of Radius of Radius of
    black hole event spaghettification
    (sun=1.0) horizon (km) relative to
    ———- (km) event horizon
    ——— ——— ————-

    3 8.86E0 3.05E3 3.44E2
    10 2.95E1 4.56E3 1.54E2
    30 8.86E1 6.58E3 7.42E1
    100 2.95E2 9.82E3 3.32E1
    300 8.86E2 1.42E4 1.60E1
    1,000 2.95E3 2.12E4 7.16E0
    3,000 8.86E3 3.05E4 3.44E0
    10,000 2.95E4 4.56E4 1.54E0
    19,150 5.66E4 5.66E4 1.00E0
    30,000 8.86E4 6.58E4 7.43E-1
    100,000 2.95E5 9.82E4 3.32E-1
    300,000 8.86E5 1.42E5 1.60E-1
    1,000,000 2.95E6 2.12E5 7.16E-2
    4,000,000 1.18E7 3.36E5 2.84E-2

  236. “3 8.86E0 3.05E3 3.44E2″

    Dang, it’s hard to format text into columns unless I put them into HTML tags. The 4 numbers per line are as follows:

    mass of black hole in solar masses
    radius of event horizon in kilometers
    radius of spaghettification point in kilometers
    radius of spaghettification point relative to the event horizon (dimensionless)

  237. Ron

    So, if a bowl of spaghetti is at the center of a BH and time is reversed, will a person get spit out?

  238. Osakaguy

    @Tom Marking

    Good to see the real numbers, thanks. What do you think about my comments above?
    In particular: #comment-130788

    I still don’t understand how any matter, observer or not, could reach the singularity assuming all black holes eventually evaporate. I’m imagining this shell of “forever falling” matter just past the event horizon that can’t get to the center before the whole thing evaporates in 10^100 years.

    Maybe I’m missing some key point. Any feedback would be appreciated!

  239. Tom Marking

    @Osakaguy “Wait, isn’t Simon (#comment-130255) above right? As you fall past the event horizon (assuming the black hole is large enough to allow safe passage at this point) time will pass normally relative to yourself, but the future history of the entire universe will start to flash by outside. Since time is practically stopped at the event horizon relative to the outside world, the outside world will end up in its heat death phase which will allow the Hawking radiation to give out more than the black hole receives from the microwave background.”

    That may be the right interpretation assuming that the black hole evaporation time is in the reference frame of the external universe. Of course, Hawking radiation is a quantum mechanical addition to the standard black hole theory of general relativity. There are a number of problems with it such as the frequency of the radiation at the event horizon having to be infinite in order for photons to be visible to the outside universe. Also, when a black hole evaporates it apparently destroys all of its information content which causes a black hole information paradox. So I doubt very much that this will be the final interpretation.

  240. Osakaguy

    @Tom Marking
    Thank you very much for your response. I figured there were additional complicating factors. (There usually are!)

  241. Tom Marking

    @Osakaguy “Thank you very much for your response. I figured there were additional complicating factors.”

    Also, assuming Hawking radiation is real then the falling observer has to pass through a region of intense blackbody radiation which is what Hawking radiation is. Even assuming a supermassive black hole (~ 4 million solar masses) and spaghettification doesn’t get you outside the event horizon, then the Hawking radiation may fry you as you get closer and closer to the event horizon. So perhaps it is only a charred cinder that actually crosses the event horizon. So lots and lots of hazards to worry about around black holes.

  242. Tom Marking

    Here is some more numbers for you. Someone asked about how long it would take for the observer to hit the singularity once they cross the event horizon. Well, I track it from the event horizon until the falling observer gets spaghettified. Let’s assume a supermassive black hole with a mass of 4 million solar masses. The event horizon is 11.8 million kilometers. Let’s drop our observer from rest from an altitude of 50 million kilometers above the event horizon. Let’s assume that the black hole is nonrotating, has no electrical charge, and that there are no material obstructions in the path of the falling observer.

    Then, according to my calculations the falling observer starts out with an acceleration of 139,000 meters per second per second (this will still not due him in since his head and feet will be accelerating at the same rate roughly at the beginning). 671 seconds (11.2 minutes) our intrepid astronaut has now accelerated to half the speed of light according to his own watch. A remote observer would measure an elapsed time of 804 seconds (13.4 minutes) and a red shift of almost 1.5 looking at light coming from the falling astronaut. The astronaut will be 11.6 million kilometers above the event horizon at this point.

    737 seconds (12.3 minutes) into his journey or 997 seconds (16.6 minutes) as measured by the external observer, our astronaut is about to cross the event horizon. He is travelling at 70 percent the speed of light and only 1200 kilometers above the event horizon. His red shift as seen by the remote observer has skyrocketed to more than 200 and will rise to infinity as seen by the remote observer.

    From the poor, unfortunate astronaut’s point a view, just a fraction of a second later at 737 seconds and a bit, he crosses the event horizon and he has winked out of existence as far as the remote observer is concerned. But the falling astronaut is accelerating at 1.37 million meters per second per second and the end is coming soon. Just 45 seconds after crossing the event horizon our poor astronaut has reached the point of spaghettification and his journey ends (782 seconds = 13.0 minutes) after takeoff. He has reached an altitude of 11.5 million kilometers beneath the even horizon and only 300,000 kilometers from the singularity (or more than 97 percent of the way from the event horizon to the singularity).

    Of course, this scenario has left out lots and lots of things such as black hole rotation, Hawking radiation, etc. But in this classical scheme in with supermassive black holes your time within the event horizon is short, less than a minute or so from your point of view. So enjoy the scenery while you can. It won’t last!

    Enjoy!

    ***************************************************************************

    Program to compute what happens when an observer falls into a black hole
    The black hole is assumed to be nonrotating and with zero electric charge
    The falling observer is initially at rest
    A human is assumed to be ripped apart when the differential force exceeds 5.0 times body weight

    Mass of the black hole = 4.00E6 solar masses
    Initial altitude of observer above event horizon = 5.00E7 km

    Radius of the event horizon = 1.18E7 km
    = 7.90E-2 A.U.
    Distance from center where humans are ripped apart = 3.36E5 km
    = 2.25E-3 A.U.
    = 2.84E-2 x EvntHor
    Alt. above event horizon where humans ripped apart = -1.15E7 km
    = -7.67E-2 A.U.
    = -9.72E-1 x EvntHor

    1st column = elapsed time for the falling observer (sec)
    2nd column = elapsed time for the external observer (sec)
    3rd column = acceleration of falling observer (m/s^2)
    4th column = velocity of falling observer (relative to speed of light)
    5th column = altitude of falling observer above event horizon (km)
    6th column = red shift of falling observer as seen by external observer

    0.00E0 0.00E0 1.39E5 0.0000c 5.00E7 0.0000
    1.56E1 1.74E1 1.39E5 0.0072c 5.00E7 0.1200
    3.12E1 3.47E1 1.39E5 0.0145c 4.99E7 0.1283
    4.68E1 5.21E1 1.40E5 0.0217c 4.98E7 0.1367
    6.24E1 6.94E1 1.40E5 0.0290c 4.97E7 0.1452
    7.80E1 8.68E1 1.41E5 0.0363c 4.96E7 0.1540
    9.37E1 1.04E2 1.41E5 0.0437c 4.94E7 0.1629
    1.09E2 1.22E2 1.42E5 0.0510c 4.92E7 0.1721
    1.25E2 1.39E2 1.43E5 0.0585c 4.89E7 0.1814
    1.40E2 1.56E2 1.44E5 0.0660c 4.86E7 0.1911
    1.56E2 1.74E2 1.46E5 0.0735c 4.83E7 0.2009
    1.72E2 1.91E2 1.47E5 0.0811c 4.79E7 0.2111
    1.87E2 2.09E2 1.49E5 0.0889c 4.75E7 0.2215
    2.03E2 2.26E2 1.51E5 0.0967c 4.71E7 0.2323
    2.19E2 2.44E2 1.53E5 0.1046c 4.66E7 0.2434
    2.34E2 2.62E2 1.55E5 0.1126c 4.61E7 0.2550
    2.50E2 2.79E2 1.58E5 0.1207c 4.56E7 0.2669
    2.65E2 2.97E2 1.60E5 0.1290c 4.50E7 0.2793
    2.81E2 3.15E2 1.63E5 0.1374c 4.44E7 0.2922
    2.97E2 3.32E2 1.67E5 0.1460c 4.37E7 0.3057
    3.12E2 3.50E2 1.70E5 0.1548c 4.30E7 0.3198
    3.28E2 3.68E2 1.74E5 0.1638c 4.23E7 0.3345
    3.43E2 3.86E2 1.79E5 0.1730c 4.15E7 0.3500
    3.59E2 4.04E2 1.83E5 0.1824c 4.06E7 0.3663
    3.75E2 4.22E2 1.89E5 0.1921c 3.98E7 0.3835
    3.90E2 4.40E2 1.94E5 0.2020c 3.88E7 0.4017
    4.06E2 4.58E2 2.01E5 0.2123c 3.79E7 0.4211
    4.21E2 4.77E2 2.08E5 0.2230c 3.69E7 0.4417
    4.37E2 4.95E2 2.15E5 0.2340c 3.58E7 0.4638
    4.53E2 5.14E2 2.24E5 0.2454c 3.47E7 0.4877
    4.68E2 5.32E2 2.33E5 0.2573c 3.35E7 0.5134
    4.84E2 5.51E2 2.44E5 0.2697c 3.23E7 0.5414
    4.99E2 5.70E2 2.56E5 0.2827c 3.10E7 0.5720
    5.15E2 5.90E2 2.70E5 0.2964c 2.96E7 0.6057
    5.31E2 6.09E2 2.85E5 0.3109c 2.82E7 0.6431
    5.46E2 6.29E2 3.02E5 0.3261c 2.67E7 0.6850
    5.62E2 6.49E2 3.23E5 0.3424c 2.51E7 0.7324
    5.78E2 6.69E2 3.46E5 0.3598c 2.35E7 0.7867
    5.93E2 6.90E2 3.73E5 0.3785c 2.18E7 0.8500
    6.09E2 7.11E2 4.06E5 0.3987c 1.99E7 0.9248
    6.24E2 7.33E2 4.45E5 0.4209c 1.80E7 1.0154
    6.40E2 7.55E2 4.92E5 0.4452c 1.60E7 1.1281
    6.56E2 7.79E2 5.51E5 0.4723c 1.39E7 1.2738
    6.71E2 8.04E2 6.26E5 0.5029c 1.16E7 1.4719
    6.87E2 8.30E2 7.24E5 0.5380c 9.14E6 1.7625
    7.02E2 8.60E2 8.54E5 0.5789c 6.53E6 2.2454
    7.18E2 8.96E2 1.04E6 0.6279c 3.71E6 3.2779
    7.34E2 9.53E2 1.30E6 0.6884c 6.38E5 9.2877
    7.37E2 9.97E2 1.37E6 0.7020c 1.20E3 236.5756
    7.37E2 – 1.37E6 0.7024c -1.67E4 –
    7.49E2 – 1.71E6 0.7663c -2.76E6 –
    7.65E2 – 2.30E6 0.8704c -6.57E6 –
    7.80E2 – 1.56E6 0.9914c -1.09E7 –
    7.82E2 – 7.81E5 0.9985c -1.15E7 -

  243. Tom Marking

    “7.82E2 – 7.81E5 0.9985c -1.15E7 -”

    Also, at the point where you are spaghettified you will be travelling at 99.85 percent the speed of light. It ought to be one hell of a ride. Any volunteers?

  244. Here are some statistics concerning Hawking radiation for various sized black holes. As you can see, the blackbody temperature caused by Hawking radiation is tiny even for the smallest of black holes. For example, for a 3 solar mass black hole the blackbody temperature is 0.02 millionths of a degree Kelvin which is probably below humanity’s ability to even measure. The total power for a 3 solar mass black hole is 10 millionths of one trillionth of one trillionth of a watt so this means this black hole is really, really dark. It would take it 570 million trillion trillion trillion trillion trillion years to evaporate due to Hawking radiation which is much, much longer than the age of the universe.

    ***************************************************************************

    Hawking radiation statistics for black holes

    1st column = mass of black hole in solar masses
    2nd column = blackbody temperature in degrees Kelvin
    3rd column = total power in watts
    4th column = evaporation time in years

    3 2.06E-8 1.00E-29 5.66E68
    10 6.17E-9 9.00E-31 2.10E70
    30 2.06E-9 1.00E-31 5.66E71
    100 6.17E-10 9.00E-33 2.10E73
    300 2.06E-10 1.00E-33 5.66E74
    1,000 6.17E-11 9.00E-35 2.10E76
    3,000 2.06E-11 1.00E-35 5.66E77
    10,000 6.17E-12 9.00E-37 2.10E79
    30,000 2.06E-12 1.00E-37 5.66E80
    100,000 6.17E-13 9.00E-39 2.10E82
    300,000 2.06E-13 1.00E-39 5.66E83
    1,000,000 6.17E-14 9.00E-41 2.10E85
    4,000,000 1.54E-14 5.63E-42 1.34E87

  245. Todd W.
  246. It seems there was a slight problem with my program. I was including the relativistic time dilation factor (i.e., gamma) for only the velocity and not for gravity when computing acceleration. Fixing this problem, I get the following numbers for the same scenario (i.e., an astronaut dropped from rest at 50 million kilometers above the event horizon of a 4 million solar mass black hole).

    The following differences exist between these numbers and the first set of numbers. The observer crosses the event horizon at 896 seconds instead of
    737 seconds or 159 seconds later. The velocity during the crossing is only 45 percent the speed of light instead of 70 percent the speed of light. Also, the acceleration goes to zero instead of increasing once you reach the event horizon since the mass of the falling observer goes to infinity at the event horizon. This means the astronaut can last 85 seconds after crossing the event horizon instead of 45 seconds in the previous set of numbers.

    The acceleration reaches a maximum at an altitude of 9 million kilometers above the event horizon and goes down to zero by the time the falling observer reaches the event horizon. This is in keeping with the gravitational time dilation factor becoming infinite right at the event horizon. So including the total time dilation factor gives you an additional 40 seconds of life within the event horizon. Of course, you still wind up getting spaghettified.

    1st column = elapsed time for falling observer (sec)
    2nd column = elapsed time for external observer (sec)
    3rd column = acceleration in meters per second per second
    4th column = velocity relative to the speed of light
    5th column = altitude above the event horizon (km)
    6th column = red shift (dimensionless)

    0.00E0 0.00E0 1.39E5 0.0000c 5.00E7 0.0000
    1.96E1 2.18E1 1.01E5 0.0066c 5.00E7 0.1193
    3.92E1 4.36E1 1.01E5 0.0132c 4.99E7 0.1269
    5.88E1 6.54E1 1.01E5 0.0199c 4.98E7 0.1346
    7.84E1 8.72E1 1.02E5 0.0265c 4.97E7 0.1425
    9.80E1 1.09E2 1.02E5 0.0332c 4.95E7 0.1505
    1.18E2 1.31E2 1.03E5 0.0399c 4.93E7 0.1587
    1.37E2 1.53E2 1.03E5 0.0466c 4.90E7 0.1672
    1.57E2 1.75E2 1.04E5 0.0534c 4.88E7 0.1758
    1.76E2 1.96E2 1.05E5 0.0602c 4.84E7 0.1847
    1.96E2 2.18E2 1.06E5 0.0671c 4.80E7 0.1938
    2.16E2 2.40E2 1.07E5 0.0741c 4.76E7 0.2032
    2.35E2 2.62E2 1.08E5 0.0811c 4.72E7 0.2129
    2.55E2 2.84E2 1.09E5 0.0882c 4.67E7 0.2229
    2.74E2 3.06E2 1.11E5 0.0954c 4.61E7 0.2333
    2.94E2 3.28E2 1.12E5 0.1027c 4.56E7 0.2440
    3.14E2 3.50E2 1.14E5 0.1101c 4.49E7 0.2552
    3.33E2 3.73E2 1.16E5 0.1176c 4.43E7 0.2667
    3.53E2 3.95E2 1.18E5 0.1252c 4.35E7 0.2788
    3.72E2 4.17E2 1.20E5 0.1330c 4.28E7 0.2914
    3.92E2 4.40E2 1.23E5 0.1410c 4.20E7 0.3046
    4.12E2 4.62E2 1.25E5 0.1491c 4.11E7 0.3184
    4.31E2 4.85E2 1.28E5 0.1573c 4.02E7 0.3330
    4.51E2 5.07E2 1.31E5 0.1658c 3.93E7 0.3483
    4.70E2 5.30E2 1.35E5 0.1745c 3.83E7 0.3646
    4.90E2 5.53E2 1.39E5 0.1835c 3.72E7 0.3818
    5.09E2 5.76E2 1.43E5 0.1927c 3.61E7 0.4002
    5.29E2 5.99E2 1.47E5 0.2021c 3.50E7 0.4198
    5.49E2 6.22E2 1.52E5 0.2119c 3.38E7 0.4409
    5.68E2 6.45E2 1.57E5 0.2220c 3.25E7 0.4637
    5.88E2 6.69E2 1.63E5 0.2325c 3.11E7 0.4884
    6.07E2 6.93E2 1.70E5 0.2434c 2.97E7 0.5154
    6.27E2 7.17E2 1.77E5 0.2547c 2.83E7 0.5450
    6.47E2 7.41E2 1.85E5 0.2666c 2.68E7 0.5779
    6.66E2 7.66E2 1.93E5 0.2789c 2.52E7 0.6146
    6.86E2 7.90E2 2.02E5 0.2918c 2.35E7 0.6560
    7.05E2 8.16E2 2.12E5 0.3054c 2.17E7 0.7034
    7.25E2 8.42E2 2.23E5 0.3196c 1.99E7 0.7584
    7.45E2 8.68E2 2.35E5 0.3346c 1.80E7 0.8234
    7.64E2 8.95E2 2.46E5 0.3503c 1.60E7 0.9021
    7.84E2 9.23E2 2.57E5 0.3668c 1.38E7 1.0001
    8.03E2 9.53E2 2.66E5 0.3839c 1.16E7 1.1274
    8.23E2 9.84E2 2.67E5 0.4013c 9.34E6 1.3030
    8.43E2 1.02E3 2.54E5 0.4185c 6.93E6 1.5692
    8.62E2 1.06E3 2.10E5 0.4339c 4.42E6 2.0499
    8.82E2 1.10E3 1.02E5 0.4445c 1.84E6 3.3947
    8.96E2 1.19E3 9.43E1 0.4467c 1.22E3 158.0323
    8.96E2 – 0.00E0 0.4467c -1.01E4 –
    9.01E2 – 0.00E0 0.4467c -7.83E5 –
    9.21E2 – 0.00E0 0.4467c -3.41E6 –
    9.41E2 – 0.00E0 0.4467c -6.03E6 –
    9.60E2 – 0.00E0 0.4467c -8.65E6 –
    9.80E2 – 0.00E0 0.4467c -1.13E7 –
    9.81E2 – 0.00E0 0.4467c -1.15E7 -

  247. nochnoy

    We’ve just translated this in Russian :)
    http://translated.by/you/ten-things-you-don-t-know-about-black-holes/
    Great post, thank you Phil!

  248. Kop

    I don’t know if this has already been said (I’m not going to read through all those comments), but you neglected to mention Hawking Radiation on point 7. Also on number 10, you need to remember that the event horizon’s radius doubles because the event horizon is simply the distance from the singularity at which light cannot escape gravity. F=(m1*m2)/(r^2). Solving for r, if you double m1, you double r to keep the F at which light can’t escape the same. You should’ve learned that in Algebra. Other than those two, this was a very good article.

    On the matter of Hawking Radiation, who came up with the idea first, the Romulans (who use artificial singularities to power their warp propulsion, as opposed to matter-antimatter) or Hawking?

  249. Kop– I didn’t want to complicate issues by introducing Hawking radiation into a post that was already very long. It was a conscious decision.

    Also, your using Newtonian physics about the event horizon is not correct. You need to use Einsteinian math to be correct, despite what you may have learned in algebra class. It doesn’t have to do with force, it has to do with the warping of space. The idea that the Schwarzschild radius calculation happens to work with Newtonian math is coincidence more than anything else.

  250. Mark W Allen

    Thanks Phil,

    That was very interesting !

    You have obviously done your homework and gone to a lot of trouble in the process.

    So I hate to put a dampener on your wonderful work, but if nobody has ever been close enough to: observe and measure/test (the definition of science), such a phenomenon isn’t this all mere conjecture as are many theories that other so-called ‘scientists’ purport as fact ?

    I really must question such statistics/measurements after having seen the Report on the Hubble Probe.
    Particularly, the miscalculations/errors of the Hubble think-tank and the speculations that were reported as fact, that is until it was discovered that in many instances they were wrong (surprise)!

    Sorry, I have seen far too much of this type of thing (eg. Hubble), but yours is a jolly good read and does stretch the imagination somewhat and that’s a good thing according to Einstein.

    I hope you find the truth !

  251. Dave H

    Fascinating blog. Thanks. The video is excellent – a superbly clear and concise explanation even I could understand.

    @ Mark W Allen:

    Someone who makes his living as an astronomer is an “actual” scientist ;D

  252. Michael

    I was reviewing section
    7) Black holes aren’t always dark
    8) Black holes aren’t always dangerous.

    And I would like to ask a questions. If lets say the sun was replaced with a black hole of equal size, is there not a chance that the heat created by items rubbing together could equal that of which is produced by the sun. Thus avoid the whole death by freezing.

  253. Sherry

    My first time reading this blog, really good explaination. I know about 3 of them…

  254. Reika Fcoh

    STATEMENT:

    1) It’s not their mass, it’s their size that makes them so strong.

    MY STATEMENT: In a Way confused and i disagree

    I agree size dose make them strong but isn’t the gravity which really makes them strong i mean if it a had a low gravity then the chace that things getting caught by them would drop and things might actually have a chances to escape them.

    And i do relize that the size of something has something to do with its gravity but isn’t also so true that mass also has the same affect i meant to esacpe a black hole you need escape velocity which depends on On the mass of the object(Black Hole).
    If the Object is largely massive, and if so the gravity is very strong, therefore the escape velocity need is very high in speed. A lighter mass Object would, of course, have a low gravity and a small escape velocity rate.

  255. Fujiko Macvey

    The deluded folks at the electric universe site take pleasure in bashing the black hole singularity idea. While singularities in theories point to a breakdown in the ability of the theory to handle an extreme situation, the electric universe crew don’t even understand basic orbital mechanics properly.
    It is one thing to criticise singularities in black hole models, but quite another thing to utterly ignore a huge amount of data, observation and workable theories from the whole of astronomy on solar fusion, orbital mechanics and redshift.

  256. Cheyenne

    “Black holes can be low density. ”

    It’s really beginning to annoy me that I don’t understand this concept better!

    These Top 10 posts are freaking awesome and timeless. These are my favorites to look back through.

  257. Cheyenne

    i quit on science

  258. Aaron

    holy cool! i read through the entire thing and now i really want to read that book

  259. Lisa

    hey i am in 5th grade and i read a book on black holes by Dana Meachen Rau and i started wondering can a black hole ….
    1. Get to full that things can fall out
    2. can black holes explode
    3. Suck in an entire planet/Solar System

    if you have time can you try to post something to in form me on those questions, please and thank you

  260. Lisa,

    Concerning Black Holes.

    There are two types of Black Holes. Some are only as big as big stars in their mass (relating to their gravity)

    And others are as massive as millions upon millions of stars.

    1) Can Black Holes get to full that things can fall out?

    yes, this is one theory, but not the most common, well known theory. The theory is that pieces of black holes can be ejected/ thrown out.

    2) Can black holes explode?

    I’m not aware of any exploding Black Hole Theories but there are theories where Black Holes can throw off pieces of themselves. Again this the same theory described above is not the most common theory.

    3) Can Black Holes suck in an entire planet/Solar System?

    Large black holes can easily suck in many surrounding stars. Smaller Black Holes can also do this if the stars are close enough to the Black Hole. This would be considered a joining together process rather than sucking in process, however.

    If you don’t really understand all the answers you could ask your mom or dad to explain them to you.

  261. alfonzo

    hahhaim confuzed sooomuch i think i just wasted 16 hours of my life ha but that was interesting

  262. Travis

    If the gravity at the event horizon equals the speed of light, is light suspended at the event horizon?

  263. aishwarya

    these are the facts most of us know.
    cool facts should be like this:
    when you approach a black hole you can see the back of your head since the light rays are bent due to gravity of black hole

  264. tony

    THIS WAS TOO LONG TO READ!!!!!!!!!!!!!!!!!!!!!!!!! IT WILL TAKE YOU ABOUT TWO DAYS TO READ THE WHOLE THING!!!!!!!!! PLEASE MAKE IT SHORTER!!!!!!

  265. addison

    tats kewl im doin a report on black holes ;-D

  266. aishwarya,

    “cool facts should be like this:
    when you approach a black hole you can see the back of your head since the light rays are bent due to gravity of black hole”

    I think the cool facts would go more like this:

    When you approach a black hole somebody else, through a distant telescope, might be able to see the back of your head, along with other body parts, because spaghettification has begun.

    Travis,

    “If the gravity at the event horizon equals the speed of light, is light suspended at the event horizon?”

    According to General Relativity gravity always travels at the speed of light everywhere. Light reaching the event horizon from any angle would accordingly never escape falling into the black hole. If it is tangent to the event horizon at its approach it might orbit the event horizon before its waves and photons are terminated one way or another. The speed and physicality of light waves seemingly could not be suspended since it must accordingly always travel at light speed relative to its surrounding field.

  267. GeorgeYello (clubpenguin nickname)

    Um, Ok Lets See… First Of All, You Shouldn’t Put A lot Of ( ) In The Artical. Secondly, You Have Me All Confused In This Black Hole Artical. What If The Gravity Was Weak, Huh? Then You Could, “Part Your Space Shuttle” Far Away From A Black Hole. Lastly, You Need To Make This More Clear! I Can’t Even Know Certain Stuff About Them! I Am In Summer School, And I Used This Artical To Help Me Out! Shame…

  268. I understand that light can not escape a black hole–but–does light actually exist in a black hole even though it can not be seen?

  269. SMBH

    Im sure black holes have a greater significance in the universe than now supposed. Possibly, something to do with the dark matter effect which comes up as halos around galaxies with black holes in their center. Its too much coincidence, if we are to discover the hidden dimensions we really need to understand singularity ( black holes, big bangs ).
    I hope NASA spends more time on some serious science and not this stupid manned missions. MORE HUBBLES PLEASE!!

  270. Leslie

    #10 has me thinking .. you said: If you were to rope off the solar system out past Neptune, enclose it in a giant sphere, and fill it with air, it would be a black hole!

    so I wonder what if it a planet was added? Still a black hole?

    and not being good enough to do the math but curious enough to ask the question .. could the universe be a black hole?

  271. TJ

    hey nice facts i enjoyed reading them

  272. Travis

    I really enjoyed the article, but I was confused a bit by the last point.
    From what I understand, you are saying that the radius and volume to the event horizon is the same thing as the radius and volume of the black hole. You yourself said that the event horizon is not the same thing as the black hole itself, and this makes sense, as the event horizon is nothing more than the point where no matter can escape the gravitational pull.
    What I’m trying to say is this: I feel like in the last section you are finding the density using the gravitational field(specifically where it is strong enough to capture light), rather than the actual matter itself.

  273. lucky kalra

    as it is said in this article that black holes are not always black..but on wikipedia page on ‘event horizon’ i’ve also read that light from beyond the horizon can never reach the observer..so my question is can we see black holes glowing or it is just a hypotheses that they are glowing as light from beyond horizon can’t reach the observer..?

  274. Eduardo J

    Number ten is SO weird… the others are strange, but having a black hole that isn’t very dense is such a foreign concept…

  275. robo

    so you can’t go back in time throw a black hole even if you could survive entering one?

  276. Souvik Das

    @Lisa Says:
    1. no; since the more mass it sucks in the bigger it gets. say, how can you expect that a hungry monster to starve and die of hunger if you keep feeding it?
    2.at the very end of its life its supposed to get annihilated in a final outblast of energy, thus it explodes
    3.yes

  277. Maik

    10 / 10, yeah !

    When we find some missing mass or need to make a little adjustment to the gravitational laws, the universe itself might be a black hole.

    Slight problem is that I’ve come to dislike the idea of black holes. I’m starting to think they dont exist, but that’s quite controversial and I’m not yet capable in working it out in a physics-proof or anything :(

  278. sweedle

    hey Phil……your info will be of great help to me in my physics project!! :P well keeping that aside….i really appreciate how you clear out those misconceptions so clearly…….:)

  279. dig dug

    what i don’t get is that if it can bend space infinitly giving enough mass, then how is the funnel “perception” wrong. I know what your saying about the object itself being spherical but its position in space….

  280. dig dug

    acctualy information is not lost in a black hole but projected across the universe…some plummer guy figured that out, and hawkins tends to agree…..finnaly

  281. You said that black hole has high attracting power , then how the earth will be in its orbit when sun is replaced by a black hole?

  282. What happens to the moon’s orbit when earth is replaced by a black hole of same mass and same size of earth?

  283. anonymous

    all black holes are bigger than the sun thats why the sun cant become one

  284. Dakota

    I am 18 years old studying to be a cosmologist one day. i’m looking for experts in this field to talk to and maybe explore theories with. drop me a line at my email and lets talk.

  285. rhobere

    So I can’t help but feel like the “low density black hole” thing is more of a technicality based on how you define a black hole. If you define it as the dead star that collapses to a tiny point and creates inescapable gravity, there are no low density black holes. What is generally defined as the black hole is actually the volume of space that experiences the gravity of this object at a certain magnitude. With this definition, the whole ‘adding mass increases the radius linearly’ thing is not only rudimentary, but also a bit of an insignificant point to make. Gravitional acceleration is inversely proportional to the distance of measurement, but its directly proportional to an object’s mass (a = Gm/d^2). Using 6th grade algebra, you can easily prove that this results in a linear radial increase to exceed a certain speed when mass is added. The same result can be proven for the electric force as well (a = kQ/d^2). If you add more charge, the distance at which a force can be measured at a certain magnitude increases linearly.

    The only reason your argument sounds significant is because you’re increasing the mass of something and looking at how that effects its forcefield while thinking that the forcefield IS the physical shape of the object inside of it. For size, you should be thinking about the dead star at the center. When this new mass actually makes it to the dead star (not just past the event horizon, but all the way to the dead star at the center), you can expect the size of the dead star to change exactly like the balls of clay would. As a parallel, if you assume the clay balls have equal electric charges where you measure 1 Coulomb at 1 meter and you combined them, although the radius of the physical clayballs doesn’t double, the radius at which you measure 1 Coulomb WILL double to 2 meters.

    So yes, the black hole acts exactly like the clay balls except only if your metaphor permits that the clay ball is the insanely dense dead star at the center and the event horizon as a point where the clay balls’ electric fields maintain a certain strength.

  286. Kaiden

    I am very interested in blackholes, and have some very interesting questions (if those whom have superior knowledge on the subject would please humor me). Im a highschool student, and am thinking about writing a couple of essays on blackholes. Just contact me at my email. Thanks

  287. BANERJEE HOLE

    I THOUGHT MANY THINGS TO WRITE, BUT NOTHING COMING OUT OF BRAIN. PERHAPS MY BRAIN IS A BH.

  288. Yoron

    You lose me there Phil?

    “In fact, inside the ergosphere space is moving faster than light! Matter cannot move that fast, but it turns out, according to Einstein, space itself can.”

    Either you have a link to Einstein stating it, or you mean that this is a later interpretation of Relativity? I tried to look it up but could find no historic reference to him stating that? As far as I understand it Einstein defined it as a geometry? Would then be equivalent to stating that parts of the SpaceTime geometry then can be seen as ‘moving’ FTL? Can you prove that?

  289. Jones

    That was cool……most informative……totally awesome………. Star trek is all wrong – you cant outrun a blackhole and blackhole is spherical………great!!!!!!!!!

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