# Ten things you don't know about the Earth

By Phil Plait | September 8, 2008 8:00 pm

Look up, look down, look out, look around.

— Yes, "It Can Happen"

Good advice from the 70s progressive band. Look around you. Unless you’re one of the Apollo astronauts, you’ve lived your entire life within a few hundred kilometers of the surface of the Earth. There’s a whole planet beneath your feet, 6.6 sextillion tons of it, one trillion cubic kilometers of it. But how well do you know it?

Below are ten facts about the Earth — the second in my series of Ten Things You Don’t Know (the first was on the Milky Way). Some things I already knew (and probably you do, too), some I had ideas about and had to do some research to check, and others I totally made up. Wait! No! Kidding. They’re all real. But how many of them do you know? Be honest.

1) The Earth is smoother than a billiard ball.

Maybe you’ve heard this statement: if the Earth were shrunk down to the size of a billiard ball, it would actually be smoother than one. When I was in third grade, my teacher said basketball, but it’s the same concept. But is it true? Let’s see. Strap in, there’s a wee bit of math (like, a really wee bit).

OK, first, how smooth is a billiard ball? According to the World Pool-Billiard Association, a pool ball is 2.25 inches in diameter, and has a tolerance of +/- 0.005 inches. In other words, it must have no pits or bumps more than 0.005 inches in height. That’s pretty smooth. The ratio of the size of an allowable bump to the size of the ball is 0.005/2.25 = about 0.002.

The Earth has a diameter of about 12,735 kilometers (on average, see below for more on this). Using the smoothness ratio from above, the Earth would be an acceptable pool ball if it had no bumps (mountains) or pits (trenches) more than 12,735 km x 0.00222 = about 28 km in size.

The highest point on Earth is the top of Mt. Everest, at 8.85 km. The deepest point on Earth is the Marianas Trench, at about 11 km deep.

Hey, those are within the tolerances! So for once, an urban legend is correct. If you shrank the Earth down to the size of a billiard ball, it would be smoother.

But would it be round enough to qualify?

2) The Earth is an oblate spheroid

The Earth is round! Despite common knowledge, people knew that the Earth was spherical thousands of years ago. Eratosthenes even calculated the circumference to very good accuracy!

But it’s not a perfect sphere. It spins, and because it spins, it bulges due to centrifugal force (yes, dagnappit, I said centrifugal). That is an outwards-directed force, the same thing that makes you lean to the right when turning left in a car. Since the Earth spins, there is a force outward that is a maximum at the Earth’s equator, making our Blue Marble bulge out, like a basketball with a guy sitting on it. This type of shape is called an oblate spheroid.

If you measure between the north and south poles, the Earth’s diameter is 12,713.6 km. If you measure across the Equator it’s 12,756.2 km, a difference of about 42.6 kilometers. Uh-oh! That’s more than our tolerance for a billiard ball. So the Earth is smooth enough, but not round enough, to qualify as a billiard ball.

Bummer. Of course, that’s assuming the tolerance for being out-of-round for a billiard ball is the same as it is for pits and bumps. The WPA site doesn’t say. I guess some things remain a mystery.

3) The Earth isn’t an oblate spheroid.

But we’re not done. The Earth is more complicated than an oblate spheroid. The Moon is out there too, and the Sun. They have gravity, and pull on us. The details are complicated (sate yourself here), but gravity (in the form of tides) raises bulges in the Earth’s surface as well. The tides from the Moon have an amplitude (height) of roughly a meter in the water, and maybe 30 cm in the solid Earth. The Sun is more massive than the Moon, but much farther away, and so its tides are only about half as high.

This is much smaller than the distortion due to the Earth’s spin, but it’s still there.

Other forces are at work as well, including pressure caused by the weight of the continents, upheaval due to tectonic forces, and so on. The Earth is actually a bit of a lumpy mess, but if you were to say it’s a sphere, you’d be pretty close. If you held the billiard-ball-sized Earth in your hand, I doubt you’d notice it isn’t a perfect sphere.

A professional pool player sure would though. I won’t tell Allison Fisher if you won’t.

4) OK, one more surfacey thing: the Earth is not exactly aligned with its geoid

If the Earth were infinitely elastic, then it would respond freely to all these different forces, and take on a weird, distorted shape called a geoid. For example, if the Earth’s surface were completely deluged with water (give it a few decades) then the surface shape would be a geoid. But the continents are not infinitely ductile, so the Earth’s surface is only approximately a geoid. It’s pretty close, though.

Precise measurements of the Earth’s surface are calibrated against this geoid, but the geoid itself is hard to measure. The best we can do right now is to model it using complicated mathematical functions. That’s why ESA is launching a satellite called GOCE (Gravity field and steady-state Ocean Circulation Explorer) in the next few months, to directly determine the geoid’s shape.

Who knew just getting the shape of the Earth would be such a pain?

5) Jumping into hole through the Earth is like orbiting it.

I grew up thinking that if you dug a hole through the Earth (for those in the US) you’d wind up in China. Turns out that’s not true; in fact note that the US and China are both entirely in the northern hemisphere which makes it impossible, so as a kid I guess I was pretty stupid.

You can prove it to yourself with this cool but otherwise worthless mapping tool.

But what if you did dig a hole through the Earth and jump in? What would happen?

 Where my own hole through the Earth ends up.

Well, you’d die (see below). But if you had some magic material coating the walls of your 13,000 km deep well, you’d have quite a trip. You’d accelerate all the way down to the center, taking about 20 minutes to get there. Then, when you passed the center, you’d start falling up for another 20 minutes, slowing the whole way. You’d just reach the surface, then you’d fall again. Assuming you evacuated the air and compensated for Coriolis forces, you’d repeat the trip over and over again, much to your enjoyment and/or terror. Actually, this would go on forever, with you bouncing up and down. I hope you remember to pack a lunch.

Note that as you fell, you accelerate all the way down, but the acceleration itself would decrease as you fell: there is less mass between you and the center of the Earth as you head down, so the acceleration due to gravity decreases as you approach the center. However, the speed with which you pass the center is considerable: about 7.7 km/sec (5 miles/second).

In fact, the math driving your motion is the same as for an orbiting object. It takes the same amount of time to fall all the way through the Earth and back as it does to orbit it, if your orbit were right at the Earth’s surface (orbits slow down as the orbital radius increases). Even weirder, it doesn’t matter where your hole goes: a straight line through the Earth from any point to any other (shallow chord, through the diameter, or whatever) gives you the same travel time of 42 or so minutes.

Gravity is bizarre. But there you go. And if you do go take the long jump, well, your trip may be a wee bit unpleasant.

6) The Earth’s interior is hot due to impacts, shrinkage, sinkage, and radioactive decay.

A long time ago, you, me, and everything else on Earth was scattered in a disk around the Sun several billion kilometers across. Over time, this aggregated into tiny bodies called planetesimals, like dinky asteroids. These would smack together, and some would stick, forming a larger body. Eventually, this object got massive enough that its gravity actively drew in more bodies. As these impacted, they released their energy of motion (kinetic energy) as heat, and the young Earth became a molten ball. Ding! One source of heat.

As the gravity increased, its force tried to crush the Earth into a more compact ball. When you squeeze an object it heats up. Ding ding! The second heat source.

Since the Earth was mostly liquid, heavy stuff fell to the center and lighter stuff rose to the top. So the core of the Earth has lots of iron, nickel, osmium, and the like. As this stuff falls, heat is generated (ding ding ding!) because the potential energy is converted to kinetic energy, which in turn is converted to thermal energy due to friction.

And hey, some of those heavy elements are radioactive, like uranium. As they decay, they release heat (ding ding ding ding!). This accounts for probably more than half of the heat inside the planet.

So the Earth is hot in the inside due to at least four sources. But it’s still hot after all this time because the crust is a decent insulator. It prevents the heat from escaping efficiently, so even after 4.55 billion years, the Earth’s interior is still an unpleasantly warm place to be.

Incidentally, the amount of heat flowing out from the Earth’s surface due to internal sources is about 45 trillion Watts. That’s about three times the total global human energy consumption. If we could capture all that heat and convert it with 100% efficiency into electricity, it would literally power all of humanity. Too bad that’s an insurmountable if.

7) The Earth has at least five natural moons. But not really.

Most people think the Earth has one natural moon, which is why we call it the Moon. These people are right. But there are four other objects — at least — that stick near the Earth in the solar system. They’re not really moons, but they’re cool.

The biggest is called Cruithne (pronounced MRPH-mmmph-glug, or something similar). It’s about 5 kilometers across, and has an elliptical orbit that takes it inside and outside Earth’s solar orbit. The orbital period of Cruithne is about the same as the Earth’s, and due to the peculiarities of orbits, this means it is always on the same side of the Sun we are. From our perspective, it makes a weird bean-shaped orbit, sometimes closer, sometimes farther from the Earth, but never really far away.

That’s why some people say it’s a moon of the Earth. But it actually orbits the Sun, so it’s not a moon of ours. Same goes for the other three objects discovered, too.

Oh– these guys can’t hit the Earth. Although they stick near us, more or less, their orbits don’t physically cross ours. So we’re safe. From them.

8) The Earth is getting more massive.

Sure, we’re safe from Cruithne. But space is littered with detritus, and the Earth cuts a wide path (125 million square km in area, actually). As we plow through this material, we accumulate on average 20-40 tons of it per day! [Note: your mileage may vary; this number is difficult to determine, but it’s probably good within a factor of 2 or so.] Most of it is in the form of teeny dust particles which burn up in our atmosphere, what we call meteors (or shooting stars, but doesn’t "meteor" sound more sciencey?). These eventually fall to the ground (generally transported by rain drops) and pile up. They probably mostly wash down streams and rivers and then go into the oceans.

40 tons per day may sound like a lot, but it’s only 0.0000000000000000006% the mass of the Earth (in case I miscounted zeroes, that’s 2×10-26 6×10-21 times the Earth’s mass). It would take 140,000 million 450,000 trillion years to double the mass of the Earth this way, so again, you might want to pack a lunch. In a year, it’s enough cosmic junk to fill a six-story office building, if that’s a more palatable analogy.

I’ll note the Earth is losing mass, too: the atmosphere is leaking away due to a number of different processes. But this is far slower than the rate of mass accumulation, so the net affect is a gain of mass.

9) Mt. Everest isn’t the biggest mountain.

The height of a mountain may have an actual definition, but I think it’s fair to say that it should be measured from the base to the apex. Mt. Everest stretches 8850 meters above sea level, but it has a head start due to the general uplift from the Himalayas. The Hawaiian volcano Mauna Kea is 10,314 meters from stem to stern (um, OK, bad word usagement, but you get my point), so even though it only reaches to 4205 meters above sea level, it’s a bigger mountain than Everest.

Plus, Mauna Kea has telescopes on top of it, so that makes it cooler.

10) Destroying the Earth is hard.

Considering I wrote a book about destroying the Earth a dozen different ways (available for pre-order on amazon.com!), it turns out the phrase "destroying the Earth" is a bit misleading. I actually write about wiping out life, which is easy. Physically destroying the Earth is hard.

What would it take to vaporize the planet? Let’s define vaporization as blowing it up so hard that it disperses and cannot recollect due to gravity. How much energy would that take?

Think of it this way: take a rock. Throw it up so hard it escapes from the Earth. That takes quite a bit of energy! Now do it again. And again. Lather, rinse, repeat… a quadrillion times, until the Earth is gone. That’s a lot of energy! But we have one advantage: every rock we get rid of decreases the gravity of the Earth a little bit (because the mass of the Earth is smaller by the mass of the rock). As gravity decreases, it gets easier to remove rocks.

You can use math to calculate this; how much energy it takes to remove a rock and simultaneously account for the lowering of gravity. If you make some basic assumptions, it takes roughly 2 x 1032 Joules, or 200 million trillion trillion Joules. That’s a lot. For comparison, that’s the total amount of energy the Sun emits in a week. It’s also about a trillion times the destructive energy yield of detonating every nuclear weapon on Earth.

If you want to vaporize the Earth by nuking it, you’d better have quite an arsenal, and time on your hands. If you blew up every nuclear weapon on the planet once every second, it would take 160,000 years to turn the Earth into a cloud of expanding gas.

And this is only if you account for gravity! There are chemical bonds holding the Earth’s matter together as well, so it takes even more energy.

This is why Star Wars is not science fiction, it’s fantasy. The Death Star wouldn’t be able to have a weapon that powerful. The energy storage alone is a bit much, even for the power of the Dark Side.

Even giant collisions can’t vaporize the planet. An object roughly the size of Mars impacted the Earth more than 4.5 billion years ago, and the ejected debris formed the Moon (the rest of the collider merged with the Earth). But the Earth wasn’t vaporized. Even smacking a whole planet into another one doesn’t destroy them!

Of course, the collision melted the Earth all the way down to the core, so the damage is, um, considerable. But the Earth is still around.

The Sun will eventually become a red giant (Chapter 7!), and while it probably won’t consume the Earth, it’ll put the hurt on us for sure. But even then, total vaporization is unlikely (though Mercury is doomed).

Planets tend to be sturdy. Good thing, too. We live on one.

Conclusion

Well, that cheery thought brings us to the end of my list of things you may or may not have known about the Earth. I had lots more. How much does the atmosphere weigh? What’s the average mass of a cloud? Stuff like that, but these are the ten I liked best. If you’ve got more, feel free to leave them in the comments!

But remember the main point here: you live on a planet, and you may not know all that much about it. The only cure for that is learning, and that’s driven by wonder. Keep wondering, and keep learning. And don’t forget to look around.

Credits:

Original billiards images from Fictures.

GOCE image courtesy ESA.

Cruithne animation from Wikipedia.

Mt. Everest original from Joe Hastings.

The nuked Earth image was created by me for my second Q&BA episode.

CATEGORIZED UNDER: 10 Things, Astronomy, Cool stuff

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1. JohnB

When I was in high school I used to dream about how far away I could get from my home town of Idaho Falls and yet still remain on this planet – sort of a variation on tunneling through the center of the earth. Turns out there are some French controlled islands in the Indian Ocean that fit the bill. The mapping tool you linked to was a way cool means of confirming this. I still have yet to get there; I’ve only gotten as far as Yemen.

2. mk

Great stuff! Thanks.

But… um even though their first album was in ’69… I think it’s safer to call Yes a ’70s Prog band. ;^}

3. Really enjoyed this one Phil. Wouldn’t you know it, I actually learned something

4. Awesome factoids! Is factoids the proper word? It’s like facts, but cooler. I did not know about the “other” natural satellites. Nor did I realize that it would be smoother than a billiard ball if scaled. Something fun to share with my tutees.

“What would it take to vaporize the planet?”

A Vogon constructor fleet. Of course.

5. I usually lurk around here, but I have to say this was the most delightful post about jumping through, and destroying the Earth I’ve ever read. Err. Hmm.

(And as an artist, thanks for crediting your images! )

6. Ron

If we’re going to go below the ocean surface, how can you possibly miss Mt. Lamlam on Guam? Sitting on the edge of the Mariana Trench, it has to be the record holder for most vertical gain, at least on one side….

7. Good article on fun science, this is the stuff that keeps you in my reader, you really need to do more like it.

8. Gary Ansorge

Phil: Last time I looked, one orbit around Earth took about 90 minutes, not 42.

GAry 7

9. Guy Mac

#11. The summit of Mt. Everest isn’t the farthest point from the center of the Earth! Mt. Chimborazo in Ecuador is….

10. Robert L

Quick question:

Is cruithne orbiting the Earth-Sun L5 point?

cheers,
Robert.

11. Eric

Phil,

As usual, your science is impeccable. But your musicology… Yes was not an acid rock band of the 60’s, but rather a progressive rock band, active from the very late 60’s to the present day. Keep up the great astronomy work, and I’ll loan you some of my albums. :^)

Cheers!

12. Greg in Austin

“Of course, the collision melted the Earth all the way down to the core, so the damage is, um, considerable. But the Earth is still around.”

Don’t you mean, “But the Earth is still an oblate spheroid?”

8)

13. Greg in Austin

*crickets*

14. drksky

@Greg
No, he meant that it still existed (around) and did not comment on its general shape (round). But that that point I believe it probably would have been banana-shaped.

15. Eric, you mean like 90125, or Fragile, or The Yes Album?

I’m a big fan of Yes, which is why I quoted them. “Acid” may be the wrong term, but their lyrics are/were trippy, and I think the label fits. Maybe not Hendrix, but still pretty weird.

16. Quiet Desperation

I knew 9 of those. Didn’t know about Cruithne.

Maybe I should start a blog.

17. Will the new book be available on the Kindle? I hope so.

18. Robert L: No Cruithne is in an elliptical orbit that crosses Earth’s. L5 is a Trojan point that is *on* Earth’s orbital path.

19. Len Bonacci

@Gary Ansorge:

The trip to the other side of the Earth takes 42 minutes (Douglas Adams must have smiled at that), the round trip back to your point of origin therefore takes 84 minutes. Low earth orbiting satellites are a little farther from the surface, so they take longer, your 90 minutes or so.

20. A professional billiard player would not, in fact, notice if a ball was only as out-of-round as Earth; they all are. In fact, the manufacturer of the first computer trackballs couldn’t find billiard balls close enough to actually round; at the time there were no standards for how round one must be, and nobody would promise anything.

I’d like to see some evidence, beyond old speculation, that a star like the sun actually becomes a red giant. We have the “main sequence”, but that’s merely descriptive. It is a big step from there to stars stately marching along the implied path. You can talk about what you expect ought to happen as stars “use up” their fuel, but that’s not the same thing as observational evidence of stars in transition. I know we have seen lots of stars change brightness and color, in degrees much smaller than could be called explosions. How many of those actually changed “as expected”?

In the absence of such evidence, maybe you could label your expectation as speculation, as other branches of science would.

21. David

Great post Phil! This is why I read your blog and I already pre-ordered the book. Are you already working on another book?
I didn’t know the Earth had 5 “moons”. That is news to me. I will have to look into that some more.

22. Greg in Austin

Isn’t one of the “moons” a big chunk 0′ rocket parts from the Apollo program? Seems I read that somewhere…

8)

23. Melissa

If you jump into a hole through the center of the earth, you’d fall down, then up …forever? I do believe you’ve discovered the long sought after perpetual motion machine! But, um, what about friction…

24. Greg in Austin
25. JP

Yes, this is off-topic but I couldn’t just keep this BS to myself…
I was watching the “700 Club” with Pat Robertson (not recommended viewing) and he is talking about something he made up called “reciprocity”, which he says means that for every action there is an equal and opposite reaction (As in, Jesus loves you more when you give Pat money). He said that this give-and-you-shall-receive thing is the same force that “makes airplanes fly and sends rockets to the moon.” And that this reciprocity is “just as real as the law of gravity.” Another great example of out Fundamentalists using science when it works and rejecting it when it doesn’t.

26. That was fascinating stuff. I learned some things I did not know. But why did I crack up when I read this:

“OK, one more surfacey thing: the Earth is not exactly aligned with its geoid”

It sounds sort of kinky actually. I have the same problem.

27. Heinz Pierce

Great and fun science Phil, thanks.

I’d have to say though, that Yes would definitely be defined as a prog rock band, but in Phils defense, I would classify Tales of Topographic Oceans as acid rock. No one could create that album without being under the influence of something. Of course “tales” is my favorite Yes album.

28. elgarak

Liar!

(No, your post was awesome and well-written. But you headline was dead wrong, as far as I am concerned.)

29. Baz

Earth is 6.6 sextillion (10^21) tons ; amount of stuff falling to Earth daily is 40 tons; wouldn’t that be 6 x 10^-21 of the mass of the earth, taking about half a million trillion years to double in mass?

(all corrections gratefully received: the only time I ever have to deal with numbers like this is with my credit card bills).

30. The hole in the Earth idea has been written about many times, but after thinking about it a few years ago, I came up with several twists I have not seen nor heard about anywhere. I started writing them down, and was just getting warmed up after 3000 words. I seriously could write 10k words on it, and it would be so so so much fun. But who would publish it?

Maybe I’ll do it and post it here. But I have other ideas like that, and they’d make a great book…

31. Great blog post! I feel like today wasn’t wasted after all because I learned new things 😀

32. t8m8r

word usagement

33. kuhnigget

“The Death Star wouldn’t be able to have a weapon that powerful. The energy storage alone is a bit much, even for the power of the Dark Side.”

I find your lack of faith disturbing… (aiming psychic whammy at the bad astronomer).

34. You’ve made a little mistake in the billiard ball calculations. First the specification from that page is 2.25″ +0.005 -0.000 not +/-0.005. That changes the result quite a bit but more significantly that spec is the diametrical size and tolerance not the surface roughness.

I could not find any specification for roughness height of billiard balls but I did play billiards last week and I’ve been stuck doing a lot of surface roughness measurement this year. I would estimate the roughness height of a billiard ball to be much better than 250 micro inch (.00025″) and more likely 50 micro inch (0.00005″) or less. Now that I think about it, you’d have to intentionally add texture to the mold to cast phenolic at worse than 250 micro inch roughness height.

35. Sarafan

great post, just one complaint, (thats mostly unrelated to the material discussed):

“For example, if the Earth’s surface were completely deluded with water (give it a few decades)-”

I know what you’re trying to hint at, but isn’t it a tad disingenuous to perpetuate the “Climate Change->KevinCostnerWaterWorld” myth. Polar ice melting is a serious issue that could potentially effect millions of people, but there isn’t enough water on Earth, liquid or solid, to completely cover it’s surface. The Jurassic period, for example, was a time of increased global temperatures and a complete lack of polar ice caps, and consequently increased sea levels, however its pretty clear dinos had significant solid surface to tread.

36. Solomon

As a practiced nitpicker, I’m afraid I’ll have to disagree with your conclusion that the Earth is not sufficiently round to be considered smoother than a billiard ball.

The criterion, as you’ve described it, is that there must be no bumps or pits of greater than 28 km; but, then you say that the equatorial bulge is worse than this because Earth’s diameter there is 42.6 km larger than pole to pole. If we treat the bulge as a bump that just happens to go all the way around the world, we’d just have to shave the whole thing down by 21.3 km to get a sphere matching the polar diameter. This is certainly less than the 28 km criterion, so the pool game is still on.

Of course, we could do better by considering the bulge to be a sort of bump and the polar regions to be a sort of pit. If we do that, then we can say that each represents a 10.7 km deviation, meaning that, even were the Marianas trench at one of the poles or Everest on the equator, the total height deviation would still be less than 28 km.

37. Davidlpf

Well Nathan the some of the stars that are changing in color and in brightness are Cepheid variable stars which are in a number of unstability strips in the HR diagram. These strips are from on phase of development to another. Oh the temperature is not just changing by a few degrees.

38. Paul Hutch: That’s interesting, I read it as meaning no more than a 0.005 inch deviation, but you’re saying it means the diameter must be within that range? The BCA rules do indeed say +/-, but I don’t know how official that is.

That does change things, but interestingly, it leaves us without a roughness measure for balls! I would think that has to be in the rules somewhere. Any ideas?

39. Solomon, I disagree. I think the Earth would be too out of round by the rules’ definition. It would flop around the table!

40. RamblinDude

Great post! That was so much fun.

Gary Ansorge Says: “Phil: Last time I looked, one orbit around Earth took about 90 minutes, not 42.”

At the surface?

41. Gary Ansorge

Len Bonacci:

Tanks for the correction. I musta been more tired than I thought, reading the 20 minute trip to earths CENTER as a round trip.

Sarafan: As I recall from the movie Water World, some of the “excess” H2O came from deep inside earth and some from space, but it’s been some time since I last watched the show. I suppose if Shoemaker/Levy had impacted here (besides frying a number of good friends) it would have precipitated (snark) a lot of water, but how much,,,does anyone know?

GAry 7

GAry 7

Great post. I admit to not being so learned on a few of those (though which shall remain a mystery).
It would, however, be wise for you to investigate 10 things you don’t know about the Power of the Dark Side!™

43. Phil what a fantástic read! Thanks for the welcome dose of science (and hope that we cannot really blow up our planet!)

44. John

Nice blog just one point though.

“Even smacking a whole planet into another one doesn’t destroy them!”

What about a large gas planet colliding with an Earth like planet! And surely a really large rocky planet could smash a smaller one to pieces, although this would have to be extrasolar.

45. Gary Ansorge

Oh yeah, by the way,,, a solar powered laser, collecting the total solar energy output, could blow up earth in somewhat less than 160,000 years(maybe a couple of weeks???). But as I recall, the Death Star did it nearly instantly. Must have had access to a (Dyson) type III civilization???

GAry 7

46. Davidlpf

PLus Nathan also if you look at clusters of stars, in globular clusters most of the stars in the cluster are white dwarfs, then the second most popular stars are in the K and M type stars. These stars burn their hydrogen fuel at extremely low rates because gravity forces the atoms together and since they are such low mass stars gravity fewer atoms per unit time to fuse so the fuel last longer. Then the next largest group would be probably be giants that would have the same surface temperature as the K and M stars but be much larger because now there burning hydrogen, carbon or silicon depending what part of the cycle it is in. Then you would have some main sequence F and G type stars probably second or thrid generation in cluster and if you took a spectrum you find things like oxygen and other “metals”. Depending on the age of the cluster you might a couple larger and hotter types of stars but most of these burnt out a long time ago because of the larger mass they burn their fuel a lot faster (gravity controlled). You see, we do not see one star through out its lifetime but we can observe a group of stars that all started out about the same time and in relative isolation from other stars because most globular clusters are orbit outside our galaxy. How do think astronomers came up with the model that they use.

47. Gary Ansorge

PPS:
Phil:
I’ve been passing on the Science 2008 debate answers from Obama since they sent me the results, but I’m really glad you posted that here. You have a lot more readers than me.

Gary 7

@Gary 7,
“But as I recall, the Death Star did it nearly instantly. Must have had access to a (Dyson) type III civilization???”

Remember, ‘The Dark Side of the Force is a pathway to many abilities some consider to be unnatural.’

49. djlactin

typo: item 4. “…if the Earth’s surface were completely deluded with water …” heh.

50. BMcP

Sadly I did better with the Milky Way (8 out of 10) then with the Earth (6 out of 10). :O

51. U747

I was sort of surprised to learn that the earth’s gravity varies as much as it does across the surface. I assumed it must have varied some, but if you google image search: ‘gravity map’ – you’ll see some neat images. I’d like to know more about that, actually.

52. Quiet Desperation

The hole in the Earth idea has been written about many times,

Jasper Fforde uses them in his Thursday Next novels as a form of intercontinental travel.

53. antaresrichard

Hey, is that Lister I see lining up on the cue balls?!

54. Dave Hall

JP Says:

Pat Robertson and “reciprocity”

Another great example of out Fundamentalists using science when it works and rejecting it when it doesn’t.

And did you ever notice how most evolution deniers still rationalize “Social Darwinism?”

Oh and Phil: Stem to Stern is cromulent but horizontal. How about Keel to Masthead? or Base to Apex? Bottom to Top? Ass over Teakettle??

55. Dave Hall

djlactin Says:

typo: item 4. “…if the Earth’s surface were completely deluded with water …” heh.”

And what is wrong with that? Haven’t you ever seen a mirage? Was he supposed to say diluted?

56. Yes’ Jon Anderson is well capable of trippy lyrics. But I think he could crank those out without pharmaceuticals. He was born trippy. Of course, 90125 was Yes at an apogee from the world of acid rock (Tales from Topographic Oceans was the perigee). Yes continues to enjoy success with albums and tours because unlike some ostensibly progressive bands that rose to prominence in the 1970s (I’m looking at you, Genesis), Yes continued to play the complex music with the freaky time signatures that made them famous. (/YesRave)

And nice post on all the, ya know, Earth stuff.

57. justodude

so, as a lost fan, i must admit that number five is interesting. last season a polar bear ended up in the sahara, and using the mapping device the other side from the sahara is in the pacific ocean between australia and the U.S. coincidence? who the hell knows, it’s lost.

58. Perth, Australia is just about opposite Bermuda. Coincidence?

Some decades back the US blew up a bomb in the water near Bermuda and listened for shock waves in Perth.

59. Thomas Siefert

5) I’d build a 20 meter tower right next to the hole and every time I popped up and fell down again I would go: “WOO HOO”.

60. Mark G

Great article!

61. Chip

BA wrote:
“…The biggest is called Cruithne (pronounced MRPH-mmmph-glug, or something similar). ..”

I laughed out loud!

But really – that’s a great lecture about Earth! I learned a lot. Thanks!

62. Anna Lazaro

63. Tom

Dear me. GOCE is an ESA spacecraft. NASA isn’t launching it, it’s going up on a Russian rocket.

http://www.esa.int/esaLP/LPgoce.html

You’re welcome
Tom

64. A very interesting read, thanks.

65. Perhaps being too serious here, but I’d dispute that an implausible technology makes something Fantasy rather than SciFi. Under that definition the majority of things called SciFi (The Time Machine, Star Trek, Doctor Who, etc) would in fact be Fantasy.

66. Marco D

Great post and interesting until the very last sentence. Thanks!

67. chithanh

“Assuming you evacuated the air and compensated for Coriolis forces, you’d repeat the trip over and over again, much to your enjoyment and/or terror. Actually, this would go on forever, with you bouncing up and down.”

As you and the Earth form another Hulse-Taylor binary now, gravitational waves will be emitted as you pass through the earth, which eventually cause your trip to come to a halt in the center of mass of the system.

68. “That’s why NASA is launching a satellite called GOCE (Gravity field and steady-state Ocean Circulation Explorer”

Nope, that’s ESA, actually. GOCE isn’t launched from the US, either, it will be launched from Russia:

“Preparatory activities for the launch of ESA’s GOCE satellite from the Plesetsk cosmodrome in northern Russia had to be stopped yesterday afternoon (Sunday 7 September) by Eurockot due to an anomaly identified in one of the units of the guidance and navigation subsystem of the launcher’s upper stage (Breeze KM ).

http://www.esa.int/esaLP/LPgoce.html

69. Nigel Depledge

Hey, I got 7/10. Woo-hoo!

Phil, you seem less than amused (on your flickr page) about your antipodeal point. At least that’s in the warmish Indian Ocean. Mine is about 900 miles to the SE of New Zealand’s South Island which, at 54.4° South, puts me in the Southern Ocean. Brrr!

Oh, yeah, for all those pointing out “deluded” as a typo: I assume you meant deluged, Phil. Is it, or not really?

70. ptbam

Cruithne is pronounced “croy-nya”. It is an old Gaelic word. I am always amazed when people say it can’t or won’t impact the Earth as if another near Earth object could not disrupt its orbit. As for me, until I see a picture of it, I will assume it is the “mother ship”…….:)

71. Andy

Phil,

Great post! Thanks for that!

On item 9) “Mt. Everest isn’t the biggest mountain.”: ¿So what?
Mt. Everest may not be the tallest mountain but being at its apex is the highest you can go in the Earth’s atmosphere without actually flying.

72. Oh, for heaven’s sake. I’m so used to typing “NASA” that my fingers just did it without my thinking. It’s funny how often that happens. I corrected the comment about GOCE, and also changed the launch date, which I just found out has been delayed. Thanks or pointing that out.

Deluged” typo fixed too. Sigh. I should expect a couple of typos in a post this long. Next time, I’ll run it past Mrs. BA first!

73. Jim

Nice article, Phil. Forwarding it to my friends.

I had heard that the “Earth’s Moon” is actually in orbit around the Sun. The Moon’s (apparent?) solar orbit always curves toward the Sun and never away. Something like a 13ish sided polygon with rounded corners. A satellite in close orbit about the earth would trace a sinuous orbit about the Sun. The Earth’s orbital velocity about the Sun is about 30 kilometers per second whereas the orbital velocity of a satellite in close Earth orbit is about 7.7 km/s (so the satellite never goes retrograde and the orbit about the Sun is not a loop-de-loop or whatever). Is this the case? If so, one could argue that the Moon does not really orbit the Earth.

74. On destroying the Earth —

At a distance comparable to the Earth’s orbital radius, would a supernova (type Ia or type II) be powerful enough to vapourise the planet? If so, roughly how far away might a planet need to be in order to survive total destruction?

Just curious…

75. Frank

“Even weirder, it doesn’t matter where your hole goes: a straight line through the Earth from any point to any other (shallow chord, through the diameter, or whatever) gives you the same travel time of 42 or so minutes. ”

Surely if your hole did not pass directly through the centre of the earth, the small difference in gravity on the side of the hole where the earth is thicker would send you crashing into the wall. Or did I not understand this correctly?

76. Don Snow

Neat article.

Earlier tonight, I was wondering about the Earth. What a coincidence.

Thanks.

77. http://www.qntm.org/?destroy discusses many methods of destroying the earth. It’s a great read, but…depressing.

78. Koldun(as)

Really great stuff. One of my favorite posts in your blog.

79. Great articles. Thank you for make me laugh on earth.

80. kris

Regarding #5. You reference a tool to show opposite sides of the earth and describe it as otherwise worthless. How untrue! I’ve heard of someone making an Earth Sandwich http://www.npr.org/templates/story/story.php?storyId=5492174 using such a tool.

81. KeaponLaffin

And noone linked to this classic for #10?
http://qntm.org/?destroy

82. Jim

Frank, it needs to be an evacuated tube with frictionless walls. If you were to travel through a straight hole going from the equator to the Earth’s center and out. You would probably spend your time sliding on the West side of the hole to the center of the Earth and the East side of the hole returning to the surface. You would start out with about 1700 kph velocity from the Earth’s spin which would drop to zero when you reach the core. Then you need to accelerate back to 1700 kph as you decelerate from the core.

If the planet is spinning, which it is, and you wanted to have a hole passing through the Earth where you did not collide with the wall, what would your trajectory and the path of the hole be? If you started on the Earth’s axis (and the Earth was of uniform density), you would follow the axis through the Earth. If you started on the equator, you would have about 1700 kph starting velocity from the Earth’s spin, so you would miss the center of the Earth by quite a distance.

Instead of a hole, you wear a device that isolates you from the effects of nuclear strong and weak forces as well as electromagnetic, but not gravity. Also isolates you from Phil’s wrath at suggesting such a device…

Remember, the only thing that keeps you from falling into the Earth’s core is van der Waal’s force. If you took away electrostatic repulsion, you’d fall in!

83. Doug

#5 says it would take 20 minutes to get to the center of the earth and that you would accelerate the entire way. Are you assuming that the jumper would be in some type of vacuum tube? If not then terminal velocity says that it would take something like 32 hours to get to the center and that’s assuming constant terminal velocity. Due to decreased gravitational pull as you approached the center terminal velocity would actually be decreasing meaning the ride to the center would be even longer.

Am I wrong?

84. Very interesting, well written. kudos

85. Oh, well, if you enter the stem to stern definition, there are some other peaks to consider as well. You do the math.

I suspect you are nationalistic about all this. 😉 Hawaii is a cool place though. But so is Tibet!

86. Frank

Thanks for clearing that up for me Jim, I appreciate the effort. The more you think about the whole thing, the more pointless it seems. There are too many interactions to take into account.

87. I’ve never seen that http://qntm.org/?destroy. That’s pretty funny! But they have some errors: for example, it wouldn’t take an equivalent mass of antimatter to destroy the Earth. Given E=mc2, and an energy of 2×1032Joules, it would only take a mass of about 2 trillion tons of antimatter to generate the energy needed to vaporize the planet. That’s a big chunk, a cube 10 km on a side with the density of rock. I don’t happen to have that lying around, so I think we’re still safe.

88. Javlington

J

89. Jim, this may surprise you, but you would actually slide down the east side on the way down, and west on the way up!

Think of it this way: at the surface, you are traveling east at some velocity (on the Equator, about 1000 km/hr or so). As you move down the tunnel, the eastward linear speed of the tunnel is dropping, eventually reaching zero at the core. So you are traveling to the east faster than the tunnel is, and so you’d hit the east side of the wall!

This is one of those things I mentioned in the post that most people don’t think of. I have more, and like I said I’d love to write them all down sometime.

90. My hole through the earth comes out at approximately … well, the latitude is that of the Strait of Gibraltar, and the longitude is that of the southernmost tip of Greenland. From which, if you wish, you can calculate where I live.

As a child, I used to imagine going out in a boat to that location (though I hadn’t located it so precisely back then) and dropping rocks into the ocean to build myself an island. Would have taken … a few trips.

91. TR

Saying “dagnappit” doesn’t make it right.

92. Ken Welles

Great job Phil.
There is one anomaly in your thru-the-earth scenario unaccounted for. Falling thru the earth will equal one half orbit exactly only if the earth is uniform density. Because the iron core is much denser than the outer bits, the difference between orbit and fall-thru is about 2 minutes (falling thru is quicker).

93. I’ve always wanted to live in a place where I could have and meet my antipodean counterpart. They all keep turning up as fish. Great site – love the facts that seem to debunk 2nd grade Science in many cases. Too bad this 2nd Grade science is what most people remember.

94. Phil, because the core is denser than the mantle, acceleration doesn’t decrease much for the first half of the trip down. The decreased pull from the rock you’ve passed is more or less counteracted by the increased pull from proximity to the core. So your acceleration actually peaks at a little over 11 m/s^2 when you hit the core/mantle boundary, and then drops off rapidly after that.

As for destroying the planet, my favorite method is here:
http://lablemminglounge.blogspot.com/2008/02/how-to-destroy-earth-isotope.html

95. Karl Kulling

Phil, 42 minutes is NOT the minimum orbit period around Earth. It is in fact 84.4 minutes, which is known as the Schuler period. The equation for the period of a circular orbit is 2*pi/sqrt(g*R^2)*r^(3/2), where r is the radius of the orbit, and g is the gravitational attraction at the surface of the planet, and R is the radius of the planet. Plug in R for r, and you get 2*pi*sqrt(R/g), and using the Earth’s radius for R, you get 84.4 minutes. Anyway, your number is about half of this, but I haven’t put much thought into why that is.

96. Karl Kulling

Just a quick addendum to my last post. I didn’t see that you were calculating the time to go from one side to the other, instead of the round trip time to come back again. Sorry.

97. What if I already “knew” all these things? Do I get a refund? 😛 Actually, I think a combination of these things has been published over at Live Science throughout the years, but it’s still great stuff. I don’t mind refreshing my memory, and of course getting involved in the debates as to what exactly one means on certain points. For instance, I did NOT know about Mt. Chimborazo in Ecuador. So even though I had your top ten list, your commenters gave me a gem.

98. If we wanted to destroy Earth, we could try slamming ourselves into the Sun.

Cheers 😀

99. Roy

If the ocean is filling up with small dust particles at a rate of 20-40 tons of material per day, are there any scientific studies showing how this might affect rises in sea levels?

100. RL

Great post. This is and a couple of the previous posts are why I come to this site. I do have a couple of questions and comments.

1. If you did compress the Earth to the size of a billiard ball, would it become a black hole and have an event verizon, or is it still not dense enough?

2. I had read somewhere (a science site) that the see level over the next thousand or so years is expected to drop 200 – 300 feet. I forget the actual reason for this, but it wasn’t evaporation. Now I need to track down the answer. Does anyone else recall this?

3. The power of the Death Star is not powered by the dark side of the Force. If you may recall from the the end of Star Wars episode 2, the plans for the Death Star were obtained by Count Dookuu from a technologically advanced alien race. By the time the Death Star was operational, the Death Star was run by skeptics who no longer believed that the Force exists. (As a kid I loved the scene where Vader says the line someone already quoted above while choking the Death Star officer…how everyone forgot about Jedis and the force in 20 years is puzzling). According to many Star Wars wiki sites, the Death Star is powered by hypermatter. Whatever that is!

101. Jiff Woods

Planet Rock! Yeah!

102. Wow, didn’t realize there was so much information I wans’t aware of, great post.

103. !AstralProjectile

(Apologies if I have missed seeing this point in a previous post.)

#5 is a nice exercise, but it seems to make the assumption that the density of the Earth is invariant with depth. In reality I think it would take a much shorter time, because acceleration would not fall off as quickly with increasing depth.

104. BobbyEarle

Great post, Phil…

You know, I had one of those 10km/3 chunks of antimatter lying around here somewhere, but just like the one sock you lose in the laundry…I seem to have , uh, misplaced that antimatter somewhere.

105. DPSisler

Excellent! Excellent! Excellent! This is great outreach. I would use this, if I was a teacher. There are some great thoughts here for further study. I suggest you keep this up on a weekly (?) basis, though I suspect that this pace would be hard to maintain – it’s a great way to start a Tuesday.

106. Tony

What a bunch of crap – you ALL must live in another universe! Everyone knows the EARTH IS FLAT!!!!! (and if you are Hindu, you also know it is balanced on top of an elephant which is standing on turtles – What are they standing on, you might ask?! Ha Ha!! The turtles go all the way down, stupid).

107. Tim G

Phil once recommended a DVD movie based on a novel written by a former colleague of his called “The Krone Experiment”. I bought the novel and the story deals with #5.

Based on crude data on the density of the earth as a function of distance from the center, I was able to build a computer model to simulate this “orbit”. My model was based on five layers each of which had a unique density as a linear function of distance from the center.

Because the distribution of mass in the earth is not even, the orbit does not behave like a linear spring. In fact, my model had maximum gravity of 10.45 m/sec^2 at 3460 km from the center. When an object passes through the center upon being released from a mid-latitude location, it traveled 9848 meters per second and took 19 minutes and 11 seconds to get there.

108. I have read on a lot of sites that little dwarfs exist near the earth’s core. They are very powerful.. Can it be true? Also we have come across reports saying that there are real alien bases under the oceans and elsewhere on the earth..

109. Darrin M

My Gods, man, do you realize what you’ve done?! You’ve awakened the wrath of a thousand angry Star Wars fans! Not all are so mild-mannered as myself…

Anyway, they’re gonna tell you that the Death Star is powered by Hypermatter (yes, it’s fake, but it’s sci-fi), and that the Death Star can generate as much energy in one blast as a star produces in a month.
Which, while impossible, is still hawsome.

/nerd rant

110. Gary Ansorge

RL: I recall reading somewhere(years ago) that compressing Earth to approximately one meter in diameter would result in a black hole. With the mass and diameter data given here, I could calculate it, but since I haven’t had my first cup of java yet, that might be an excessive undertaking (snark).

Only two trillion tons of anti-matter? Hey, no problem. We could just extract it from Pat Robertsons,,,gluts,,,
Reciprocity? I guess he really meant REACTION. Reciprocity usually means “give and take”,,,as in “You give me money and I’ll take it”.

Forgetting the Jedis and the Force in only 20 years? Well, when the Catholic church became a secular religion in the third century, the Bishops managed to forget Christs statement that “God IS love” with all of the subsequent abuses attendant upon that. Still, they did have a couple of centuries, so maybe you have a point,,,

Ah, hypermatter,,,meaning “beyond matter”, sort of like “supernatural”,,,

A drop in sea level would occur if we entered an ice age, an event I would personally love, as I have some Nordic ancestry and really dislike this appalling heat. Please bring back snow skiing in the Aiderondacks in summer.

GAry 7

111. MarkH

Okay, #5 was pretty much the coolest thing I’ve learned in a while.

Oh and Phil: Yes was prog, not acid rock. I have a total proghead friend who would rip you up one side and down the other for uttering such heresy.

112. Michelle

T’was very interesting!!!

I knew Everest was full of it…

113. Gary Ansorge

Some years ago ( am I giving my age away with those kinds of statements?) I read a ScjFi story that proposed building a maglev train in an evacuated tube, running several km underground. The train picks up velocity during its free fall phase, glides along on its frictionless mag fields to its destination, then rises back to the surface. Total energy costs for a 5000 km trip (assuming room temp. super conductors) approaching zero,,,of course, the author neglected to mention energy costs for keeping the tube evacuated of air but,,,hey, it would probably be more cost effective than flying, driving or any other surface transport.

,,,on the other hand (good thing I keep a few spares around) if we just removed earths atmosphere we could build such a device on the surface,,,
oh, wait, I forgot about the birdies,,,never mind,,,

GAry 7

114. Michael Purcell

A great article! Note that in point 6 you misspelled “efficiently” as “efficeintly”.

115. Gary Ansorge

Just as another aside, since mater is stronger in compression than extension, what would be the tallest mountain we could have (on earth, skip Mons Olympus). Was wondering, since in Dubai they’re building a hotel that, when finished, may be as tall as 2900 feet (it’s currently over 2500 ft high). A really TALL mountain would make a cool launch platform for access to near earth orbit,,,

GAry 7

116. Cheyenne

One of your coolest posts ever BA! H’Awesome! This is why I have this on my reader! Cha-ching….

117. Phil, I have a comment about the centrifugal vs centripetal discussion. I am not a physics major but when I see arguments like this I try to figure out if there is a misunderstanding of terms.

First, I’d like to say that the car turning is a bad choice to use as an example because of the general public’s limited education in the mathematics of physics, especially dealing with rotation. I found the example using linear acceleration much more helpful. If we explain how inertia and acceleration interact in a linear system shouldn’t the explanation transfer to a turning car example by analogy?

In either case, let’s discuss the ‘fictitious’ force in another way. Here is my example.

You are sitting in a car which is at rest, let’s say it is waiting for a traffic light to turn. When the car accelerates there are two ‘forces’ at work. One is the physical acceleration of the car, the other is the force pushing you back in your seat. Nothing is actually exerting a force against you, it is explained by inertia, but you definitely feel something. I’m afraid of using centrifugal or centripetal because of my limited physics background so please feel free to insert the appropriate label. The force propelling the car is real, the force you feel pushing you back is the real but virtual opposite to the force acting upon the car. This opposite force is actually caused because of the difference between the acceleration of the car and the acceleration of your body. The reason for the difference in acceleration is inertia but when explaining centrifugal vs centripetal forces, doesn’t it make sense to say that the difference in acceleration is what we feel is what we are labeling centripetal force?

Accusing me of getting my math/physics wrong is like accusing a blind man of getting the colors of the rainbow wrong. In other words, tell me what’s wrong with my suggestion is fine but all flames/personal attacks will be ignored.

118. Charles

Phil,

Superb explanations that can be easily understood by lay people. Science can and should do a better job of such things, leaving hyperbole out of it as you have done here. Well done, sir!

119. i’m pleased to add my positive feedback to this swath of comments – what great addressing of many of my child-hood ponderings and debunking of myths. really interesting and humorous. thanks so much, it brightened my morning.

i like creative things 😉

120. Shnakepup

I always thought Cruithne was pronounced “CROOTH-nee”. Where did all these other, crazier proununciations come from? BTW, Phil, have you ever read Stephen Baxter’s “Manifold: Time”?

http://en.wikipedia.org/wiki/Manifold:_Time

121. L Ron Hubbub

Yes? An “acid” band? You, sir, are talking out of your nether region. Progressive? Yes. Prog Rock? Yes. Art Rock? Yes. Acid? That’s a negatory.

122. I recently got into an argument in a science community about if you drilled a hole through the Earth, what would be the air pressure at the center of it. One guy was claiming that the pressure would be zero (since gravity would be zero), but clearly he didn’t have a good grasp of the physics involved – if nothing else, if that were true then all the air on the Earth’s surface would “fall” into the hole. I argued that it had to be greater than the surface air pressure of 1atm~14psi, or else it wouldn’t be able to support the column of air above it, but I didn’t feel like doing (or even setting up) the actual integration to determine what the value should be.

123. Daniel

Regarding earth as billiard ball. The problem with roundness is caused by its spinning motion, right? If it’s neatly racked up, waiting for the break, then it isn’t spinning at all, is it? At which point, it should be pretty perfectly round, I would think (if perhaps a bit too wet).

Or, to think of it another way: if you blow up a billiard ball to the size of the earth then spin it, wouldn’t it go out of round as well?

124. kuhnigget

@RL:

“If you may recall from the the end of Star Wars episode 2, the plans for the Death Star were obtained by Count Dookuu from a technologically advanced alien race. ”

I find your reference to the latter Star Wars films, most disturbing! [[Leveling psychic whammy again…]]

125. AWESOME! Thanks Phil.

Do more of these! There’s probably a gazillion other things that I don’t know about Earth.

126. Tim G

zandperl

It should be extremely high–10^290 atmospheres or perhaps more.

At the surface, the pressure goes up by a factor of e (2.718..) every 7.4 km. But this distance (the scale height) depends on temperature, gravity, and composition as well.

Assuming that composition and temperature does not change (a BIG assumption) and taking into account how the density of the earth varies, I got something like 10^290 atmospheres.

127. Tim G

zandperl,

I’m also assuming that the radius of the whole is small so that the volume is small so that the air pressure at the earth’s surface is virtually unaffected.

128. Todd W.

@Tim G

So, you’re saying that the jumper’s ears might pop a little?

129. David Kelsey

I know this is not really on topic, but I don’t know who else to ask – why should energy have any precise relationship with the speed of light, whether squared or not? Part Two – has anyone actually checked the accuracy of e=mc squared? If so, how? I don’t mean mathematically, but physically. And what is the explanation of two light beams radiating at 180 degrees not resulting in a relative speed for an observer riding one of them of double the speed of light? And how does all this relate to the beams in the hadron collider meeting at the speed of light each? I think we should be told.

130. I tak issue with the death star assertion.

So for a weapon to blow up a planet it would require 2 x 10^32 Joules, which seems a lot to our h-bom standards. But the Death star is no ordinary weapon, it’s the size of a small moon. According to most sources, the Death star is around 80 km in radius. I would only assume that a ship of that size is mostly because of the enormous amount of fuel it carries for a single shot.

That would be precisely around 2.1 x 10^15 cubic meter of fuel, to be exact. What kind of fuel? Let’s see.

We don’t know about how it works, but it’s a finely advanced technology, so let’s assume that the empire was able to come up with a way to harness energy directly from matter, e=mc^2 fashion. Assuming they could convert 1% of all mass to energy, to get 2×10^32 joules one would need 3 x 10^17 kg of that fuel.

Now if we put both numbers together, the fuel of the death star has a density of 150 kg per cubic meter, wich puts it right beside styrofoam. I assume they choose a light material so the death star wouldn’t colapse under it´s own gravity.

They could use a small proton star, which would allow a more smaller size ship, but would probably cause some relativistic havoc..

Therefore, mr. BA, please refrain from your denigrition of the Empire’s military force or else.

(ps. I’m not that much star wars fan, I am just a math fan with love for that kind of problems)

131. Dave Hall

L Ron Hubbub Says:
Yes? An “acid” band? You, sir, are talking out of your nether region. Progressive? Yes. Prog Rock? Yes. Art Rock? Yes. Acid? That’s a negatory.

BS! We dropped penty of acid while listening to YES.

All those terms (presumably from Wikipedia) really define off shoots of Acid (or psychadelic) rock. I can guarantee you We did not make such fine distinctions back in the ’60s and early ’70s when we were listing to the stuff for the first (of many) times.
I am sure all that parsing came when some dead heads grew up, sobered up and tried to create a masters thesis on the only thing they ever thought they understood. No sense wasting 8 years of college and 7 years grad school in the American Studies Department.

Progressive Rock, Prog Rock, Art Rock–its all ROOTED in Acid Rock. The only difference is the amount of pretention.

Now back on topic: Phil–You mean the earth doesn’t have a creamy nougat center?? BUMMER!

132. BA says: “The orbital period of Cruithne is about the same as the Earth’s, and due to the peculiarities of orbits, this means it is always on the same side of the Sun we are. From our perspective, it makes a weird bean-shaped orbit, sometimes closer, sometimes farther from the Earth, but never really far away.”

Not quite right. Cruithne spends a good bit of time opposite Earth. Where that animation gets it wrong is that is simply looping 1 year of orbit over and over again. But with each orbit, the bean shape shifts position. Its center traces a horseshoe in Earth’s orbit every ~700 years. Also, its orbit doesn’t look like a “bean” from “our” perspective. Its orbit looks like a bean from a sun-centered rotating frame perspective. Here’s my page on Cruithne, with graphics and an animation illustrating these points:

http://www.orbitsimulator.com/gravity/articles/cruithne.html

133. Qev

@Invader Xan: From a quick back-of-the-Windows-Calculator bit of math, a typical supernova would release enough energy that an Earth-like planet would be vaporized even if it were 20 AU from the star. That’s ignoring the neutrino output, of course.

134. David D.G.

Holy cow, another Yes fan — and it’s the Bad Astronomer himself! I even had that very song running in my head this morning. Kudos for your cool musical taste, Phil!

~David D.G.

135. The hole-through-the-earth problem is a neat one. You can get into a bit of math, a bit of physics.

About the Coriolis force: assuming free-fall (i.e., drop a bowling ball), what would the shape of the hole be? Something like a big skinny “S”? That’s for one trip. What about the first 100 cycles? What would a graph of the path, drawn in the circle of the Earth, look like? And would it really come out at the antipode? Where would it really end?

Gary: I think I remember that one. Or at least, a plan for linking London and Paris with a line-of-sight tunnel. Coast halfway down, give it a little kick at the center, then coast back up to the other end. Like a pendulum. (??? Is the math the same (as for a pendulum) ???) Exercise for the obsessive: what would be the tilt at the “tunnel station”? How far down at the mid-point?

RL: “… the Death Star is powered by hypermatter. Whatever that is!” It’s the same thing as faster-than-light travel, which makes it possible for the Enterprise to go from one end of the galaxy to the other before the final commercial. And the same as Orson Scott Card’s “ansible”, which makes it possible to get messages from one end of the universe to the other, on the same page of the novel.

“… launch of ESA’s GOCE satellite from the Plesetsk cosmodrome …”

We may have to re-think our launch strategy now that Mr Putin is taking the Soviet Union back to the Old Days.

Jim: “… that the “Earth’s Moon” is actually in orbit around the Sun.” True. That’s why some people want to call the Moon a planet. I’m all for that. If they can demote Pluto by committee, they can promote the Moon the same way. Then we wouldnn’t be just an earth-moon system, but a binary planet.

136. Hi, Phil. I’m Peter with J-List, you came by my booth with Lee at the San Diego Comicon, and I started reading your blog after that. I have a new hobby — printing out blog posts like this and reading them in the bath with my son. (Er, long story, but we do get a lot of quality study and discussion time in the bath.)

137. Karl Kulling, I never said an orbit is 42 minutes. I said jumping into the hole and going from Point A to Point B is 42 minutes. That’s half an orbit.

138. And fine, I changed acid to progressive.

139. mk

Dave Hall…

Hmmm, well ALL rock-n-roll came from Blues and Country. But we don’t call it that do we? Yes is a Progressive/Art Rock band. And since their career spans several decades maybe calling them a ’70s prog band isn’t fair. But a ’60s Acid rock band? Way less than accurate.

Not that it matters! heh.

140. Jim: I dithered over adding something about the Moon’s orbit. Yes, the Moon’s path is always concave to the Sun, but I don’t think that matters much. If the Earth orbited the Sun farther out, the Moon’s solar path would be a curly overlapping wave like other moons.

The Moon is gravitationally bound to the Earth, and that’s what counts. It orbits the Earth, which orbits the Sun. The Earth is the primary.

141. Also, about Yes, I could have sworn they had more than 1 album from the 60s! I changed the date too.

142. mk

Sorry Phil. Posted same time as you.

Just having some fun. ;^}

143. Phil:
I think you made a typo in your calculation for how much the earth gains in mass every day. 40 metric tons / mass of the earth ~ 10^-20. This corresponds to 10^-25 earths per second.

144. PJG

It would be interesting to see how falling through the center of the moon would work differently.

145. Dolpa

What an irritating writing style. (ding ding ding ding ding as an example).
I found myself having to look away from the screen a few times in disgust.

Couple that with the fact that the article wasn’t even that interesting, and I’ve just lost several minutes of my life that I can never get back.

146. Greg
147. gopher65

Wow, a lot of diggs on this one:).

148. Cheyenne

I want more of these articles! As soon as I get home Amazon is getting a nice pre-order for a certain book called “Death from the Skies!”. Cool cover by the way.

Adam Savage even wrote a review of it? How cool is that?

149. Tom Marking

“If you make some basic assumptions, it takes roughly 2 x 1032 Joules, or 200 million trillion trillion Joules.”

This is an interesting calculation that deserves more detail. Let’s start with the potential energy of an infinitesimal mass dm:

dE = -G * M * dm / r

dE — potential energy (joules)
G — gravitation constant (6.67E-11 m^3 / (kg – sec^2)
M — mass of earth below radius r (kilograms)
dm — infinitesimal mass (kilograms)
r — radius from the earth’s center (meters)

If we treat the infinitesimal mass as a thin layer of the earth’s surface and if we assume that the earth as uniform density (5,500 kilograms per cubic meter) then we have:

dm = 4 * pi * rho * r^2 * dr

pi — 3.14…
rho — density of the earth (kilograms per cubic meter)
dr — thickness of shell of uniform radius (infinitesimally thin)

Also, we have:

M = (4/3) * pi * rho * r^3

Putting this altogether we have:

dE = (-16/3) * pi^2 * G * rho^2 * r^4 * dr

Integrating from r to 0 we get:

E = (16/15) * pi^2 * G * rho^2 * r^5

where E — total energy (joules) needed to remove all material shells to an infinite distance

Plugging in some numbers:

pi = 3.14…
G = 6.67E-11 m^3 / (kg – sec^2)
rho = 5.5E3 kg / m^3
r = 6.37E6 m

So E = 2.23E32 joules which agrees with the figure the BA stated.

150. You definately need to do a part two! Very cool. Forwarding.

151. Aleksandar

Why all the talk about Star Wars

Some time ago, in a collaboration between some rabid fans and a guy with astrophysics diploma, fans created back story that Death Star is powered by annihilating tachyonic matter or something… Somehow Lucas Arts got with those people and published that stuff…

152. Dave Hall

mk Says:
Hmmm, well ALL rock-n-roll came from Blues and Country. Yes is a Progressive/Art Rock band. . . Not that it matters! heh.

If ya really wanna go back all music came from banging sticks together–well maybe not all–just punk (don’t shell me about that–I’m a punk fan, albeit an OLD one) Blues and Country may be the origin of Rock, but the apple fell far from the tree. The stylistic leap from Acid to Progressive/Art is shorter and not as obvious. I still think it is more a matter of pretention. Kind of like Spinal Tap

Now Phil: About the Earth’s Creamy Nougat Center . . .

153. Goku definitely has enough energy stored up in his lowest super saiyan form to vaporize the earth.

154. > I’ve never seen that http://qntm.org/?destroy. That’s pretty funny!

You’ve never seen that? It’s an Internet classic! You need to put the Earth Advisory Board graphic up somewhere on the blog.

Here’s a nerd analysis of the Death Star:

155. Greg in Austin

@David Kelsey,
“I know this is not really on topic, but I don’t know who else to ask – why should energy have any precise relationship with the speed of light, whether squared or not? Part Two – has anyone actually checked the accuracy of e=mc squared? If so, how? I don’t mean mathematically, but physically.”

Do you mean something other than lighting a match, burning wood or some other fuel? Something other than converting chemical energy of two metals in an acid to electrical energy, like a battery? Maybe you mean something more advanced, like using any one of the historic or existing particle accelerators:
en.wikipedia.org/wiki/List_of_accelerators_in_particle_physics

Or do you mean test it physically on a big scale, like nuclear fission or fusion, aka. atomic bombs?

I’m not well versed in particle physics, so I don’t have a good analogy off the top of my head. The closest things I can think of are experiments to measure the speed of light, and measuring the amount of energy released from combustion. The whole principle of the nuclear bomb is to take a relatively small amount of matter (like 1,000 kg, or 2,000 lbs) and releasing from it a devastating, and catastrophic, amount of energy. I think that pretty much checks out.

As to your other question, Relativity gets kind of wonky at and near the speed of light. For an observer riding a beam of light, the rest of the universe pretty much comes to a halt. But it takes nearly an infinite amount of energy to move any significant amount of matter to the speed of light. But light is made up of particles, and not matter, which is why they are called “particle accelerators” instead of “matter accelerators.” They are not colliding any significant amount of matter, but pieces of atoms. Incredibly small particles, not something one can see or hold, and certainly not enough to be any danger.

8)

I lost “it” at #6; I’ve heard of sinkage heat, but I didn’t remember. Same for #7, Cruithne type objects.

The rest was fairly standard [just kidding, great post!], so I guess I’m a bit miffed that we didn’t hear about the average mass of a cloud. What do you want, us making our own research?! 😉

Gravity is bizarre.

Um, it is rather spherical geometry that is goofy. And irrational. (Remember π?)

But perhaps gravity can’t be separated from 3D.

I actually write about wiping out life, which is easy.

Oh, yeah? If it is so easy, why have life survived 4 Gy and ~ 10 mass extinctions? I think you mean relatively easy.

157. mk

OK Dave. I hear ya. Pretense it may be.

As far as Rock-n-roll and the apple and the tree? Well I don’t think it “fell” far from the tree. Early Chuck Berry and Carl Perkins sounded very bluesy and country, respectively. But the apple did ultimately “roll” far from the tree, that’s for sure!

158. Ryano, you’re right. I made a unit conversion mistake there (and dagnappit, that’s what I’m helping The Little Astronomer with in her math this week!). I fixed it. Thanks!

159. Tom Marking

“At a distance comparable to the Earth’s orbital radius, would a supernova (type Ia or type II) be powerful enough to vapourise the planet? If so, roughly how far away might a planet need to be in order to survive total destruction?”

“@Invader Xan: From a quick back-of-the-Windows-Calculator bit of math, a typical supernova would release enough energy that an Earth-like planet would be vaporized even if it were 20 AU from the star. That’s ignoring the neutrino output, of course.”

A type Ia supernova releases approximately 1.0E44 joules of energy. At a distance of 1 AU the fraction of this energy impacting an earth-sized planet is 0.25 * (6370/149.6E6)^2 = 4.5E-10. So the earth-sized planet receives about 5.0E34 joules of energy which is 250 times more energy than it takes to vaporize it (2.0E32 joules).

That being the case I wonder how astronomers explain the 3 planets orbiting around the pulsar PSR B1257+12 which has presumably gone through a supernova event. The three planets A, B, and C orbit at 0.19, 0.36, and 0.46 A.U.s from their neutron star, respectively. Why weren’t these guys blasted into oblivion during the supernova event?

[Wow, this thread attracted several trolls!]

yes, dagnappit, I said centrifugal

Wow, BA and xkcd both ranting!

But while xkcd has a point (you can use centrifugal forces for modeling), if I nitpick I believe that Phil seem to misunderstand the meaning of fictional forces. Those are defined by physicists as caused by inertia. (As I believe another commenter reasoned out from scratch, well done!) Masses simply follows curvature, they don’t respond to a “real” force by accelerating in a non-curved space.

Btw, one can also think of it like this: if you want to do a complete model of a rotating object you can never eliminate centripetal forces fully, only simplified models assuming point objects or neglecting centripetal forces let you do this. So centripetal forces are “more fundamental” simply by geometry.

OTOH the concept of force is, like all complex and/or convenience concepts, contingent. It is, as Frank Wilczek says, “conspicuously absent from our most advanced formulations of the basic laws. It doesn’t appear in Schrödinger’s equation, or in any reasonable formulation of quantum field theory, or in the foundations of general relativity.”

161. Santoki

Isn’t this a matter of scale? It’s hard for a human to destory the planet, because we’re so tiny and feeble. But it would be effortless for a black hole to swallow up the earth.

Or how about when the sun turns into a red giant? Won’t it swallow up the earth then? Destroying the earth won’t be hard for the sun to do.

Why weren’t these guys blasted into oblivion during the supernova event?

I believe the hypotheses is that they assembled “out of the ashes” from the blast (and possibly previous planetary system). Sort of choring up the idea that planets are really easy to assemble, too.

163. Phil, this post is a winner.

@ Nathan Myers:

In the absence of such evidence, maybe you could label your expectation as speculation, as other branches of science would.

Thanks for confirming that you are here just for the purpose of trolling.

Jut to not let this be labeled as a “labeling” comment, let me end with noting that there isn’t any need for the label “speculation” in science. Science has facts, theories, tests. Davidlpf discussed some reasons why star evolution is a theory, and for example increasing metallicity with increasing generation number is but one test among, I’m sure, many others, that such a theory passes.

165. Tom Marking

“It should be extremely high–10^290 atmospheres or perhaps more.
At the surface, the pressure goes up by a factor of e (2.718..) every 7.4 km. But this distance (the scale height) depends on temperature, gravity, and composition as well.
Assuming that composition and temperature does not change (a BIG assumption) and taking into account how the density of the earth varies, I got something like 10^290 atmospheres.”

Another interesting calculation that I can’t resist. The basic equation is:

dP = -rho * g * dz

dP — infinitesimal change in air pressure (pascals)
rho — air density (kg / m^3)
g — accleration due to gravity (m / s^2)
dz — infinitesimal change in altitude (meters)

For an ideal gas:

rho = (W / (R*T)) * P

W — molecular weight of gas (0.029 kilograms per mole for air)
R — ideal gas constant (8.31 joules / (deg Kelvin – mole))
T — air temperature (288 deg Kelvin for standard atmosphere)

Assume an isothermic atmosphere so T is constant. Then we have:

dP/P = (-W*g / (R*T)) * dz

The accleration due to gravity, g, will diminish as you drop down the hole reaching zero at the center of the earth. If the earth’s density is uniform then the following equation can be used for g:

g = g0 * (z^3 / Re^3)

g0 — accleration due to gravity at earth’s surface (9.81 m / sec^2)
z — altitude above center of the earth (meters)
Re — radius of the earth (6.37E6 meters)

Putting these equations together we have:

dP/P = (-W * g0 * z^3 / (R * T * Re^3) * dz

Integrating the left side from P0 to P and the right side from Re to 0 (surface down to center of the earth) we have:

P/P0 = exp(W * g0 * Re / (4 * R * T))

P0 — air pressure at the surface (101325 pascals)
P — air pressure at the center of the earth (pascals)

Plugging in some numbers:

W = 0.029 kilograms per mole
g0 = 9.81 meters per second per second
Re = 6.37E6 meters
R = 8.31 joules per degree Kelvin per mole
T = 288 degrees Kelvin

P/P0 = exp(189.3) = 1.6E82

This is substantially less than 1.0E290 because it takes into account the fact that the gravitational acceleration decreases with depth. But at such overwhelming pressure air will be squeezed into a solid so that the traveller will not be permitted to pass. We therefore require the tunnel through the earth to be evacuated.

166. David Rickel

Around the time the original Star Wars came out, there was a theory that magnetic monopoles would catalyze the decay of protons (I guess it’s still a theory). So, fire a beam of magnetic monopoles at a planet, its protons decay into (what? positrons and some non-baryonic particle?) lighter particles, releasing tons of energy. Monopoles hang around, catalyzing more proton decay, and within seconds–poof, no more planet.

No more Death Star either–that much energy release isn’t going to do their shields any good.

167. spat

Waterworld could indeed happen, it’d just have to have the dirt level out

Average ocean depth is probably somewhere around 2 miles, bulldoze the mountains into the sea and drop the average depth to 1 mile and you’ve got a waterworld. The trick isn’t that we don’t have enough water, it’d that the land is too mounded up

After all, you could have 10 times the water and still be able to mound up enough dirt for a few people to live on, but you could have 1/10 the water and if you flattened out the land (and seafloor) enough it would all be covered deep enough so you couldn’t see the bottom

maybe some sort of super-earthquake disaster where the continental plates breakup in to small chunks and the whole earth vibrates for days.

168. Tom Marking

“The accleration due to gravity, g, will diminish as you drop down the hole reaching zero at the center of the earth. If the earth’s density is uniform then the following equation can be used for g:

g = g0 * (z^3 / Re^3)”

Egad! I screwed up. That’s not the correct equation for g. It turns out that g drops off linearly with depth reaching zero at the center of the earth (for a earth of uniform density):

g = g0 * (z / Re)

g0 — accleration due to gravity at earth’s surface (9.81 m / sec^2)
z — altitude above center of the earth (meters)
Re — radius of the earth (6.37E6 meters)

Putting these equations together we have:

dP/P = (-W * g0 * z / (R * T * Re) * dz

Integrating the left side from P0 to P and the right side from Re to 0 (surface down to center of the earth) we have:

P/P0 = exp(W * g0 * Re / (2 * R * T))

P0 — air pressure at the surface (101325 pascals)
P — air pressure at the center of the earth (pascals)

Plugging in some numbers:

W = 0.029 kilograms per mole
g0 = 9.81 meters per second per second
Re = 6.37E6 meters
R = 8.31 joules per degree Kelvin per mole
T = 288 degrees Kelvin

P/P0 = exp(378.6) = 2.6E164

So a different number but way too high for air to remain a gas. The tunnel through the earth must still be evacuated.

169. @Torbjörn: If you don’t know the answer, just say so. Curiously enough, real scientists really do identify ideas as speculation, sometimes their own, sometimes even foundational, without shame. For example, biologists discuss wildly varied scenarios for the ultimate origin of life on earth, hoping someday to identify something testable. It takes a serious case of defensiveness to fear the word.

170. Awesome, awesome, awesome. Thank you!

171. Paul A.

BTW
“It Can Happen” is a song from the album 90125 by the middle 80s version of YES. Love the quote.

172. Tom Marking

Nathan: “I’d like to see some evidence, beyond old speculation, that a star like the sun actually becomes a red giant. We have the “main sequence”, but that’s merely descriptive. It is a big step from there to stars stately marching along the implied path.”

One of the best pieces of evidence is that we see stars at all of the intermediate steps. For example, the sun is spectral type G2V. Actually the V (Roman numeral 5) part is what’s called the luminosity class. In this case V means main sequence. Now, what must happen to a star like the sun to go from a main sequence yellow dwarf (G2V) to a red giant (MxIII) or red bright giant (MxII)? Well, it must travel through luminosity class IV which means subgiant. These are stars that have just left the main sequence and are expanding towards red giant status. And we see plenty of these.

There are also stars that seem to be intermediate between two luminosity classes and they are denoted like “V-IV” meaning intermediate between main sequence and subgiant, or “IV-III” meaning intermediate between subgiant and giant. So we see plenty of stars at every phase of the evolutionary pathway. That’s the main evidence that our understanding of the pathway is correct.

Studies of star clusters also confirm this picture. If you take a star cluster composed of stars that turned on at roughly the same time and you plot the temperature and luminosity on a H-R diagram you will see something peculiar. The stars in the lower righthand corner are on the normal main sequence. But going upward and leftward you will arrive at a point where the curve trends sharply upward and to the right. These are stars that have left the main sequence and evolved towards red giant status. Indeed, you can measure the age of the entire star cluster by measuring where this main sequence turnoff happens.

173. Magnus Björk

Absolutely excellent stuff!

When I heard your factoid about earth giving away 45TW of its core heat, I just had to divide it by the surface of the earth. Turns out that it’s about 0.08W/m^2. As a comparison, clear sunshine at noon is about 1000W/m^2. If I were to invest in solar power or earth core power, I know which one to choose…

Thanks for this post. It’s an absolute gem.

174. Greg in Austin

@Nathan,

“I’d like to see some evidence, beyond old speculation, that a star like the sun actually becomes a red giant. We have the “main sequence”, but that’s merely descriptive.

In the absence of such evidence, maybe you could label your expectation as speculation, as other branches of science would.”

Are you claiming that there is no evidence that the sun will one day become a red giant?

Where did this information come from:
http://www.astronomynotes.com/evolutn/chindex.htm
http://www.nineplanets.org/sol.html
http://www.universetoday.com/2008/01/31/will-earth-survive-when-the-sun-becomes-a-red-giant/
What about the hundreds, if not thousands, of research papers, journals, and articles on the subject.

“For example, biologists discuss wildly varied scenarios for the ultimate origin of life on earth, hoping someday to identify something testable.”

Ahh, I think this is the real reason for your earlier question. Science can’t explain the ultimate origin of life (nor does it try to), therefore, even things that have nothing to do with the origin of life must be suspect?

Now, I believe you are incorrect. I think there is in fact real evidence that our sun will one day turn into a red giant. Do you agree?

Alternatively, if you don’t think there is enough evidence, perhaps you would like to do some research yourself, and tell us all here what kind of star we DO have. I would be interested in knowing what you conclude will happen to our sun in say 5 billion years or so.

8)

175. alfaniner

I like the way this was presented. Most articles of this type start with “10 Myths about…” and proceed to list each item, then negate it. The problem is, people tend to remember the paragraph headings, rather than the content, which is why many myths are hard to kill.

176. Just to add to the wonder: if you took a particle that doesn’t interact with normal matter (say something like a neutrino, but not moving as fast as they generally do) and dropped it at the equator, it would travel (through the Earth most of the time!) on an elliptical orbit. However, in that case the orbit would be centered on the Earth’s center of mass rather than having a focus there.

(Usually approximations apply: spherical, uniform density Earth, etc. Void where prohibited by law.)

177. codimension4

“there is less mass between you and the center of the Earth as you head down, so the acceleration due to gravity decreases as you approach the center.”

But aren’t we also reducing the distance between you and the center of the earth, which would drive acceleration up? (Dividing by the square of a smaller number?)

Or is the mass decreasing such that the change in distance has not very much impact?

178. Bryan

#1 is horribly incorrect.

“OK, first, how smooth is a billiard ball? According to the World Pool-Billiard Association, a pool ball is 2.25 inches in diameter, and has a tolerance of +/- 0.005 inches. In other words, it must have no pits or bumps more than 0.005 inches in height. That’s pretty smooth.”

+/-.005 is the tolerance, not the surface finish. It means the overall diameter of the ball can be 2.245 up to 2.255 and still be acceptable beyond the nominal dimension of 2.250. You want the surface finish, something that isnt even all that special is spec’d out at 63 micro inches.

.005″ grooves would be somewhat noticeable to the naked eye, not smooth at all.

179. Diego

I live in Valparaiso, Chile.. thanks to the map tool i just realized i would get to china, near Xi’an actually!

180. Here’s another thing that you didn’t know about the earth: It’s actually GROWING!

Or so says Neal Adams. When I pointed out that his kooky theory breaks very basic laws of physics, he called me an “indoctrinated fool”.

I’m so honoured.

181. Brian

I’m confused by number 10. The force required to throw a rock into space is trillions of Joules? What about rockets and the space shuttle? I tried to look up how many Joules the solid rocket boosters expend, but could not determine it. It seems like it would be less than the figure described here. Can anyone help me with this? Thanks!

182. Tom Marking

Some more things you probably didn’t know:

11.) The entire surface of the earth was covered by several kilometers of ice from 800 to 600 million years ago (Snowball Earth)
hypertexttransportprotocol colon forwardslash forwardslash www dot snowballearth dot org

12.) 90 billion tons of microorganisms inhabit the earth’s deep hot biosphere.
hyperttexttransportprotocol colon forwardslash forwardslash www dot physorg dot com forwardslash news135860146 dot html

13.) A species of bacteria has been revived after being entombed in salt crystals for 250 million years
hypertexttransportprotocol colon forwardslash forwardslash www dot spaceref dot com forwardslash news forwardslash viewnews dot html?id=231

14.) Since Karl Gauss first measured the earth’s magnetic field strength in 1835 it has been decreasing ever since. The dipole field is getting weaker by 5 percent every century.
hypertexttransportprotocol colon forwardslash forwardslash www dot phy6 dot org forwardslash earthmag forwardslash gauss dot htm

15.) We know that the earth’s outer core is liquid because S-waves produced during earthquakes are not able to pass through it.
hypertexttransportprotocol colon forwardslash forwardslash en dot wikipedia dot org forwardslash wiki forwardslash Shadow_zone

16.) The earth’s inner core rotates faster than the mantle and crust by about 0.4 degrees per year.
hypertexttransportprotocol colon forwardslash forwardslash news dot nationalgeographic dot com forwardslash news forwardslash 2005 forwardslash 08 forwardslash 0825_050825_earthcore_2 dot html

17.) The South Atlantic Anomaly is an area over South America in which the Van Allen radiation belts come the closest to the surface of the earth. Satellites that pass through this area are affected and may suffer from electrical glitches.
hypertexttransportprotocol colon forwardslash forwardslash www dot astronomycafe dot net forwardslash qadir forwardslash q525 dot html

18.) During the Permian-Triassic mass extinction event 250 million years ago 96 percent of all marine species on the planet perished. It was caused by the Siberian Traps volcanic event which was the largest volcanic episode during the last 500 million years.
hypertexttransportprotocol colon forwardslash forwardslash en dot wikipedia dot org forwardslash wiki forwardslash Siberian_Traps

19.) Sprites are large scale electrical discharges that occur above thunderstorms. They can send tendrils that extend up to an altitude of 90 kilometers.
hypertexttransportprotocol colon forwardslash forwardslash en dot wikipedia dot org forwardslash wiki forwardslash Upper-atmospheric_lightning

20.) The Toba supervolcano on the island of Sumatra erupted 75,000 years ago. It was the largest volcanic eruption of the last 20 million years. It almost wiped out one particular species, Home sapiens, whose population dropped to about 10,000 people.
hypertexttransportprotocol forwardslash forwardslash tobavolcano dot googlepages dot com

183. hi,is tomrrow a day to live or not?

184. Davidlpf

I think Tom has spent too much time in the spam filter.

185. Tom Marking

“I’m confused by number 10. The force required to throw a rock into space is trillions of Joules?”

Think of the energy needed to launch the top 10 meters of the earth’s surface into space. Then think of the energy needed to launch the next top 10 meters into space, and so on and so on until nothing is left. That’s where the trillion trillion joules comes from. The mass is substantially more than just launching a rocket.

186. Tim G

Forget what I said about air pressure that would be 10^290 atmospheres. I had quickly modified an existing computer model to use the ideal gas law and hastily posted the results. When the air pressure gets high enough, the space between the molecules get small and the air gets difficult to further compress. The air pressure would probably stay below 10^6 atmospheres. I’m a little embarrassed.

187. Andrew

Tom Marking calculated the gravitational binding energy of a uniform sphere as:

>E = (16/15) * pi^2 * G * rho^2 * r^5

Coincidentally, I did this kind of calculation a few months back (an SF book had a comet colliding with the Moon and shattering it, and I wanted to check the plausibility of that idea). You can simplify the expression by substituting the expression for total mass back into it, and get E=(3/5) M*M/R. I haven’t figured out the effect of the fact that the Earth’s core is more dense than the crust, but I’m pretty sure that that effect will increase the energy required to dissect the Earth.

Andrew

188. Brian

Hi Tom, thanks for responding. However, in the article he says that ONE rock requires trillions of joules. Was this just a misprint; and he meant to say the Earth’s crust?

189. Tom Marking

“You can simplify the expression by substituting the expression for total mass back into it, and get E=(3/5) M*M/R.”

That’s dimensionally incorrect – kg^2 / m. You want joules which is
kg – m^2 / s^2. The correct formula is:

E = (9/15) * G * M^2 / r

M — mass of earth (5.97E24 kilograms)

Plugging this in with the same numbers for G and r yields 2.2E32 joules
which is the same number as before.

190. Tom Marking

“in the article he says that ONE rock requires trillions of joules.”

Yeah, you’ve got Phil there on semantics. The quote is as follows:

“You can use math to calculate this; how much energy it takes to remove A ROCK and simultaneously account for the lowering of gravity. If you make some basic assumptions, it takes roughly 2 x 1032 Joules, or 200 million trillion trillion Joules.”

It certainly doesn’t take 2.0E32 joules to remove one measly rock. Phil is talking about the entire earth there, not one rock. It could have been phrased better but I think we understand what he meant.

191. Brian
192. Tom Marking

“I think Tom has spent too much time in the spam filter.”

Or, as I like to put it:

Hey buddy, moderate THIS!

193. Tom Marking

“But aren’t we also reducing the distance between you and the center of the earth, which would drive acceleration up? (Dividing by the square of a smaller number?)”

Let’s say you fall through the hole to a point half way between the surface and the center of the earth. You are twice as close to the center which means that the force of gravity should be 4 times as great. But the force of gravity is also proportional to the amount of mass enclosed in a sphere with a radius equal to your distance to the center. If the density is uniform then this sphere which is 1/8th the volume should have 1/8th the mass as well. Multiply these factors together and you get a gravitational force of 1/2. Hope this helps.

194. @Tom Marking: I don’t say there can be no direct observational evidence. There could be, but I don’t know what it would look like. (By contrast, for instance, natural selection has been directly observed, myriad times, both in the laboratory and in nature.) The circumstantial evidence is very suggestive, but it depends on a lot of possibly shaky assumptions. By the way, your ten things about earth are way, way better than Phil’s. Don’t neglect, though, the South American asteroid strike 3Mya that may have done in the glyptodonts.

I suspect 1e32 J would be enough. Each bit you loft makes the rest easier. The last rock is free.

195. dR dMO

How about if you nuked the Large Hadron Collider just as it was getting up to full revs and producing small black holes & Higgs bosons or whatever, with a bunker busting 1000 megaton bimb, and all the black holes started eating everything and all the Higgs bosons started, I don’t know..bosing all over the place, would that destroy the planet or just turn us all into brain munchers?

196. Davidlpf

What shaky assumptions such as gravity, nuclear theory, particle theory, relativity, thousands of hours of obervations, thousands more hours of data reduction. You even admit you do not what the evidence would look like what if we have the evidence and you do not know it.

197. Andrew

Tom wrote:

“You can simplify the expression by substituting the expression for total mass back into it, and get E=(3/5) M*M/R.”

That’s dimensionally incorrect – kg^2 / m. You want joules which is
kg – m^2 / s^2. The correct formula is:

E = (9/15) * G * M^2 / r”

You’re right of course – I forget the G.

198. Ken Zutter

Regarding the smoothness of a billiard ball- As a machinist, I should tell you that a manufacturing specification generally calls out the surface smoothness of the object. This is different than size tolerance, and for general purpose objects would be specified at 63 RMS. This would translated to a smoother surface that your +/- .005 inch tolerance calculations.

199. Davidlpf: Of all the things there are to know, the fraction that I know will never nudge above zero. But at least I know that, and I don’t pretend otherwise. Do you? Which is worse, not to know, or to think you know what isn’t so? Which is better, to think you know something, but for for unsound reasons, or to know the reasons are unsound?

I don’t expect you to answer these questions. Quick, fetch the stick!

200. A couple more things to add to this list are: The largest “super volcano” in the United States, probably largest on Earth. The one that produced the Colorado Rocky Mts. The actual largest asteroid impact crater on Earth. The one that destroyed the ancient world and produced the Northern Rocky Mts.

See them at beholdgiants.com

201. Davidlpf

The reasons we know what we do is based on sound observations and theory, The reason they are sound is because the results can be duplicated by anyone at anytime giving the proper training and equipment.
It is a fact we know very little about the universe but this is why there are scientists. They do not claim that their thoeries are based on unsound principles. All science is based of observation and experiment combined with theories. We have over two hundred exo-planets found based of the fact that gravity works the same around distant stars as well as here on earth. They have been also confirming observations by planets transiting in front the star and dimming the star slightly and also through by taking spectrum of the stars. There is no evidence that plasma or electricity has any effect on large structures like the galaxy. What we do know is that stars in the outer regions of the galaxy are rotating around the center of the galaxy faster then they should. As we understand things only gravity could effect this motion so either there is more matter that we can see or gravity works differently in different areas of the galaxy. This missing mass or “dark matter” can come in different forms. We have thousands of hours just looking at stars and their spectrum to figure out what is going in them
so we have a good idea of what will happen to sun in about 5 billion years. Great example of how much force that is needed for nuclear fussion to happen is H bombs, they actually need a U based based fission bombs to ignite. Now if you look at stars they are really massive, massive enough that in the cores that have all the mass from top layers all the way to the bottom applying force on them, actually it is enough force to overcome repulsion that protons have against each other through the electric force. As mentioned above in another post there is evidence that smaller stars last longer the mor massive stars.
Also if the a fraction of knowledge is never going to raise above zero, therefore any all knowledge is zero. I did not go trolling on to somebody elses website and start insulting them and the posters there. you have not shown one bit of proof or told us your qualifications you just say you do not know what your about then give an insult.

202. Greg in Austin

@Nathan Myers,

What is your question again? lol

At first you say you want evidence, and people here provide it.

Then you say scientists just speculate, which several people here disagreed and showed why.

Then you say you don’t know anything, and that its better to say you don’t know than to pretend you do.

Thanks!

8)

203. Davidlpf

[crickets]

204. Jose

Can someone please explain the Nathan Myers paradox? I’m speculating he doesn’t have internet access. If he did, he could have had the answer to his original post in the time he took you to write it. But if he doesn’t have internet access, how is he able to view blogs and post comments to them? My mind is spinning.

205. Davidlpf

Jose, his mind just can not handle the truth. He probably has scene the answer but does not want to accept for some reason.
Nathan, chirpchirp.

206. Jose

@ Davidlpf
One more question. How do I know that noise is crickets? Everyone has always told me it’s crickets, and I’ve seen plenty of main sequence crickets in my day. Yet I’ve never actually seen a cricket making that noise. Has anyone? In the absence of such evidence, please refer to that sound as “grating mildly squeaky summer night noise”, as other noctusoundologists would.

207. I disagree, I think toasters are nice.

208. JimB-Australia

One of the most interesting articles that I have read for a long time.
Glad the boss is not looking over my shoulder, I’ve spent most of the afternoon reading all the comments as well.
Look forward to more of the same type articles.

209. Shikhar

no.9 Mt. Everest isn’t the biggest mountain.

The picture you have shown isn’t Mount. Everest.
thts it. I am from Nepal by the way.
peace..

210. Shane

What happens to you if you stop in the middle of the earth? are you being pulled equally in all directions and therefore floating?

211. Shane

And while I’m here asking questions, I note above a brief debate about water levels. in the spirit of scepticism I have tried to do my own reading on climate change. Through this I read that “the U.N. Intergovernmental Panel on Climate Change’s medium-range emission scenario for greenhouse gases, a rise in sea level of between 8 and 17 inches is predicted by 2100. … Even 17 inches is likely to be high, because it assumes that the concentration of methane, an important greenhouse gas, is growing rapidly. Atmospheric methane concentration hasn’t changed appreciably for seven years, and Nobel Laureate Sherwood Rowland recently pronounced the IPCC’s methane emissions scenarios as “quite unlikely.” ”
(Patrick J Michaels – CATO – 23-2-2007)

This guy is obviously anti-climate change but he argues persuasively and quotes lots of science that looks reputable (to my untrained eye).

Don’t yell at me, I’m just interested.

212. chudez

if the Earth were shrunk down to the size of a billiard ball … a lot of people who bought real estate would be very very annoyed.

213. @Greg: I did not say “scientists just speculate”. I said real scientists aren’t afraid to identify their speculations. Fake scientists announce their speculations as fact, and then get angry when they’re called on it. So, get angry all you like.

@Davidlpf: “As we understand things…”? Do you have even the faintest idea what you’re talking about? (No, we don’t need to know your answer to that. Quick, fetch the stick!)

As far as I’m concerned, Tom Marking can take over this blog any time. He hasn’t written one stupid thing that I’ve seen. BTW, Tom, looking back at your calculation, I see that you did take into account the shrinking planet, so 2e32 it is (plus heat of vaporization). The energy released in a supernova might not be distributed spherically, but biased strongly toward the poles, as we find in the hourglass shape of the remnants, perhaps shielding the planets enough to leave behind the diamond cores of the gas giants.

214. Phil

If you measure between the north and south poles, the Earth’s diameter is 12,713.6 km. If you measure across the Equator it’s 12,756.2 km, a difference of about 42.6 kilometers. Uh-oh! That’s more than our tolerance for a billiard ball. So the Earth is smooth enough, but not round enough, to qualify as a billiard ball.

But, the difference for each to the average is less than the 28km required, so I guess that means it does qualify?:P

215. StevoR

Thanks BA awesome post although I think I knew most of them already! 😉

Five Eratjhly quasi-Moons you say? Hmm …

1) Isaac Asimov mentioned the quasi-moon ‘toro’ (I think) in one of his science books I read ages ago

2) Cruithne was mentioned in Stephen Baxter’s excellent hard Sf novel ‘Space’ (Manifold series)

3) .. and I heard about the Saturn booster from one of the Apollo missions (XII?) becoming another quasi-moon – if not exactly a natural one …

BUT what are the other two? Are you counting the Moon maybe? If so that still leaves one other quasi-Moon .. which is .. Hmm .. anyone? Please?

As for the destruction of the Earth when the Sun becomes a red giant star -I thought a recent study showed that the Earth will be destroyed even though, owing to mass loss via the solar wind, the Earth will have moved outwards slightly. Apparently, if I remember right, the Earth will raise a
tidal bulge on the Sun and tidal factors will cause it to spin inwards until
it falls into the outer layers of the Sun where it will be destroyed. Although maybe after orbiting for a while within the Suns outermost
layers!

(I beleive Betelgeuse actually has a companion star in this position -orbiting within the supergiants outer atmosphere!) 8)

Of course Icould ask how you’d know how much anyone else knows & how you know what we don’t know but that’d just be silly! 😉

Again THX! Great post – you ought to put it into a book form for posterity! 😉

216. StevoR

The BA noted :

8) The Earth is getting more massive.

Sure, we’re safe from Cruithne. But space is littered with detritus, and the Earth cuts a wide path (125 million square km in area, actually). As we plow through this material, we accumulate on average 20-40 tons of it per day! [Note: your mileage may vary; this number is difficult to determine, but it’s probably good within a factor of 2 or so.] Most of it is in the form of teeny dust particles which burn up in our atmosphere, what we call meteors (or shooting stars, but doesn’t “meteor” sound more sciencey?). These eventually fall to the ground (generally transported by rain drops) and pile up. They probably mostly wash down streams and rivers and then go into the oceans. …

““The silt in a houses eaves probably contains a minute amount of interplanetary material.”

Source : Page 70, ‘The Universe and Beyond’, Terence Dickinson, Camden House, 1992.

Oh & BA I did check & you said 4 *other * objects – apart from the Moon – stick near Earth’s vicinity. So far I’ve got Cruithne, Toro & maybe, if it counts, that Saturn V stage that’s been drifting about ever since 197?. Hmm .. What ones am I missing?

217. StevoR

D’oh! Italics and 8 + ) = 8) format stuff up.

I meant to put Phil’s stuff in italics and 8.)

Gee .. sure wish I could edit here. Sigh.

218. Jorge

Just thought I’d mention, I think you used the word “affect” wrong in #8 (lots of people do). I’m pretty sure it should be “the net *effect*” rather than the net “affect”

Neato article though

219. Greg in Austin

@Nathan,

“In the absence of such evidence, maybe you could label your expectation as speculation, as other branches of science would…

Curiously enough, real scientists really do identify ideas as speculation, sometimes their own, sometimes even foundational, without shame.”

I say that real scientists gather evidence to test their hypotheses, and when the hypothesis is True or False, they report that data as fact. The word “speculation” is not part of the process.

http://www.sciencebuddies.org/mentoring/project_scientific_method.shtml

220. The Star Wars Technical Commentaries at theforce.net actually run the numbers to make the Earth blow up as described here, as well as it appears in the movie, where a significant chunk of mass is blown away at a far faster spead, a noticeable chunk of the speed of light which is, of course, magnitudes more ridiculous.

Here’s the link, don’t know if it’ll get past the auto-scrubbers. I’ll leave it as the “Website” field too.

http://theforce.net/swtc/ds/index.html

221. Tom Marking

“As far as I’m concerned, Tom Marking can take over this blog any time. He hasn’t written one stupid thing that I’ve seen.”

Yes, I see my evil plot to take over this blog is proceeding as planned. There will be no mention of man crushes on washed up former Star Trek actors when I’m in charge… Hah, hah, hah (evil laugh like on the radio program “The Shadow”).

BTW, it seems I’ve said plenty of stupid things on this blog from time to time. How do I know? Well, Celtic Evolution, Quiet Desperation, and Mr. Torbjorn Larsson tell me so.

222. Tom Raywood

Too much English on the ball…

As stipulated, the standard diameter for a pool ball is 2.25”. If we accept that standard is met if any/every measure of the ball’s diameter is within .005” of that amount [inclusive], this necessarily means that any measure of the ball’s diameter can be as low as 2.245” or as high as 2.255”.

Since this .005” tolerance accurately represents 0.22% of the ball’s diameter, this means that any measure of the ball’s diameter must fall between 99.78% and 100.22% of the established standard.

The established standard for the earth’s diameter is its average diameter of 12,735 kilometers. 99.78% of that length rounds up to 12,707 kilometers. 100.22% of that length rounds down to 12,763 kilometers.

The earth’s polar diameter rounds up to 12,714 kilometers. Since this is greater than 12,707 kilometers it fits within the tolerances at issue.

The earth’s equatorial diameter rounds down to 12,756 kilometers. Since this is less than 12,763 kilometers it also fits within the tolerances at issue.

Thus…

No matter where you measure the earth’s diameter the results fit within the 0.22% tolerance.

Taking the difference between two separate measurements has no bearing on these specs.

If the earth were shrunk down to the size of a pool ball it would be round enough to cue up on.

This of course is why the earth’s photograph looks as round as it does to the naked eye.

Tom Raywood

223. Aaron

“That is an outwards-directed force, the same thing that makes you lean to the right when turning left in a car.”

224. Davidlpf

Ok Nathan Myers we going to play name that logical fallacy. Here is a list of logical fallacies from the new england skeptics society. I will give a number that coresponds to the logical fallacy listed on their page and give a couple of examples from things you have posted.
http://www.theskepticsguide.org/logicalfallacies.asp

1) Ad hom, Fetch the stick, constant insults towards me, Phil Plait and many other posters.
2)Ad ingorantiam-this states that since astronomers do not exactly how things work in space therefore your explaination is just as valid but the evidence shows it isn’t.
3) arguement from authority- you keep stating scientists know that certain things stated here are not true but show no proof of this claim. Also the tedious defination of irony posts, trying to make people think that others do not know what that word means.
5)Arguemenat from personal incredulity- you do not know how gravity works or how scientists come to there conclusion so you assume your way of seeing things is the correct way of seeing things.
6)confusing associaton with causation-charged particles in a region must be plasma,magnetic fields , stars are made of made plasma, therefore the entire universe must be controlled by plasmas.
7)confusing unexpalianed with unexpalianable, you think since astronomers call something dark matter or dark energy so you think astronomers do not know what is causing this, astronomers have a good idea what dark matter could be, still general do not know what dark energy is but that is what scienctist do they explore the universe and try to figure out what is going on.

11) moving goalpost-You do not really set any goalposts so it is very early easy for you to move them.
20) unstated major premise-kind of goes with the previous one, you make claims that someone does not what they are talking about but you do not put an idea of your own or stick to it.

I would like to point a couple things out to you
a)This blog is Dr. Plaits and if he wants me to leave I will but this not up to you.
b)Leave the childish name calling somewhere else
c)the name calling is making it very clear you do not know what you are talking about
d)The universe works on the principles of gravity, EM , weak force and the strong force. Yes we know very little at the moment that is why there are scientists to keep finding out how things work.
e)But coming in here accusing people that they do not know how things work or whining over a word or two is not getting many supporters.
f)here is the thing you lose on the ohysics and lose on the logic, here is a little bit of advice go find a first year astronomy and physics text book and learn a little more.

225. Bob

Anyone who grew up watching Bugs Bunny knows that all it takes to destroy Earth is a Q32 Explosive Space Modulator. Properly utilized it will cause an Earth shattering KABOOM!

Thanks, Phil, for another highly enjoyable piece!

226. Dann Corbit

If the sun will turn into a red giant, then there must be 1.0 solar mass red giant stars around somewhere. Can you point me to one?

I often hear this statement about the sun turning into a red giant but I don’t think it makes a lick of sense. Otherwise, all aging starts would turn into red giants and we would see zillions of 1 solar mass red giants.

227. Dann Corbit, there’s this new thing on the web called “Google”. If you type “solar mass red giant” into it, you’ll find all sorts of things. Try looking up “Arcturus”.

228. charleigh

Thanks, I really enjoyed your atricle. I learned something and you made it humorous as well, so it was easy to read about it.

229. Isaac Segura

on “Jumping into hole through the Earth”…
when you get at the center of the earth you will experience another force(s) from all around you pushing you at all directions because all the matter of the earth is around you. this force will be stronger at the center of the earth, this will take some of the energy and actually you will not reach the other side, you will be close but not enough, at every pass at the center of the earth you will lose momentum and will end up at the center of the earth.
you are not being pushed just down (where is down anyway?), but pushed at the center. and that’s where you end up.

230. juan

i guess that if you dug a hole through the earth and jumped in it, you wouldn’t ‘fall’ any further than the nucleus, as once you reach it there would be no gravity pulling you elsewhere, would there?

231. D

Taht was an interesting and entertaining read.. well done.

232. a stumbler

I’ve learned that the most quakes and tsunami’s are caused by the gravity of the moon and the sun. When we have a lunar eclipse the quakes and tsunami’s will be heavier because the earth is in the middle, between the sun and the moon. This causes the earth to become more eliptic due to gravitational forces.
When we have a solar eclipse, the sun and the moon are on the same side, thus pulling harder on the surface of our planet, focusing on one spot. This is most of the time the cause of the bigger (biggest) quakes and tsunami’s…
If you dont believe this, check out some world news for quakes or tsunami’s when a solar eclipse has ocurred.

greetz from the netherlands

233. Credit to John O’ Keefe and the New York Times from 1989 for the pool ball discussion:

http://query.nytimes.com/gst/fullpage.html?res=950DE6DE143DF930A35753C1A96F948260

I also agree that smoothness and diametric tolerance are not the same thing. I could not find a smoothness spec for pool balls either.

234. ray

thank you.

235. Jim

Phil says: Jim, this may surprise you, but you would actually slide down the east side on the way down, and west on the way up!

Jim thinks… Jim Sez Duh…

236. I recently saw a show about man’s journey to the bottom of the Marianas trench. I could have sworn that the entire time I was in school I was told this was a completely impossible dream that only the most sturdy robots of the future would be able to complete for us. To find that 2 men did this, and in 1960! To me it’s an amazing adventure, similar to the trip to the moon. Either way, if something goes wrong, no one is on their way to rescue you. I think one of the things most people don’t know is that we have actually been to the very deepest bottom of the ocean.

237. I learned new things 😀

238. David Kelsey

Greg in Austin

What I meant was the unit of energy is joules (?), and the unit of mass is kilograms, and the speed of light is measured in what, kph? If you insert different units of measurement, you get a totally different answer. I cannot understand how the units used in the equation so conveniently work out to give the right answer. I mean, the answer might have been joules = kilograms times 1.03456 times the speed of light squared, but it doesn’t, it is exactly the speed of light squared. Please go easy on me, I haven’t been to school since 1946, and I was no good at maths then either.

Re the second part, is the scientific world now accepting that the speed of light is not finite after all? You say the rest of the universe effectively comes to a standstill near the speed of light, but we are standing on it, and we know it doesn’t. Don’t we? So what does it all mean, Alfie? If it is all notional, and purely mathematical, what does it tell us about the real world?

Finally, there is a nagging thought at the back of my mind that virtually every scientist there ever was, no matter how bombproof and all conquering he may have seemed in his day, has eventually been proved wrong. Who’s to say Einstein won’t join them in due course?

239. John

@ David Kelsey

“the speed of light is measured in what, kph?”

Haha, after saying that hardly anyone will pay attention to what you are saying. You can find the basics on this stuff on google, wikipedia or any Physics textbook. The speed of light can be measured in whatever you want, but the SI units required for equations are metres per second (m/s). You can round this up to : c = 3*10^8 m/s

“If it is all notional, and purely mathematical, what does it tell us about the real world?”

It tells us that the real world behaves according to these equations, since each component represents a real life variable or constant, the solution must also too.

“Finally, there is a nagging thought at the back of my mind that virtually every scientist there ever was, no matter how bombproof and all conquering he may have seemed in his day, has eventually been proved wrong. Who’s to say Einstein won’t join them in due course?

Well fortunately for all of us the result of Einstein’s original theories have been tested many times, and has resulted so far with most of our modern electronics, including the main components of the computer system you’re using now. You have a common misconception that scientific equations are only numbers and symbols, whereas each of these represent a physically changing or constant part of the real world, and technological advancements have been the direct result of understanding these equations.

Of course many theories have been disproven by experiments, and many theories are still to be even tested, and some we just don’t know how to test yet.

Therefore we have a vast library of scientific “knowledge” whose content is completely “factual”. From this stems a large base of fully working technology.

Therefore religious beliefs aren’t a substitute for scientific principles, as religions are faith based beliefs, and science is “fact”.

240. sdgfasdf

Thank you for clarifying that the Earth can’t be easily destroyed. It really annoys me when a friend tells me that H-bombs that governments have would destroy and blow up a giant chunk of Earth and kill everything.

241. sgeek

@sdgfasdf
Actually, the H-bombs and similar could easily kill all higher life forms. The earth itself is pretty hard to destroy, but we’re quite capable of killing ourselves and most other life on the face of this planet. It’s anyone’s guess how long it would take for a new intelligent species to arise – some life forms would survive, but they’d have a whole lot of evolving to do.

@David Kelsey
“E=mc squared” has practical applications, and has had at least since the 1940s. Among other things, we use it to predict the yields of atomic warheads (whether fission-based or fusion-based). In the atomic chain reaction over Nagasaki when the Americans bombed it in 1945, for example, roughly 1 gram of matter was converted into energy. The equation had already been experimentally verified, though I won’t pretend to understand the details of how.

242. lenf

Nicole,
I think
‘WHACK!’
that mentioning Vogons on a blog dedicated to science
‘WHACK!’
‘WHACK!’
Just sayin.

243. tommy

in the opening paragraph you say ‘Unless you’re one of the Apollo astronauts, you’ve lived your entire life within a few hundred kilometers of the surface of the Earth’ surely you would be a lot closer than a few hundred? Marianas trench 11km or aeroplane 10 km ish

244. alex

wouldnt blowing up all our nukes on top of the earth compress it? i read somewhere (i think “brief history of time” that there was probably enough tritium in the ocean to create a nuke powerful enough that it would create a black hole at the center, i think that would be a nice conciliation prize.

a note about e=mc^2, it means mass is energy, and vice versa. when an atom decays, it had been noticed that the two particles masses added up did not equal the mass of the origional atom. the mass had been converted to a different type of energy(mostly heat, and light).

the beauty/hideousness of science is that no matter how many times you test a theory, it can never be proven true. though its a pity that no matter how hard you work, nothing can be proven absolute(it only takes one credible test to prove you wrong), but this does keep several thousand scientist with jobs.

245. StevoR

This may be answered elsewhere already but if so I haven’t yet found out :

I’m really curious to know & reckon the post should have listed what the 4 Earthly quasi-moons are -so far I’ve got :

1) Cruithne, which stars in Stephen Baxter’s Manifold series novel ‘Space’

2) Toro, an small asteroid captured in a similair type orbit than Cruithne and perhaps the first such object found mentiione dby Isaac Asimobv inone of his science books.

3) Maybe, if it counts, that Saturn V stage fromone of the Apollo missions (12?) that has been drifting about ever since 197? and was once mistaken for an asteroid.

Leaving me with at least one and possibly two quasi-moons missing …

Oh & I did check BA & you said :

” 4 *other * objects – apart from the Moon – stick near Earth’s vicinity.” So its not Luna …

So please tell me, am I right so far and what ones am I missing?

—-

PS. Is it recommended practice / good netiquette to put thename sor tags of people you areresponding to in bold? I’m not sur eif it is but thought it may be the custom … perhaps?

246. StevoR

Arrghh! Typos as ever -and no way to fix the oiginal post here. *SIGH *

So I’ll have to correct here :

2) Toro, an small asteroid captured in a similar type orbit to Cruithne’s and perhaps the first such object found which was mentioned by Isaac Asimov in one of his science books.

It notes there that :

Three other near-Earth asteroids (NEAs), 54509 YORP, (85770) 1998 UP1 and 2002 AA29, which exist in resonant orbits similar to Cruithne’s, have since been discovered. Source :Wikipedia : Cruithne page linked on my name above.

Oddly enough none of them is the Toro mentioend by Asimov … & one seems not to be in the quasi-moon orbital relationship at presnt … so I’m still a bit puzzled.

248. Click my name to shift to a more recent thread – thewtareing hole sone which this is linked too.

Ah the lameness of ‘no-links’ filter here … *Sigh *

249. That’s the watering holes thread I mean …

Ah, the frustration of typos being impossible to correct and edit or even preview here… *Sigh*

Don’t know if its bad netiquette or not – apologies if so but I think I’ll post an above post on the Watering holes thread too in the hope of actually getting an answer.

250. Jim

Wow, Phil is a total dork.

251. Jyoti

As a kid i had always wondered about what wud happen if i begin digging from one point and keep digging till i reach the other side of the earth .. 😀

252. the earth cant be distroyed when scientist say that the earth is going to blow up that is not true because god would not let that happen so if you think that this is true then wait and see that the earth will bad will ever happen!!!!!!!!!!!!!!!!!!

253. patience stanton

hi my name is patience and me and my friend are doing a report on the earth for our science lab class,,and we were just wanting to know same things about the earth that most people wouldnt know..or just dont realy see.. thank you!

254. Vickyfin

Finally I heard a physics class that’s so fascinating..!

255. Deepinder Singh Bhatti

Great Stuff man! It’s really interesting and full of information.

256. Bob B S

Wow! That was a thoroughly interesting read. Thanks Phil. I scored 4/10. But aren’t 2 and 3 just one thing?
Regarding the smoothness of Earth: surely that would be related to localised differences rather than the overall differences? For example, the ridge of mountains that make up the Himalayas occurs within a very small distance relative to the Earth’s circumference. Reduced to billiard ball size, that ridge on the surface could be easily detected in comparison to the smoothness of an average billiard ball?
From diametrically opposite of Madrid… (approximately)

257. Alan

Very interesting article. I must say, though, that while many of you are brilliant with numbers, your writing skills leave something to be desired.
I suppose it has something to do with the dominant hemisphere of the brain…I’m terrible at math, but grammer, syntax, etc. have always come
naturally to me; I always thought it was because I did pay attention in English class (and I took Advanced-Placement courses)and was also an avid reader. Obviously, though, you are all readers as well, yet proper use of the English language has not rubbed off on most of you (Jorge is an exception, noting the difference between the meaning of “affect” and “effect”). Though, a lot of the mistakes are probably just typos, to which we all fall victim.
I think we depend on labels entirely too much; however, as a musician and serious collector, I must say that these people are right: “Yes” is a prog. rock band. And there isn’t a difference, as one person obviously thought, between “prog” rock and progressive rock. “Prog” is an abbreviation for progressive. Also, it’s the music, not the lyrics, which determine a band’s categorical status. “Yes” was a very musically progressive band–meaning they weren’t sticking to simple blues-based rock, but were incorporating classical and jazz elements into their music.
Great piece; I would like to see more like it.

258. We really need alternate fuel sources on this planet. It is taking forever for people to find other sources such as solar and wind. But maybe we should be focusing on the geothermal potential of the earth it self instead. So much energy just below our feet just ready to be harvested.

259. I’ve written a bit about destroying the Earth as well. My most extreme method was to set up a nuclear chain reaction using the hydrogen of the Earth’s oceans.

That’s 0.8*10^20 kg of hydrogen. Assume a perfect conversion of H to He, at 6.68 MeV per hydrogen atom. One hydrogen atom weighs 1.67*10^-27 kg. 1 MeV is 1.6*10^-13 J.

Multiply it out and it gives 5.1*10^34 J.

> they talk about the amount of energy needed to destroy the world as 2×10^32 J

5.1*10^34 J is greater than 2*10^32 J, so blowing up the oceans would do it, even allowing for the non-optimal placement of explosives.

> This is why Star Wars is not science fiction, it’s fantasy. The Death Star wouldn’t be able to have a weapon that powerful.

It wouldn’t have to. It’d just have to tickle the oceans into a chain reaction. And remember that the results from the Death Star’s weapon didn’t result in complete vapourisation, just turning the planet into a collection of asteroids. From an energy point of view, the Death Star is not ruled out.

260. Chris

This man is an idiot…He obviously has no schooling in statistics. I’m referring to the pool ball thing, 0.005 is a manufacturing tolerance not a measure of roughness. 0.005 is the allowable deviation that is specified to whoever is making these approved pool balls. In any texts I’ve ever read (I’ve read quite a few Chemical Engineering Fluid and Materials text books) roughness is always referred to as a lower case epsilon. This is the true number you’d need to find to make a just comparison.

Anyways I didn’t read any of these wacky theories and fake numbers after that. This guys some goofball that sits around and comes up with these crazy ways to make numbers say crazy things…the only problem is that he isn’t educated enough to have any of it make sense.

261. Brandon M. Sergent

I don’t suppose I should expect freedom of speech to be tolerated among “scientists” eh Phil?

Perhaps I should have gushed about your obvious intelligence and creativity, Neh?

Sure is fun being a parasite, eh? Enjoy your royalty checks Arty. It’s not like anyone has to die a penniless slave to keep you comfortable, oh wait.

262. SAMI

FANTASTIC!!

263. bob
264. St Johnny

very impressive!
excellent article.

265. Are we heavier during the day than at night, since during the day the centrifugal force of rotating around the sun pushes toward the Earth, and then at night, being outside of the swing, are we lighter? Obviously the difference is negligible but I’ve always wondered if there was a difference.

266. priscilla

I hope to major in astronomy this coming fall…

I have so many things I wanna learn…

its funny cause not to long ago I had the weirdest dream about
Earth & Mars & the Sun.. l0l

I love it! it terrifies me to think of when & how the earth will change again (wichh I know will) ='(

267. Zack

Isn’t centrifugal force imaginary? We just talked about this in my physics class, and there is no such thing. It is only used to describe the opposite of centripetal force. The definition from my physics text is as follows: “Any force that causes an object to follow a circular path is called a centripetal force. Centripetal means “center-seeking,” or “toward the center.” Sometimes an outward force is also attributed to circular motion. This outward force is called centrifugal force. Centrifugal means “center fleeing,” or “away from the center.” In the case of whirling a can that is attached to a sting, it is a common misconception to state that a centrifugal force pulls outward on the can. If the string holding the whirling can breaks, it is often wrongly stated the centrifugal force pulls the can from its circular path. But in fact, when the string breaks the can goes off in a tangential straight-line path because no force acts on it.”

So in closing, all centrifugal force is, is a description of what looks like is happening, not what is actually going on.

268. Martin P. Lohr

The WPA rules now say the Diameter of the pool balls are 2 14 (+.005) inches. http://www.wpa-pool.com/index.asp?content=rules_spec n The spec does not allow for an undersize ball, but it can be oversized. The diameter than would imply a roundness of + or – .0025 of a ball of a diameter of 2.2525 inches. There is no spec of surface finish or roughness. Technically a pool ball could be an oblate speriod as long as it fell within those tolerences. I purchases ball bearings years ago and the manufacter had a list of different specs for his balls.. Size was the easiest for him to control. Something like +-.0001 for a batch of a few thousand. The roundness was on the order of .00005 from highs to lows. He also gave a surface finish in microns which would be a divot or bump at any single point. I assume pool balls are cast than rounded to size. ( I have never sean a seam on one). Id on’t know if any of this will support any of your statements- It has been too many years for me to keep track of that many decimal points. It was great reading

269. Martin above is on the right track, to a machinist, +/_.005 can be a large tolerance but the surface finish is whats key to comparing a pool ball to the earth. Machinists have been working to and measuring tolerances to +/- .0001 for the last hundred years. For example you could easily have a number of threaded shafts (bolts for example) that have a diameter well within a +/_ tolerance of .005 but they would have a very rough surface, or you could polish a number of shafts until you could use them as a mirror to shave in, and they could still easily be +/- .005 difference in diameter. This still isn’t to question the comparison of the earth and a pool ball, it is just to explain a little about tolerances and surface finishes.

270. Kevin

“Earth” is not supposed to be capitalized.

271. Jeff

Fact 5 = Wrong.

terminal velocity is 9.8 meters a second not 7.7 miles a second.

272. Jeff

or Kilometers i should say sorry.. its not 7.7 kilometers a second

273. Jeff– I hate to point this out to you, but you are in fact the one who is wrong. Terminal velocity doesn’t play into this, as I pointed out, since the air is removed. And when you pass the center it’s not a terminal velocity, it’s a maximum velocity since you’ve been accelerating all the way down. Also, the acceleration near the surface is 9.8 meters per second per second.

274. Ender

I bet Jeff could make the Kessel run in less than 12 parsecs…

275. wench

Aside from the info, which has just spun my brain around once or twice (in a good way), the sheer number of replies on this post is boggling. 328? And here I am making a comment to bring it up to 329…

276. wench

Ok, so on the publishing thing on your monograph on the hole in the earth: you can either web-based publish in a blog like this (10k words? really) ort you could try self-publishing on Kindle on Amazon.com, or paper on-demand publishing on Lulu.com or some other self-publishing place.

I’d buy it. It would be like a modern monograph. I love the concept of monographs; they’re so nifty. I know the modern application isn’t quite the same as the Victorian one, but I still get the image of a 19th century nerd huddled in a dark office somewhere scratching away with a quill pen on the survival rates of non-native beetles in sea caves, or something like that.

What about Discover Magazine? You write for them, this is sort of on-topic for your job description; wouldn’t they publish it?

277. Sman

6) The Earth’s interior is hot due to impacts, shrinkage, sinkage, and radioactive decay.

I didn’t read all 300+ comments, but wouldn’t the heat from the impacts, shrinkage, and sinkage have reached an equilibrium by now(disregarding current influx of meteoroid debris)??? So, wouldn’t the Earth’s interior heat be the result of radioactive decay?

Assuming that one could make an argument for heat from the sinking of the plates, but isn’t that also the results of convection generated by decay?

278. Bob

I heard that you can destroy Earth by getting everyone in China to fart at the same time, and it’ll cause an explosion that will obliterate Earth.

Or something.

279. Terry

I only pick up bits and pieces of this stuff as a hobby, but didn’t you grossly oversimplify, well, everything? More to the point, didn’t you state a lot of theories as fact for the sake of keeping this article easy to understand? A lot of your statements need an accompanying qualification (many scientists believe…)

280. Rotimi

This is very interresting……… I have to show it to my science teacher!

281. Holbik

Actually, one thing in there was wrong.

“This is why Star Wars is not science fiction, it’s fantasy. The Death Star wouldn’t be able to have a weapon that powerful. The energy storage alone is a bit much, even for the power of the Dark Side.”

No, the death star could have a weapon powerful enough. They could just ask Chuck Norris to visit the planet in question and stomp really hard.

Or, if they cant get Chuck Norris, they could use antimatter bombs. I think a few of those about the size of a large houses would do the trick. Of course, I didn’t actually do the math, that’s an estimation.

282. You mean, I can stop digging??

283. Jessie Anand

Its good that reviled or discovered some facts to tell us, but always i have one mysteries doubt i.e., in the last point you said earth is hard to destroy….. how it is possible some say earth going to be demolished in coming years???? what is your intelligent answer for it??? please clarify my doubt…..

284. Nathan

Jessie, I’d say that the Earth being hard to destroy just proves how far-fetched those theories are that predict that it will be destroyed soon. I assume you’re referring to the 2012 thing and the religious fundies predicting the rapture or whatever.

285. The pool ball calc is wrong. He has used the diameter tolerance and NOT the surface roughness tolerance. Obviously not an engineer!

A basketball is probably a more correct comparison.

286. Mauna Kea is the tallest mountain earth. However, it’s neighbor Mauna Loa is actually the BIGGEST mountain on earth. I’ve been to the top of Mauna Kea and it’s amazing how you can go from 85 degrees to 30 degrees at the summit… in Hawaii! Be sure to pack a parka if you go.

287. Phil, you know the earth IS flat, right? It’s just a matter of picking the proper coordinate system:

If you let
X = east/west
Y = north/south
Z = up/down

…then the earth is indeed pretty flat (disregarding little wiggles like Everest and deep see trenches)

/Z

288. tov

i wish they would teach this in school, highschool stinks.

Phil, great article! I really did enjoy your passage – especially with all the humor. However, I MUST note that I find it very interesting when scientists explain how GOD created our planet. All the details were left out in Genesis, so I look to explanations such as yours. Although, I’m well aware that scientists don’t half believe the Bible. Most scientists believe this world is all coincidence – I find that being extremely naive, but that’s just me and millions of other Christians around the planet. Anyway, again….great stuff!

290. Lluís

But if 42,6km of difference between the maximum and minimum diameter makes the Earth not round enough, that would mean that a billiard ball of 6cm of mean diameter would have to have a maxium difference of around 0,2mm between its maximum and minimum diameter.

Is that level of acuracy even possible? (I’m not assuming anything, I really don’t know)

i believe star wars is considered science fiction due to the fact that fiction means fake.

292. kishore

Fine . i learnt some thing about our planet

293. Clive

Phil, great article! I really did enjoy your passage – especially with all the humor. However, I MUST note that I find it very interesting when Christians explain how GOD created our planet. All the details were left out in Genesis, so I look to explanations such as yours. Although, I’m well aware that Christians don’t half believe science books. Most Christians believe this world is special– I find that being extremely naive, but that’s just me and millions of other scientists around the planet. Anyway, again….great stuff!

294. Brittany

Ummm………. Mt. Kilumanjuaro (I spelled it wrong) is the world’s tallest mountian. It is located in Alaska.

@361. Clive

Ok, Clive. I believe that was a bit unnecessary. I have my thoughts & you have yours. Just because we men & women discover (a fraction) of how WE THINK the universe came to be, doesn’t mean there’s no deeper meaning behind it all.

Most scientists (and followers) always try to “intellectualize” GOD and/or the Bible. We obviously don’t all have the same IQ. Since that’s the case, GOD is no bigger than the limitation of most scientific minds. Just because YOU might not believe, doesn’t mean it’s not reality. In fact, you believe in quite a few things you’ve never seen or touched – I don’t have to “know you” to understand that. It’s way too common for mankind.

There’s a large majority of scientists and a large majority of Christians – most with contrasting beliefs. Who’s right? The answer is half & half. GOD did create everything you understand as the universe. He just let “man” discover a few things to indeed reveal that He is GOD, the creator.

296. Gabriel

Actually, Mauna Kea still isn’t Earth’s largest, from stem to stern, mountain. Mount Lamlam, an extinct volcano located on the pacific island of Guam, is the largest. Mount Lamlam’s “stem” reaches to the far depths of the Marianas Trench which is, according to you, 11,000 meters below sea level. Regardless of the fact that Mount Lamlam only peaks at a little over 1,000 feet above sea level, according to your logic, it is Earth’s largest mountain.

297. hilary

hey thats cool!i only knew about 2 of these things so i learned alot! but i really dont get some of the math stuff. is it true that if saturn was shrunk into something the size of a person, it would be alot lighter than me?:P

298. steven

299. lolbifrons

>But it’s not a perfect sphere. It spins, and because it spins, it bulges due to centrifugal force (yes, dagnappit, I said centrifugal). That is an outwards-directed force, the same thing that makes you lean to the right when turning left in a car. Since the Earth spins, there is a force outward that is a maximum at the Earth’s equator, making our Blue Marble bulge out, like a basketball with a guy sitting on it. This type of shape is called an oblate spheroid.

There is no such thing as this force. The only force acting on the mass of the earth on such a large scale is gravity. Inertia is what causes the mass of the spinning earth to travel forwards and gravity is what keeps it curving. Inertia therefore seems to “pull” on the earth, bulging it, but that’s just an inherent property of matter. It is not a force.

300. Joe Schmoe

Number 2 is wrong.

If you read the article, you can see the author finds that the difference between the north-south and east-west diameters is 42.6km. The author is right in that this is above the tolerance of 28km bumps and divots, but what he forgets is that this difference is not distributed on every single ‘edge’. In fact, one could consider the height of the bump on the poles/depth of the divot on the equator as only 42.6/4=10.65km. This is within the error tolerances, even if you add the ocean trench and mountain peaks.

301. Clive

Which god? No – come on now, don’t flabber and jabber and pussyfoot around. WHICH god? YOUR god? The god YOU chose to worship? Not Ymir? Not Zeus? Not the Ungambikula?

Sorry, what was that? Ahhh – your very own god that (and that of your parents and grandparents I expect.) How very, very convenient. And, as you say, “unnecessary”.

302. The Old Wolf

This is science at my level… painfully intriguing but without the math that kept me from being a chemist (*wail blubber sob*). Fascinating ideas here, and thanks for taking the time to post them for us armchair scientists! 😀

303. Ok, while the earth does intrigue me, I’m WAY more interested in what’s going on in space. There’s physics and properties that we can’t even begin to understand…well maybe Hawking can, but us mortals can’t even get our brains around things like time travel and black holes…that’s what I like to ponder.

304. Kereshen

Cool stuff

305. willy

I agree with “Joe Schmoe” above:
It seems to me that the Earth is just within round by the billiard ball spec, as the deviation from the *mean diameter* is less than the one-way tolerance.

The International Union of Geodesy and Geophysics gives the mean radius of the Earth to be 6,371.0km, which gives a mean diameter of 12,742.0km.

Polar deviation from mean diameter (your number for polar diameter):
(12,713.6- 12,742.0)/(12,742.0) = -0.0022 or -0.22%
Equatorial deviation from mean diameter (your number for equatorial diameter):
(12,756.2 – 12,742.0)/(12,742.0) = +0.0011 or +0.11%
Compare to the billiard ball’s deviation of
+/- (0.005 / 2.25) => +/- (0.0022) or +/- 0.22%

So on the smaller diameter it runs right against the limit of -0.22%, but on the larger it is comfortably within bounds with +0.11% .

306. Ummm, what?

“The earth is so huge that a fictional skydive to the very center of the planet would take a staggering 32 hours.”

-this is from National Geographic and the Bathroom Reader says the exact same thing, so I am confused by this article. Is it because you’ve removed air from the equation? Incredible difference. I think the airful? air-laden? example is more interesting, it gives you an idea how big the earth really is, since skydiving is usually a mere few minutes. Just my three cents but imagine a 32 hour freefall, actually it would probably get old pretty quick.

308. William Lafrance

Concerning #1, the Mariana Trench isn’t in fact the surface closest to the centre of the Earth. The Earth’s geological features are accurately represented by this picture: http://www.enjoyspace.com/uploads/editorial_cases/avril2009/climat/geoid.jpg
Although your calculations seem sound upon first glance, there are many other factors to be taken into account. Please review.

309. Sarah

I don’t think that if you dug a hole straight through the center of the Earth you would keep falling back and forth. If there were no air resistance then that would happen. But there is air ressistence. If you really went back and forth then scientists would have made prepetual motion machines by now. Each object has it’s own gravity so if you drilled a hole through the object you could create a perpetual motion machine. The rest of the paper was good though! Now I know eight more things about the Earth! (I already knew two and seven.)

310. Paul

Can the earth’s atmosphere be ignited, and what would that take?

311. Tuck Finn

Awesome post! It really is amazing what weirdness may come to light when we make interesting comparisons, like shrinking the Earth down to the size of a billiard ball. And I’m fairly pleased to hear that the Earth is somewhat safe from being vaporized.

I always enjoy the accessibility of this blog, as it must appeal to quite a range of people. I’m sure that many of the interested parties could care less about the “hard science” behind your posts, but I always enjoy reading comments that, respectfully, illuminate errors or elaborate on scientific facts. In this particular post, I noticed the comment as well as the debate surrounding centrifugal force, and it struck me as an easy one to get stuck in. I remember my dad telling me about centrifugal force when I was a kid, and ever since I have had the benefit of knowing its principles, which have applied quite well in my short-ish life. However, when I learned in Physics class that this so-called “centrifugal force” is somehow imaginary? I was crushed. The explanation, on the other hand, does little to make me believe that using centrifugal force as a rough description of what’s going on, as its defined properties are easy to see and experience. Nonetheless, the true story behind centrifugal force is an interesting one…

A very basic physics principle is that an object with no force acting upon it will either stay still, if its initial velocity was 0, or it will continue in a straight line at exactly its initial velocity. This is why if you throw an object in space it will, more or less, move in a straight line (until it hits something, or experiences some gravity from another mass, or, I suppose, experiences some sort of electromagnetic force). An object on Earth, however, will yield the very familiar arcing trajectory that any beer-pong aficionado is well aware of. This is because gravity, a force, introduces a curve to the ball’s motion by accelerating it downward, while the ball’s momentum carries it across. Any force that accelerates an object in such a way that it introduces a curve is said to be creating centripetal acceleration. It is when this force acts on an object unevenly that “centrifugal force” is experienced. For example, consider a ball at the end of a stretchy, massless cord. If we swing the ball around a center pivot until the circle it creates is exactly perpendicular to the ground, we will have found the exact velocity of the ball (the speed at which it is orbiting the circle) necessary, based on the centripetal acceleration provided by the tension in the cord (with a stretchy cord, the farther it’s stretched, the greater the force, so to reach the appropriate force it need only stretch to the appropriate length). Keep in mind that, despite the fact that the cord is continuously pulling the ball in towards the center, the ball “wants” to move in a straight line. Because of this, if we increase the velocity of the ball by spinning it faster, the ball will “try harder” to go in a straight line, and the tension in the cord will no longer provide the necessary acceleration for ‘orbit’. At this moment, the cord will stretch until it reaches a new equilibrium at a new, increased, length. To an observer, it would most certainly seem as though there is a force being exerted on the ball that is causing it to stretch the cord, however, it is really a lack of sufficient inward force, rather than an outward force, that causes the chord to stretch.

This example is a far stretch from talking about the axial rotation of Earth, but the principles are the same. Each particle within the Earth is in motion, and trying to move in a straight line, but Electromagnetic tension, the force which keeps all matter together, keeps them anchored, for the most part, to the Earth’s center of mass. In places where the electromagnetic force is weaker, say, because of the exact elemental makeup of the region in question, the centripetal acceleration may be insufficient compared to another region, leading to differences in mass distribution. Additionally, the angle between an object and it’s center of rotation will affect how much centripetal acceleration is required to maintain an orbit, which is why the Earth may experience ‘bulging’ around the equator.

Fascinating, right? I hope that this has been informative and non-offensive.

312. Tuck Finn

“Additionally, the angle between an object and it’s center of rotation will affect how much centripetal acceleration is required to maintain an orbit, which is why the Earth may experience ‘bulging’ around the equator.”

Oops! It’s the the distance, rather than the angle, between an object and its center of rotation that alters the necessary centripetal acceleration. That is, of course, when angular velocity (how quickly the object completes a 36oº rotation) is constant, as the Earth’s rotation is. Pardon the mix-up.

Be well. Good day.

313. “The hole in the Earth idea has been written about many times,”

The earliest I know is by one of the Professors in Lewis Carroll’s “Sylvie and Bruno” stories.

314. Suresh

It is very interesting, but there is a mistake. The actual height of Mt. Everest is considered to be 8848metres.

315. Democrat

centrifugal force doesn’t exist. It’s centripetal force. “Centrifugal force” is how people refer the the sensation they feel due to centripetal force.

316. Republican

Centripetal acceleration exists. But no centripetal force. Centripetal acceleration is always due to one of the four fundamental forces: gravity, electromagnetism, weak or strong nuclear force.

317. John

The smoothness factor as compared to a billiard ball is a bit of an exaggeration, but I guess it depends on what you consider smooth. The Earth would be within the tolerance level of a billiard ball but it has some relatively “sharp” mountains and valleys whereas the billiard ball’s imperfections are very gradual. If human hair (diameter of about .001 in) was stuck on a billiard ball, it would still fall within the tolerence level but you would feel it with little difficulty. Therefore a shrunken Earth would feel more like a scratched and scuffed-up billiard ball that would probably be discarded in even the seediest pool hall.

318. Brian

I think the tolerance would not be violated in the case of the oblate spheroid. The tolerance is defined as +/- 28 km. You argued that the difference between the smallest and largest diameter is 42.6 km, which is bigger than 28 km, so it wouldn’t pass. However, that would only violate the tolerance if it was +28, -0. If you were manufacturing the earth, to meet the specifications of D=12735 +/- 28km the surface would have to lie within the spherical shell region defined by an outter diameter of 12,763 km and an inner diameter of 12,707 km. The oblate spheroid would lie entirely within this region, so it would not violate the tolerance. Depending on where on the oblate spheroid the largest mountains and deepest trenches are located, they could cross this region and violate the tolerances, but the shape itself is not in violation.

319. Wally

From ATS – > Interesting ‘things’.
Wiki about the hollow Earth: “The mass of the planet also indicates that the hollow Earth hypothesis is unfeasible. Should the Earth be largely hollow, its mass would be much lower and thus its gravity on the outer surface would be much lower than it is.”
How would you calculate the mass of a hypothetical ‘hollow Earth’? (Since the Moon is also suspected to be hollow.. and the rest are too far away for an accurate calculus)

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