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?
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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
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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?
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| 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.
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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.
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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.
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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.
September 8th, 2008 at 8:22 pm
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.
September 8th, 2008 at 8:27 pm
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. ;^}
September 8th, 2008 at 8:28 pm
Really enjoyed this one Phil. Wouldn’t you know it, I actually learned something
September 8th, 2008 at 8:32 pm
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.
September 8th, 2008 at 8:34 pm
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! )
September 8th, 2008 at 8:38 pm
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….
September 8th, 2008 at 8:48 pm
Good article on fun science, this is the stuff that keeps you in my reader, you really need to do more like it.
September 8th, 2008 at 8:54 pm
Phil: Last time I looked, one orbit around Earth took about 90 minutes, not 42.
GAry 7
September 8th, 2008 at 8:59 pm
#11. The summit of Mt. Everest isn’t the farthest point from the center of the Earth! Mt. Chimborazo in Ecuador is….
September 8th, 2008 at 9:01 pm
Quick question:
Is cruithne orbiting the Earth-Sun L5 point?
cheers,
Robert.
September 8th, 2008 at 9:18 pm
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!
September 8th, 2008 at 9:19 pm
“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?”
September 8th, 2008 at 9:20 pm
*crickets*
September 8th, 2008 at 9:24 pm
@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.
September 8th, 2008 at 9:26 pm
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.
September 8th, 2008 at 9:26 pm
I knew 9 of those. Didn’t know about Cruithne.
Maybe I should start a blog.
September 8th, 2008 at 9:26 pm
Will the new book be available on the Kindle? I hope so.
September 8th, 2008 at 9:27 pm
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.
September 8th, 2008 at 9:29 pm
@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.
September 8th, 2008 at 9:30 pm
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.
September 8th, 2008 at 9:30 pm
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.
September 8th, 2008 at 9:34 pm
Isn’t one of the “moons” a big chunk 0′ rocket parts from the Apollo program? Seems I read that somewhere…
September 8th, 2008 at 9:34 pm
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…
September 8th, 2008 at 9:35 pm
www.spaceflightnow.com/news/n0209/12apollostage/
September 8th, 2008 at 9:36 pm
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.
September 8th, 2008 at 9:36 pm
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.
September 8th, 2008 at 9:37 pm
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.
September 8th, 2008 at 9:37 pm
Liar!
I knew 9 of your ten points. Admitted, I didn’t know about Cruithne. Thanks for that.
(No, your post was awesome and well-written. But you headline was dead wrong, as far as I am concerned.)
September 8th, 2008 at 9:49 pm
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).
September 8th, 2008 at 9:49 pm
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…
September 8th, 2008 at 9:50 pm
Great blog post! I feel like today wasn’t wasted after all because I learned new things
September 8th, 2008 at 9:55 pm
word usagement
September 8th, 2008 at 9:55 pm
“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).
September 8th, 2008 at 9:56 pm
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.
September 8th, 2008 at 10:04 pm
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.
September 8th, 2008 at 10:07 pm
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.
September 8th, 2008 at 10:09 pm
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.
September 8th, 2008 at 10:14 pm
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?
September 8th, 2008 at 10:16 pm
Solomon, I disagree. I think the Earth would be too out of round by the rules’ definition. It would flop around the table!
September 8th, 2008 at 10:16 pm
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?
September 8th, 2008 at 10:17 pm
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
September 8th, 2008 at 10:17 pm
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!™
September 8th, 2008 at 10:21 pm
Phil what a fantástic read! Thanks for the welcome dose of science (and hope that we cannot really blow up our planet!)
September 8th, 2008 at 10:26 pm
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.
September 8th, 2008 at 10:29 pm
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
September 8th, 2008 at 10:30 pm
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.
September 8th, 2008 at 10:31 pm
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
September 8th, 2008 at 10:48 pm
@Gary 7,
“But as I recall, the Death Star did it nearly instantly. Must have had access to a (Dyson) type III civilization???”
No, they just had access to the Full Power of the Dark Side.
Remember, ‘The Dark Side of the Force is a pathway to many abilities some consider to be unnatural.’
September 8th, 2008 at 10:53 pm
typo: item 4. “…if the Earth’s surface were completely deluded with water …” heh.
September 8th, 2008 at 11:06 pm
Sadly I did better with the Milky Way (8 out of 10) then with the Earth (6 out of 10). :O
September 8th, 2008 at 11:27 pm
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.
September 8th, 2008 at 11:31 pm
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.
September 8th, 2008 at 11:34 pm
Hey, is that Lister I see lining up on the cue balls?!
September 8th, 2008 at 11:44 pm
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??
September 8th, 2008 at 11:45 pm
[…] hoy es fiesta en Madrid, la entrada de hoy correrá a cargo de Phil Plait: diez cosas que no sabías sobre la Tierra. El título original está en presente, pero una vez que lo hayas leído, ya no tendrá sentido de […]
September 8th, 2008 at 11:48 pm
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?
September 8th, 2008 at 11:53 pm
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.
September 9th, 2008 at 12:14 am
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.
September 9th, 2008 at 12:50 am
[…] att ha läst Phil Plaits inlägg Ten things you don’t know about the Earth var jag tvungen att prova kartsidan han länkar […]
September 9th, 2008 at 1:31 am
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.
September 9th, 2008 at 1:33 am
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”.
September 9th, 2008 at 1:33 am
Great article!
September 9th, 2008 at 1:57 am
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!
September 9th, 2008 at 2:04 am
you’re coooool….. i think i’ll buy your book..hehe
September 9th, 2008 at 2:05 am
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
September 9th, 2008 at 2:22 am
A very interesting read, thanks.
September 9th, 2008 at 2:37 am
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.
September 9th, 2008 at 2:44 am
Great post and interesting until the very last sentence. Thanks!
September 9th, 2008 at 2:45 am
“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.
September 9th, 2008 at 2:57 am
“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
September 9th, 2008 at 3:03 am
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?
September 9th, 2008 at 3:04 am
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”…….:)
September 9th, 2008 at 3:23 am
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.
September 9th, 2008 at 3:31 am
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!
September 9th, 2008 at 3:32 am
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.
September 9th, 2008 at 3:35 am
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…
September 9th, 2008 at 3:56 am
“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?
September 9th, 2008 at 4:00 am
Neat article.
Earlier tonight, I was wondering about the Earth. What a coincidence.
Thanks.
September 9th, 2008 at 4:08 am
http://www.qntm.org/?destroy discusses many methods of destroying the earth. It’s a great read, but…depressing.
September 9th, 2008 at 4:16 am
Really great stuff. One of my favorite posts in your blog.
September 9th, 2008 at 4:18 am
Great articles. Thank you for make me laugh on earth.
September 9th, 2008 at 4:34 am
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.
September 9th, 2008 at 4:36 am
And noone linked to this classic for #10?
http://qntm.org/?destroy
September 9th, 2008 at 4:37 am
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!
September 9th, 2008 at 4:43 am
#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?
September 9th, 2008 at 4:44 am
Very interesting, well written. kudos
September 9th, 2008 at 4:53 am
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! 
September 9th, 2008 at 4:58 am
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.
September 9th, 2008 at 5:07 am
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.
September 9th, 2008 at 5:08 am
Brilliantly written, Phil. Looking forward to reading your future articles!
J
September 9th, 2008 at 5:10 am
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.
September 9th, 2008 at 5:10 am
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.
September 9th, 2008 at 5:31 am
Saying “dagnappit” doesn’t make it right.
September 9th, 2008 at 5:38 am
[…] http://blogs.discovermagazine.com/badastronomy/2008/09/08/ten-things-you-dont-know-about-the-earth/ […]
September 9th, 2008 at 5:57 am
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).
September 9th, 2008 at 6:00 am
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.
September 9th, 2008 at 6:10 am
[…] The the whole scoop clicking here. This entry was posted on Tuesday, September 9th, 2008 at 8:54 am and is filed under le Chat Marchet. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site. […]
September 9th, 2008 at 6:16 am
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
September 9th, 2008 at 6:19 am
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.
September 9th, 2008 at 6:29 am
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.
September 9th, 2008 at 6:29 am
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.
September 9th, 2008 at 6:33 am
[…] still didn’t know some of these things about earth. Gee, I wonder what made all those “planetesimals” smack together in […]
September 9th, 2008 at 6:34 am
If we wanted to destroy Earth, we could try slamming ourselves into the Sun.
Cheers
September 9th, 2008 at 6:37 am
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?
September 9th, 2008 at 6:40 am
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!
September 9th, 2008 at 6:41 am
Planet Rock! Yeah!
Jiff
www.anonweb.net.tc
September 9th, 2008 at 6:47 am
Wow, didn’t realize there was so much information I wans’t aware of, great post.
September 9th, 2008 at 6:59 am
[…] Ten things you don’t know about the Earth | Bad Astronomy | Discover Magazine. Phil Plait, the creator of Bad Astronomy, is an astronomer, lecturer, and author. After ten years working on Hubble Space Telescope and six more working on astronomy education, he struck out on his own as a writer. He has written two books, dozens of magazine articles, and 12 bazillion blog articles. He is a skeptic, and fights misuses of science as well as praising the wonder of real science. […]
September 9th, 2008 at 7:02 am
(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.
September 9th, 2008 at 7:10 am
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.
September 9th, 2008 at 7:15 am
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.
September 9th, 2008 at 7:19 am
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).
September 9th, 2008 at 7:23 am
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.
September 9th, 2008 at 7:24 am
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..
September 9th, 2008 at 7:31 am
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
September 9th, 2008 at 7:38 am
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
September 9th, 2008 at 7:48 am
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.
September 9th, 2008 at 7:55 am
T’was very interesting!!!
I knew Everest was full of it…
September 9th, 2008 at 7:55 am
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
September 9th, 2008 at 7:58 am
A great article! Note that in point 6 you misspelled “efficiently” as “efficeintly”.