by - September 21, 2009 - 11:49 AM
Of course, falling all the way through the Earth is impossible, since its core is molten. But it’s a fun thought experiment nevertheless, and one which The Straight Dope‘s Cecil Adams tackled some thirty years ago — but which I still find fascinating. So there’s this hypothetical tube. Made of some indestructible material that doesn’t get melted from the molten-ness of the Earth’s core and protects you from getting cooked on your way down (and back up). If you ignored all the KEEP BACK signs and clumsily fell into the hole, what would happen?
You’d fall, obviously, picking up momentum as you went. As you approached the center of the earth the pull of gravity would decline and eventually (at the center) cease, but inertia would keep you going.
Once past center, though, the pull of the earth’s mass behind you would begin to slow you down, at exactly the opposite rate that you’d accelerated. You’d come to a complete stop just at the brink of the Antarctic end of the tube, where you’d have an opportunity to wave gaily to the bunny rabbits or whatever they have out there before beginning to fall back in the opposite direciton. This process would continue forever.
Once we start figuring for the effects of atmospheric friction, of course, the situation changes. After a certain point in the course of falling you’d reach a top speed called “terminal velocity,” where air resistance would counteract the accelerating effects of gravity. With less momentum, you’d only fall a relatively short distance past the center of the earth before you stopped and started heading in the other direction. Eventually you’d reach equilibrium at the earth’s center.
Okay, well that would never happen, obviously. How about another burning question: what would happen to an astronaut who took off their helmet in space? After all, this is something that could actually happen, though NASA has a pretty rigorous psychological testing regimen that would theoretically weed out anyone wacky enough to rip off their space suit helmet in outer space (if this is even possible; astronaut X would probably need a friend’s help). (Of course, there was that cross-country-driving, diaper-wearing astronaut — but that’s another story. I’m sure she’s perfectly sane.) In any case, here’s how it would go down, according to Damn Interesting:
For about ten full seconds– a long time to be loitering in space without protection– an average human would be rather uncomfortable, but they would still have their wits about them. Depending on the nature of the decompression, this may give a victim sufficient time to take measures to save their own life. But this period of “useful consciousness” would wane as the effects of brain asphyxiation begin to set in. In the absence of air pressure the gas exchange of the lungs works in reverse, dumping oxygen out of the blood and accelerating the oxygen-starved state known as hypoxia. After about ten seconds a victim will experience loss of vision and impaired judgment, and the cooling effect of evaporation will lower the temperature in the victim’s mouth and nose to near-freezing. Unconsciousness and convulsions would follow several seconds later, and a blue discoloration of the skin called cyanosis would become evident.
Though an unprotected human would not long survive in the clutches of outer space, it is remarkable that survival times can be measured in minutes rather than seconds, and that one could endure such an inhospitable environment for almost two minutes without suffering any irreversible damage.
Any other burning questions? Let us know in the comments!
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As for removing one’s helmet in space, don’t forget the fact that if one was holding their breath, the lungs would possibly rupture from the sudden decompression into the near vacuum of space. Capillaries in the skin and eyes would begin to rupture. Nitrogen bubbles would form in the joints and the bends would begin. It would be a nasty way to go.
posted by Gordon Daily on 9-21-2009 at 12:32 pm
What happens if I go in the “Authorized Personnel Only” door?
posted by Hyacinth on 9-21-2009 at 12:35 pm
So I guess the new BSG series was pretty true to form in the episode where two people had to move from one air lock door two another via the vacuum of space. It was only a matter of seconds (probably around 10 or 20), and they were covered in thermal blankets. Both survived undamaged, though one needed an oxygen chamber for a while.
posted by nutmeag on 9-21-2009 at 1:10 pm
Why does a hot shower (vs. a tepid shower) dry out your skin?
posted by bev on 9-21-2009 at 1:29 pm
I have heard before that you could live through being exposed to space without suit if it is a short period. One thing I have always wondered though is what would happen if you took off the helmet and took a deep breath? I know nothing would come in but could you even make your lungs do this? Would they freeze or burn up? Would you just choke?
reCaptcha: divorced posies
Good name for an unsuccessful grunge band from 93
posted by Alex on 9-21-2009 at 1:35 pm
Could God microwave a burrito so hot, that he himself could not eat it?
posted by Steven on 9-21-2009 at 1:36 pm
Wouldn’t you start to slow down as you approached the center of the earth? Since gravity’s pull is in direct proportion to the mass of the object, as you reach the center of the earth, the mass at the center is less, therefore decreasing the effect of gravity. This coupled with the effect of friction on the falling body, would result in the object slowing down as it approached the center. Or is the pull of gravity a constant throughout the “fall”, depending solely upon the gross mass of the object?
posted by David on 9-21-2009 at 1:36 pm
On the falling through the earth bit, the one thing that everyone ignores is that to pump that tube full of breathable air the intense pressures made by the weight of air just a few miles down would crush you into a fine jelly and/or burn you up, not long after terminal velocity and infact the terminal velocity would keep decreasing because the air density would increase… until effectively you’d be stopped before reaching the center, because your acceleration would decrease as the mass above becomes greater and greater changing the rate of acceleration of free fall to less and less. The falling through the earth bit would only work with an evacuated tube.
posted by chris on 9-21-2009 at 1:46 pm
where on earth is that hole in the picture? literally, where on earth is it?
posted by the creature on 9-21-2009 at 2:14 pm
Creature….that hole is in Utah. It is the Bingham Canyon Mine. One of the few man made objects visible from outer space. 2-1/2 miles wide by 3/4 miles deep. It produces 12 lbs of copper for every one tone of ore.
Impressed? Don’t be, it was on Modern Marvels while I was at home during lunch. ;)
posted by TXCherokee on 9-21-2009 at 2:38 pm
Actually, just the thought of traveling through that hole in the earth creeps the hell out of me. I am more than a little claustrophobic so even the thought of dropping into the hole and then slowing as I reach the center, and maybe not even making it to center, let alone coming to the other side just to keep sliding back and forth INSIDE the earth!!! just really freaks me out!!!! (breathe. breathe. breathe.)
posted by Hyacinth on 9-21-2009 at 2:48 pm
bev:
The hot water is more effective at removing the natural oils that coat your skin. With less of this protective hydrophobic layer, water can more easily evaporate from your skin, leaving you feeling skin-dry.
Alex:
Consider the mechanism of inhalation. When you inhale, your diaphragm contracts, creating a slight partial vacuum in your lungs (i.e. the pressure in your lungs is slightly less than the pressure outside your body). Of course, contrary to popular geeky T-shirts, vacuums don’t suck. Instead, what happens is the higher pressure outside pushes air into your mouth, down your windpipe, and into your lungs.
(Anyone who has waded into neck-deep water can tell you that it’s a bit harder to breathe in that position. In order to inhale, your diaphragm and rib muscles must work against the increased pressure of the water in order to reduce the pressure in your lungs to a pressure lower than that outside your mouth. If you try to use a garden hose as a snorkel, you’ll quickly find that the water pressure forces all the air out of your lungs the first time you try to inhale.)
So, if you exhaled completely into the “vacuum of space” sans helmet and then tried to inhale, what would happen? Not much. There would be no pressure acting against your diaphragm or chest, so you could expand your lungs to full capacity without any more effort than if you were inside the spacecraft, but with effectively zero pressure outside your mouth, there would be nothing to force anything into your lungs. You could go through the actions (i.e. muscle movements) of gasping for breath, but no matter how you expand and contract your lung volume, effectively nothing will go in or out.
Of course, this would all likely be moot if you’d tried to hold your breath while opening the helmet. As any scuba diving instructor will explain, your lungs are amazingly flexible, but only to a point. If the pressure inside your lungs is contained (such as by holding your breath while ascending underwater or holding your breath while opening your spacesuit), your lungs will get to the point they are full, and then the alveoli will tear.
(Lungs are like a paper bag. You can inflate and deflate them as much as you’d like, but if they’re completely full and you try to force them further, they will tear.)
So, if you try to hold your breath, it is likely that you will cause injury to your lungs, and the nature of the injury is such that you can end up with bubbles from your lungs entering your arterial circulation. If a bubble obstructs a small artery, that’s an embolism. If it happens to lodge in the brain, you’re looking at a cerebral arterial gas embolism, which looks and works practically the same as a stroke. (The good news is that if your space-buddy can get you back in the airlock quickly and put you under pressure, the bubble(s) may be compressed enough to pass through, thereby saving your life.)
So, long story short, if you’re about to have to make a vacuum field trip, do what scuba instructors would tell you to do and make a nice “Ooooooo…” sound as you let off the pressure. It may just save your life. (And if you let me come with you on your space trip, I’ll throw in a free scuba class, even the checkout dives, hehe.)
posted by CJ the Scuba Geek on 9-21-2009 at 3:38 pm
Blend of both these topics: Astronauts in the movie “Sunshine” (by Academy Award winning director Danny Boyle of Slumdog Millionaire fame) must cross between two airlocks between ships; they use the depressurization of opening the lock to propel themselves from one chamber to the other (kind of like topic #1), also going through space, feeling the effects of extreme depressurization (like topic #2).
Fantastic flick. Unbelievable, but fantastic.
posted by Joel on 9-21-2009 at 3:51 pm
Let’s not forget about the rotation of the Earth. If we fell through a hole that went directly down to the center of the Earth, through the core, and out the other side, we would constantly keep slamming against one side. Granted, each time you hit the wall is about a couple miles or so depending on the width of the hole. Still, not my most enjoyable form of amusement and excitement.
posted by Steven on 9-21-2009 at 4:06 pm
The hole in the Earth problem is actually a well known physics calculation. The folks at hyperphysics (http://hyperphysics.phy-astr.gsu.edu/HBASE/Mechanics/earthole.html) do a neat derivation showing that the total period of your Earthly oscillation would be 84.5 minutes. More impressive, however, is the 17,700 mph you would be traveling as you pass through the center.
posted by Ron on 9-21-2009 at 4:07 pm
The “hole in the Earth” picture above is from the diamond mine in Mirny, Russia…
if you are environmentally-sensitive, I recommend you do NOT look it up…
jes’ sayin’
clever reCaptcha – eawell beloved
*snort*
posted by Goliath The Pickle on 9-21-2009 at 5:12 pm
I’m not sure the effects of removing a helmet in space would be quite so dramatic as several posters have theorised, including the bends and ruptured capillaries. Normal atmospheric pressure is roughly 15 psia (pounds per square inch above an absolute vacuum). Space, assuming a perfect vacuum, is 0 psia, resulting in a 15 psi pressure gradient. If my quick calculation is correct (as it’s been a few years since I took fluid mechanics), that’s that same difference as ambient to roughly 35 feet underwater.
While I’m sure it’s unfomfortable, I don’t think you’re going to go all “Total Recall” or suffer decompression sickness.
posted by Matt on 9-21-2009 at 5:20 pm
One night in college, some friends and I had an animated discussion about what would happen to a person in space. (We’re two mechanical engineers and an astrophysicist, so these types of discussions happen.) One voted for blood boiling + explosion, one for freezing, and one for suffocation. To resolve our argument, we turned to google and found this: http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html
What we found most interesting was the account of a pressure suit that failed during test in 1965, exposing the test subject to a near vacuum, and how the last thing he remembers before passing out was the water on his tongue beginning to boil in the low pressure. That would be a creepy sensation.
posted by Kathryn on 9-21-2009 at 7:15 pm
what would happen to a country let’s say America if there is a really really huge nature disaster that practically destroy and limp everything from electricity, water system and even the government and military?
posted by Ronald on 9-22-2009 at 7:42 am
“While I’m sure it’s unfomfortable, I don’t think you’re going to go all “Total Recall†or suffer decompression sickness.”
No, you wouldn’t go all “Total Recall”, but it would be more lethal than, say, being stuck in a room full of nitrogen at 14 PSI. As noted in the description, the oxygen exchange of your lungs depends on atmospheric pressure, so assuming you haven’t managed to pinch your nose shut, you’re going to wind up passing out fairly quickly.
I’m a little skeptical of the “survive two minutes without ill effects” claim, though, because there is actually a recorded instance of somebody “sucking space”. Three cosmonauts were killed by decompression when Soyuz 11′s pressure equalization valve opened up in orbit. (It’s supposed to open while the capsule descends under parachute.) They were all dead well before that.
From astronautix.com:
“The crew have haemorrhages in their brains, blood in their lungs, and nitrogen in their blood. The flight recorder shows that four seconds after the depressurisation began Dobrovolsky’s breathing rate went to 48/minute (normally 16/minute), asphyxiation began, and 20 to 30 seconds later he was dead.”
It is worth mentioning that this was not an explosive decompression — the spacecraft was decompressing relatively slowly through a valve, such that the flight recorder even captured the sound of air hissing out near the commander’s seat. Two crewmen even had time to unstrap themselves before losing consciousness. (Not the commander, Dobrovolsky, who was closest to the valve.) They would likely have lost consciousness even faster in an explosive decompression. (It actually took about 210 seconds for the capsule to completely depress, by which time they were all dead.)
It is interesting how often the NASA accidental (and non-fatal) depress is cited, and how rarely the *fatal* Soyuz 11 accident is cited.
posted by Calli Arcale on 9-22-2009 at 11:07 am
Oh, and you can indeed get decompression sickness (aka “the bends”) this way. If you manage to get repressurized in time to avoid death, you may wind up with bubbles of nitrogen in your blood. This depends on what kind of air you were breathing prior to depressurization, though. Soyuz 11 was pressurized to roughly 1 atm with a typical oxygen/nitrogen blend. This is why the cosmonaut’s autopsies showed nitrogen in their blood; the catastrophically low pressure had caused it to come out of solution.
Spacesuits are normally only pressurized to 5PSI (because at 14 PSI, they’d be impossible to bend), using pure oxygen. Spacewalkers have to prebreathe pure oxygen for many hours before to purge nitrogen from their blood so as to avoid getting the bends. If you do a pre-breathe like this, you could avoid getting decompression sickness during a brief decompression.
posted by Calli Arcale on 9-22-2009 at 11:24 am
If you poured near boiling water into one ice tray and cold water into another, which would freeze first?
We had a debate in my college chem class about this… some said the cold in the freezer would shock the hot water and it would freeze first, but others said that the cold water has less heat energy to lose.
posted by Amy on 9-22-2009 at 5:48 pm
Re: the boiling water question,
I’ve heard that cold water boils faster than hot water. I don’t know if that’s true or not, but it might be relevant somehow.
My own question:
What would happen in the astronaut experiment if you were to keep some kind of flow of oxygen – like those things scuba divers use to breathe? How would being in a vacuum affect you if breathing weren’t relevant, basically?
I desperately want to know what it would feel like on one’s skin. Would it feel like you were expanding, since there’s no air pressure?
posted by Tiffani W on 9-22-2009 at 10:14 pm
David, regarding slowing down at the center of the Earth…
No, you would not begin slowing down as you reached the center of the Earth.
The acceleration acting on you would decrease the closer you got to the center. At the center, your acceleration would be zero, but your speed would be very high. The instant you passed the center of the Earth, you’d being slowing.
posted by grover on 9-23-2009 at 3:51 am
I have issue with someone who paraphrases the work of someone else and fails to give a proper citation.
I’m not balking at the science calculations. Rather, the words used to describe and present them.
Dr. Tyson’s NOVA/ScienceNow writers should receive credit for your work.
posted by KIR on 9-25-2009 at 11:35 am
to tell the truth you would keep faling for ever!
posted by Emily95907 on 4-12-2010 at 10:48 am