Infinite freefall

January 16, 2013 10:25 PM

If you were to somehow freefall infinitely – no ground or water below, just air forever – what would you die from?

Would you die from the heat of the air compressing below you? Constant exposure to rushing wind on your skin? Would you somehow last long enough to die of dehydration? Let's assume the air is dense enough for you to breathe.

posted by ethansh to Science & Nature (25 answers total)

I suspect something like hypothermia would get you. I'm guessing that heat from wind at terminal velocity wouldn't do much to counteract the constant withdrawal of heat from your body by the same wind. As well, the ambient temperature, absent the kind of weather that develops at ground level, would likely be above freezing but not much more than that.
posted by fatbird at 10:30 PM on January 16, 2013

I'm gonna guess some combination of dehydration & exposure within a few days.
posted by rhizome at 10:31 PM on January 16, 2013 [1 favorite]

Terminal velocity is around 120mph. Which is no big deal for a few minutes, but non-stop for days and it might start to tear your body up like an old flag.
posted by qxntpqbbbqxl at 10:35 PM on January 16, 2013 [1 favorite]

Dehydration. With no water supply most people end up dead in 5 or 6 days.
posted by Chocolate Pickle at 10:47 PM on January 16, 2013

The wind would increase your insensible losses (of moisture from skin), so the dehydration will happen faster than if you were in a still fall. Hypothermia from inability to maintain body temperature would definitely contribute. I'm not sure which would do you in first, though.
posted by cobaltnine at 10:55 PM on January 16, 2013

After much thought, I think hypothermia would get you long before dehydration. At an ambient air temperature of 50 degrees, free falling (if I trust the above commenters that terminal velocity is around 120mph) will get the windchill down to 35 degrees (I used the formula on this National Weather Service page). Within a couple hours you'd be dead from the cold.
posted by vytae at 10:58 PM on January 16, 2013 [6 favorites]

Depends on the temperature of the surrounding air and the degree of protection afforded by whatever clothing you happened to be wearing, I would think. That said, it's down to a race to kill you between exposure and dehydration. Dehydration will pretty much always kill you within 3-5 days, but exposure can kill much faster than that if you are not adequately protected from your environment. If it wasn't particularly cold and you were wearing enough clothes to protect you from the battering of the wind, then dehydration would kill you in 3-5 days, but since the temperature of the environment is unspecified we can't really say whether you'd die sooner than that or not.
posted by Scientist at 11:00 PM on January 16, 2013 [1 favorite]

I think in some cases, heart attack. Scared shitless free falling for that long.
posted by JohnnyGunn at 11:14 PM on January 16, 2013 [1 favorite]

I'd swear I remember reading something once that claimed that the bodies found on the ground after planes have broken up at high altitude often are missing their clothing because friction from the air at terminal velocity (and spinning or tumbling, I suppose) is enough to strip off street clothes. But since I'm not finding any corroboration in a cursory search, maybe I'm misremembering some morbid joke involving the Mile High Club.
posted by XMLicious at 11:20 PM on January 16, 2013

Stephen Peck, if you believe his fun little novella "A Short Stay in Hell", thinks dehydration is the way you'd go.
posted by lmindful at 11:24 PM on January 16, 2013

This is called being in orbit and you die from lack of oxygen.
posted by three blind mice at 12:48 AM on January 17, 2013 [2 favorites]

xkcd has an interesting conclusion in the article: From what height would you need to drop a steak for it to be cooked when it hit the ground?
posted by flif at 2:52 AM on January 17, 2013 [2 favorites]

I'm going to assume you have enough oxygen through this journey.

Wind chill and hypothermia will depend on what the atmospheric temperature and what you are wearing. The closer your starting temperature is above freezing the more dramatic the effect.

For example, at 120mph and an atmospheric temperature of 20°C, the wind chill effect will be negligible. It brings it down to 18°C. But if the atmospheric temperature is 10°C it comes down to 2°C with wind chill, which can kill you in prolonged periods. If it's 5°C it goes down to -6°C and you're in trouble quickly.

So, wind chill by itself will not kill you unless it is already below about 10°C. Dehydration is the next option. Wind will strip moisture from the skin and taking a drink would be hard. But you're talking a fair amount of time for that to kick in. Depending on how well fitted your clothes are, how covered you are etc you could last days.

The most likely option, IMHO as a non-scientist, is stress on the body. It would be incredibly tiring to maintain a comfortable position and the risk of not doing so is spinning. With no mechanism to stop yourself spinning your heart and circulatory system is going to have problems keeping up, your tongue will be rolling about in your mouth and you will black out and ultimately die.
posted by MuffinMan at 2:56 AM on January 17, 2013 [3 favorites]

"If you were to somehow freefall infinitely – no ground or water below, just air forever – what would you die from?"

Ebullism, combined with hypoxia.

Your question presumes air... which would only exist in an atmosphere, in a state of gravity... which means a large object with mass which you'd eventually crash into.

Since there is no ground or water below, there is no gravity for an atmosphere. Therefore, you'd have to be freefalling in a vacuum. You'd probably have 12 seconds or so of consciousness, before blacking out.
posted by markkraft at 3:49 AM on January 17, 2013

> a large object with mass which you'd eventually crash into.

Ah, but what if you were falling in a stable orbit through a gaseous ring around a neutron star, or oscillating up and down in a tunnel through a planet?
posted by Phssthpok at 5:01 AM on January 17, 2013 [1 favorite]

Your question presumes air... which would only exist in an atmosphere, in a state of gravity... which means a large object with mass which you'd eventually crash into.

Yeah, and I remember doing problems in physics class with massless rope and pullies. You have to accept the hypothetical as it's given.

I think the convection of the air would make hypothermia the most likely cause of death, followed by dehydration.

People talk about stresses on the body from falling but please bear in mind that astronauts in orbit aren't in "zero gravity". They are in free fall. It does not tear their bodies apart or give them heart attacks from being scared.
posted by Tanizaki at 5:48 AM on January 17, 2013

Heart attack. Several of them.
Long before dehydration kicks in.
People get heart attacks in much more controlled "free falls."
posted by Kruger5 at 6:06 AM on January 17, 2013

Dehydration kills in days. Exposure kills in hours. At that wind speed, you'd loose body heat very quickly unless the air temp was near body temperature.

Having been in a free fall (albeit a short one), I didn't have one single heart attack. Also, my street clothes were just fine. But, I wasn't falling for hours.
posted by ghostiger at 6:23 AM on January 17, 2013

Are we also assuming the density of the air remains constant through magic?
posted by dmd at 6:48 AM on January 17, 2013

ghostiger has it. If you're lucky and the air is cold, you'll die of hypothermia. If you're not and it's warm, dehydration will get you in ~3 days. Probably fewer because of the high winds.
posted by Aizkolari at 6:54 AM on January 17, 2013

Your question presumes air... which would only exist in an atmosphere, in a state of gravity... which means a large object with mass which you'd eventually crash into.

Unless you, the air, and the container you both are in are all falling at the same rate, and your horizontal trajectory to the source of gravity is such that you are always the same distance away, in which case you would be in orbit, and you would die of dehydration if you didn't have any water. The longest continuous time in space is 438 days.
posted by ultraviolet catastrophe at 7:07 AM on January 17, 2013

Heart attack or shock.
posted by windykites at 7:52 AM on January 17, 2013

Going into a flat spin could kill you. There's some information on it here.
posted by topoisomerase at 8:28 AM on January 17, 2013

For those of you who can't deal with a hypothetical, why don't you try assuming this experiment is taking place in a vertical wind tunnel, where you can maintain the 120 MPH terminal velocity of freefall indefinitely. According to Wikipedia, skydivers report "the sensation is extremely similar to skydiving" and certainly the physics is the same as what the OP is describing.

Relevant to the question, it appears that the current world record for indoor freefall is just over 3 hours. This video showing part of the attempt might give some clues about what would go wrong if you kept going indefinitely.

Previous world records were about 1.5 hours, 1.75 hours, and 2 hours, so those give you some idea of how long people feel they can maintain this without starting to feel over-exhausted etc.
posted by flug at 9:35 AM on January 17, 2013 [2 favorites]

One practical difference between freefall in skydiving and what the OP is asking about, is that in an un-ending freefall with no parachute involved, one probably could adopt different positions than, for example, the standard stable skydiving freefall position that seems to be the basis of the indoor freefall endurance attempts.

The basic limit to the indoor freefall record attempts seems to be the limit of endurance in maintaining the standard stable freefall position for a long period of time. Possibly a position with the back facing into the wind, something like a fetal or cannonball type position, would be less tiring and allow you to survive longer without becoming exhausted--if you could maintain stability and if the disadvantages of the lower profile, higher windspeed position didn't outweigh the advantages.

Also, here is a related ask.mefi that has some interesting data and information.
posted by flug at 10:01 AM on January 17, 2013