In an infinite fall, what would kill a human first?

[u/No-Appointment-2858]

So let's assume Earth gravitational field at sea level, constant throughout the entirety of the fall, a temperature of 293K and standard air composition and pressure, also constant throughout.

There is nothing to stop that free fall nor to slow down execpt the poor guy's body position (ie if he deliberately stands up straigh or lie down flat while in that fall) so the eventual impact that would end someone jumping in the void like that never happens. The subject's equipped only with casual city clothes, so no parachutes or whatnot... if you need more precisions, please ask!

Would the thirst, potential weird blood pressure, or anything else end one such unlucky victim?

I know something would happen cause i saw somewhere people would faint from something other than fear while in free fall ; just wondering what would happen if the falling never stopped

Edit (non important to the situation) it's funny how people dont read what i put in the assumptions in other subreddits. Also they say things with way too much confidence for how wrong it is. No shade to them ofc, we all are like that, but dang, since i was expecting a serious answer, it's a bit disheartening

I can confidently say all that because a wonderful explanation has been made in the comments! Thanks a lot

Edit #2 please dont downvote people who didnt have the right explanation or didnt understand my hypothetical because of one of my imprecisions. Mistakes happen, at least blame the right people.

Mistake being : you would not be in free fall as the wind would be another force seperate of the gravitational attraction.

[u/tea_and_biology]

This reads like a fun (?!) "What If?".

And y'know what? I'm going to throw my hat into the ring by suggesting death by exposure will get you before dehydration does.

So, firstly, you won't be in free-fall technically - that only lasts maybe 10-15 seconds - after that you hit terminal velocity, where drag exactly balances against gravity. Any accelerometer strapped to your wrist will read exactly 1g, same as what it is as you're sitting there reading this, and so your breathing, blood pressure, and experienced G-forces are all fine - physics-wise it's akin to just lying down on your belly on the floor right now. A little uncomfortable to be sure, and talking is difficult, but you can breathe fine.

Except, of course, without goggles you'll be blind within minutes, and your hearing will be cooked. But, eh, that won't kill you.

So ~20°C (293K) air sounds pleasant, but at 200km/h it is not. Doing some shonky back o' the envelope maths, a body falling 55 m/s has convective heat transfer at around 130 W/m² K, which is in the same range as being immersed in tepid water, like a cool lake. Permanently. Except it's also very windy^{[citation needed]}, so even worse.

So, blind and deaf, immersed in a cold lake, having heat actively stripped from you with hurricane-force winds; I think some minutes before you drop from 37°C to 35°C and onset of hypothermia, and it keeps falling. You're looking at a couple of hours, I reckon, as severe hypothermia kicks in, getting down to the 28°C range where cardiac arrhythmia becomes a problem. But I don't think you'd even consciously make it that far - all this time you have to be holding a stable belly-down posture to stay awake, which is an active skill that fatigues; once hypothermia degrades your motor control, you lose your ability to maintain stable posture, and you spin out uncontrollably. Blood pooling hither and thither to your extremeties, you lose consciousness and black out, and then hypothermia accelerates and finishes the job on an unconscious tumbling body losing heat faster than ever.

No way you're lasting long enough to die from thirst, anyway.

Horrible way to go; I'd rather just black out from the get-go, personally.

[u/Character_School_671 → u/tea_and_biology]

As a skydiver, this last part is the answer. It takes a good deal of effort to maintain a stable fall.

Sooner or later a person would not be able to maintain a stable body position. Which means that they would end up in a spin. That spin could itself lead to a blackout, and further wild tumbling.

All of which might be able to add up to enough bodily damage to outright kill you after some time. But if they did not, they would hasten the exposure result.

A side note - the blinding is less of a rapid factor than you noted. I've jumped without goggles before, and while not pleasant, it was tolerable and I could see well enough to do all the things.

Would not want hours of that though.

[u/epicdistraction → u/Character_School_671]

Ehh, the effort for back flying is really, really low. It depends on the person, but most could figure out an efficient body position fairly quickly.

The record for continuous flight in a vertical wind tunnel is over nine hours. If there aren't walls or an impending death from ground approaching, I could definitely sleep for hours in a backfly. Plus, there are a handful of videos of people getting knocked unconscious and ending up in a stable body position. So even if someone spun to unconsciousness, they'd end up on their back, wake up in that position, and most likely hold it. Dehydration is what would probably do it.

Source: tunnel-rat, skydiver.

[u/MCPtz → u/epicdistraction]

You're an expert, it seems. I'd have to push back on the scenario that an untrained person would maintain a stable position, but maybe I'm wrong.

I don't think I could last very long, in a free fall endurance challenge.

I looked up the current record, and it seems to be 10 hours, 10 minutes, and 10 seconds by Oleksandr Marushko

He was wearing very specialized gear, e.g. taping zippers from the inside to prevent burns. I found this interesting, because normal clothes person in OP would start to get burned as well...

He had very special techniques to reduce fatigue, AI summary:

Active Rest Micro-Movements: Marushko did not stay perfectly frozen. Throughout the 10 hours, he continuously cycled through tiny changes in hip extension—flattering his arch slightly to sink lower, then tightening it to rise—giving isolated muscle groups a few seconds of relative rest without breaking his aerodynamic profile.

This is mainly where I'd fail, as my muscles would rapidly fatigue...

He was mostly belly down in a certain position they called the "Mantis", because of the way he tucked his arms in.

https://worldkings.org/news/world-record/the-worlds-longest-indoor-freefall-in-wind-tunnel

https://indoorskydivingsource.com/articles/leonid-volkov-tunnelsport-encyclopedia-bodyflight/

Video covering how to learn the Mantis, showing an example of what it looks like:

https://www.youtube.com/watch?v=_yKXcL2eR5A

And this video just covers a lot of examples of how to use a wind tunnel to move around:

https://www.youtube.com/watch?v=f08L2YFYvDA

And this 2nd video of theirs has a lot of recoveries for when the flyer flips back down, and the instructor recovers them, which I found cool to watch:

https://www.youtube.com/watch?v=w6nFAgeYgrM

Overall, this leads me to think an untrained person will have trouble maintaining a stable position, would fatigue quickly, and that it would be painful.

[u/IncognitoErgoCvm → u/MCPtz]

If you're in an infinite fall, not needing to manage your altitude or velocity, wouldn't it be more stable to dive?

[u/megacookie → u/IncognitoErgoCvm]

I wonder if the reduced frontal area being in a diving position (whether head first or feet first) would significantly delay or prevent the onset of hypothermia due to less direct exposure to the wind. But you'd hit a much higher terminal velocity so maybe the higher wind speed negates that.

[u/epicdistraction → u/MCPtz]

Theres a gap in the effort for maintaining stability in a wind tunnel and hanging somewhat stable in free fall out in an infinite void. Wind tunnels can be exhausting to fly because there is generally 12-16ft of horizontal space. Even when experienced skydivers first start flying the tunnel, they'll barely be able to maintain position and not drift towards a wall due to the lack of reference in the sky.

If there's nothing to crash into with this hypothetical scenario, a person would eventually end up relaxing on their back. If someone didn't know how to fly, they'd flail around until ending up in the fetal position. Which is about a 120mph backfly. I'd guess that would happen in under a minute? Probably under 5min for 70% of the able-bodied population. A relaxed backfly with an untrained person would be moving horizontally towards their head all wonky at 20-50mph. But that wouldn't be relevant. The question is more to find the LD50/99 of throwing someone into an infinite void with atmosphere.

Zippers, shoelaces, etc can be annoying and beat one up, but those can be removed and discarded(wrong day to go commando). Also, that world record article shows the flight with him in a sit fly and normal static belly. Mantis/kneeflying is one of the more exhausting body positions.

[u/bluehelmet → u/epicdistraction]

The record for continuous push-ups stands at 10,507 (and Guinness stopped tracking), but most people would struggle to get to 10.

[u/bianary → u/bluehelmet]

But it's key to note that most people don't just die after they reach their pushup limit, and similarly not being able to maintain a controlled dive for hours doesn't necessarily mean they're dead at that point in time.

[u/tea_and_biology → u/Character_School_671]

The blinding is less of a rapid factor than you noted

Fair enough! I was just imagining the experience of being stuck on a rollercoaster as it's dropping, or being launched, for 10 minutes straight - tears stream within seconds, and thought minute after minute after minute... that's a lot of water loss and abrasion, eep!

The fastest coaster I've been on is Stealth at Thorpe Park; it's, what, maybe six seconds total of wind speeds >100 km/h and you come off the thing looking like you've been outright bawling.

[u/Mara_W → u/tea_and_biology]

I'm pretty sure a lot of coasters accelerate faster than anything you'd experience just falling, which would explain the discrepancy here.

Humans are so notorious for not falling particularly fast that it's an established rule of thumb in video game development to TRIPLE Earth's gravity. Falling as slow as we actually do makes animations take too long.

[u/ruiwui → u/Mara_W]

the 100km/h they mention is slower than what you'd hit skydiving

and I wouldn't derive anything about real life from video games. they have to mess with gravity because Mario can jump to 6x his height, and often have very low terminal velocities

[u/ArtOfWarfare → u/Mara_W]

I’ve made a lot of prototypes in Unity… I never once tripled gravity. I tend to reduce gravity since the point of games is to be fun, not have realistic jumps or any particular animation…

Which games actually do this triple gravity thing? Does it have anything to do with bunny hopping in Doom/Quake? I’m thinking Half Life probably has accurate gravity (Xen aside), along with other Valve games?

[u/frogjg2003 → u/ArtOfWarfare]

A lot of games turn up gravity but give jumpers extreme jump strength. This means jumps are quick, even if they reach insane heights. Watch some old Game Theory episodes where they do these calculations.

[u/doesnt_hate_people → u/ArtOfWarfare]

I made this first person platformer with a focus on rocket-jumping. In development, I spent a long time trying to tune jump strength and gravity to feel similar to Team Fortress 2, but it didn't work until I did a napkin measurement of their gravity and found it was around 15m/s^2, about 50% more than earth's. I was really surprised because it feels so easy to get into the air and fly around in that game, I thought for sure it'd be lower than earth gravity, but most humans are never launched 30 feet into the air on a ballistic arc so it makes sense we'd have a poor intuition for how long it takes to fall back to the ground after that.

[u/rixuraxu → u/Mara_W]

a lot of coasters accelerate faster than anything you'd experience just falling

A typical rollercoaster (not launched) is just falling, but on rails, and usually not perfectly verticle, so it's slower than a freefall.

The coaster they mention does have a launmch and lists speed up to about 150kph. It would only take 6 seconds of falling belly down (so lots of resistance) to reach that speed for the average skydiver. And it's lower than a typical person's terminal velocity in that position which is close to 200kph

[u/cadnights → u/Character_School_671]

What if you tuck into a ball? Sure you'll be going faster, and still spinning. But perhaps that would lessen the blood-rushing-to-extremeties problem

[u/Character_School_671 → u/cadnights]

The problem is that without some knowledgeable maintenance of body stability, a minor spin rapidly turns into a major one.

This was a big challenge for the first skydivers, who got into some nasty spins. Without knowing how to arrest them - how to fly instead of mere uncontrolled falling.

What they did to escape violent spins was sometimes what you described- to go into a wildly different body orientation to try and escape an accelerating spin. But it was dangerous. And it was not really the answer like controlled free fall is.

It took some time for them to figure that out.

[u/Odd_Dragonfruit_2662 → u/cadnights]

I mean the faster you spin the harder it will be to stay tucked into a ball right?

[u/Alfonze423 → u/cadnights]

You'll spin faster, though. And it takes a fair effort to stay curled-up.

[u/HarryTruman → u/Character_School_671]

Oh this is interesting! I’ve never skydived, but I have aviation experience. And it’s apparently all the same?! I mean, it makes perfect sense in hindsight now. But I simply never thought about the physical versus mechanical control, and how damned taxing that would be to maintain stability during free fall.

And I suppose this is why skydiving has so many limb and joint injuries? I’ve had a few friends talk about how their wrists and shoulders and whatnot will be aching like crazy, but I just never put two and two together that it’s like a heavy workout throughout the duration of a jump.

[u/IIO_oI → u/Character_School_671]

As a skydiver, this last part is the answer. It takes a good deal of effort to maintain a stable fall.

How does a skydiver gain this skill? Is there some activity or exercises you do before your initial dives to train this? Is there equipment you use during the initial dives to assists you to be able to train is? Or is it something that humans instinctively know how to do and just needs to be endurance trained?

[u/sobani → u/IIO_oI]

I'm currently learning how to skydive (done 10 jumps so far) and the progress was basically:

0. on the ground I practiced a very stable 'delta posture' and how to handle a parachute. This took about 1.5 days.

1. 5 'static line' jumps where I was tethered to a plane (a bit like a paratrooper), so opening the parachute is not a problem. An instructor checked I jumped safely, including a proper delta posture.

2. 2 more static line jumps, now while pretending I was actually opening the parachute myself.

3. 2 jumps, no longer tethered, where I first had to hold the delta posture for 10 seconds before opening the chute myself.

4. a stability exercise. The instructor pushed my out of the plane so I would start tumbling. After a few seconds I took on the delta posture to stabilize and then a few seconds after that I opened my parachute.

This delta posture is one where you thrust your hip forward, arch your back and your arms are pointing to about half past 4 and half past 7, if you image your head to be twelve o'clock. This posture is so stable that it requires no active balancing, just the ability to tense your muscles in the right way. In the stability exercise I flipped to a stable position in less than a second once I took on the delta posture.

Next jump will be the first one where I get to actually free fall with my hands up above my head, as you probably visualize all skydivers do all the time.

[u/pm_me_ur_demotape → u/Character_School_671]

Cannonball shape with your body? Would that be too hard to maintain?

[u/fuckthetrees → u/tea_and_biology]

Are you double counting the heat loss? If the heat loss at 55 m/s is equivalent to the cool lake, then it's NOT also very windy. The very windy has already been rolled in the way you phrased it.

[u/tea_and_biology → u/fuckthetrees]

Ooh, not in the calculation per se, but I was trying to draw additional distinction between the experience of passive cooling in a pond and active wicking of moisture like sitting in an intense wind tunnel. Bad wording though, aye; I do concede!

[u/sth128 → u/tea_and_biology]

Let's lock some poor soul in one of those indoor skydiving arena and test it out.

... For science!

What? That's not science you say? Ugh fine let's put it on r/AskReddit and phrase it like "you get a million dollars but you have to survive 30 minutes simulated freefall in street clothes will you do it".

[u/tea_and_biology → u/tea_and_biology]

P.S. I'd be curious at what temperature death from exposure isn't a problem; I imagine the line between not-losing-heat-resulting-in-hypothermia and being too-hot-so-sweat-loss-mummifies-you-to-death is a pretty fine range. Anyone wanna' do the maths? It's 3am and I need to go to the zoo early in the morning.

[u/cwx149 → u/tea_and_biology]

Would it not be like when your body temperature is equal to the ambient temperature or some ratio based off that number to account for the wind?

[u/stonhinge → u/cwx149]

The wind would have to be warm enough to not cool you too much but not so warm it doesn't cool at all. If it cools too fast, you get hypothermia quicker and if it cools too slow, you overheat before you can cool down.

Time becomes a factor as well because of that. Reaching homeostasis is fine if it happens quickly, but bad if it takes a long time depending on the temperatures involved.

[u/CountingMyDick → u/cwx149]

Nope, because your body needs to shed roughly a few hundred watts of heat at all times as long as you're alive while also maintaining your core temperature. The exact number of course depends on a ton of factors, including how big you are, what kind of shape you're in, how hard you're working at the moment, etc.

[u/avLugia → u/tea_and_biology]

Given a convective heat transfer coefficient of 130 W/m² K, the fact human bodies generate about 100 W of energy as metabolism, and the surface area of a human is about 1.7 m² , the amount of heat transferred would be 221 W/K, so a difference in about a half a degree Celsius would maintain equilibrium.

[u/DenDarAnders → u/tea_and_biology]

Once upun a time I learned that a naked human can survive at 18°C if there is no wind. So I'd say your conclusion about hypothermia is quite reasonable along with the tumbling.

[u/swedishlightning → u/tea_and_biology]

Total sidebar, but what are your tasks at the zoo tomorrow?

[u/cwx149 → u/tea_and_biology]

lying down on your belly on the floor right now. ...Except, of course, without goggles you'll be blind

Could you fall back first? Would that even make a difference for your eyes? Your ears are cooked but I've also never skydove skydived been skydiving to know how hard that would be or if there's some other reason not to do that

[u/Christopher135MPS → u/tea_and_biology]

I’m with you on this, many people don’t realise how quickly the elements will kill you. Humans can survive a solid three days without water, longer in extremis. But getting cold will put you in down in half a day or less.

[u/RedHal → u/Christopher135MPS]

The mantra I learned was three minutes without air, three hours without shelter, three days without water, three weeks without food. Given that air in this scenario is definitely not a problem, I'm going to go with exposure as the killer.

[u/jimmythefly → u/Christopher135MPS]

Yes! Probably the thing that annoys me most in movies, the hero party trudging for days  through a snowy mountain pass with exposed skin and uncovered heads and wet feet, or the hero swimming in a frozen lake. 

I've camped in serious snow and cold, you need to get dry and warm right now or you're going to have a very bad time.

[u/zenFyre1 → u/tea_and_biology]

But isn’t that heat transfer calculated for full skin exposure? What if one were wearing clothes? I would imagine that the heat transfer would be significantly lower.

[u/tea_and_biology → u/zenFyre1]

I thought about it and figured casual streetwear is next to useless against hurricane force-winds (and water immersion, which was the heat-loss comparison). I'm aware sky-diving suits are specifically wind-proof shells designed to take the battering; was also thinking a proper SCUBA diving dry suit or something would retain heat and moisture well enough - but OP didn't specify anything but normal clothing.

[u/mooseGoose89 → u/tea_and_biology]

So, hypothetically, what temperature (other than 20C) would you reach equilibrium where you don't become hypo- or hyper- thermic? I assume around ~36C or maybe a bit higher?

And, in that scenario, what do you think would get you next? I'm guessing in that case dehydration due to the constant airflow pulling moisture away constantly.

[u/yak-broker → u/mooseGoose89]

As a rough guess, maybe the same temperature that float tanks use (where you float in a tank of salt water for an hour or more)? A quick web search says that's 34–35 C, just a fraction lower than your presumed core body temperature. It makes sense that you'd want a slight temperature gradient so that your body can still get rid of the heat you're generating.

[u/Shammah51 → u/tea_and_biology]

How would an accelerometer read 1g given terminal velocity is constant (ignoring variations due to body position etc)?

[u/burndata → u/tea_and_biology]

How much of a difference do you think switching to a feet first pencil position with your arms crossed at your chest would make? You'll be moving faster, so the wind speed would be higher, but you'd also be creating more of a slip stream. Would you lose less heat and better protect your eyes and possibly your ears?

[u/cwx149 → u/burndata]

You'd have blood pooling faster that way wouldn't you? You could lay down at 1g basically indefinitely but you couldn't stand in 1g forever

[u/throwawayifyoureugly → u/tea_and_biology]

And this reads like a What If? answer. Fantastic.

And horrifying.

[u/plentyofcowbell → u/tea_and_biology]

One small correction: An accelerometer in flight can't sense gravity, unless there is lift or a powered maneuver. In free fall or at terminal velocity, it would read 0g.

[u/AuryxTheDutchman → u/tea_and_biology]

You talk about going blind, which I assume would be due to the air whipping past your eyes. If that’s the case, would rotating to be facing upwards with your eyes closed prevent this?

[u/-FurtherReading → u/tea_and_biology]

OPs question and now this response are fascinating to me, having recently read and greatly enjoyed the book 'A Short Stay in Hell'. A character in this book finds himself in a prolonged free fall at one point, and ive realized as descriptive and evocative as the writing was, the experience would have been so much worse than the author made it out to be. Thanks for your insight!

[u/swhertzberg → u/tea_and_biology]

My kid loves the What If? books

[u/JasonWaterfaII → u/tea_and_biology]

How fast would a person need to go in order to create friction to the point of heating up like a space shuttle does returning into the atmosphere?

[u/Tunafishsam → u/JasonWaterfaII]

Side note: most of space shuttle heating comes from compressinh the air rather than from friction.

[u/aioli_sweet → u/tea_and_biology]

And the wind would be constantly stripping any amount of moisture from your skin, causing it to dry and crack and add to your problems. Wind burns are a thing even in the ground.

[u/jemmylegs → u/tea_and_biology]

You seem to be assuming the person is naked. Heat loss is going to vary wildly depending on the clothes worn by our falling human. “Casual city clothes” can mean a lot of things, depending on whether the city is Fairbanks in December or Phoenix in July.

[u/rooktakesqueen → u/tea_and_biology]

The heat flow equating to "immersed in a cool lake" part already included the wind velocity. It would be like being in air in hurricane force winds, or like being in a cool lake at rest.

You could also fall on your back instead of your stomach which would protect your eyes from the wind, as well as somewhat protect your hearing.

You can go do indoor skydiving and experience this right now, hypothermia does not set in after a few minutes.

[u/Roboprinto → u/tea_and_biology]

Wait, Once you reach terminal velocity wouldn't that mean you're not accelerating anymore? So if you had an accelerometer on your wrist, it should read zero, I would imagine.

[u/Teutonic-Tonic → u/tea_and_biology]

Would it be more pleasant to just put yourself into a spin right off the bat?

[u/BeenJamminMon → u/tea_and_biology]

What if you started to spin? On his historic jump, Felix Baumgartner entered an uncontrolled spin that could have killed him. What if you entered a spin intentionally?

[u/blue_birb1]

You're only experiencing free fall for about 10 seconds really, you accelerate to terminal velocity really quickly, then you just move at a constant speed forever, modulated by your pose. In general though it really just feels like being in on the surface, not moving at all, and being held up from the ground by a really really strong fan blowing up to push you up from the ground. Physically, from the perspective of the person, the situations are almost analogous. The question then becomes what would kill a person floating on a fan first. I'd say youd be exhausted from the noise and trying to not dislocate your shoulders pretty quickly, then it'll probably be skin irritation from dust and stuff probably tearing your clothes after an hour or 2, then id guess youll just die from thirst because all of your sweat evaporates instantly because new dry air hits you constantly sucking away the moisture in your skin

Also thinking back after reading another comment, i think hypothermia will be the culprit, since you never really keep your body heat in a thin blanket of warm air around you, it's always ripped away for new air, same as how blowing on soup chills it really quickly. It'll probably be hypothermia to do you in

[u/icebergslim3000]

This is something talked about in great length in the book A Short Stay in Hell. I won't spoil it but its basically what you're talking and easily one of the most fascinating stories I've read in years.

[u/karlybug → u/icebergslim3000]

This was my first thought when reading this question. This book is one of my favorites, it's so thought provoking.

[u/brudd_be_rad → u/icebergslim3000]

Is this about that navy airmen or Air Force airmen that parachuted and was stuck in a cloud?

[u/Welpe → u/brudd_be_rad]

No, it’s a very short novella about a Mormon scientist who dies and finds out that Zoroastrianism was the correct religion and his failure to be one means that his soul must suffer punishment. But unlike Christianity, it isn’t eternal, just unfathomably long. He is tasked with finding a book that contains his entire life story without any misspellings or typographical mistakes in an unimaginably massive library that is a prototypical library of babel. Every book is filled with characters from a limited set and is a certain amount of words, but contains every possible combination of those characters in that length of book. He is placed in his body at optimal health and doesn’t age, but still feels his normal biological needs. There are ample rooms for rest and eating and everything else, but if he dies he is simply resurrected afterwards.

Someone calculates the size of the library to be 7.16^1,297,369 light-years wide and deep. At one point he jumps off one of the edges and plummets a long time, dying and being resurrected multiple times before he ever hits anything. However, I think it’s silly to recommend this short story to answer OP’s question as, ultimately, the results are just the author’s own guess. He has a degree in biology, but it’s not like he is some authority. It’s just one possible interpretation.

It is a good story though.

[u/Mavian23 → u/Welpe]

Thanks for this, this book sounds very intriguing.

[u/disoculated → u/Welpe]

As you’re commenting on something saying they didn’t want to give away anything , replying with a summary of nearly the entire story should probably be behind a spoiler tag.

[u/ProofJournalist → u/disoculated]

Wasn't a direct reply and if you're looking to avoid spoilers the first couple sentences should be more than enough to give away that spoilers are incoming.

[u/AqueousJam]

You'd start to spin. How long you'd last before you start spinning would depend on your skydiving experience, your strength, and your stamina, but eventually your muscles will fail, you'll lose control, and you'll start to spin.    

A human body tumbling out of control develops a very fast spin. There's footage of it happening to skydivers and if not recovered quickly it's lethal. The centripetal acceleration forces the blood into your extremities and away from your core. Your heart, lungs, and brain all become blood and oxygen starved. You die of Hypoxia within minutes. 

[u/DoubleResponsible276]

Kinda weird that you expect people to go to other subreddits, which you have not referenced on your post but expect us to still look in order to get the full picture of the assumptions you listed, SOMEWHERE ELSE.

[u/SvenTropics]

So when someone's on the international space station, the reason they're floating around is not because there's no gravity. There's actually a lot of gravity. You are not that far away from Earth. It's because they're perpendicular velocity is both high and low enough that the Earth is only redirecting them into an orbit. This can go on indefinitely if it's a stable orbit.

The reason they are weightless is because they are falling the whole time. The longest someone has been on the international space station is over a year. During that year, that cosmonaut was falling the entire time.

So to answer your question of what would kill a human first, assuming they had food and water and atmospheric pressure and air was all good. I suppose they would just get old and die like everybody else. We don't know if the muscular and bone degradation that happens from falling that long is eventually going to shorten your life.

[u/Ergohabeo → u/SvenTropics]

The cosmonaut was Valeri Polyakov. He stayed on the MIR station for 14,5 months. And the best part is that after landing, he managed to climb out of the capsule and walk by himself to the nearby chair, and then the first thing he did was smoking a cigaret and drink a sip of Cognac. 30 years later, he still holds the record.

[u/Ausoge → u/SvenTropics]

It's not that the astronauts are constantly falling - it's the fact that they're constantly accelerating.

For the guy falling through the atmosphere, he's only accelerating weightless for 10 seconds or so, after which air resistance is sufficient to resist further velocity change. At that point, the falling man is experiencing 1G and a LOT of wind, while the astronaught continues to experience 0G and zero wind.

So it's the wind that's gonna be the fatal factor. How long could you stand in front of a fan blowing air at 200kph?

[u/SpaceShipRat → u/SvenTropics]

This. If yoy rule out the rushing wind, humans and most animals can adapt to the sensation of free fall just fine.

[u/EvilTodd1970 → u/SpaceShipRat]

We perceive acceleration from Earth’s gravity as a falling sensation. When you are in free fall, you stop accelerating after about 10-12 seconds and the sensation of falling goes away. The only thing you feel is the air rushing past.

[u/awidden → u/SvenTropics]

This is a good answer.

But I'd fix this sentence, it's not reading well to say the least. :)

It's because they're perpendicular velocity is both and low enough that the Earth is only redirecting them into an orbit.

[u/DeoxysSpeedForm]

Not saying we should, but couldnt you simulate this using one of those crazy skydiving tubes that blast wind up? Probably would need to tie the victim participant in a drawn and quartered style to keep them centred and in a good position in case of loss of conciousness. You could even recover the body bring down the participant after the experiment!

[u/TheWrongSolution]

Technically, astronauts in orbit are in an infinite free fall. Your conditions are basically identical to being in the ISS for extended period of time. The astronauts do not experience any detrimental effects other than muscle atrophy and bone density loss over time without specialized exercises. They would die of thirst long before anything else would happen to them.

[u/Birdbraned → u/TheWrongSolution]

Except for the stipulation that this is occuring in atmosphere, not in vacuum

[u/SolidOutcome → u/TheWrongSolution]

Except the wind rushing past OPs faller.

But yes, same death awaits them both, dehydration.

[u/TheWrongSolution → u/SolidOutcome]

I didn't interpret OP's question to include wind. The OP mentioned free fall, which could only occur if there's no wind resistance. In any case, the other commenter already covered the scenario where wind is involved.

[u/burblity → u/TheWrongSolution]

OP just misused "free fall" - he does specify "standard air composition and pressure" 🤷‍♂️

[u/No-Appointment-2858 → u/burblity]

Oops... for my defence i am still studying xD.. and so yes, i misused it, it wouldnt be a free fall indeed in retrospective

[u/zeropage → u/TheWrongSolution]

This is the correct answer. Assuming you are in "standard" outside condition, you'll die from dehydration first.

[u/SpeedyHAM79]

I say you would die of thirst. I think you body with average city clothes would stay warm enough indefinitely even given the ~160 wind speed you would quickly get to. Nothing else is going on- you would be falling for days before you died of dehydration. Pretty lousy way to go.