A lack of the strong force obviously would kill you quickly. Presumably instantly. But that isn’t something you are likely to experience or come close to experiencing.
It seems that with heat there is a curve to where it is most deadly. At 0K the air solidifies and all your heat needs to radiate away instead of being conducted away and you’d live for at least several minutes in the vacuum left. But at, say, -100C, would you die quicker?
I hadn’t thought of lack of sleep, but that is another one that does kill, surprisingly.
I’m assuming that if there is a lack of light the vitamin deficiency can be compensated with supplements or possibly even just a normal diet would keep you alive for weeks, months or possibly years.
I was trying to avoid death by trauma incidents in this which is why I didn’t include bleeding out or disease.
Lack of room to move produces suffocation and death in a couple minutes. e.g. soft sand cave-in or attack by large constricting snake.
So if the magic chamber has a stasis field you’re screwed after however long you can hold your breath.
You’re in trouble sooner if the stasis extends inside your skin to prevent blood from moving in your veins. In that case unconsciousness is probably 5 seconds away.
Going further down that rabbit hole, if all molecular motion is stasis-ified, you’re dead instantly. All cellular chemical processes are forcibly halted and you’re also flash-chilled to 0K.
Exactly how your water would react to being at 0K but not allowed to move from a liquid to a solid state is a mystery. Magical boxes induce a lot of mysteries like that.
It’s a pretty well established fact of aviation physiology that below about 0.4 atmospheres, even pure oxygen won’t properly perfuse your lungs. Remember it’s not simply physics here working against an inert semi-permeable membrane; there’s a lot of biology going on too. And we’re operating waay off the design point of alveolar epithelial cells, RBCs, etc.
I spent a few minutes googling unsuccessfully for a good cite, but its true.
The critical measure is partial pressure of oxygen. To a good approximation it doesn’t matter what else is in the air (or not in the air) - what matters is the amount of oxygen in an absolute sense. How many molecules there are per unit volume. This is measured as the partial pressure of a gas. In sea level air the partial pressure of oxygen is 0.21 * 101kPa = 20kPa (or 160mmHg). You will function perfectly so long as this is maintained. That would get you to about 12km - 39,000ft altitude with pure O[sub]2[/sub].
What makes things harder is that oxygen is transported by the haemoglobin in the blood. Haemoglobin does not have a linear adsorption with respect to the pressure - it has a pronounced knee. Which is really why it works. Haemoglobin adsorbs O[sub]2[/sub] when the partial pressure is above about 60mmHg, and loses it when it the pressure drops below. This allows the haemoglobin to adsorb O[sub]2[/sub] from the lungs and to deposit in tissues efficiently. The upshot of this is that there is a very significant knee in the partial pressure of O[sub]2[/sub] that will keep a human alive. Once the partial pressure drops below about 60mmHg you quickly stop adsorbing O[sub]2[/sub]. And your tissues will be unable to take any O[sub]2[/sub] out, even though there is still plenty of bound O[sub]2[/sub]. And you die - quite quickly. Yet only a small rise in partial pressure is needed to keep things working. Humans are perilously close to the edge climbing Everest. This is why measuring O[sub]2[/sub] content of blood in medicine is so critical. Only a small drop in O[sub]2[/sub] levels can signal catastrophic loss of actual O[sub]2[/sub] availability to the body. This is why supplemental oxygen is so popular and useful - even a small rise in O[sub]2[/sub] levels has a major knock on effect because of this knee.
In normal air concentrations you get to this cut-off partial pressure at about 12,000ft. This is why this altitude is a magic number in aviation. A pressurised aircraft must be able to get to this altitude before it runs out of emergency oxygen if there is a pressurisation failure. Above 10,000ft unpressurised aircraft need oxygen.
Not true. A 14.7-psi atmosphere in which the partial pressure of O2 is 3 PSI contains a lot of diluent, which absorbs heat and results in modest peak combustion temperatures. Remove all that diluent and keep the O2 pressure at that same 3 PSI, and you will achieve significantly higher combustion temperatures, causing the fire to propagate much more quickly.
In this case the danger would be the remaining nitrogen dissolved in your blood turning into gas from the sudden pressure drop, causing a severe and possibly fatal case of the bends.
With the nitrogen having only been at a partial pressure of ~11.7 psi before removal, I would not expect a whole lot of N2 dissolved in the blood. If the partial pressure of N2 suddenly drops that much, it’s like SCUBA diving at just 33 feet for an extended length of time and then suddenly swimming up to sea level.
During recreational SCUBA diving, standard practice at the end of the dive is to perform a “safety stop,” in which you hover at a depth of ~20 feet for a few minutes, allowing excessive quantities of N2 to leave your body via your lungs before you ascend that final 20 feet. I would guess that this practice provides a wide margin of safety, and that you could probably ascend from 33 feet (or have all the N2 suddenly removed from a 14.7-psi room) without suffering the bends.
Thanks for your detailed post. Here’s what I don’t understand, though: I’ve been hiking considerably above 12,000 ft all day and, while I can feel it, I’m certainly not running out of oxygen.
Everest base camp is over 16,000 ft, and people rest there for days before attempting the summit. They generally don’t use supplemental oxygen until well over 20,000 ft. That’s significantly above the 12,000 ft. figure you provided.
Regarding the sudden change in pressure alone, I agree that the bends is probably not a major problem. But if whatever is removing the nitrogen from the atmosphere doesn’t also remove it from the air in your lungs and interior spaces, the pressure change is going to be a bitch. All of a sudden, the gas inside you is going to want to take up ~5 times as much volume, which might rupture your alveoli and eardrums. This is why you don’t hold your breath while scuba diving.
Nitrogen in the blood is enough of a concern that astronauts conducting a spacewalk spend some time breathing pure oxygen to purge the nitrogen from their lungs before going from station air (a sea level mix) to space suit air (which is low-pressure oxygen-only mix).
Is NASA doing this for no reason? Obviously they think that nitrogen in the blood is enough of a worry to have a special procedure for purging it before a spacewalk.
NASA is certainly an agency possessed of an abundance of caution. If anything could go wrong, they’ve hopefully got a procedure to prevent it.
The scuba organization PADI has over 100,000 members world-wide, and their guidelines indicate that there’s little risk from going from 2 atmospheres to 1 atmosphere in terms of dissolved nitrogen, which is the same reduction in this case. Now, I’m sure a few people are still injured while following those guidelines, but I doubt the incidence is very high or they’d change the guidelines.
What Francis Vaughn was saying is that at about 12,000 ft the decrement in performance from reduction in oxygen perfusion gets significant enough that the FAA’s idea of safety requires countermeasures. It’s not like at 12,001 ft everybody drops dead instantly.
Oxygen perfusion *tries *to declines any time you’re above sea level. For the first few thousand feet a typical healthy person has enough excess lung capacity to offset this by simply breathing deeper and faster. As you climb, eventually that coping strategy runs out of headroom. From that point upwards, actual perfusion declines. At first it manifests as being short of breath, or low on stamina. But brain function seems mostly unaffected.
Eventually as you climb higher, brain function starts to decline too. That’s around 10,000 to 12,000 feet for typical folks and 12-14,000 for unusually healthy athletic folks. Most folks don’t notice their own degree of impairment until it gets real big.
Artificially boosting the partial pressure of oxygen in the lungs with free-breathing supplemental oxygen is a coping strategy that works fine from that point upwards. The higher you go the more extra oxygen it takes. But you can, in principle, completely offset the effects of altitude by breathing a rich enough mixture. More typically climbers actually breath a less-rich compromise mixture. This reduces, but does not eliminate the effects of altitude.
Eventually, at around 25,000 feet, even breathing pure oxygen at ambient pressure will begin to produce perfusion below normal sea level 100% levels. And again performance will start to decline again as you go higher, even breathing 100% oxygen from a full-face mask.
The solution above there is pressure breathing, where oxygen is mechanically rammed into the lungs at greater than ambient pressure.
That solution runs out of capacity around 55,000 ft. Above there we can’t stuff the oxygen in hard enough to perfuse even adequately, much less fully, without risking bursting alveoli. That’s the point where pressure suits become essential to survival. It’s not a matter of “blood boiling” or people bursting. It’s a matter of oxygen perfusion.
We, and real experts, can certainly bicker about which specific altitudes to use for the various cutoffs. The atmosphere’s pressure declines continuously at a fully predictable rate. Conversely, the exact physiological response of any given human varies from minute to minute much less as measured across a whole population across years. So the regulatory cutoffs and the rules of thumb practitioners use are to some extent arbitrary. But they’re not just anally extracted; there’s real science and real experimental backup behind them.
LSLGuy covers it nicely.
12,000ft is the point above which you start to become impaired - and you can’t be trusted to pilot a plane. The trouble with hypoxia is that you don’t feel like you are running out of oxygen, actually you feel fine. Euphoric even when it gets worse. But you make bad decisions. This is why you must descend to 12,000 before the oxygen runs out. The danger isn’t that you die, but that you make it to say 16,000 and run out of oxygen. Then you start to make poor choices, like - “hmmm, this seems OK really, perhaps we should be OK to keep going as we are.”
18,000ft and you are dropping off the curve and things are going to get grim. The steepness of the curve from OK to really bad is frightening.
The body can acclimatise, and can stand longer at high altitudes, but you need at least a week. Hence 16,000 is probably a good location for Everest’s base camp. You will be operating well under par - and it will show - but you are not going to die. Time spent there will enable you to function better at higher altitudes. As LSLGuy notes - these are average numbers, and the exact numbers for the haemoglobin functions is dependant upon a range of factors determined by blood chemistry. But nobody is functioning well on Everest, and people die with monotonous regularity.
Thanks again for the detailed explanations. I am still surprised that the altitude limits are as low as they are. There are hundreds of thousands of people who live above 12,000 ft. I wonder if there have been studies done on their mental capacity that show this effect.
Next time I go to altitude I’m definitely going to try some cognitive tests there and at sea-level.
Long term people living at high altitudes adapt to some extent. Higher red blood cell numbers are the big one. So they make up for the poorer transportation of oxygen with more haemoglobin. Down-side is that blood is thicker, and that carries with it a raft of issues.
This brings with it the question of athletes training at high altitudes (or reduced partial pressure of oxygen through other means). With some idea that they get a form of natural blood doping.
This site is devoted to the topic of high altitude medicine, and has some interesting tools to allow you to see the effects.
I don’t get this chamber. A chamber that is completely absent of water means that if there’s a person inside it, then she’s a mummy. No heat and he is a Popsicle. No oxygen, and a bunch of crazy chemical reactions are going to happen once all the oxygen compounds in your body suddenly lose their oxygen atoms (all the H2O becomes just H for example)