How much air pressure could a human survive in?
I believe that is dependent upon how long s/he has to acclimatize to the environment. You could slowly increase the pressure to 10,000 psi, and the guy will probably not suffer any (since the pressure within his body will rise equivalently with the outside air). Offer him 10,000 psi via a stick of dynamite, however, and his bodily response will be significantly less comfortable.
And do you intend to have this person breathing air? A person can withstand perhaps 100 atmospheres of pressure if they aren't breathing air - divers do it. If they are breathing air, the limit is just a handful of atmospheres. Not sure exactly how many it takes before oxygen becomes toxic, though.
I know that you cannot breath if you are under half a meter of water. I mean you cannot use a snorkel because of the pressure on your lungs.
As Russ pointed out, divers are exposed to significant pressures. In fact, the main problem from a certain pressure onward is the toxicity or other unwanted biochemical effects of the breathing gasses, not the "mechanical" pressure itself. For instance, normal air becomes problematic beyond the 7 or 8 bars (although you can go to 15 bars if you're of the reckless kind). But that's because of nitrogen toxicity and oxygen toxicity, not because of the "pressure". If you adapt the breathing mixture (with helium), you can go to much higher pressures. There have been experiments with breathing liquids and then you can go to very high pressures indeed.
Man, I'd forgotten about that. I haven't heard anything about it since the early 70's. Now I remember seeing that little rat playing around in the bottom of a tank full of super-oxygenated water. Didn't they at some point have even better results using some sort of fluorocarbon liquid in lieu of water?
And there's one technique, which as far as I know is still rated 'Top Secret' by the US government (as if I care), wherein pilots of high-performance aeroplanes saturate their bodies with xenon gas, then have the cockpit filled with the stuff. It supposedly lets one remain functional up to about 30 g's. I incorporated that into my SF novel over 25 years ago.
So can people breath in liquid oxygen? I mean apart from the fact it is cold, would it be possible?
No. First off, as you mentioned, it is cold. One's respiratory tract and lungs would freeze solid. It would have to be evaporated first. Additionally, pure oxygen is deadly poisonous.
Russ and Vanesch are both right. There are two problems: one is that at high enough partial pressure the N2 in air becomes toxic, and the other is that under these pressures air becomes heavier and just from mechanics breathing becomes very hard work. One can address these by going to heliox: a helium-oxygen mix, and the record is somewhere around 30 atmospheres.
You have not shared this with us. Still have signed editions?
On recreational diving oxygen is considered toxic beyond partial pressure of 1.6bar (~67m dive on air) and Nitrogen is starting to become toxic beyond partial pressure of 3.2bar (~ 30m dive on air). If one wants to go much deeper then that he have to use mixtures with lower % of Oxygen then air, lower % of Nitrogen then air and Helium. As far as I remember the world record for "dry" diving (inside a recompression chamber) is around 700meters (~70bars).
It works for rats because they can't choke (or vomit). You can't o it so easily in primates unless they are anesthetized because of the gag reflex.
The main practical problem for larger animals is that the carrier liquid contains such low concentrations of oxygen that you have to flow a huge volume through the lungs to get enough oxygen transferred - I forget the figures but it's something like a fire hose.
I never submitted it for publication. It started as a grade 10 English project, and got out of hand. (Sort of like Greg's computer science project. ) Although it is completed, as in done from beginning to end, it isn't finished. It's over 500 pages, but a large part of that should be excised. I have a couple of problems in that regard. One is that I choose my words very carefully (more than I do here), so it kind of hurts to delete them. The other is that I haven't been able to write a damned thing since I went on the anti-depressants for my ADD almost 10 years ago.
One of the major problems is that it's supposed to be SF, not Sci-Fi or Fantasy. I extrapolated modern technology to something that I foresaw for the future. By the time I finished writing it, some bastards invented my ideas so I had to keep going back and rewriting it to get ahead. To give you an indication of the time-frame, two of the main characters are a 65-year-old Korean war Sabre pilot and a 35-year-old Viet Nam F-4 pilot. Their wives are the other two main characters, who (essential to the plot) were in a USO performance near Phnom Penh.
If I do seek out a publisher, I'm seriously thinking of just adding an introduction page stating that it was written in the 70's and should be read with that in mind.
I was unaware of that fact about rats. I'm pretty sure, though, that I also saw a man in a tank breathing super-oxygenated fluorocarbon. In the following interview, he said that he had a huge issue with getting that first lungful in, because he felt that he was drowning, but then acclimatized rapidly. Expelling the fluid at the end of the experiment was the worst part for him. This is something that I can't cite, though, because I can't remember where I saw it. It was either SciAm or some science show on TV, but it was decades ago and my memory works for a few minutes at best.
Isn't that from the movie "The Abyss"?
A: Which part of the quote?
B: I can't say, because I never saw 'The Abyss'.
I know that liquid breathing exist but the image of a rat being placed in the stuff and slowly looking like it is dying and then it starts breathing is from the movie The Abyss. First movie with CGI btw.
Will you let anyone read it? I would like to read it.
Let me fix it first.
I read a long time ago that xenon gas was deadly poisonous, at least that is what the San Francisco Chronical science editor wrote, after he toured the Lawrence Livermore Lab nuclear reactor during an open house a while back.
Separate names with a comma.