Deep water vs the human body.

Inspired by the BP debate.
What exactly would happen to a human body at the depth of the BP oil spill, given that you could even get it down that deep ?

you would be completely crushed by the pressure. Do you want to see equations to back this up?

Not me! :wink:
But no, I’d like gory details. Would that body be crushed into a sphere*, or remain identifiable as a body?
*The strongest shape, iirc from my 5th grade physics.

I doubt it would be spherical. I have heard that a styrofoam cup taken to that depth will be crushed into a lump about the size of a sugar cube.

I’ve heard that too, which is what made me wonder about a body. I don’t have any idea how much air is entrapped in us. Mostly water.
If you sent a water baloon to that depth it would likely retain its size and shape.

Styrofoam cups retain their shape to a surprising degree. An average styrofoam cup, stuck in a sock and attached to a standard oceanographic CTD/Niskin bottle array and sent on a deep cast will look like a tiny shotglass replica of it’s original self. It will be less foamy, because the gas has been forced out of it, and it will often be somewhat rippled, as the gas-forcing-out process obviously contorts the styrofoam somewhat. I used to have a beer wrap cooler thing that was the size of a shot glass - That was a very deep cast.

I found some examples:

Lets say you put on a scuba system that has an unlimited amount of gas and it can provide any gas mixture you want with any gas type/mixture ratio/combo.

Now start swimming downwards. Note the following number are rough. I aint writing a Wikepedia article here.

Normal air (80 percent nitrogen,20 percent oxygen). Starting at about 100 feet, the nitrogen basically makes you “drunk”. Nearing 200 feet, you are REALLY drunk and could possibly pass out. Also in this depth range, the oxygen starts to become toxic and can make you go into uncontrolled convulsion.

So fine, wanna go deeper? Lower the concentration of the O2. The O2 convulsion problem is solved. You can get rid of the nitrogen/drunk problem by using Helium instead.

Using a helium/low oxygen mix will get you down to about 1000 feet deep. But, around that level, now the helium causes a different form of convulsions. Ironically, putting a little bit of nitrogen back in helps with the helium convulsions.

If you want to go much deeper you are screwed though. About the only other gas you could use is Hydrogen. And, if I recall correctly, you still get convulsion problem with it, just at a bit deeper level.

And, not only do you have these problems, at these depths the gas mix is getting “thick” enough that just breathing in and out sufficiently is a problem. And if you can’t do that properly, then the CO2 your body is trying to expel builds up in your lungs, which can also cause convulsions/blackouts.

So, unless you are in a submersible, a human body in the water is limited to something like the 1000-2000 foot range without invoking some serious, different, and likely militarily secret technology (and even then, its quite possible even they don’t have any fancy answers).

Humans aren’t make of styrofoam. We do however have bits of us that are not solid, and these would indeed crush to essentially zero volume. The sinues in the skull, and clearly the lungs would crush down to have no air volume - which means about a further litre of volume below where the lungs get when you breath out fully. Also of course your trachea, pharynx, and nasal passages would probably fill with some liquid of another. If it isn’t seawater you might guess the next bit. This really assumes the use of concrete overshoes to get you to this depth, with no chance to do anything but try to hold your breath. If you are allowed preparation you won’t crush.

Most of the rest of the body is pretty imcompressible. Apart from the gas filled spaces there is no reason that the human body will actually deform at all. Humans can dive to remarkable depths so long as they can keep the gas pressures inside themselves high enough to balance the water pressure. The big trick is managing the gasses so they don’t kill you. Oxygen is remarkably toxic at pressure. Currently 2000 feet seems to be the record for diving. The diver did not squash into a tiny cube.

As billfish678 seems to imply, I’ve heard that the enormous pressures at those depths actually wouldn’t cause much of a problem for most of our bodies: it only causes problems for gaseous spaces. So if you tried breathing normal air or oxygen, your lungs would be crushed long before you got down to that depth, but if you could find some way to eliminate those gaseous spaces (ie. by breathing some sort of liquid), the body wouldn’t get compressed at all.

My impression was that if you sent a corpse down to that depth, but filled its lungs and sinuses filled with a liquid, nothing would really happen to it. It wouldn’t get compressed at all. But the problem for divers is that you can’t just fill their lungs and sinuses with liquid as easily as that. :slight_smile:

Wow. Thanks for the links.

I remember reading something a while back abour a liquid air that could be breathed, but when I wiki’d it I got this. That ain’t it.
It was to be used in medicine somehow iirc.

Years of my life spent at sea - at least I have something to contribute because of it. :slight_smile:

This is!

CMC fnord!


Given that there are a number of critters (e.g. whales) that swim from the surface to impressive depths without being crushed at all (let alone “completely”), I’d be interested to hear what makes the human body vastly different. It’s clear that any pocket of gas will be compressed, but much of the body doesn’t contain gas (in a gaseous state).

A closed gas-filled object would be “crushed”. Humans are not closed gas-filled objects. We can equalize the pressure within us. As others have said, the limits are not of our anatomy but of our physiology.

O.K., the hollow, compressible parts of a human are lungs, trachea, and air space in the head. Why wouldn’t these just fill up with sea water as the air bubbles out while the body sinks? It seems that kind of water pressure would be pretty invasive.

Even if you used a liquid breathing system as shown in The Abyss with your lungs, breathing passages and sinuses purged of all gases, what about your inner ear and eustachian tubes? Filling those with liquid would be a problem.

Yep! Pretty cool concept. Not yet ready for the masses yet.

As usual, the Mythbusters have done it: Deep Sea Diver Squeeze. (Warning for people with delicate stomachs!)

They created a full human analog with internal organs, blood, a skeleton, etc. (not shown in the video), put it in an old-style diving suit and helmet with atmospheric air supplied from the surface, lowered it to 300 feet, then cut off the air supply, which was countering the water pressure. (So it’s not exactly the same as a SCUBA dive.)

The result is shocking, and rather gross, but unbelievably cool.

It seems to me that there would be some effect at the molecular level. I don’t know what’s inside the cell’s wall, but if it’s gaseous the cell could compress.
Now I do. Cytoplasm, and a lot of other stuff. Looks kinda fragile to me, as does the whole human body. But it’s not, really.
I’ve heard the pressure is around a ton.