Comments by "Rob Fraser" (@krashd) on "National Geographic" channel.

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  2. There is 14.5lbs of pressure pressing against every inch of your body but you don't feel it because it has always been there, humans (and all sea-level dwelling creatures) have evolved to effortlessly endure this, it is the pressure from the atmosphere (air) pushing down on you and is known as "1 atmosphere" of pressure. In space 200 miles above our head there is no atmosphere, just vacuum, so no pressure aka zero atmosphere. But although the difference between zero and 1 is 200 to 300 miles upward, the difference between 1 and 2 is just 33 feet (a tiny bit over 10 metres) downward. This is because we move from air in to water and water is so many magnitudes denser than air, it is seriously heavy. Also for every 10 metres after that pressure again increases by 1 atmosphere. Humans can safely dive to about 60 metres, or 6 atmospheres, before the pressure becomes detrimental and exhausting to move around in. A typical submarine can safely operate around 400 metres (40 atmospheres) and even then the pressure is like having the entire weight of a car pushing on every single inch of the submarine's surface, any weak spot could cause a submarine to implode like someone standing on a balloon. The Atlantic ocean is typically about 3 and a half kilometres deep, that's 3,500 metres, at that depth anything containing air, even a thick sold steel barrel, would be crushed like a beer can. This is why the stern of Titanic was utterly wrecked while the bow wasn't - the bow filled up with water over two hours as Titanic was slowly sinking, when the bow broke off and fell to the ocean floor it was full of water and so it wasn't crushed, but the stern which was raised up out of the water was empty of water, so when the bow snapped off and the stern started to fill with water it fell faster than it could fill up and all of the pockets of air - cabins, corridors, tanks, containers, air pockets between compartments - all crumpled and imploded sending bits of the stern flying as they burst inwards under the pressure. This is why the stern has little or no plating still on it and why it has a massive debris field around it. I know this post is a bit more info than you asked for, but no, no one would be alive by the time the stern reached the bottom, anyone still inside it (and there were hundreds unable to get up on deck) would have died in the first minute as it plummeted beyond 300 metres, all of the spaces people were in would have smashed in on them killing them instantly. As scary as it would have been it still would have been a much faster death than the hundreds who spent 5 to 15 minutes freezing to death up on the surface.
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