When you’re on dry land there’s pressure all around from the air but because it’s equal to the pressure inside our bodies, we don’t notice it. But at a kilometre under sea level, the pressure is 1,500 pounds per square inch. That’s like the weight of a small car pushing on every square inch. So you can see how even machines have to be incredibly tough to be able to withstand that pressure without crumpling like an old pop can.
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