I was watching Pirates of the Caribbean: Dead Man's Chest and they refer to "the crushing depths". At what point in history did people make this association? It seems to me, like "the cold of space", like something that people a few centuries ago would have no knowledge of.
You can feel the pressure on your eardrums from a deep dive, and I'm sure it feels very much like high pressure to a modern diver. But would people who didn't have any experience with high pressure recognize it as such?
I can also imagine ancient people dropping some object down that would get crushed and seeing the results, but someone would have to think to lower the right kind of object down to the right depth, and understand what happened to it.
On the other hand people are clever, so given evidence, I could certainly believe this association was made even in antiquity. So I'm interested in the first recorded reference of the "depths" being "crushing", or something similar.
Thanks!
Discoveries like this can’t be pinned down because they are so simple you can’t rule out that someone may have discovered them independently of the scientific advances of his time.
It’s a common experience that when you put something on top of yourself, you experience its weight as pressure. Lay your hand flat on a table and put a brick on top: you will definitely feel that pressure. It’s not a stretch from there to understand that if you are diving underwater, there is a column of water on top of you. Everyone knows that water has weight, so why would you not feel that weight?
And in fact, you can physically feel the pressure, and remove all doubts. It’s not just your ears popping – you will feel it on every part of your body that has an air cavity, mostly your chest and lungs. There were no scuba tanks back in the day, no positive pressure breathing aids. You took a deep breath at the top and then you held your breath and dived. Try doing that now, and you will definitely feel the crushing pressure on your chest as the air inside compresses and the ribs try to push in. It may not be huge, mostly because you can’t dive very deep on a single breath, but it’s definitely perceptible.
So even if we could find the oldest record of someone who explicitly mentioned “crushing deeps”, it wouldn’t mean he was the first person who understood. It could well be prehistoric man from before written history.
That said, we can certainly set some deadlines. Archimedes stated his law around 200 BC, that buoyancy equals the weight of water displaced. He must have understood hydrostatic pressure to posit that. Some time later, there are lots of Romans running around building complicated hydraulic systems to move water that depend on precisely measuring the “head” or net water pressure that makes it flow. It’s a good bet that anyone who built cisterns, large baths or holding tanks (where you have to taper the walls because they have to be thickest/strongest at the base where pressure is highest), water distribution systems and plumbing, must have understood the basics of hydrostatic pressure. It would then seem unlikely that they didn’t know how hydrostatic pressure increases with depth.