The deeper you descend in the ocean, the more intense the pressure. I recently heard famed undersea explorer and Titanic discoverer Robert Ballard say that at the depth of the sunken Titanic, the pressure is in the tons per square inch – and would crush an exposed human in no time.
I’m having trouble reconciling this with photos of fragile cups, plates, and other artifacts on the seabed, near the wreck of the Titanic. Given that the water pressure is so great down below, how have these delicate objects survived intact? Heck, a three-foot drop from the kitchen counter is enough to break them in pieces. You would think at a pressure of tons per square inch, a plate would be shattered to atoms in nanoseconds.
No big mystery. Cups, saucers and other ceramics are quite strong internally and have significant compressive strength but they are brittle and subject to fracture if sharply hit, due in part to the presence of internal micro-fractures that form during the firing process. If the pressure is equalized across the surface of the object they could survive high pressures under the ocean quite easily.
Just to say what Astro said in different words. With respect to hollow objects - if they fill with water on the way down then there is no pressure gradient across them so they don’t collapse.
Russell, what Astro said about china or similar objects is true. But to give you a better picture, if you take a styrofoam cup, and sink it to hundreds (or even tens) of feet under water, it will shrink and be compressed down to a fraction of its original size. That’s because its construction is largely air pockets, and the styrofoam structure is weak in compression (think of squeezing it between your fingers), so the water pushing on all sides (including the inside) causes it to shrink. Try to squeeze a china plate between your fingers however, and you’ll understand the difference.