Think rocks plunge straight to the ocean floor?
At the deepest place on Earth, they actually sink painfully slowly.
If you dropped a stone into the Mariana Trench, it wouldn’t rocket downward like it does through air. Gravity would accelerate it only for a short moment before water resistance takes over. Once the drag force balances gravity, the rock reaches what physicists call terminal velocity—and from that point on, it sinks at a constant, surprisingly sluggish speed.
For a typical fist-sized rock, that speed is about 1.6 feet per second. At that rate, reaching the trench’s staggering 36,000-foot depth would take nearly six hours. Even much heavier or denser objects don’t fall dramatically faster; they might shorten the journey to around an hour, but no more.
This slow descent highlights just how powerful water resistance really is. Compared to air, seawater behaves like a dense cushion, absorbing energy and limiting speed. In the deep ocean, motion is not about free fall—it’s about balance, drag, and patience.
The Mariana Trench isn’t just deep.
It’s a place where gravity still rules, but physics unfolds at a far slower pace.
Source:
Merali, Z. (2012). Into the Mariana Trench. Science, 336(6083), 1090–1093
