How long would a pebble take to reach the bottom of the Mariana Trench?

22nd July 2009

Asked by: Merlin Hetherington, Spain

Located in the Pacific roughly halfway between Japan and Papua New Guinea, the Mariana Trench is the deepest part of the ocean, and plunges down over 10,900m below sea level. A pebble dropped overboard would take just over an hour to reach the pitch-black seabed, where temperatures hover just above freezing and the pressure is over 1000 times higher than at the surface.

5 issues for £5 when you subscribe to BBC Focus Magazine