Hey, Vsauce, Michael here! Down here. But which way is down? And how much does down weigh? Well, down weighs about 1/100 of a g/cm3 . It is light, and airy, which makes it a great source of insulation and buoyancy for waterbirds. But if you let go of down, it falls down. So that's which way down is, it's the direction that gravity is pulling everything. Now for someone on the other side of the Earth, my down is their up, but where are falling things going? Why do things fall? Are they being pushed or pulled? Or, is it because of TIME TRAVEL.