If the Universe Is Teeming with Aliens ... WHERE IS EVERYBODY?: Seventy-Five Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life

by Stephen Webb

Oort Cloud comets that delivered water to our planet—water that we still drink every day. At first glance this suggestion makes sense. Some planetologists argue that the very early Earth would have been too hot to hold on to large oceans of water, so the water we have now must have been delivered from space;