"Where is everybody?" The question became known as Fermi's Paradox. In 1950 the physicist Enrico Fermi asked this question while discussing the possibility of extraterrestrial civilizations. People reasoned that an advanced civilization able to travel at only a fifth the speed of light would be able to colonize the galaxy in a million years. Our Milky Way Galaxy is more than 13,000 million years old. On Earth, after its surface cooled from molten lava to solid rock, only a tiny part of its...