Alien factories could be a sign of life outside our solar system. Astrobiologists have come up with two basic ideas for how to find life on planets outside the solar system. The first is to look for telltale gases inexoplanets’ atmospheres, such as oxygen and methane, that would suggest the presence of some rudimentary life form, like bacteria. The second involves searching for radio or laser signals from some advanced alien civilizations—a longer shot, since the signals would have to be beamed in our direction — and who knows if aliens use lasers or radio? Read more here.