Greetings, E.T. (Please Don’t Murder Us.)<br />Writing in Scientific American, the former chairman of SETI, John Gertz, argued<br />that ‘‘a civilization with malign intent that is only modestly more advanced than we are might be able to annihilate Earth with ease by means of a small projectile filled with a self-replicating toxin or nano gray goo; a kinetic missile traveling at an appreciable percentage of the speed of light; or weaponry beyond our imagination.’’<br />With exobiology, Vakoch realized, he didn’t have to settle on one discipline: ‘‘When<br />you think about life outside the earth, you get to dabble in all of them.’’<br />As early as high school, Vakoch began thinking about how you might communicate with an organism<br />that had evolved on another planet, the animating question of a relatively obscure subfield of exobiology known as exosemiotics.<br />Your guess about each value in the Drake Equation winds up revealing a whole worldview: Perhaps you think life is rare,<br />but when it does emerge, intelligent life usually follows; or perhaps you think microbial life is ubiquitous throughout the cosmos, but more complex organisms almost never form.<br />Even if a small fraction of alien civilizations out there would be inclined to shoot a two-kilogram pellet toward us at half the speed of light, is it worth sending a message if there’s even the slightest chance<br />that the reply could result in the destruction of all life on earth?
