If you've ever seen the 1951 sci-fi classic The Day The Earth Stood Still, you may remember the scene in which the flying saucer lands in Washington, and Klaatu the alien emerges, holding in his hand what looks to the terrified humans like a weapon. After a soldier shoots Klaatu, Gort the robot emerges from the spaceship, and employs his otherworldly powers to disarm the soldiers and reduce a tank to scrap metal. It's only then that the wounded Klaatu rises to reveal that what he had in his hand was a miniature telescope, capable of seeing father into space than existing human observatories. From the script: KLAATU: It was a gift. For your president. (Glances at the broken object ruefully) With this, he could have studied life on other planets. Okay, that was just from a movie. But the paradox that the scene raises might well turn out to be a real one, if we ever actually make contact with terrestrials, who most likely will come from a vastly more advanced...