Human history shows that when two civilizations meet for the first time, it doesn't always turn out that well for one of them. And plenty of scientists—Stephen Hawking included—fear that humankind may end up on the losing side of a meeting with extraterrestrials. Now a couple of astronomers from Columbia University have put forth an idea they say could keep aliens from locating Earth in the first place: use giant lasers to hide the planet. The paper by David Kipping and Alex Teachy was published in the Monthly Notices of the Royal Astronomical Society on March 31. ("Despite the timing," the society's executive director tells AFP, "it's really not an April Fool's joke.") Kipping and Teachy's idea centers on the transit method, which is how humans, via NASA's Kepler spacecraft, search for habitable planets, reports Space.com.
It involves detecting dips in the brightness of a star caused when an orbiting planet moves directly in front of it. A giant laser or group of lasers would "fill in the missing starlight," Teachy says in a video outlining the idea. Depending on how thoroughly you wanted to conceal the Earth, it would take anywhere from 30 to 250 megawatts emitted for 10 hours, once a year. Lasers can even be used to cancel out attributes "such as oxygen," Teachy says in a press release, to make Earth appear to be a "dead world." But their idea could also be applied in reverse: The sun's light could be manipulated as we passed in such a way that would make it clear something artificial was happening, signaling our presence. (These celebrities say they've already had close encounters with ETs.)