Images and captions 
 
 A 22W laser used for adaptive optics on the Very Large Telescope in Chile. David Kipping, an astronomer at Columbia University in New York, said he first considered this idea when he heard about the strangely dimming star that was detected recently by NASA's Kepler space telescope. Alien scientists, argued David Kipping and Alex Teachey, may be trying to find habitable planets using the same technique we do -- searching for a slight dip in light when a planet "transits" between the star it orbits and the telescopes watching it. "Other advanced civilisations would surely be aware of this technique..." 
 
 Within the wavelength spectrum of visible light, the transit signal could be masked with a monochromatic laser emitting about 30 million watts (MW) for 10 hours at a time, once a year. "There is an ongoing debate as to whether we should advertise ourselves or hide from advanced civilisations potentially living on planets elsewhere in the Galaxy," Kipping said in a statement. Such a "cloak" that concealed all wavelengths would take about 250 megawatts of power, with lasers blasting at different wavelengths, the researchers said. Credit: ESO / G. Hüdepohl 
 
 Further information 
 
 The new work appears in "A Cloaking Device for Transiting Planets", David M. Kipping and Alex Teachey, Monthly Notices of the Royal Astronomical Society, Oxford University Press, in press.
– 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.)