A 22W laser used for adaptive optics on the Very Large Telescope in Chile. A suite of similar lasers could be used to alter the shape of a planet's transit for the purpose of broadcasting or cloaking Earth’s location.
Humanity has pondered the question of intelligent life beyond our planet for hundreds of years and just within the 20th century actually began transmitting signals to welcome and find these beings. Extraterrestrials are statistically likely to exist given the estimated number of possibly habitable planets in our galaxy.
But some leading scientific thinkers, such as Stephen Hawking, have warned against searching for alien civilizations, citing humanity’s own brutal experiences when civilizations have discovered each other here on Earth.
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“We only have to look at ourselves to see how intelligent life might develop into something we wouldn't want to meet,” Hawking said in his 2010 Discovery Channel series, Into The Universe with Stephen Hawking. “I imagine they might exist in massive ships, having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonise whatever planets they can reach.”
With humanity's own history of domination and conquest firmly established, the discovery of the Americas by Europeans for example, professor David Kipping and graduate student Alex Teachey from Columbia University in New York have suggested humanity hide certain tell-tale signs of Earth’s existence — the same signs by which humans currently search for extraterrestrials — to cloak Earth’s location from any alien civilizations that may be searching in our galactic neighborhood.
According to the Royal Astronomical Society, publisher of Kipping and Teachey’s research, scientists can currently find Earth-like planets by observing a dip in light when a planet moves directly in front of the star it orbits, an event know as a transit. Using this technique, NASA’s Kepler space observatory has already confirmed more than 1,000 planets, with tens of these worlds similar in size to Earth.
It is assumed alien civilizations could use the same method to find habitable planets outside their own, including Earth.
According to Kipping and Teachey, by emitting a continuous laser at the star where aliens might live for about 10 hours, once a year, it would be enough to compensate for the dip in light and eliminate Earth’s transit signal when it occurs — effectively masking the planet’s location.
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"Alternatively, we could cloak only the atmospheric signatures associated with biological activity, such as oxygen, which is achievable with a peak laser power of just 160 kW per transit,” Teachey said. “To another civilization, this should make the Earth appear as if life never took hold on our world.”
The Royal Astronomical Society suggests, beyond cloaking Earth’s location, the lasers could be used for communication and making first contact with aliens. Hiding Earth’s transit may be too obvious and actually attract attention, which could be a good thing if we are discovered by friendly aliens. If so, the researchers believe the same lasers could also be used as means of communication.
"There is an ongoing debate as to whether we should advertise ourselves or hide from advanced civilizations potentially living on planets elsewhere in the Galaxy,” said Kipping. “Our work offers humanity a choice, at least for transit events, and we should think about what we want to do."
