A laser cloaking device could help us hide Earth from advanced extraterrestrial civilizations, at least according to a new paper written by two Columbia University astronomers. The idea is not completely new, with numerous prominent scientists - including Stephen Hawking - warning of the dangers of Earth making its presence known to intelligent life on other planets.
When searching for alien life, humans typically look for transits, the dip in light that occurs when a planet moves directly in front of the star that it orbits. This is the main method used in the Kepler mission and similar projects, although the new study warns that alien scientists might use this same approach to pinpoint the location of our planet, which is in the "habitable zone" of the sun, where the temperature allows for liquid water and the promise of life.
If extraterrestrials locate Earth, they might want to take advantage of its resources, causing the authors to speculate that their visit could mirror the one that took place when Europeans first travelled to the Americas.
The team proposes that the transits could be hidden through laser cloaking by aiming a laser beam directly at a star where aliens might inhabit. When transits take place, the laser would be switched on to compensate for the dip in light, thus preventing them from using it to determine our location.
How would this be accomplished? The team believes that a continuous 30 megawatt laser could be utilized for around 10 hours, once a year, and claims that this would be enough to destroy the transit signal in visible light. However, the energy needed to conduct this procedure would be roughly equal to that collected by the International Space Station (ISS) in one year.
Additionally, for the use of a chromatic cloak that would be effective at all wavelengths in addition to visible light, scientists would need a large array of tunable lasers with a total power of a whopping 250 megawatts - around eight times the energy collected by the ISS each year.
"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 kilowatts per transit," said Alex Teachey, co-author of the study. "To another civilization, this should make the Earth appear as if life never took hold on our world."
The team believes that the lasers could also be used to modify the nature of light from the sun in order to make it obviously artificial, opening up the potential to use it as a means of communicating through the transmission of information along the laser beams.
"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 David Kipping, co-author of the study along with Teachey. "Our work offers humanity a choice, at least for transit events, and we should think about what we want to do."
The team believes that the findings could be utilized by the Search for Extraterrestrial Intelligence (SETI) to expand their search for alien radio signals to a potential search for artificial transits.
The findings were published in the March 30 issue of the Monthly Notices of the Royal Astronomical Society.
