By Lola Gayle, Editor-at-large
Many of us are inclined to think that aliens really do exist. As a matter of fact, a 2015 YouGov poll found that more than one in two people in the UK, Germany and the US believe there is intelligent life somewhere out there in the universe.
Despite this, several prominent scientists have cautioned against broadcasting our presence to intelligent life that may be lurking somewhere out there in the Universe. This includes noted theoretical physicist Stephen Hawking, according to the Royal Astronomical Society (RAS).
Personally, I think he’s changed his mind after we learned in April 2016 that Hawking, along with billionaire Yuri Milner, was backing the $100 million Breakthrough Starshot initiative. The project aims to send tiny “spacecraft” to Alpha Centauri, the nearest star system, 25 trillion miles from Earth. Perhaps he now just wants to find them before they find us.
That being said, what if we wanted to hide from alien civilizations? Especially if it’s possible they might employ the same techniques to find Earth-like planets, such as looking for the dip in light when a planet moves directly in front of the star it orbits.
These events are called “transits,” and are the main way that the Kepler mission and similar projects search for planets orbiting other stars, referred to as exoplanets. Kepler has already confirmed more than 1,000 exoplanets using this technique, with tens of these worlds similar in size to the Earth.
But what if we want to hide? What then? Well, two astronomers at Columbia University have suggested that we could potentially use lasers to conceal our planet from the prying eyes of extraterrestrial civilizations.
Professor David Kipping and graduate student Alex Teachey speculate that alien scientists may use the transit approach to locate our planet, just like Kepler. We’re clearly in the habitable zone of our Sun, thus making us a prime target. Plus, Earth has a vast supply of useful resources, and experts fear an alien invasion could be as devastating as when Europeans first traveled to the Americas.
In 2016, Kipping and Teachey made the proposal that we could mask any transit our planet might make by using controlled laser emission, with the beam directed at the star where the aliens might live. When the transit takes place, the laser would be switched on to compensate for the dip in light.
According to the authors, emitting a continuous 30 MW laser for about 10 hours, once a year, would be enough to eliminate the transit signal, at least in visible light. The energy needed is comparable to that collected by the International Space Station in a year. A chromatic cloak, effective at all wavelengths, is more challenging, and would need a large array of tuneable lasers with a total power of 250 MW.
“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. To another civilization, this should make the Earth appear as if life never took hold on our world,” Teachey said.
But what if we want to broadcast our presence instead? The researchers suggest the lasers could also be used to modify the way light from the Sun drops during a transit to make it obviously artificial, and thus broadcast our existence. The authors suggest that we could transmit information along the laser beams at the same time, providing a 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.”
According to Royal Astronomical Society’s Dr. Robert Massey, “Given that humanity is already capable of modifying transit signals, it may just be that aliens have had the same thought. The two scientists propose that the Search for Extraterrestrial Intelligence (SETI), which currently looks for alien radio signals, could be broadened to search for artificial transits.”
Kipping and Teachey made their proposal in a paper published in the Monthly Notices of the Royal Astronomical Society.