What if there is extraterrestrial intelligence out there in the universe, but the aliens turn out to be hostile? Think "Independence Day" rather than "E.T." If that's the case, world leaders may want to give Alex Teachey and David Kipping at Columbia University's Cool Worlds Lab a call before our visitors show up.
In a new paper, Teachey and Kipping outline how to create a cloaking device for our planet, to hide us all from the view of alien civilizations who may be looking for a new target for their latest long-distance Starkiller Base.
It sounds like an elaborate April Fools' Day prank for the sci-fi set, but the paper was published online Wednesday in the journal Monthly Notices of the Royal Astronomical Society with an awful lot of calculations to back it up.
The concept basically reverse-engineers the primary method that human astronomers currently use to find exoplanets. That is, look for the small dips in light from distant stars that we see when their planets pass in front of them on their orbital paths. In the video below, Teachey explains how we could use lasers to artificially "fill in" the same dips in light from our own sun that the Earth creates for alien observers.
"We've calculated that it would take somewhere between 30 and 230 megawatts of power at peak intensity," Teachey explains. "The solar array on the International Space Station gathers enough energy to get this amount of power in the course of a single year."
The same method could also be used to mask evidence of Earth's atmosphere, by "tuning" the lasers to cover up the evidence of things like oxygen and ozone in our atmosphere. That way, alien astronomers observing our solar system might see that the third planet around our sun is in the habitable zone, but it would appear to be as dead and dry as the moon.
But would hiding behind a laser cloaking device guarantee that no hostile alien civilization ever finds us? It's tough to say, but I wouldn't bet on it. The so-called transit method of detecting planets that we're talking about isn't the only way to spot a planet.
Planets can also be detected by the way their gravity pulls on their star, an effect a laser probably couldn't cover up so easily.
Also, there's the decades' worth of radio and other signals that we've been sending out into space for some time now.
"We've already exposed ourselves," Douglas Vakoch, president of METI International, told us last month in a CraveCast episode. (METI stands for Messaging Extra-Terrestrial Intelligence.) "Let's not just let accidental leakage be our ambassadors, let's decide what we want to say to another world."
Teachey says his cloaking method can also be used for controlling that message and announcing our ourselves rather than hiding, as Vakoch and advocates of METI prefer.
"You could use the same laser array to make that shape (of the dips in the sun's light caused by a transiting Earth) look artificial," he explains. "So another civilization out there might observe this and say 'that can't be natural, therefore there has to be an advanced technological civilization living there.' And in fact you could even encode information in these laser beams."
In other words, we must never let the laser cloaking array fall into the hands of alien spies so that they can relay the message across the cosmos that their last attack actually missed and hit Jupiter instead.