Here’s Why Trying to Camouflage Earth from Aliens Would Backfire

In a recent paper penned by Columbia University professor David Kipping and graduate student Alex Teachey, the two astronomers suggest that humanity could create a ‘cloaking device’ made of giant lasers that could hide the existence of Earth from any voyeuristic alien civilizations.

And why would we want to do that? For one, Stephen Hawking has warned us that making direct contact with aliens may turn out the same as when North American Natives made contact with Christopher Columbus — except in this scenario, Earth would be on the receiving end of the smallpox-laden blankets and genocide.

But before getting into how preposterous the idea of a giant laser cloaking device is and why it wouldn’t even work, let’s investigate how exoplanet detection works in the first place.

Using the Transit Method

Back in 2009, NASA launched the Kepler Space Telescope (so named after Johannes Kepler, the first scientist to combine physics with astronomy) into an Earth-trailing orbit around our Sun. Kepler’s four reaction wheels, devices that use electricity to rotate in a specific direction to make Kepler rotate in the opposite (and intended) direction, allowed it to maintain a constant and fixed field of view on some 145,000 stars for four years.

After years of looking at the same patch of sky and stars, data transmitted back to Earth by Kepler was analyzed to find stars whose light had been dimming periodically. These dips in starlight are known to be caused by orbiting exoplanets crossing in front of their host star, and that’s how Kepler was able to find over 1,000 (and counting) confirmed exoplanets in our galactic neighborhood.

This is also the same method which found that still-perplexing star (KIC 8462852) that periodically dims by upwards of 20% (which led to the pseudo-scientific assumption that it’s aliens).

Determining Habitability

By examining the amount of sunlight being blocked by a planetary body (ie. 0.1%) and the frequency of these dips (ie. Earth would dim the light of our Sun once every 365 days), astronomers can determine how far away an exoplanet is from its host star and how big the exoplanet is.

Once those values are determined and potentially habitable planets are identified (ie. planets that are of the right size and temperature to support liquid water), astronomers can have more powerful telescopes turn their lenses towards the exoplanet in question and attempt to measure its atmosphere indirectly using spectral analysis (different elements block out different wavelengths of light).

With a powerful enough telescope and enough time, astronomers will eventually be able to find a world that very closely resembles our own Earth. And this is exactly the method that aliens might use if they were looking for a habitable world to study (or colonize?) — like Earth.

The Cloaking Device

Kipping and Teachey propose using giant lasers to shoot light out into space on the far side of the Earth (opposite to the Sun) that would the mimic light emitted by our Sun.

This way, when aliens look at our Sun in a Kepler-like survey, instead of seeing Earth move in front of it and block out a tiny percentage of light (and thereby signaling that our planet exists), they would instead see no dip in light at all — because giant lasers are compensating with their own added luminosity.

But in order to adequately cloak Earth, the laser would need to perfectly match the wavelengths and spectra of light emitted by the Sun (there’s one engineering miracle right there) and be able to emit this light from the dark side of the Earth (opposite of the sun) at all times, which could only feasibly be accomplished with a space laser that perfectly follows along the outside of Earth’s orbit (and that means a lot of propellant for course corrections).

The problem with this proposal is that this giant laser could potentially act as a beacon to any alien civilization rather than a cloak, a way for us to yell “hey, we’re over here” from across the cosmos. If the light emitted by said lasers didn’t match the light emitted from the sun, aliens looking at the sun’s spectra would see that approximately 0.01% of its light was of a completely different origin, and they would eventually be able to determine what that origin was and the purpose behind it (that we were hiding from them).

And of course, if aliens were to find out that we were intentionally trying to hide Earth from them, their very first inclination would be to zip over here real quick and have a look at why we were doing that.

And What About Direct Imaging?

Even if we were to build this giant cloaking laser and have it work perfectly, there’s still the problem of direct imaging. Our next-generation telescopes (coming online within the next decade) will be capable of taking direct (and somewhat detailed) images of exoplanets around their host stars, similar to how Hubble is currently able to capture detailed images of far away stars.

Assuming that these Christopher Columbus-like aliens have better technology than our own (they’d need to in order to be able to travel here, after all. And if they couldn’t, then we don’t really need to hide!), then direct imaging for them would be no problem. In fact, direct imaging would probably be the preferred method of finding habitable exoplanets, assuming one had powerful enough telescopes to do so, thus reserving the transit-detection method for discovering smaller objects like exo-asteroids and exo-comets.

So, Are We Doomed?

Not necessarily. Instead of trying to transmit artificial light as a means of hiding Earth from aliens, we could use a giant laser to encode a message for alien life. And if we wanted to avoid colonization by aliens, a little bit of trickery would be involved here.

Instead of transmitting a message that reads “Hi, we are peaceful beings, please don’t conquer us,” we could say something like:

“A cataclysm has stricken our world. We’ve polluted our planet to the point that it is toxic and acidic, and all life as we know it will soon perish. If there are any benevolent beings out in the cosmos, please come to our aid!”

With some luck, any hostile or unfriendly aliens would likely shy away from such a message, not wanting to waste their time trying to colonize a toxic world. After receiving such a message, it’s probable that only the friendliest of friendly aliens would bother to attempt making contact with a doomed civilization — and maybe they could become our friends (assuming they find our S.O.S. trick amusing).

And, who knows, if our environmental track-record keeps going the way it’s going for another couple of decades, we may actually need to send a message like that out into the cosmos anyways. Better sooner rather than later.