A lot of our search for Earth-like planets (and, by extension, for life as we know it) hinges on transiting planets. These are planets that pass in front of their host star in such a way that the transit is visible from our perspective. The movement of the planet in front of the host star makes the light from that star dim or flicker, and we can use that to determine all sorts of things about distant worlds — including how suitable they may be for life.
Some scientists have suggested that we should hope that Earth is a transiting planet from the perspective of some other world that hosts intelligent life. In other words, our best shot at finding aliens might be hoping that they're using exactly the same methods of planetary detection that we are, and that they can see the passage of Earth in front of the sun with their telescopes. If we made a lot of noise in the direction of those theoretical planets, we might get their attention faster.
Or we could point lasers at them instead.
Professor David Kipping and graduate student Alex Teachey, both of Columbia University, decided to see how much laser light it would take to mask the dimming caused by our planet's transit. According to their math, it would take about 10 continuous hours of shining a 30 MW laser once a year to eliminate the transit signal in visible light. Actually replicating every wavelength of light emitted by the sun would take about 250 MW of power.
"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 in a statement.
This assumes, of course, that the aliens in question haven't already figured out more sophisticated (or just very different) methods for detecting a planet's habitability. It's possible that they'd catch on to our little laser show pretty quickly.
But we could use our lasers to be even louder. Instead of cloaking ourselves, we could make our transit signature so darn weird that aliens would have to take notice.
There's a big, interdisciplinary debate about whether we should try to contact intelligent life from other planets. To be fair, it's possible that we'd really, really regret it. Humans are kind of the worst, so intelligent life has a pretty bad track record so far.
"Our work offers humanity a choice, at least for transit events, and we should think about what we want to do," Kipping said in a statement.
But it could also be really great. And hey, the chances are slim anyway — especially now that we know it's pretty easy to hide from our best method for detecting Earth-like planets. I already worry that people are ignoring my texts because they hate me. Now I get to wonder if aliens might be pointing lasers at us because they think we're gross, and they just can't even.