Mostly, we humans use lasers for silly purposes like trolling NFL players or blowing things up. But lasers can be incredibly effective communication tools, especially across long galactic distances. So it stands to reason that if aliens were trying to contact us directly, they’d be firing lasers at us, or each other, but SETI has, alas, found bupkiss in its laser search.
Nathaniel Tellis and Geoffrey Marcy had a pretty smart idea: Since lasers are a communication tool, and they’re fairly easy to spot, let’s search the galaxy for them. So they scanned 67,000 individual spectra that were credible choices for lasers looking for any signs and, well, they found nothing from aliens. Which is undeniably a bummer, although the science behind the idea, they note, could be refined for a much broader search.
This doesn’t rule out the existence of aliens one bit, mind you. After all, there’s no particular reason to assume alien civilizations are more advanced than our human one. Nobody in ancient Rome was running around with a laser and even our modern society doesn’t fire a lot of lasers into space. But it does mean that any aliens who might be out there aren’t using lasers to communicate with us or each other just yet. Or if they are, they haven’t discovered us yet, which makes a pretty good argument for hefting a laser into space and seeing if we can get anybody’s attention.