I’m not going to debunk the Pentagon’s recently declassified UFO videos.

It’s not that I think they’re actually aliens. It’s not even that I think they’re unexplainable, or that they’re obviously some particular thing or other. And although science communication experts frequently debate the effectiveness of debunking as a strategy, that’s not the source of my reluctance either. It’s because for an astrophysicist like me, there’s very little motivation to do it.

You might be surprised at this. I’m a scientist! I want to know how things work! I am interested in mysteries, and this is a mystery about space, right?

Well, no. This is a set of videos recorded by instruments in a military aircraft, showing indistinct objects within the Earth’s atmosphere. The real explanation for them is almost certainly going to be something well outside my main area of expertise, which includes cosmic phenomena such as the behavior of dark matter in galaxies and the extreme conditions of the early universe. While I’m interested in technology and physics in general, I’m not a military tech aficionado, and while weird atmospheric optical effects are interesting, that’s not really what gets me out of bed in the morning.

I don’t know for sure that the explanation will be a straightforward one, but any attempt to figure it out will certainly involve a deep understanding of both those realms. Because what I’d be working with are videos taken by complicated, specialized instruments in an extremely unusual reference frame (high-speed travel through the air), and I’d have to tease out the geometry of all that, not to mention the instrumental effects that come along with whatever tech these cameras are using. That’s going to be a lot of work.

People are doing it, of course, including a few of the more adventurous of us astronomers. There are some very good forum posts, videos and other places where those who are interested are breaking down the sightlines, speed vectors, and camera movements, explaining how entirely human-made aircraft or balloons can look erratic and spooky on video in exactly this way. You can read those posts and get a feel for what the analysis involves. Maybe you’ll be convinced, maybe not. But you’re unlikely to see a large number of astronomers jumping into the fray, for the very reasons above; this just isn’t our bag.

It’s not that we don’t think aliens exist. To the best of my knowledge, most of us do. Life appears to have arisen on our own planet as a result of the extreme conditions of the early Earth, possibly in the vicinity of an undersea hydrothermal vent, where volatile chemicals and plentiful energy likely helped stray amino acids come together to make the first simple lifeforms.

We have good reason to believe such conditions can exist elsewhere in the universe—maybe even elsewhere in our own solar system. While Mars may be the poster child for the possibility of local alien life, given the growing evidence that it once had a thicker atmosphere and liquid water on its surface, Jupiter’s Europa and Saturn’s Titan and Enceladus might hold even more promise.

These, along with a handful of other moons of the gas giants, appear to have liquid water trapped underneath their icy surfaces, heated by the tidal stretching and squeezing induced by their close orbits around the giant worlds. Enceladus famously has giant plumes of carbon compound–rich water escaping its surface through cracks. There’s even evidence that some of these moons hide their own subsurface hydrothermal vents, providing all the ingredients we currently think necessary for life as we know it.

And that’s just in our cosmic backyard. Thousands of other stars in our Milky Way galaxy are known to have their own planets, and estimates suggest that something like one in 10 of those planets might have the kinds of surfaces and temperatures that could potentially sustain liquid water. Which means that they, too, could harbor life. And that’s not even counting all the exomoons.

The idea that Earth is fully unique, the one inhabited world in the universe, or even the Milky Way, seems a bit absurd.

But I digress. We were talking about grainy movies of unidentified objects in the air, weren’t we?

As far as I can tell, the only thread connecting these videos to anything involving aliens is science fiction. We have a long cultural history of telling stories of advanced civilizations living among the stars—civilizations that have much faster spaceships than we do, and that choose to use those spaceships to come see us and buzz around a bit. After all, if we had the ability to visit planets around other stars, we might do something similar.

But that’s an argument about human nature, not astrophysics. There is nothing at all connected to our current understanding of the real world that points us toward “technology of intelligences originating from a different planet” as an explanation for things we see in the clouds. When astronomers search for life out there in the universe, we start not with science fiction, but with a logic grounded in what we know about the stars.

One thing we know: space is big. The distance to the closest star to our Sun, Proxima Centauri, is so large that even light takes more than four years to cross the expanse, and the fastest spacecraft we’ve ever built would take more than 70,000 years. Whatever tech an alien civilization might have, it’s reasonable to assume they would take the short option first, and send an electromagnetic signal. Or perhaps they would build some large, obvious, electromagnetic radiation–absorbing structure in their own backyard. With programs like the Search for Extraterrestrial Intelligence (SETI), we’ve searched for both. So far, no luck.

There have over the years been a few tantalizing hints of things that perfectly legit astronomers have proposed might be alien constructions—a weird dimming by an otherwise well-behaved star, for instance, or an interstellar asteroid. We are open to the possibilities. We discuss them, and do the calculations, because we see a real, strange thing, out there in the cosmos. So far, alas, it’s looking like ordinary planetary science can explain the observations better than alien tech, but if other evidence comes along, we’ll jump on it.

Meanwhile, we’re continuing to search for aliens who aren’t transmitting or building anything at all. The most likely way we’ll find extraterrestrial life is via the observation of exoplanets—those numerous planets orbiting other stars. We’re just getting to the point where we can make detailed observations of the chemistry of exoplanet atmospheres. If we can directly image an exoplanet, or see it pass in front of its star, we can search the spectrum of its light for signatures of chemical balances that only biological organisms can produce, whether they be microbes or mushrooms or megafauna.

These studies are in their early stages, but the hunt for biosignatures is developing into one of the most exciting projects in astronomy today. When we finally find other life in the cosmos, the evidence will likely be in the form of an unusual set of spectral lines seen in the stretched-out starlight reflecting off or filtering through the atmosphere of a distant, untouchable world.

I don’t think it’s completely impossible that hyperadvanced aliens could come to visit us on Earth—being careful for some reason to first evade every sky-monitoring system we have, and leaving no observable trace other than the confusion of a handful of Navy pilots.

I do think it’s incredibly unlikely, and I think when starting with only a few grainy hard-to-interpret videos, the jump to aliens is so extreme that it would take something much more compelling than what anyone has seen so far to get me to even begin to walk down that road. Even if I wanted to spend the time to dig up Navy aircraft camera manuals and work out the flight geometry, my reward would likely be a long and tedious debate with a dedicated audience spanning the spectrum from those who think UFOs are a fun idea to people dedicated to proving they’re real.

So, with apologies to those who would like me and my colleagues to leap into these waters, I think for now most of us will be sticking to space. There’s a great big universe out there, and a whole lot of worlds to choose from. Maybe one of them holds something amazing.

This content was originally published here.