Astronomer explains why you'll probably never meet an alien

Contributed by
Dec 14, 2012, 4:31 PM EST

Astronomer, lecturer and author Phil Plait, the creator of Bad Astronomy, spent 10 years working on Hubble Space Telescope, followed by six more working on astronomy education. But now he's a full-time writer explaining the uses (and misuses) of science, which he'll be doing regularly here at Blastr .

You wake up, still in your fighting gear. You're in a jungle filled with strange noises. Looking up, you see a vast planet filling the sky, and it dawns on you that you're on an alien world. And hey, what's that clicking sound? And why are there three little red laser lights on your chest?

And then a moment later you're blown away by Predators. Or, at least, that's what would happen if you were a human in the movie Predators. Or an episode of Star Trek. Or The Twilight Zone. Or ...

Hmmm, Hollywood seems to use this idea a lot, so much that it's become cliché. Of course, Hollywood can actually be a lot more distant from reality than any actual alien planet. So it's a fair question: Are there aliens out there who might kidnap humans and put them through all manner of nefarious exercises?

I'm thinking no. And for two reasons: The odds of there being intelligent aliens somewhere in the galaxy, space-faring aliens, are incredibly low, and even if they do exist they'd be so far away that getting here would be a serious problem. Enough that the trip wouldn't be worth it.

Here's how those two problems break down:

Alien scum

Are we alone? We can't have Grays/Predators/Omicron Persei 8ers kidnapping, probing and memory-wiping us unless they exist in the first place.

We humans, clever as we are, have only just dipped our toes into space travel. And it took a long time for us to get here. Face it, we're newcomers: For the vast majority of time the Earth has existed, life hasn't had too much brainpower. The first scrappy microscopic life popped up around 3.6 billion years ago, but humans have only been here for maybe 100,000 years, if you're feeling generous.

That's a tiny ratio: Humans missed out on 99.997 percent of the time Earth has been inhabited! If you had a time machine and set it to go randomly anywhere in Earth's past, the chances are about 90 percent that you'd find no life at all, or at best a layer of goo floating in the ocean.

The point here is that this will probably hold true anywhere we look for life in the universe. When we finally travel to other stars and find Earth-like planets, the chances are pretty good that most of them will have simple life on them. No dinosaur-filled jungles, no proto-Vulcans, nothing like that whatever. It'll be a rare planet indeed that even has something resembling animals, and rarer one yet with anything near our technological level.

Now, you might suppose there's a planet orbiting some star that's older than Earth. After all, the galaxy has been around for 10 to 12 billion years! Maybe an Earth-like planet formed a million years before ours did, fostering an alien civilization that's now in advance of where we are.

That's possible, but you have to bear in mind the timescale: A million years isn't a whole lot in the lifespan of a planet, but it is a very long time when you're talking about the lifespan of civilization! I'm not sure what aliens that far advanced would do for fun—assuming they have fun—but it sure seems likely they wouldn't have much interest in poking or prodding or hunting us. Well, they might have scientific interest in us, as we do of ants and slime molds and such, but I can't imagine we'd be much of a challenge to hunt a la Predators.

So there's our problem with life: If we seek out and eventually discover new life forms, we'll find they're either way behind us or way ahead of us. Either way, it doesn't really support the Predators scenario.

Deep space, nein

"But c'mon, you pointed-headed scientist," I hear you thinking (Blastr lent me its Krell thought-reading device, so I know that's what you're thinking). "There are gazillions of planets out there. Certainly some must have intelligent, space-capable life!"

Well, first off, Mr. Smartypants, "gazillion" isn't a real number. But let's assume you're right: Let's say there are intelligent races out there, maybe even well in advance of us.

But that's a long way from having them come visit us and whisk us away to a game preserve. Literally, a very long way.

The nearest planetary system discovered outside of our own is around the star Epsilon Eridani, about 10 light-years away. That's close! The Milky Way galaxy is 100,000 light-years across, so that implies there are millions of planets out there. We still haven't found any Earth-like worlds—though that discovery may be only a handful of years away—but it's reasonable to think the nearest may be 100 light-years away. Even if one bucks the odds and has intelligent life, remember that 100 light-years is 600 trillion miles.

If you tried to drive that distance in your car, it would take comfortably more than a billion years. Better pack a lunch.

Even with the fastest space probes we can reasonably think of, it would take centuries to get there—or, more to the point, for them to get here. And if they're farther away, make that millennia.

So it seems a safe bet that if they're out there, they aren't exactly knocking at our door.

"But wait!" I hear you thinking again (seriously, I need to shut this damn Krell thing off). "What about warp drive? Hyperspace? Wormholes?"

Well, yeah, those are cool, but they're not real. At least, we don't think they are, and for now that's what all our knowledge of physics is telling us. As far as we can tell, the speed of light is the ultimate speed limit in the universe. Warp drive and hyperspace and anything like that not only violate a lot of basic premises of physics, but would also screw with our sense of time as well as cause and effect. The math is tricky, but it shows that if you could travel faster than light you could actually have effects preceding their causes. You could answer a phone before it rings, and you really could unscramble an egg. Even time travel would be possible in that case. That makes physicists uncomfortable, knowing they might be able to go backward in time and maybe kill their parents before they were even born. It makes birthdays really awkward.

Interestingly, wormholes—tunnels through space-time that connect vastly distant regions of space—are an actual theoretical possibility. The problem with them is they're unstable. Even if you could create one (and that's doubtful), as soon as anything—even a single photon—entered the mouth of the wormhole it would collapse, destroying your ship and disconnecting the two points in space. Call me a pragmatist, but that doesn't sound to me like a terribly useful mode of transportation.

Of course, science thrives on overturning old theories and building up new ones. Maybe we're wrong, and wormholes do exist, or hyperdrive is possible. The thing is, we don't know, and it's a thin basis on which to bet alien invasions. I prefer to stick with what we know: Those alien planets, if they even exist, are quite a hike away for just a rollicking hunt.

Into the black

That makes me both happy and sad. Sad because I'd love to know if there are other minds out there among the stars. It's a thrilling thought that the galaxy may be, as Carl Sagan put it, softly humming with life. But it's almost certainly not the case.

On the other hand, I've seen Predator, Alien and Independence Day, and I know about Romulans, Kzinti, Dilgar and the Brain Spawn. A couple of billion years and a few quadrillion miles of buffer may just work out in our favor.

But you know what? While I think the logic here is sound, it's still extrapolating from one example: us. We may be way off in our assumptions here ... and there's only one way to find out. We've barely made it into space at all, and there will come a day when we'll simply have to find out for ourselves. Will we meet Deep Space Goo, helpful energy beings or ravenous beasts?

I think we should go out and see. It's the only way to be sure.