When you get excited about Space, about exploring the Cosmos, about boldly going where no man/woman/billionaire has gone before, you’re not excited about the Universe’s two most abundant resources: dark and vacuum. You’re excited about Aliens.

“Of the 100 billion stars in the Milky Way galaxy, it’s estimated that 1 in 4 is orbited by a planet capable of fostering life.”

There’s a reason nobody ever made a sci-fi series about astronauts wearing horn-rimmed space helmets traveling among the stars collecting and analyzing soil samples. If we’re stoked about the Mars missions, it’s because we see them as first steps on the road to First Contact. We’re less interested in what’s out there as who’s out there, and most scientists working in the broad field of space agree that somebody probably is.

Of the 100 billion stars in the Milky Way galaxy, it’s estimated that 1 in 4 is orbited by a planet capable of fostering life. That’s 25 billion chances for an Arrakis, a Gallifrey, or a Vulcan. Of course, it’s also 25 billion chances to get crossways with Xenomorphs, Arachnids, or Klingons. The fact is, we have no idea what alien life might look like, or what it might think about us. But a lot of interested parties have spent a lot of valuable time speculating on that subject, and their conclusions are as diverse as the regulars at Mos Eisley Cantina.

If there’s a majority opinion floating around the observatory these days, it’s that any strangers landing on Earth would probably look a lot like us—binocular vision, bilateral symmetry, legs for walking, arms for working, fingered hands with opposable digits and so forth. The reasoning behind that position is that creatures capable of interstellar travel would have to be complex tool users, just like us, and that evolution is very good at finding the most efficient design for any purpose. Ergo, the same evolutionary forces that made us adept at technology would solve the same problems the same way anywhere in the universe, and while the Visitors might be green and have big bug eyes, they should be unmistakably humanoid.

“Poppycock!” scoff dissenters. For one thing, if all life on Earth springs from a common ancestor, then we’re all products of an original genetic bias, and there’s no reason to think alien life would be working from a similar template. For another, where we’ve adapted to the specific demands of Earth, beings evolving on distant worlds would be tailored to very different conditions. Grappling with strong gravity, for instance, they might distribute the burden among several legs, whereas a weak gravitational pull might not require legs at all. Contending with the glare of a larger sun, aliens could develop optic organs completely unlike any eyes we’re familiar with.

As to evolutionary problem solving, a cursory review of Terrestrial biota turns up many examples of disparate species constructed to achieve identical ends by very different means. What’s more, our fossil record is absolutely crawling with bizarre, other-worldly life forms that don’t bear even passing resemblance to anything alive today, each one perfectly suited to, and successful in, its time and place. Within that school of thought, the possible forms alien life could take are nearly infinite, so when that flying saucer drops its hatch, hold onto your hat.

Then there’s them what thinks creatures visiting from afar may not be proper creatures at all. They think any species smart enough to find an interstellar loophole in the laws of physics must have long ago solved the more immediate problem of extending life indefinitely, most likely by mechanical means. By this theory, extraterrestrial guests will be cyborgs, at least, and more likely full-on robots somehow animated by the minds and spirits of their creators.

Plenty of professional stargazers believe aliens may even now be living in our midst. Life as we know it may be carbon based, but that doesn’t mean life as we don’t know it has to be. Somewhere in the universe might exist silicon-based life, or iron-based life, or life with no physical form at all, ephemeral clouds of sentient energy held together by electrical attraction and mental force, beings utterly alien to our experience and comprehension. Theoretically, such beings could sail freely across the black deeps of space and settle wherever they please, including right here on Earth, invisible to our crude instruments and undetectable by our carbon-based senses.

“Whoever may or may not be out there, we spend scads of time and money trying to get their attention.”

And, finally, there are those wet blankets who are pretty sure the only intelligent creatures in the Universe are us, and probably always will be. True, even these skeptics generally agree that extraterrestrial life exists—may actually be inevitable wherever water flows and sunlight shines. But only life of the very lowest order. The sole reason complex life emerged on Earth is because, at some unlikely moment about 3.7 billion years ago, two random microbes merged to form a single cell containing organelles, small internal structures that make possible diversity of function, an event so biologically implausible, so statistically improbable, so logically preposterous, that even the most confident alien chasers have to shake their heads in astonishment that it happened even the one time. To hear intelligent life naysayers tell it, the heavens are sown with planets awash in microbial slime that will never, can never, aspire to higher station.

Whoever may or may not be out there, we spend scads of time and money trying to get their attention. According to no few Nervous Nellies, that might not be a good idea. Anybody answering our invitation, they argue, would be a naturally aggressive species with technologies far superior to our own, and they might not have our best interests at heart. Better we don’t give them our address until we’ve had a chance to meet in a neutral location and run them through Intelius.

A sensible caution, but too little, too late. We’ve been over-sharing with the Cosmos since the dawn of radio, and if anyone’s listening, they already know not just where we are, but what we are and who we are. And who knows? Maybe they’ll come visit us anyway.