I used to be a nuclear rocket engineer. Really, I was. Department of Defense, NASA, missions to Mars and other planets… for a span of about 7 years during the Reagan-Bush era, I was eyeballs deep in it. My octogenarian aunt, who has lived her whole life on an idyllic Greek island, translated a generalized awareness of my career into a presumption that I knew all sorts of secret things about space aliens and government coverups of little green men. So, when last I saw her, she invited me to talk about extraterrestrial intelligence. Well, actually, she’s asked me, with a nod and a wink, to confirm for her that those little green men exist and that the government was hiding them. Lost (and never to be found) on her was the simple reality that nothing I did put me within hundreds of miles of Area 51 or anyone who might know any “secrets” regarding alien landings, Martian invasions, contact with ‘ET Phone Home’ or the like.

But, I had to tell her something, and to tell her something I had to figure out what I believed on the subject. While the selection of literature, deep thought, speculation, pseudo-science, conspiracy theories, and analyses on extraterrestrial life is vast, I’m going to eschew it all in favor of a ground-up assessment.

Let me preface this by saying that everything I write here, apart from the basic realities of physics, is pure conjecture and personal belief. It is also written without regard to theology and religion. And, my conjecture and belief is that, yes, there is (or has been) intelligent life in the universe, and, no, we haven’t been visited by aliens.

First, the former. The universe is a big place. Really big. REALLY big. By latest estimates, there are over 100 billion galaxies in the universe. Our galaxy alone contains 200 billion stars. Total stars in the universe? Over 100,000,000,000,000,000,000,000. And, the universe is old – close to 14 billion years old. Human comprehension has no basis for understanding just how huge these numbers are, how vast space is, and how old the universe is.

Earth orbits an unexceptional star in an unexceptional location in an unexceptional galaxy. Is the existence of intelligent life on our planet so exceptional as to be unique? Is the combination of factors that led to the rise of life out of the primordial soup so unlikely that this is a one-off? Seems unlikely.

And that’s as far as I need to go in support of my belief that there is or has been other intelligent life in the universe. Your mileage may vary, you may want more than that, and there’s tons of scholarship on the subject. But, to me it’s not a particularly pressing issue, because this next bit makes my presumption irrelevant.

Consider the speed of light. Science fiction books and movies (and some peculiarities of quantum physics) aside, it is an absolute limit on the speed at which objects and information can propagate through the universe. It is this limit that forms the foundation of my belief that, no, we haven’t been visited by little green men. It’s fun to contemplate spaceships zipping along at many times the speed of light, or using wormholes to instantly travel enormous distances, but all that’s fiction or speculation, not fact. Confusing what we want to be true with what is true is a quick way to go astray from reality.

Consider, next, the age of human civilization. Order-of-magnitude, 10,000 years. 99% of human history is pre-technological. We’ve only had the ability to transmit and receive electromagnetic radiation for about 150 years.

Let’s apply the speed of light to that last time span. Our first radio signals (certainly long attenuated down to nothingness, but ignore that for now) have traveled a total of 150 light years outward from Earth. If there is another intelligence out there, doing as we are doing with SETI (i.e. listening to the sky for signs of life), it will have to be within 150 light years of Earth to have heard our civilization. Now let’s suppose that this intelligence is sufficiently advanced to engage in interstellar travel, at something close to the speed of light. And, let’s suppose that those little green men had nothing better to do than to hop on board their interstellar ships and race here the moment they heard our first little pipsqueaks. If they left the day they heard our first signal, they’d still need over 150 years to get here. Clearly, those folks haven’t been here yet, given that they’d be leaving their star today. The “round-trip” nature of signal and travel reduces the range within which little green men might hear us and come racing over to less than 75 light years.

Since they’d have to decide whether those first faint signals were worth their effort, and then load up their spacecraft and accelerate them to whatever interstellar speed they can muster (less than the speed of light), the actual maximum distance of their civilization is more like 20 or 30 light years, but let’s leave it at 75 for now. A quick Google search tells me that there are 3500 stars in that volume of space. So, the little green men would have to be at one of those 3500 stars, listening and interested in visiting. There is temptation here to go into the probability regarding planets around those stars, the probability that those planets are in the right orbit to allow the development of life, and so forth, and draw down the 3500 number to something much smaller, possibly smaller even than 1. But, I’m going to take a time-based approach instead.

We have been a technological race for a couple hundred years. We’ve been space-faring for 50 years. We witness here on Earth an ever-increasing rate of technological innovation. Some futurists have written of what they call the oncoming technological “singularity,” a point in time at which technological development will transform society so fundamentally that we cannot conceive of what it will look like, and includes our uploading our consciousnesses into machines. It’s a fascinating idea, espoused by such authors as Vernor Vinge, and worth googling. But, I won’t go into it any further here, other than noting that some of the futurists who developed the notion think it’s mere decades away. I’m not convinced it’s that close, but I think it highly likely that human civilization will cease to exist as we know it at some point in the next couple centuries. What will become of us in that time? Who knows? What’s relevant to the discussion at hand is that our time as this sort of technological civilization is measured in hundreds of years.

If we’re technological at a recognizable level for less than a millennium, it doesn’t seem unreasonable to contemplate that the little green men will experience a similar history. So, in addition to needing to be at a star close enough to hear our pipsqueaks, they’ll have to align with our civilization time-wise very, very closely. The universe is 13.72 billon years old. The Milky Way is 13.2 billion years old. Earth is 4.3 billion years old. Our technological window is 0.0000007% of the age of the universe. If the little green men’s civilization began even that tiny percentage of galactic time before ours, they’d have missed us. Combine the small number of stars close enough to have heard us and travel from with this tiny sliver of time, and you get to my probability-based conclusion that we haven’t been visited by the aforementioned little green men.

Yes, there are myriad assumptions that, made differently, alter this mix. But, even if we extend the lifespan of technological civilization by orders of magnitude, we still end up with small numbers and low probability. And, if we presume that space travel is trivial to a truly advanced civilization, and that said civilization will have been spreading throughout the galaxy for hundreds of thousands of years, we might speculate that they’ve stopped by our little rock just out of curiosity instead of in response to our radio leakage. Going down that path takes us to ancient astronauts, Erich Von Daniken and all sorts of other archeological ETs. But, I repeat the earlier admonishment about confusing what we want to be true with what is true or what we know. There is also the question of, if intelligent life expands in a recognizable form across the stars, why is there no evidence of it? Why hasn’t the Earth already been colonized? Where are they? This is dubbed the Fermi Paradox (worth googling if you’re interested).

This topic has obviously been covered to much greater depth by much bigger brains, with widely varying results. One place to start for those who want to dig more into this is with the Drake Equation. I remember being first exposed to the Drake Equation in high school chemistry class, as an amusing aside to orbitals and the periodic table. The teacher (probably Mr. Raso) applied order-of-magnitude values to most variables, and concluded with the final variable – the span of time that civilizations release electromagnetic radiation. Back then, the question was whether civilizations tended to last for tens of thousands of years or tended to destroy themselves (late 70s, cold war, ICBMs, you get the idea). As a high school kid, I thought it was wicked cool, and thought it was really a nifty bit of scholarship. I did have a niggling doubt about the willy-nilly declaration of “lets say 1 in 10 fit this variable, and 1 in 10 fit that variable,” but didn’t think much of it until I read Michael Crichton’s fantastic essay on the subject, which makes the compelling (dare I say incontrovertible?) case that the Drake Equation has no basis in science. Still, as an introduction to the questions that have to be answered, it does serve.

Which takes us full-circle to my original point – that this essay is about belief. And, more broadly and more to the point (and with concurrence from Michael Crichton), the entire question regarding extraterrestrial intelligence comes down to beliefs. We don’t even know enough to theorize within the context of scientific thought. So, are there little green men flying around our skies or hiding in our oceans? Believe what you want.

• About the Author

About Peter Venetoklis

I am twice-retired, a former rocket engineer and a former small business owner. At the very least, it makes for interesting party conversation. I'm also a life-long libertarian, I engage in an expanse of entertainments, and I squabble for sport.

Nowadays, I spend a good bit of my time arguing politics and editing this website.

If you'd like to help keep the site ad-free, please support us on Patreon.