Pollsters love to ask us whether we believe in alien life. It is an interesting topic because it straddles the line between fact and belief. So where do you stand on it? Take a minute to mentally answer the following questions with Yes, No, or Not Sure.

1. Do you believe that alien life exists?
2. Do you believe that intelligent alien life exists?
3. Do you believe aliens have visited the Earth?

Americans are pretty divided on these questions. About 50% of us believe there is some form of life on other planets (even if only akin to bacteria) while 33% are not sure. We are more skeptical about the existence of intelligent extraterrestrial life with about 38% believing they are out there while about 42% are unsure (see here). Polls also generally report that roughly a third of us believe aliens have actually visited the Earth. Apparently most of us who believe in intelligent alien life also believe that those aliens are capable of reaching the Earth.

How did your answers compare? This may surprise you, but I am completely confident that the 50% of Americans who are believe that alien life exists are completely…. right! Regardless of what you believe, it would be understandable for you to ask, how can you be so certain? Have you seen aliens? Can you show me scientific proof of alien life?

The answer is that I have a particular kind of certainty here called a “statistical certainty.” A statistical certainty is something you can be confident is true even though you may never prove it in the conventional sense. For example, I can be statistically certain that right now as you read this most excellent article, someone somewhere is thinking about bananas. Can I prove this? Obtaining clear proof, finding even one such person may be theoretically possible but practically unlikely. Still, given the number of people in the world and the commonness of bananas, I can be quite sure of it nonetheless.

Similarly, we can clearly say with statistical certainty that life does exist on other planets. Even though I’ve never seen an alien, have absolutely no scientific evidence of alien life, and no expectation of ever meeting one, I do know that the rules of chemistry and physics that gave rise to life on Earth are equally applicable on every Earth-like planet. And all available evidence tells us that there must be a huge number of such planets in our universe. So therefore, I can bank on the statistical certainty that yes, some kind of life does exist on other planets.

Is this essentially the same as a belief then? Am I simply playing word games to rationalize my belief in aliens? Absolutely not. A belief has no basis in statistical certainty. A belief exists despite of a complete lack of any basis upon which to form a even a statistical plausibility. We have no basis upon which to believe in god or ghosts or gremlins, no consistency or conformity with observable evidence, on which to base any legitimate statistical confidence.

So let’s move on now to the second question, whether intelligent life exists in the universe. I think that the 38% who believe happen to be right again – even if for the wrong reasons. (Which brings up the side question, is one truly right if they are right for the wrong reasons?)

We can reasonably bank on a strong statistical confidence in the existence of intelligent extraterrestrial life, even if it is not quite a statistical certainty. While my confidence in intelligent aliens may not be not quite as high as in alien bacteria, it is still a sensible default to assume that yes, intelligent alien life does exist somewhere. And again, this is not belief or wishful thinking, but an assessment founded upon the consistency of physical laws throughout the universe and the sheer number of life-sustaining planets that undoubtedly exist in it.

Finally, what about the third question as to whether those intelligent aliens (that we are statistically confident must exist) have ever visited Earth? On this question I go completely the other direction. There is no credible evidence that any have ever visited Earth in the past – and we would expect to find such evidence. Some alien Coke-cans littering the Nazca Desert or anything. Further, there is no logical mechanism to give one any confidence that aliens could visit us now or for that matter ever in the future. While allowing some tiny plausibility based on what we may not know yet, the tremendous gulf of time and space between us simply makes such interstellar travel diminishingly unlikely.

Many people would argue against my skepticism. Surely, they say, you’re too narrow-minded. You lack vision. Certainly a sufficiently advanced species could produce some technology to travel between solar-systems. At one time people scoffed that we could never reach the moon, and look we did it anyway!

But the problem here is our solar system is an incredibly tiny dot in an effectively infinite ocean. The gulf between stellar systems is literally astronomical. The barriers of time and space between civilizations are so fundamental that physical travel between them simply runs up against too many inviolate laws of physics. Interstellar travel is not comparable to crossing a vast ocean. It is more comparable to shrinking down to the size of a cell like Ray Palmer (The Atom) and swimming though a blood vessel. Barring some completely fantastical warp-hole technology, it is simply not happening, not ever, not for us or for any alien species no matter how advanced.

Belief that science will always find a solution to everything illustrates the fallacy of an unreasonable belief in technology. This is a dangerous belief when it delays or undermines more effective and necessary action, as it does now in the case of global climate change.

So in summary it is a statistical certainty that life exists on other planets and it would be highly surprising if some of those life forms were not intelligent. But it is extremely unlikely we’ll ever even detect signs of each other, let alone communicate or pay each other a visit. Nevertheless I fully support continuing to look for signs of intelligent life in the universe, even knowing that by the time we see such evidence they would almost certainly have been long extinct. Knowing that intelligent life existed somewhere else, even if only light-ages in the past, would change us fundamentally forever, and I think for the better.