The question in the title is a variant of “Are we alone?” Are there other sentient life forms in our galaxy? Enquiring minds want to know.
This post is prompted by a review of a new book (ALIENS: The World’s Leading Scientists on the Search for Extraterrestrial Life, edited and with an introduction by Jim Al-Khalili). I have not read the book and do not intend to. The reason? The discussion is premature.
One of the powers of human minds is to imagine (possibly the greatest of human powers) but it has a gigantic flaw: garbage in, garbage out. If our imagination has little to no data to work on we come up with quite fallacious outcomes. This is how we got demons and gods and unicorns and leprechauns.
So, what evidence do we have regarding the universe? We have optical and EMR evidence for the existence of billion upon billions of stars in our galaxy and billions upon billions of galaxies in our universe. But realize we have not known this for long. One hundred years ago, we knew that the Milky Way was a manifestation of other stars in our “neighborhood” but we though that that represented the totality our universe, too. We had observed fuzzy spots in those star fields but hadn’t acquired the evidence to recognize them as other galaxies. And while we had speculated that many of those stars would have planets about them, we had no direct evidence that was so until quite recently. The first actual planet circling another star was identified in … wait for it … 1992. So, we have been aware that there are other planets “out there” for all of 25 years. We have subsequently identified hundreds of others.
Do we have any evidence that life exists on those planets? No, but we do not have any evidence that life does not exist either. At this point, we are not yet ready to make those discoveries (although we are close).
The question in the title implies that since there are so many stars, there must also be unbelievably large numbers of planets, and if life is not an isolated accident, or divine bit of magic, occurring here and only here, then where are those other peoples? There is a mistake embedded in this question though, leading to flights of imagination fueled only by fairy dust. The universe is indeed vast, but the primary constituent of our universe is empty space, aka nothing. The next closest star to us is about four light years away from us. To go there to get direct evidence of what exists there, we would have to travel for four years at the speed of light. Since the fastest speed ever achieved by a man-made object is about 25 miles per second, and the speed of light is about 186,000 miles per second, at that speed (as an average), a trip to Alpha Centauri would take a bit under 35,000 years. If we could get their magically and then sent data back to Earth, it would take four years to get here and when it arrived the information would be four years old.
The universe is unimaginably vast, but this is also misleading because it is also vast in time. A civilization could have arisen around Alpha Centauri, to the point that it was capable of building spacecraft capable of very high speeds who could have made the trip in under 20 years, let’s say. But if this occurred 100,000 years ago, there wouldn’t have been anyone here to notice. (That doesn’t stop the imagination, of course, … Ancient Aliens!)
The universe is vast in time as well as space. In order to generate a signal that we could interpret as synthetic instead of natural, that civilization would have to exist within a small radius in space and time. If it is over 100 years out of phase with us now, we wouldn’t have a chance of detecting it. So, 100 years in time is our bubble. How many years has the universe been around? That number is 14,000,000,000 years, roughly. Our “time” as a species capable of detecting another sentient species in our vicinity is therefore about 0.0000025% of the time that has occurred to now. Considering that our spatial bubble is roughly 100 light years wide and the universe is roughly 28,000,000,000 light years wide, we have in out neighborhood, 0.0000012% of the universe’s space. Consequently, we have a combined fraction of the universe’s space and time of 3 x 10–14%. In other words, 99.99999 … 9999% of the universe is outside of our purview, either existing in the past or so far away as to be unattainable.
Something you need to know. Those extra-solar planet hunters … when they “find” evidence of yet another such planet, if that planet is, say, 540 light years away, when the light gets to us it is showing us what was going on 540 years ago. Even if there were a planet with a civilization what could produce radio waves or some such we could detect, that information is 540 years old. What is to say what will happen to us in the next 540 years? Right now our prospects of existing that long do not look good. At the rate we are shitting in our own food bowl, we might not have much of a civilization to be found by aliens.
