Are There Aliens?
On Evangelization in an Age of Science
Often in my planetarium Q&A I would be asked “Are there aliens?” I usually began by citing the fact that astronomers are the group that spends the most time outdoors at night, knows the night sky the best, and makes the fewest UFO reports. I would conclude by staring off into space and quietly say with a bit of drama “That means that alien UFOs aren’t real, or else we astronomers are working for them.” People usually laughed, but once a young man shot me a look that said “I knew it!”
I also liked and used the quote “If aliens exist, that’s profound, and if they don’t exist, that’s profound.”
All kidding aside, I would admit that I thought we were alone, at least on this side of the galaxy, and perhaps throughout the universe. I would then go through the arguments, while noting that absence of evidence is not evidence of absence.
The thumbs up argument:
· The so-called Copernican Principle. Science assumes that physical phenomena are the same everywhere in the universe, that there is nothing special about our position in it. If intelligent life is here, then it must be elsewhere.
The thumbs down arguments:
· Galaxy formation. The majority of galaxies are not spirals, and it is no accident that we are in a spiral galaxy. We know from the synthesis of chemical elements that our sun is a third generation star, that it and its planets are made of material from two previous stars. It is the density waves moving through galaxies that allow for such multiple generations. These density waves lie directly ahead of the spiral arms, in fact the arms are merely the accumulations of giant hot stars that were compressed and ignited by the waves. So spiral arms are evidence of a stellar recycling process. As galaxies merge over time they run the risk of losing their density waves: two waves in opposite directions will cancel each other. So-called elliptical galaxies have lost their density waves and are seen to have no young stars. Since these elements are necessary for life (as we understand it), a galaxy going elliptical too soon it will never have life.
· The Rare Earth Hypothesis. As mentioned in an earlier essay, our moon was created in a collision between a slightly larger earth and a Mars-sized planet now called Theia. Once formed, the moon was much closer to the earth than it is now, and the earth rotated faster (both changed over billions of years due to tidal friction). Once they cooled, entire continents became tidal pools, drained and refilled every few hours by huge ocean waves. The oceans steamed just from the tidal energy. This went on for a half-billion years before life appeared. If you wanted to experimentally recreate these conditions in a jar about a cubic meter in size, you would have to run that experiment for over 100 billion years to have even a hope of success, the odds are that long.
· Evolution. Evolutionary processes such as natural selection cannot fully explain human intelligence. This may seem surprising, since there is obvious survival value to it (that is, unless we engineer our own demise! The verdict is still out!). We now modify our environment to the extent where we are largely immune to evolution. Still, we know we are the first on earth to have this level of intelligence: no one before us split atoms or left artifacts on the moon. This is a problem because we know that biological structures needed for survival evolve very quickly. For example, some type of vision has evolved over forty times, and five times independently to photographic quality. If human level intelligence is fully driven by evolution then there should have been dinosaurs doing what we do now. From a scientific viewpoint human intelligence is an accident in a way that vision is not, even if we can postulate evolutionary steps for it.
· The Fermi Paradox. We know it is possible to build robots that are self-replicating, so-called universal constructors. Build one, send it to a nearby star where it will make copies, which then travel to the next stars, and so on. Once begun every solar system in our galaxy will have at least one such robot in just three million years. The physicist Enrico Fermi noted this and asked “So, why are they not here already?” We are talking about a level of technology not much more advanced than what we have today, and which could not be hidden. Such machines would have radio and infrared emissions that would be detectable within a few hundred lightyears of us. The counterarguments of ‘higher technologies’ have validity, but so do the counter-counterarguments (such as technological progress having cultural differences when cultures are isolated; if this is not true, if everyone figures out warp drives before building such robots, then our own warp drives are less than 200 years away. Even then, such robots would be useful for building other things such as space colonies).
In summary I would say “So we have one argument that is thumbs up for aliens, four thumbs down. We have no evidence either way. So, I say, 20% chance they are out there, 80% chance they aren’t.”
Here’s the funny thing: some people would get angry with me! There had to be aliens! It got to the point I started to say “Since there is no evidence, you can weight the arguments any way you want. If you want the thumbs up to be 90% likely and the others to be about 2% each you can, there’s no evidence to stop you. I just weight them equally.” After I started saying that the anger subsided.
Why the anger?
Recall that many science fiction stories, including movies, have a story line where aliens save humanity, often from humanity’s own follies. I have heard many people over the years quietly express hope in such a salvation. I had to conclude that my citation and analysis of these arguments for such people was not a simple disagreement but rather a threat to faith.
Today’s evangelists face a difficult situation. They proclaim the Gospel of the true Savior, who is independent of space and time. An alien savior would have no such independence. I suspect this may be the reason why some prefer the alien savior over the Biblical Savior: a fundamental difference over the nature and location of the New Heaven and New Earth. But since science tells us that our universe is not permanent, science itself hints which is the true one.
The Fermi paradox strikes me not as a paradox but as a simple consequence of the immense distances of interstellar space and the absolute limit imposed by the speed of light (and no Star Trek or Star Wars cheating with hyoerdruves and the like)
Here's a thought to append to the "thumbs down" Fermi's paradox argument.
Volume 2 of Cixin Liu's "Three Body Problem" trilogy is titled "The Dark Forest" and offers an answer to Fermi's question. He proposes that the universe is like a dark and dangerous forest. The last thing you want to do as a civilization is to let any other civilization know that you exist. There's a strong chance that other civilizations got as far evolutionarily as they did because they are fiercely protective of their own species and therefore likely to proactively attack and destroy other civilizations before the other civilization can do the same to them.
Fortunately space is so vast no other civilization has determined us to be a threat, but they certainly aren't willing to expose their existence to us.