While SETI has been around since 1960, it has yet to turn up any conclusive proof of intelligent life. The Wow! Signal, pictured at left, is one of the more mysterious signals received, but it has never repeated or been conclusively identified. However see SETI WOW!
The seven new Earth-sized planets around TRAPPIST-1, a red dwarf star 39 light-years away, renewed public speculation about extraterrestrials. Sixty years ago, the consensus among astronomers was that life’s earthly genesis was so convoluted and unlikely that we may be alone in the universe. For some physicists like Enrico Fermi, negative results from the Search for Extraterrestrial Intelligence (SETI) reinforced that pessimism. But these days, very few astronomers feel that way. The current groupthink is that the universe probably teems with life.
Early discovery steps in the near future will include spectroscopic space telescopes studying exoplanet atmospheres, offering the ability to study their composition. Earth’s habitable atmosphere exists solely because of photosynthetic plants exchanging carbon dioxide for oxygen. It would therefore be very encouraging if we detected oxygen around another world, as it may point the way toward life.
But what is life? Scientists can’t agree on a definition. Are viruses alive? They have no metabolism, they don’t feed themselves, and many biologists regard them as inanimate. Yet their RNA coding forces host cells to make lots of viral copies.
And does life begin through chemistry? If certain occurrences cause life to arise from non-living components, we want to know if it happens readily. In other words, is life easy? Or does it require extremely unlikely events?
A good argument for life being “easy” is that earthly life began almost as soon as it was possible. After the molten Earth cooled, there came a long period when asteroids and comets pummeled our surface. This violence stopped some 4 billion years ago. And bingo, the earliest fossils date from right then, within 200 million years of when it was first possible. That’s awfully quick.
A good counterargument, which makes the case for life being “hard,” is that life-origination or abiogenesis happened only once (that we know of). Every earthly creature is a descendant of that first ancestral organism. We know this because all life, from elephants to bacteria, share remarkable genetic similarities. They’re all made of amino acids and sugars with the same kinds of spirals or asymmetries. Amino acids can come with left- or right-handed twists, called chirality. But on Earth, life only uses amino acid molecules with left, handed twists, and is limited to a right-handed direction in all its sugars and DNA—the same as a corkscrew.
If life started a second time from scratch, it likely would show differences in such chirality. Now, there are at least 6 million species of bacteria (even if only 100,000 have had their genomes sequenced). But every single microbe, plant and animal we’ve examined is a descendant of that first life creation. The point: Why didn’t life start a second time, a third, or a hundredth? Four billion years have passed, and yet life originated only once. This suggests that abiogenesis is not easy, but hard.
So which is it? Fred Hoyle, who coined the term “Big Bang,” described an accidental birth of life as akin to a tornado sweeping through a junkyard and creating a jumbo jet. Supporting this, Francis Crick, the co-discoverer of DNA’s double helix, described the origin of life as “almost a miracle, so many are the conditions which would have had to have been satisfied to get it going.” (He wasn’t suggesting a spiritual origin, merely that the process is utterly baffling.) If abiogenesis is really so unlikely, then even given the immense size of the cosmos, it’s possible we’re the only example.
Of course, this assumes abiogenesis only happens accidentally. But what if advanced aliens are creating life, or if nature has immense innate intelligence? I just saw an amazing nature documentary called Flying Monsters 3D by David Attenborough, showing the first flying creatures from millions of years ago. The earliest bird wings had the same shape as modern aircraft. That airfoil configuration is necessary for all flight, and requires a wing’s upper surface to be convex. It’s hard to see how evolution could have created it. Unlike giraffes’ necks, where incremental increases offered survival advantages, a step-by-step process wouldn’t work for a wing design. A slightly wrong shape would be useless and confer no benefit. Some 400,000 cells would all have to simultaneously mutate in just the right way to create a properly shaped wing. This defies an evolutionary hypothesis.
Occam’s razor might suggest some baked-in, overarching intelligence. I’m not invoking spirituality, merely that the effect of random collisions and mutations is not always a work-able answer. So perhaps nature is inherently smart. We cannot visually see this intelligence, just as we cannot see electrical fields; and yes, this is a minority viewpoint. But if true, then the sky’s the limit for ETs.
It’s guesswork. We know of life on only a single world, so our sample size is one. And when you try to draw a line on a graph but you have just one data point, well, good luck. We’ll have no shortcuts when we probe the planetary system of TRAPPIST-1.
 Bob Berman, “Finding Aliens,” Astronomy (45, 9, September 2017, p. 10). Contact Bob about his strange universe by visiting http://skymanbob.com