Wishing ET Upon a Star
What are the odds of finding extraterrestrials? That subject has been discussed ad infinitum, but David Shiga at New Scientist thinks the odds just went up. “Solitary suns like ours are not as rare as we once thought, boosting the likelihood that there are other life-friendly solar systems in the universe.” It should be noted that “life-friendly” is not the same thing as “friendly life.” He pointed to a survey of 454 sun-like stars that showed 56% to be loners like our sun. Binary star systems had long thought to be the majority.
Binaries are bad for life, not only because they swing rocky planets into wild orbits, but also because their planets sing How Dry I Am. “Stellar companions may also interfere with the formation of comets in the outer reaches of a planet-forming disc,” Shiga wrote with help from John Chambers [Carnegie Institution], “thereby eliminating a potential source of water for rocky planets through comet impacts.”
The number of assumptions in this claim is as breathtaking as the reasoning is specious. Shiga has just taken one necessary condition out of many, and made it sufficient. This would be like Robinson Crusoe comforting himself with visions of shopping centers on his island, because there’s more level ground than he originally thought there was. Shiga has assumed the origin of life, water from comets, evolution, and progress to sentience based on … what? The slight decrease of one hurdle – binary companions.
At least the Drake Equation spelled out the assumptions (though not all of them) with a little more thought: If we knew how many stars there are and how long they lasted, and then if we knew how many stars were sun-like, and if we knew how many of those had planets, and if we knew how many of those were earth-like, and if we knew which ones had life, and if we knew which life-bearing planets had intelligent life, and if we understood the average lifetime of an intelligent civilization, then we might be able to estimate how many intelligent civilizations there are.
There are numerous other if-statements Drake left out, like the number of stars that are solitary, and the number of planets that have water. Undoubtedly you can think of others. It’s all academic, though, because without values to plug into those unknowns, and without knowing how many unknowns he neglected, the equation pretends to represent “educated” guesswork. Educated guesswork without data is indistinguishable from uneducated guesswork.