Here’s Seth Shostak pumping up SETI again, and now he’s predicting contact with aliens within 20 or 25 years, or by 2030.
I don’t buy it for a minute, and I think his whole argument is ridiculous.
As these guys always do, they have a small set of arguments. One is the argument from very big numbers: there are 1022 stars in the known universe, and the current data shows that a significant fraction of them have planets, and they’ve even observed a few of them that have earth-like temperatures.
I say, big whoop. The other big numbers we could throw around are the distances of these stars from us and each other, which completely negate the bonus of large numbers. We’re simply not going to get an accidental signal from elsewhere; signal strength is going to drop off as the inverse of the square of the distance, so we’re not going to pick up some broadcast from an alien civilization. They’re going to have to aim a signal at us (one unexceptional star out of 1022), and they’re going to have to invest a significant fraction of the energy output of their star to get the signal to us.
I would ask, from the example of the sole technological society we know about, are we doing that? Why do we expect other civilizations are going to do that, and specifically send a signal to us?
But the most objectionable part to me, personally, is the short section titled “Biology: An Easy Thing?” Life arose very early on Earth, and there is good reason to expect that we are not unusual, and the emergence of life as an outcome of normal planetary chemistry probably is common and likely. Biology is only easy, though, if you’re willing to point to a stromatolite and leap immediately to the conclusion that life will build radios. There’s a rather wide chasm there that Shostak elides. The ubiquity of bacteria in no way implies the ubiquity of technology. The specific kind of intelligent life that builds telescopes and radios and artificial intelligences is going to be really rare: I can understand how an astronomer might get excited about incremental increases in likelihood by discoveries that maybe 70-80% of stars have planets, and maybe planets orbiting red dwarf stars would have habitable zones, but those numbers do not compensate for the fact that in the 4 billion year long history of life on earth, the technology to even dream of collecting signals radiating from other stars is only a century old. Only one 40 millionth of this planet’s existence contains that kind of capability.
Add to that the likelihood that any matching civilization might be a thousand light years or more away, and that their signal (although from our example, they probably aren’t signaling; think instead of thinly scattered civilizations all listening casually and unintently for a bit of patterned electromagnetic radiation) can only be received and echoed back over a time span far greater than the duration of any of our cultures, and that puts Shostak’s 16 or 20 or 30 year bet in perspective. That’s a convenient eyeblink on the scale of the time and space SETI proponents tout as an advantage for their calculations.
I do agree with Shostak’s comments about how science isn’t shackled to the narrow hypothetico-deductive method taught in introductory science courses, and that sometimes fishing expeditions are legitimate components of a research program. But I tend to expect fishing expeditions to have slightly better rationales and expectations of useful results than SETI can provide.