RS #47: The Search for Extra-Terrestrial Intelligence
November 7, 2011 3 Comments
In the latest episode of Rationally Speaking, Massimo and I spar about SETI, the Search for Extra-Terrestrial Intelligence: Is it a “scientific” endeavor? Is it worth maintaining? How would we find intelligent alien life, if it’s out there?
My favorite parts of this episode are the ones in which we’re debating how likely it is that intelligent alien life exists. Massimo’s opinion is essentially that we have no way to answer the question; I’m less pessimistic. There are a number of scientific facts which I think should raise or lower our estimates of the prevalence of intelligent alien life. And what about the fact of our own existence? Does that provide any evidence we can use to reason about the likelihood of our ever encountering other intelligent life? It’s a very tricky question, fraught as it is with unresolved philosophical problems in probability theory, but a fascinating one.
This is an interesting question, Julia. I agree with your position. Seth Shostak gave a talk at CSICON a couple weeks ago that you might find interesting. I hope CSI posts videos soon. Hope you’re recovering well.
I felt that Dr. Pigliucci unfairly played down the Principle of Mediocrity bit. It seems to me that simpler explanation of our existence is that the advent of life on a planet is (relatively) easy. While I wouldn’t doubt that there are a decent number of steps required for life to start, it seems to me that in order to make life so rare that we are the only example of it in the universe (or even merely the only one in our own galaxy) there would be so many more precise conditions with minimal tolerances that the complexity of the process would increase dramatically over life being simple.
There’s a species of creationist argument in the evolution debate that goes “Think of all the changes that hat do happen for pond scum to evolve into man”. While, yes, there are a lot of mutations that need happen, when you get into discussing it with the person using that argument, you soon realize that they are seeing that list of specific mutations as happening one at at time, in a specific order, and the possibility of each step happening being dependant upon the step before being successful and gosh if the chances just aren’t so freaking tiny that it would take *forever* for even just one specific mutation to happen. And happening in an individual traceable line of inheritance.
The creationist is clearly not thinking of populations (as is evident in other arguments often made by them) and the parallelisms that this allows to happen. Yes, some of the mutations in list M may depend upon others, without which they themselves are detrimental rather then beneficial, but at an step N, not all remaining M(N) mutations are like that. When you consider that for a species like field mice in which there are probably 10 billion individuals on the North American prairies then one realizes just how (nearly unimaginably) many times in parallel these changes are being experimented with in the crucible of natural selection. If field mice genomes have the same rate of mutations as humans do (roughly 200 per person) then we’re talking trillions of attempts in parallel per 5 month generation.
I would suspect that an analogous type of parallelism is running throughout the galaxy on planets orbiting in their stars’ Goldilocks zones.
Given the vastness of the universe, I’m almost certain there is intelligent life out there. Finding it is still a big issue. Searching for it via microwave receivers is a good bet. It’s a reasonably clear area of the spectrum and easy to analyze huge sections of radio bands for something which stands out from the background. No known natural phenomena produce certain kinds of narrow-bandwidth signals or certain modulations, but a transmitter produces them easily.
It’s also a reasonable presumption that a highly advanced race would produce microwave emissions. Perhaps for communications, but even if not, it could be used for navigation, remote sensing (like radar), heating up plasma for fusion power etc etc etc.
Then there are some other methods that have been proposed and are being used like optical seti, which uses telescopes to look for extremely quick and very narrow band emissions of light.
This is all well and good, but it faces a huge problem. A very high gain telescope or antenna necessarily has a very narrow beam (and it has to anyway to prevent interference)
So we are basically looking at the sky through a soda straw one star system at a time.
There may be signals there. They may be receivable, but I would not expect us to find them until the day we have thousands of high gain receivers sweeping the sky.