Space.com (August 13, 2009)
"Intelligent life beyond Earth might not be as dim a hope as many scientists think, according to a new study challenging a widely held anti-ET argument.
"Many skeptics tout an idea called the anthropic argument that claims extraterrestrial intelligence must be very rare because the time it takes for intelligent life to evolve is, on the average, much longer than the portion of a star's existence that is conducive to such life.
"But now astrobiologist Milan M. Cirkovic and colleagues say they've found a flaw in that reasoning.
"The anthropic argument, proposed by astrophysicist Brandon Carter in 1983, following on his pioneering work on anthropic principles in 1970s, is built on the assumption that the two timescales - the lifecycle of a star and the time required for evolution of living and intelligent creatures - are completely independent. If this is true, Carter argued, it's extremely unlikely that these two windows of possibility would last roughly the same amount of time, and would occur at the same time.
"But that mode of thinking is outdated, Cirkovic claims. In fact, he says the relevant timescales are not independent; they are deeply entwined...."
The article is a pretty good overview of one line of thought, regarding the possibility that life exists in the universe. Cirkovik's approach seems to be that Earth, and Earth's sun, are in the Milky Way galaxy - and that the galaxy can be thought of as an environment.
That's an over-simplification, of course.
I Don't 'Believe in' Life on Other Planets - But I think it's Possible
I'm hardly one of the people who 'believe in' flying saucers in the cargo cult sense of the phrase. On the other hand, I'm not on the same page as the authors of Rare Earth, who came close to demonstrating that life on Earth is not possible. (I've read the book, and have a copy in my library - given the starting premise, it's thoughtful.)In fact, as I write this, software on my computer is processing a packet of data from the Arecibo facility, looking for a non-random pattern that shows up in a very narrow band of frequencies. Odds are, it won't have a natural origin.
The program has been around for years, and may never turn up anything: but I can control the degree to which it affects my computer's performance, and I figure that the ratio of cost (negligible) to possible reward (evidence that there are people other than ourselves around) is highly favorable.
Even if the message, when translated, says, "will you please stop transmitting 'Captain Planet' reruns!"
Algae is Life, Too
While I'm at it, a point that some discussions seem to miss: "life on other worlds" doesn't have to be Ferengi traders and Klingon warriors. Finding something like algae on Mars - or in Ceres - or anywhere other than Earth - would be finding life on another world.Background:
- "Miller/Urey Experiment"
Exobiology, Cruising Chemistry, Duke University, Durham, North Carolina
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