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Life in the Universe and Drake

Some Scientists are now saying that life in the Universe may be rarer than we thought, but they also say that on the other hand it might not.

That might sounds wishy washy but often, when you dive in deeper the science gets really interesting and you see where they’re coming from……kind-of.

Astrophysicist David Spiegel at Princeton University and physicist Edwin Turner at the University of Tokyo make this argument in their paper called “Life might be rare despite its early emergence on Earth: a Bayesian analysis of the probability of abiogenesis”

This paper is found at the arXiv website which is an archive for digital preprints of scientific papers in math, physics, astronomy, computer science etc

They construct their argument based on Bayesian reasoning which is a form of logic that lets you reason with uncertain statements.

They use this tool then to reason that life on earth could have been very common, which it is, or it could not have been as well. There’s essentially no reason to prefer one or the other.

The authors wrote:

“Although life began on this planet fairly soon after the Earth became habitable, this fact is consistent with … life being arbitrarily rare in the Universe”

My first though on reading this…”hello”…life began on earth almost as soon as it was possible. After just few hundred million years at least. It seems we’re continually pushing back the start date of life with new evidence. That seems to easily lead one into concluding that given suitable conditions, a rocky planet, an atmosphere, liquid water etc, life is inevitable and quick to arise.

But, their argument goes…It took billions of years for intelligent life to arise. If life didn’t begin early in the history of earth, we wouldn’t be here to contemplate this topic.

That reminds me of the anthropic principle….if the universe wasn’t exquisitely tuned to allow life like ours to exist, we wouldn’t be here to think about it.

Bottom line then is that you can be very encouraged and excited by the idea that life arose quickly on earth,
Just don’t be highly confident about the ubiquity of intelligent life elsewhere based on that fact alone.

The real interesting tie in that this news-item makes is with the Drake equation.
This is that equation formulated in the 1960s by Frank Drake of the SETI Institute in California that estimates the number of extraterrestrial civilizations in the Milky Way galaxy that are detectable.

I loved when Sheldon (from Big Bang Theory) described what this equation is in his usual succinct pedantic way:
“..the one that estimates the odds of making contact with extraterrestrials, by calculating the product of an increasingly restrictive series of fractional values such as those stars with planets and those planets likely to develop life…
N = R x FP x NE x FL x FI x FC x L”.

His delivery, as usual is pretty damn funny.

The factors in the equation are of course very speculative but scientists generally conclude that there may be 10,000 technological civilizations in the milky way.

That high number though depends a lot on one factor that scientists were confident about and that’s the probability of life arsing on earth-like planets. They usually assign a number close to 100%  for that but now maybe we can’t be that confident based on this latest paper. Bummer

I hope they’re wrong, but what they’re saying sounds pretty reasonable and who am I to argue against Bayesian reasoning.

The best resloution of course is to find that elusive 2nd datapoint. All this speculation is fun but the sooner we find other life the sooner we’ll know just how anomalous life is.

2 comments to Life in the Universe and Drake

  • Jim Shaver

    “I hope they’re wrong, …”

    I agree, even though we both know that what we hope to be true has no influence whatsoever on what is true. But this I believe: If we are the only intelligent life in the universe, what a pathetic waste of a universe!

  • DLC

    the Drake equation does not estimate the probability of life existing elsewhere, but of intelligent technology-using life. There may well be microbial life somewhere, or possibly intelligent life that never developed technology.
    Then recall that the final element of the equation is the killer one. (literally) The fraction of life that survives creating the means for it’s own destruction.

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