20 October 2008

Half a civilization

The International Journal of Astrobiology has just accepted an interesting paper entitled ‘A Numerical Testbed for Hypotheses of Extraterrestrial Life and Intelligence’ by Duncan Forgan of the Institute for Astronomy in Edinburgh. In the paper, Forgan applies modern estimates to the parameters in the Drake Equation and uses a Monte Carlo method to simulate many times over the number of civilizations that may have appeared in the galaxy. Using the resulting statistics, he has calculated an average value and a standard deviation for the number of advanced civilisations in our galaxy. What is more, he has been able to compare results for three different models of civilisation creation:
  1. Panspermia: Life evolves on one planet, but is able to spread to others in a system. Forgan’s method predicts 37964.97 advanced civilisations in our galaxy with a standard deviation of 20 for this hypothesis.

  2. The rare-life hypothesis: Earth-like planets are rare, but intelligent life is quite likely to emerge on them: 361.2 advanced civilisations with a standard deviation of 2.

  3. The tortoise and hare hypothesis: Earth-like planets are common, but the emergence of intelligent life is unlikely: 31573.52 with a standard deviation of 20.
Interesting results, but as Forgan points out in the conclusion to his paper, this method still suffers from the ‘garbage in—garbage out’ problem.

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