Radically Upgrading the Estimate of Alien Civilizations in the Milky Way

Heart of the Milky Way Image Credit: NASA, ESA, and Hubble Heritage Team

Heart of the Milky Way
Image Credit: NASA, ESA, and Hubble Heritage Team

You may recall the Drake Equation, the famous estimate of the total number of potential technologically advanced civilization in the Milky Way, with which we might make radio contact.

N=R_{\ast }\cdot f_{p}\cdot n_{e}\cdot f_{\ell }\cdot f_{i}\cdot f_{c}\cdot L

The right hand side of the equation, courtesy of Wikipedia are :

R* = the average rate of star formation in our galaxy

fp = the fraction of those stars that have planets

ne = the average number of planets that can potentially support life per star that has planets

fl = the fraction of planets that could support life that actually develop life at some point

fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations)

fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space

L = the length of time for which such civilizations release detectable signals into space

When the equation was first proposed, virtually no-one had an inkling of just how common planets actually are, leading to assumptions regarding the second term, which were wildly pessimistic.

Now thanks to a wave of data brought in from several planet hunting efforts, and in particular the Kepler Space Telescope, we now know that the actual percentage of stars hosting planets approaches 100. Furthermore, from the same data we also know that the presence of systems  where at least one planet orbits within a star’s habitable zone is somewhere on the order of 25%.

In a new paper in the May issue of the journal Astrobiology, Adam Frank and Woodruff Sullivan, take a new look at the equation, incorporating the new data while continuing to take a very conservative position regarding the other terms further to the right, which are obviously still very much unknown.

Here, as described by Frank in an article in the New York Times, is what they concluded:

“You might assume this probability is low, and thus the chances remain small that another technological civilization arose. But what our calculation revealed is that even if this probability is assumed to be extremely low, the odds that we are not the first technological civilization are actually high. Specifically, unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then we are not the first.”

It may be however, that not as many people here in this planet are taking time to ponder such cosmic questions under a starry night sky anymore, for the simple reason that according to another NYT article, one third of the population can no longer even see the Milky Way itself, or many of its dimmer stars, due to the pervasive problem of light pollution.



Posted in: Exo Planets

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1 Comment on "Radically Upgrading the Estimate of Alien Civilizations in the Milky Way"

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  1. Keith Pickering says:

    The really key number to derive from the Drake equation is not the number of civilizations in the galaxy, but the average distance between them. And no matter how you slice it, we are a long, long, LONG way from anyone else.

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