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## The Odds Of Intelligent Life One of the classic speculations of astronomy and biology is the uniqueness or likelihood of intelligent life in the universe. Dr. Frank Drake who is now Professor of Astronomy and Astrophysics at University of California proposed, in 1960, a mathematical framework to estimate the number of extraterrestrial civilizations in our galaxy. The equation, now known as the Drake Equation.

What’s fascinating about the equation are the kinds of variables Drake chose as contributors to the existence of a civilization. In this video, astronomer Carl Sagan describes the equation’s components and its implications to the existence of intelligent life in the galaxy:

Come up with your own estimate of life using the Drake Equation using this interactive version from Nova.

How accurate is the Drake Equation? That’s the problem. No one can really say at this point–although it does provide a plausible framework. Most of the variables are just simply guesses. Criticisms of the Drake Equation in wikipedia:

Criticism of the Drake equation follows mostly from the observation that several terms in the equation are largely or entirely based on conjecture. Thus the equation cannot be used to draw firm conclusions of any kind. As T.J. Watson states:

The Drake equation consists of a large number of probabilities multiplied together. Since each factor is guaranteed to be somewhere between 0 and 1, the result is also guaranteed to be a reasonable-looking number between 0 and 1. Unfortunately, all the probabilities are completely unknown, making the result worse than useless.

Likewise, in a 2003 lecture at Caltech, Michael Crichton, a science fiction author, stated:

The problem, of course, is that none of the terms can be known, and most cannot even be estimated. The only way to work the equation is to fill in with guesses. […] As a result, the Drake equation can have any value from “billions and billions” to zero. An expression that can mean anything means nothing. Speaking precisely, the Drake equation is literally meaningless…

One reply to such criticism is that experiments by SETI scientists do not attempt to address the Drake equation for the existence of extraterrestrial civilizations anywhere in the universe, but are focused on specific, testable hypotheses (i.e., “do extraterrestrial civilizations communicating in the radio spectrum exist near sun-like stars within 50 light years of the Earth?”).

Another reply to such criticism is that even though the Drake equation currently involves speculation about unmeasured parameters, it stimulates dialog on these topics. Then the focus becomes how to proceed experimentally.

The Drake Equation is simply another one of those questions that have to wait for more advanced instruments, theories, and discoveries in order to shed more insight. Meanwhile we can only guess.