From the July 2002 issue

The Drake Equation

Make your own estimate for the number of communicative civilizations in the Milky Way.
By | Published: July 26, 2002 | Last updated on May 18, 2023
Interactive Drake Equation
Click on the screenshot above to enter your own values into the Drake Equation and find out how many communicative civilizations in the Milky Way would exist with those values. Tom Ford
Throughout the ages, many have wondered whether intelligent life exists elsewhere in the universe. More recently, SETI scientists have wondered whether we might be able to detect signals from their civilizations.

In 1961 Frank Drake of Cornell University devised a formula to estimate the number of communicative civilizations in the Milky Way, which came to be called the Drake Equation. It consists of seven variables. If we can accurately estimate the values of these variables, such as the number of earthlike worlds per planetary system, we should have a fair idea of how many civilizations exist in the galaxy. Astronomers have a good idea for a couple of the values; some require an educated guess because astronomers, as yet, have only one civilization to work with — our own.

Use the Drake Equation to come up with your own estimate of how many civilizations might inhabit the Milky Way. Click on the image below and follow the steps, inputting your own guesses for each variable. We’ll do the math and show you what your estimates yield.

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