The Drake Equation Estimates How Many Alien Civilizations Are Out There

What are the odds that there's intelligent life beyond our planet? Good news: there's an equation for that. The Drake Equation estimates how many extraterrestrial civilizations may exist beyond our galaxy. There's just one catch.

Dr. Frank Drake

The Equation

Dr. Frank Drake presented the Drake Equation in 1961. Here it is in all its glory:

N = R* • fp • ne • fl • fi • fc • L

What does that all mean, exactly? It's a way to say that life is present on a fraction of a fraction of a fraction of the planets in the universe. Let's break it down:

  • N = The number of detectable civilizations in our galaxy. This is the number the equation is trying to find.
  • R* = The rate that stars suitable for developing intelligent life are forming.
  • fp= The fraction of those stars that have solar systems.
  • ne = The number of planets in each of those solar systems that could support life. (See how we're narrowing that N number down little by little?)
  • fl = The fraction of those habitable planets that actually contain life.
  • fi = The fraction of those life-bearing planets that actually have intelligent life.
  • fc = The fraction of intelligent civilizations that develop a technology that release detectable signs of their existence into space.
  • L = The length of time those signals have been transmitting.

Exciting as the possibility of alien life is, you can see how it's difficult to calculate our chances are of finding it—at least right now. We don't have exact numbers for most of the equation, so crunching the numbers is a challenge, at best. Still, we can theorize. The equation can result in a broad range of answers depending on how optimistic or informed the user is. Many scientists look at the equation as a useful and tool for the probability of life on other worlds.

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Written by Curiosity Staff April 15, 2016

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