Image credit: Lynette Cook  -

Drake Equation

Article Updated: 24 Dec , 2015



Image copyright: Lynette Cook

We know there’s one intelligent civilization here on Earth. But are there any more out there in the Universe. Until we actually discover the first alien civilization, there’s no way to know for sure, but astronomer Dr. Frank Drake developed an equation that helps us estimate the number of possible civilizations out there based on some numbers that we might be able to estimate. This formula is known as the Drake Equation.

Here’s the formula:

N = R* x fp x ne x fl x fi x fc x L

N is the number of civilizations in our galaxy that we might able to communicate with.
R* is the average rate of star formation in our galaxy
fp is the fraction of those stars which have planets
ne is the number of planets that can support life
fl is the number of planets that develop intelligent life
fi is the civilizations that develop transmission technologies
and L is the length of time that these civilizations transmit their signals into space

Some of these numbers are easy to calculate, like the rate of star formation in the Milky Way. There are known to be about 10 new stars formed in the Milky Way every year. Other numbers are total guess work. Traditional estimates have guessed that 50% of stars will have planets. Stars with planets will have 2 capable of supporting life. 100% of planets will develop life, of which 1% will be intelligent, and of those, 1% will be able to communicate. And a civilization is able to communicate for about 10,000 years.

If you run those numbers through the Drake Equation, you end up with 10. In other words, there are possibly 10 civilizations in the Milky Way at any time capable of communicating.

Without any real data gathered (apart from us here on Earth), there’s no real way to know how many alien civilizations are really out there. There could just be 1 in the entire Universe (us), or millions in every galaxy. As astronomers study stars and planets with newer instruments, they might be able to work out just how accurate the Drake Equation really is.

We have written many articles about the Drake Equation for Universe Today. Here’s an article about a new calculation for the Drake Equation. So, where is everybody?

There are some great resources out there on the Internet. Check out this Drake Equation calculator.

We have recorded an entire episode of Astronomy Cast about the Drake Equation. Check it out here, Episode 23 – Counting Aliens with the Drake Equation.

Source: SETI


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