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Astronomy Calculations


Drake's Equation

In the early 1960s Frank Drake setup an equation to estimate the number of communicative extraterrestrial civilizations in the Milky Way galaxy. This page has a calculator you can use to find what number of civilizations to find with your own thoughts and figures.

More to read about Drake's equation at Wikipedia:

It's now the year 2019 and it's 58 years since Frank Drake setup the equation. We know much more now and can use that knowledge to get a better number of the civilizations out there.

Search for extraterrestrial intelligence, SETI:

If you find searching for other other intelligent civilizations out in space exciting maybe you find this movie interesting:

Messier 101, galaxy

Type in your data

It start to calculate as soon you change or write new figures in the white or dark red boxes. Do not exceed the maximum number of characters, delete characters if necessary.

You use the information on your own risk! There can always be a mistake in my equations behind the calculations, check that the result is correct. Let me know if you find something wrong and I try to correct it. Some calculations are very simple done and not correct in the small details.

Drake's Equation:

The equation Frank Drake setup look like this:

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

  1. R* = the average rate of star formation
  2. fp = the fraction of those stars that have planets
  3. ne = the average number of planets that can potentially support life per star that have planets
  4. fl = the fraction of planets that could support life that actually develop life at some point
  5. fi = the fraction of planets with life that actually go on to develop intelligent life
  6. fc = the fraction of civilization that develop a technology that releases detectable signs of their existence into space
  7. L = the length of time for which such civilizations release detectable signals into space

It refer to our Milky Way galaxy.

There are already some default figures in the fields, the most common what we know today. Feel free to test other numbers and if you want to use values outside the limits, write direct in the input window.

1, __________ R* ?

We know today that 1 to 10 stars are formed in our galaxy per year. More interesting is to know how many were formed longer back in time. Say at the birth of our Sun 5 billion years ago, at that time simulations and calculations give that R* = 3 .

star formation number / year 1 to 50 (3)

2, __________ fp ?

The proportion of R* having a planetary system is probably high. Over the past 30 years, a large number of planets have been detected around nearby stars and that with a technology that can only detect the largest planets. Set fp = 0.1 to 1.0 .

proportion of R* that have planets 0.1 to 1.0 (0.5)

3, __________ ne ?

The number of planets (moons) per star that have planets capable of developing life during a stars life time. In our Solar system, Earth, Mars and maybe a Jupiter moon. Set ne = 1 to 10 .

number of planets that could support life 1 to 10 (3)

4, __________ fl ?

The fraction of planets (moons) that develop life, probably high. Set fl = 0.01 to 1 .

proportion of ne that develop life 0.01 to 1 (1)

5, __________ fi ?

The fraction of planets with life that develop intelligent life. Set fi = 0.01 to 1.

proportion of fl with intelligent life 0.01 to 1 (0.1)

6, __________ fc ?

The fraction of planets with intelligent life that develop some communication technology that can be detected. Set fc = 0.01 to 1.

proportion of fi that develop communication technology 0.01 to 1 (0.1)

7, __________ L ?

Lifetime of a communication civilization. Our radio communication civilization is about 100 years old, the Neanderthal people lasted for 300'000 years but never develop the radio, how long will we survive ? More than one communication civilization can develop during a planet / stars lifetime. Set L = 100 to 500'000. Some idea, Roman Empire lasted for 650 years, the ancient Egypt lasted for 3000 years.

lifetime of a communication civilization. 100 to 500'000 years

Results, N =

R* * fp * ne * fl * fi * fc * L   N
R* fp ne fl fi fc L = Lifetime of a communication civilization


How to interpret the results ? If N = 1 or less, then only we exists just now in the Milky Way galaxy. If N is higher than 1 we have neighbours out there.

Number of intelligent civilizations in Milky Way galaxy

Illustration of low and high N. If the N value get low, don't forget that there are billions of galaxies out there.

It doesn't has to be radio waves we are looking for, other electro magnetic spectra as light waves is also possible. Shorter wave length is easier to direct in a more narrow beam and then need less power. But radio signals is better to penetrate the dust in the galaxy. It could of course be some other technology or physic we don't understand yet.

Are we alone or not ? According to some, if aliens are as we are and want to explore the surroundings. It will take as short time as 50 millions year to explore the whole Milky Way galaxy, if that's true we should already had a visit from aliens. One problem as for human species, human will probably not last more then 300'000 years and we already used up 100'000 of those years. Other species will take over as the evolution goes on, on the other hand, maybe we take control of the evolution if we want that.

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