User:Paidgenius/Drake Equation

Frank Drake invented the Drake equation in 1960, and first described it at the Green Bank meeting. This was a meeting of scientists who agreed to make SETI (Search for Extraterrestrial Life) an official branch of science. Frank Drake was one of the important people to support this decision. The Drake equation estimates how many alien civilisations are in our galaxy. It is related to the Fermi paradox which Enrico Fermi invented in 1950, which says that if so many equations like the Drake equation predict aliens exist in our galaxy, why is there no solid evidence? See the case for and against now by clicking here! On second thoughts don't bother. Get on and read this.

Yeah, enough talk, so what is the actual equation?
Well, the equation says that

$$N = R^* \times f_p \times n_e \times f_\ell \times f_i \times f_c \times L$$

N is the number of civilisations in our galaxy we could communicate with.

R* is the rate that stars are being formed at in our galaxy.

f p  is the fraction of those stars that have planets.

ne is the fraction of those planets that could support life.

fl is the fraction of those planets that do support life.

fi is the fraction of the planets that have life, that have intelligent life. You all count as intelligent life.

fc is the fraction of the intelligent civilisations that send signals into space.

L is the length of time for which they send out those signals.

That was wonderfully boring. So, what are our chances of meeting aliens?
Well, firstly the star formation rate, R*, is equal to N* ÷ Tg where N* is the number of stars in the galaxy now (about 200 billion) and Tg is the age of the galaxy (about 20 billion years).

So if we take the values that Drake used in 1961: R* is 10/year,

fp is 0.5,

ne is 2,

fl is 1,

fi is 0.01,

fc is 0.01,

L is 10,000.

I don't care. What I actually said was WHAT ARE OUR CHANCES OF MEETING ALIENS?
10 × 0.5 × 2 × 1 × 0.01 × 0.01 × 10,000 = 10, so Drake suggested that 10 civilisations exist in our galaxy with which communication may be possible. But modern estimates are much different. It's currently assumed that N = 7 × 0.5 × 2 × 0.33 × 0.01 × 0.01 × 10000 = 2.31, which means 2.31 civilisations exist. The 0.31 obviously had an unfortunate accident, it seems.

That wasn't funny. Anyways... How can the Drake equation be so accurate?
It can't. All the probabilities assumed are complete guesswork, so the result is worse than useless. [Michael Crichton]], author of Jurassic Park said that as it can mean anything, it means nothing.

OK. So why haven't we heard anything from aliens?
Some people explain The Great Filter, which suggests that somewhere, something has stopped alien civilisations from existing. Professor Robin Hanson has eight steps from starting with a star to ending with intelligent life. These steps are:


 * 1) The right star system
 * 2) Molecules wich can create life (DNA etc.)
 * 3) Single-celled life
 * 4) Complicated single-celled life
 * 5) Sexual reproduction
 * 6) Multi-celled life
 * 7) Intelligent animals which can create tools
 * 8) Colonising space

We haven't colonised space yet. Stephen Hawking reckons we have to to survive. So if the problem is in Step 8, then our future is bleak. But nobody's made it to step 8 yet, or the galaxy would be full of colonies, so maybe that's the big problem. It would be catastrophic if we found tool-using animals on Mars, beacuse it would suggest that the problem has to be in Step 8. Then, if we stayed on Earth, we'd wipe ourselves out, and we couldn't colonise space if Step 8 has a problem in it.