So I've decided to start an equation of the week! Pretty cool, right?

Here's this week's equation:

The Drake Equation

N= N* x fp x ne x fl x fi x fc x fL

What is the Drake Equation?

The Drake Equation is a way to determine how many intelligent, communicating civilizations there are in our galaxy.

The equation can really be looked at as a number of questions:

N* represents the number of stars in the milky way galaxy
Question: How many stars are currently in the milky way galaxy?
Answer: Current estimates are 100 billion.

fp is the fraction of stars that have planets around them
Question: What percentage of stars have planetary systems?
Answer: Current estimates range from 20% to 50%


ne is the number of planets per star that are capable of sustaining life
Question: For each star that does have a planetary system, how many planets are capable of sustaining life?
Answer: Current estimates range from 1 to 5.

fl is the fraction of planets in ne where life evolves
Question: On what percentage of planets that are capable of sustaining life does life actually evolve?
Answer: Current estimates range from 100% (where life can evolve it will) down to close to 0%.

fi is the fraction of fl where intelligent life evolves
Question: On the planets where life does evolve, what percentage evolves intelligent life?
Answer: Estimates range from 100% (intelligence is such a survival advantage that it will certainly evolve) down to near 0%.

fc is the fraction of fi that communicate
Question: What percentage of intelligent races have the means and desire to communicate?
Answer: 10% to 20%.

fL is fraction of the planet's life during which the communicating civilizations live
Question: For each civilization that does communicate, for what fraction of the planet's life does the civilization survive?
Answer: This is the toughest of the questions. If we take Earth as an example, that expected lifetime of our Sun and the Earth is roughly 10 billion years. So far we've been communicating with radio waves for less than 100 years. How long will our civilization survive? Will we destroy ourselves in a few years like some predict, or will we overcome our problems and survive for millenia? If we were destroyed tomorrow the answer to this question would be 1/1,000,000,000th. If we survive for 10,000 years the answer to this question would be 1/1,000,000th.

When all of these variables are multiplied together we come up with:

N, the number of communicating civilizations in the galaxy.

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