Intelligent Life in The Universe?

I recently watched a TV show on Astronomy which got me thinking about the vastness of the Universe.

Our closest planet, our moon, is about 250,000 miles away. It takes light about a second to reach us from the moon (at the speed of light). Our galaxy, the milky way galaxy, is so immense that it takes light about 100,000 years to travel across our entire galaxy!! Scientists estimate there are about 100 billion stars (like our Sun) in our galaxy alone!

This got me thinking about how many intelligent life forms there might be in our Galaxy and low and behold there is a formula, the Drake formula, which estimates this. I'll include the formula in this post. Using this formula, conservative estimates say that there could be hundreds or even thousands of communicating civilizations in our galaxy alone!

Now for the kicker: how many galaxies are there in the universe? Well in 1999 NASA scientists calculated that there might be as many as 125 billion galaxies in the Universe, with about 3,000 galaxies (like our own, or larger) currently visible from the Hubble telescope.

So then how many intelligent civilizations might there be in the universe? Well, we know there is at least one in our galaxy, us. Drake says there could be a thousand in our galaxy alone. But lets assume there is only one, us. And if you then assume that there is 1 intelligent life form in about 1% of the 125 billion galaxies out there (some estimate as many as 500 billion galaxies) that gives you about 100 million civilizations out there. You can reduce that 1% estimate much lower and still get thousands of civilizations out there.

I think its a pretty safe bet that we are not alone in the universe, the problem is (as far as making contact) that our neighbors are very, very far away!

The Drake Formula:

The Drake Equation was developed by Frank Drake in 1961 as a way to focus on the factors which determine how many intelligent, communicating civilizations there are in our galaxy. The Drake Equation is:

N= N* fp ne fl fi fc fL

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 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 the 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 the 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, the 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 millennia? If we were destroyed tomorrow the answer to this question would be 1/100,000,000th. If we survive for 10,000 years the answer will be 1/1,000,000th.

When all of these variables are multiplied together when come up with: N, the number of communicating civilizations in the galaxy. And yes, it's very boring in the Keys!