Posted by Henry Butz on March 20, 2004 at 21:03:00:
Is there intelligent life in the galaxy? (besides what passes for intelligence down here on Earth) Of course there is. You don't need to "believe" in UFO's, Little Green Men (LGM's), or Bigfoot. You just have to multiply a few numbers together to prove it to yourself.
Let's try a simple example. If I flip a quarter in the air 100 times, will the coin ever "land on head's?" Of course it will. You can prove it to yourself. There are two possible outcomes: Heads and Tails. So, 100 x (1 / 2) = 50. You will have 50 heads for every 100 throws of a coin... ideally. Sometimes you'll get 47. Sometimes you'll get 59. But, the number of heads will always hover around 50 for each 100 throws of a coin.
Let's try a simple probability. What are the odds that heads will come up twice in a row? 1 in 4 or 25% probability. How did we calculate this? We can easily list every possibility of two flips of a coin, 'H' representing Head's and 'T' representing Tail's. We have TT, TH, HT, and HH representing all possible outcomes for two coin flips, four total. How many have Head's followed by Head's? One. So, we get 1 in 4 odds. The first lesson in probability is that we can multiple probabilities together to get overall odds. Getting Head's is 1 in 2 or 1/2. Getting Head's followed by Head's again is 1/2 x 1/2 or 1/4 or 1 in 4.
Let's try something a little more complicated. What are the odds that there is intelligent life on other planets? Or, a more practical approach, how many planets in our galaxy support intelligent life?
(aside) - hey, my highschool science teacher once asked me how many piano tuners there are in Huntington. I amazed myself by correctly determining that the answer was 3. Here's how you solve these brain teasers.
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:
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.
N, the number of communicating civilizations in the galaxy.
Let's throw some numbers around...
N would be 1,000 planets supporting intelligent life (just in our own galaxy) capable of communicating
with us. And, there are a lot of galaxies out there....