Kim Berry

Astronomy Extra Credit

4/1/00

Drake Formula & SETI

IS THERE ANYONE OUT THERE?

SETI – The Search for Extraterrestrial Intelligence - explores the fact that we are most likely not alone in the universe and that there are probably other Extraterrestrial Intelligence. With human’s technology to communicate over vast distances – millions of light years, we have been sending radio signals that spread throughout the galaxy by means of radio, television, and radar signals. SETI listens, using radio telescopes, for radio emissions from other possible advanced civilizations. – Radio waves were chosen because they are capable of traveling vast distances between stars and can be generated with reasonable amounts of power.

As these ideas surfaced, an astronomer named Frank Drake put together plans for the first search in Project Ozma for alien life form between certain stars. Nothing was detected in this first search, but astronomers were excited that the search had begun. As far as we know, no alien signals have been detected but the search is still in its beginning stages. There are 100 billion stars in the Milky Way galaxy alone and there are millions of frequencies that a signal can be received on. In response to the many complications in trying to find these signals, Frank Drake developed the Drake Equation.

The Drake Equation was developed in 1961 to focus on the factors, which determine how many intelligent civilizations could be communicating in our galaxy.

The equation is:

N = N* fp ne f1 fi fc FL

Where:

N* represents the number of stars in the Milky Way Galaxy which current estimation is around 200 billion.

fp is the fraction of stars that have planets around them. Because of recent advances in technology new planets are being discovered every month. So for now 20% is a standard estimation given by many scientists including Frank Drake.

ne is the number of planets per star that are capable of sustaining life. There are between 3 and 5 planets definitely including Venus, Earth, and Mars.

f1 is the fraction of planets in ne where life evolves. In this group a wide range of percents are used from close to 0% to 100%.

fi is the fraction of f1 where intelligent life evolves. The estimations in this category again range from close to 0% to 100%.

fc is the fraction of fi that communicate. No one knows this, so an estimation of 10% to 20% is used.

fL is the fraction of the planets’ life during which the communicating civilization live. This is the toughest question and depends on how long the race survives. If our race were killed off by tomorrow it would be 1/1000,000,000^th, but if we survived another 10,000 years, the answer would be 1/1,000,000^th.

After all the variables are multiplies together the product is N = the number of communicating civilizations in the galaxy.

The real value of the Drake Equation is not in the answer itself, but in the questions that are asked in order to answer it. With all of the guessing that occurs in the equation, many categories are considered enigmas.