canali. In Italian, the word meant "channels", but it was reported in english speaking countries as canals, and quickly fired our fascination with alien life. In fact, until Viking landed, it was believed by some scientists (and at least considered by most) that at the very least vegetation existed on Mars. However, even the bleak truth about Mars didn't change most peoples belief in Alien life. Although contact has still yet to be made (unless you believe in U.F.O.'s) with any alien civilization, there have been mathematical attempts to figure out just how many civilizations there may be out there. Drake's EquationThe most well know of these is Drake's Equation. It tries to calculate the number (N) of alien civilizations in the universe. His equation is:N=PR*L R* is the rate of star formation in the galaxy, which has been fairly accurately calculated to 2 or 3 stars per year. L is the average lifetime of a technologically advanced civilization. P is another special equation, which represents: P=fnneflfifc Now, in case you are wondering just what that means (I know I did), fp stands for the average fraction of stars which have planets about them. ne represents the average of those planets which are earth-like. fl Is the average of those which develop life. fi is the average of those which develop intelligent life. fc is the average of those that develops the ability to communicate with other civilizations (radio communication is considered inter-stellar communication here). Since that is a lot of 'those', I'm just going to summarize. Basically, you take the number of stars in the universe, multiply that by the percentage of stars that form planets, multiply that by the percentage of those planets that are earth-like, multiply that by the percentage of those planets that develop life, multiply that by the percentage of those that develop intelligent life, and multiply that by the percentage of those intelligent civilizations that can communicate with other civilizations. In the end, you will have P. Once you have all of that, you can use Drake's Equation to calculate that number of civilizations out there you can communicate with, and then the average distance between civilizations. Unfortunately, since the majority of these figures aren't clear cut, it's hard to calculate N very accurately, instead it is usually calculated with a variety of figures, and then charted. Here is one of these charts for your convenience:
Now then. The figures at the top represent values of P. Remember, P is a percentage of stars that will develop life capable of inter-stellar communication (**Note** to make things easier on me, I am going to omit "capable of inter-stellar communication" when referring to civilizations, but that is still to be understood). On the left are values for the average life span of a civilization. There are two numbers (or 1 and a dash) in each square. The top number represents the number of civilizations that will exist in the universe at any given moment. The number on the bottom represents the average distance between each civilization, in light years. In case you were wondering, there is a reason that "capable of inter stellar communication" was stressed. There is a very big difference between capable of inter stellar communication and the ability to travel between the stars. Inter-stellar travel is a very difficult task, not to be balked at. Anyway, back to the chart. As you can see, only very optimistic estimates of the life time of a civilization and P give rise to civilizations with little distance between them. Of course, bear in mind that we have only been a civilization with inter-stellar communication for 100 years. If we were the average civilization, even given the very optimistic estimation of p at 1%, we would have to exist for another 9900 years for the life-time of a civilization to be long enough to allow for inter-stellar communication. After all, if we civilizations were separated by 2000 light years, it would take 2000 years for a message to be transmited. Even then, with a 4000 year wait until you get a response, it'll be a short conversation (you only have 10000 years to talk before one of you goes extinct). Of course, with the current threat of nuclear weapons, war, and who knows what else, it is still not 100% certain that we will be able to make it another 100 years, so it would be a bit premature to assign civilizations a life time of 10000 years. |