Lately there has been much talk about aliens, spaceships and comets. Comet Hale-Bopp is departing, and so far I haven't noticed anything more alien than the usual. Abductions and invasions aside, is there anything to life elsewhere? Just now, might there be someone light years away wondering if they are alone?

      Scientists do not know for sure if there is other life elsewhere, and they seem to be divided into two opposing sides. One group believes life here is unique and that we are alone. The other group believes that life is a common thing (precious that it is) and that the universe is teeming with life. Both sides have a rationale for their conclusions.

      Those who believe we are alone argue based on how rapidly humans have spread across the planet. They claim that once a civilization masters space flight, it would take the civilization only a few thousand years to colonize planetary systems near their homes, and only a few million years to colonize the whole galaxy. They assume that humans are driven to colonize and that all other life forms would be driven also. They ignore the possibility of a civilization that does not seek contact and would rather be left alone.

      The other group, who believe that the universe has a multitude of life have a basis for their opinion too. These folks believe that stars like our Sun are common, as are planets around the stars. They also believe that life is not uncommon, and neither is intelligent life. Much of this theory is owed to a man called Frank Drake.

      Frank Drake was a U.S. astronomer who came up with what is called the Drake Equation. Drake believed it was possible to estimate the number of civilizations by multiplying together the probability of each condition necessary for it.

     The Drake Equation  begins by estimating the number of Sun like stars in our galaxy, then estimating a probable number of Earth-like planets around those stars.  Estimating how many of these planets might have life is pretty tricky, but 1 in 100 is accepted as a good estimate. They further estimate that 1 in 10,000 of these civilizations will have advanced to a technical level.  The bottom line, is that being very conservative, they estimate 1000 advanced civilizations in our galaxy. And given there are billions of other galaxies, it is easy to believe we are not alone!

     The Drake Equation is filled with uncertainties, and there are some estimates that cannot now be proved or disproved.  Nevertheless, even with pessimistic estimates, the equation suggests that we are not alone. So why haven't we had "first contact?" Are we searching for life elsewhere? The answer might surprise you. Yes, we are searching, listening to be more precise, in a program called SETI.

     SETI (Search for Extraterrestrial Intelligence) "listens" on radio signals using large radio telescopes. SETI scans literally millions of radio wavelengths to search for signals from other civilizations. Some proposed searches will scan over 100 million frequencies! Are we broadcasting? Yup, television stations and defense radar transmission are powerful and travel for many light years out into space where they could be received by anyone listening on those frequencies.

     Life has existed on Earth for at least 38 billion years, a major portion of the planet's existence. Many astronomers believe that life has formed in numerous other places in the universe. So far, our searches have not turned up anything, but the universe is a very large place.