The question of whether we are alone in the universe has been one that has preoccupied mankind for many centuries. One can imagine prehistoric man pausing from his work to look up into the night sky and wonder what the lights he saw really were, whether they were gods, or whether they might even be alive. Scientists are not immune from the same sense of wonder, and over fifty years ago they first began monitoring the skies in the even some extra-terrestrial civilization should attempt to contact us. At first these efforts were rather haphazard, but they became more systematic with time, and today a vast array of radio telescopes are pointed towards the sky trying to detect a signal which would show us that we weren't alone, under the name of SETI. Yet in all that time, nothing has shown up. Is it that we don't know where to look or what to look for, or is there really no one at home?
Before we become too pessimistic over the chances of finding life other than our own, or even give up looking, we should keep a number of facts in mind. First of all, fifty years is a very short time compared to the age of the universe, which is measured in billions of years. Furthermore, the universe is so big that it's very possible that even if life does exist on some faraway world, we may just be too far apart to become aware of each others existence, because as Einstein pointed out, nothing can travel faster than the speed of light, and that includes information. We may take the position that if a civilization is far enough advanced technologically, much more than ourselves, they should be able to overcome these limitations through some kind of warp drive, but what if Einstein was right after all?
There are also a number of philosophical considerations. Most exo-biologists currently believe that if the proper conditions exist for the development of life, as they did on Earth billions of years ago, life must necessarily come about. But what if the development of life on Earth was due to some kind of freak phenomena, which may not be duplicated in other places. Even if life did gain a foothold someplace else, and progress as it did here, who's to say that if a race becomes sufficiently advanced technologically, it wouldn't destroy itself, as we nearly did and as the Krell race did in the movie Forbidden Planet. Or, if they didn't destroy themselves, what if they evolved to the point where they became beings of pure energy, and had absolutely no interest in communicating the fact of their existence to us, who they would probably regard as we regard the lowest form of insect life. This isn't to say that we shouldn't continue our search for intelligent life in the universe, just that we shouldn't expect to find it overnight. And even if we never find it, what we discover in the process of looking is likely to make the search more than worthwhile.