"Two possibilities exist: Either we are alone in the Universe or we are not. Both are equally terrifying." - attributed to Arthur C. Clarke
If we are not alone, then why haven't we heard something already? It very well could be that the distance between intelligent civilizations is simply too far and we simply haven't had the capability to receive the correct type of signals for long enough. After all, we haven't been able to receive radio waves for all that long, really. On the scale of time of the universe, whole advanced civilizations could easily miss each other by millions of years simply because their star got started that much earlier or later than the other civilization. Others who are less than 100 lightyears distant could have seen our signals by now, if they were tuned to the correct frequencies and happened to be looking in the correct direction. Even so, it would take another 100 years or so for any reply to reach us, assuming they have the technology to produce one and that we're listening on the right frequencies and in the right direction at the right time. It could simply be a grand game of chance and we simply haven't be playing it long enough.
Here's another viewpoint I've heard mentioned before. Look at a primitive tribe in Africa who knows nothing about radio waves. Radio waves with all sorts of information could pass through them every minute and yet they simply don't know of its existence! As a matter of fact, satellites are constantly sending whole catalogues of information right through their villages, with lots of information which could easily revolutionize their lives, and yet they know nothing about it at all! What if we're the same with respect to other civilizations? What if their methods of communication (higher dimentions, hyper-space, tachyons, etc., happen be passing right though us currently and we simply don't see it. We're sitting here looking for smoke signals and they're sending radio waves.
How long would an advanced civilization last, however? Maybe they wouldn't usually get to the stage of traveling amongst the stars? Maybe something else happens first and we simply are not old enough to know what that could be? Many people have theorized that maybe an advanced civilization would blow itself up, or destroy itself in some other way, long before they would be capable of making contact with us or anyone else. The movie "Forbidden Planet" talks about one such scenario. But, maybe there's another? Maybe a truly advanced civilization stops producing radio waves after only a few hundred years? After all, sending out radio waves is rather wasteful of energy. Arthur C. Clarke, the inventor of the satellite, theorized in a later story about the possibility of a solid ring around the equator with antennas sending and receiving tight beams of information to and from the surface. Even today, scientists are busily working on the idea of beaming information directly to satellites instead of allowing the transmissions to spread out as much as they do currently, in order to save energy.
Maybe a civilization tends to turn inward as it grows older. We, today, are finding that social interactions on the Internet, role playing games, and other forms of virtual reality, seem to be a fascinating and time consuming thing for many people. What if a truly advanced civilization could live inside an advanced virtual reality, becoming whatever they want, living wherever they want, virtually visiting far away places, far away times, even other whole virtual worlds? Would such a civilization really need to seek outside for anyone else? Maybe as a civilization advances it tends to turn more and more inward and thus disappears from the rest of the universe. If this is the norm, then we would stand a really small chance of detecting other civilizations and an even smaller chance of being recognized or visited in any way.
Maybe instead of seeking other life elsewhere in the universe, we should be developing a graph of possible futures for a civilization. We may be surprised to find that only a very small number of possible futures actually result in a civilization which is detectable!
Some comments from the previous blog: "mike", Date: 2011/01/05 Thanks for your article. I truly enjoy reading and thinking of the possibilities but I am profoundly disappointed that in this day and time of exploding knowledge & abilities in technology & communication so few people seem to be interested in these type of questions. Instead the public obsessions are in which sports teams will win this time or which celebrity is making news. I think we are looking for smoke signals and a newer form of communications just may lead to an inpouring of welcomes (wishful thinking though). Thanks again. "maureen", Date: 2011/01/05 Detectable by whom, with what instruments? The human eye cannot detect even all physical reality not to mention other possible realities.