I'm one who thinks the misnamed "Fermi's Paradox" is a serious problem for the hypothesis that there are advanced extraterrestrial civilizations. (I say "misnamed" because the Fermi Question is not a paradox. It's a reductio argument against the view that advanced extraterrestrials exist.)
All it would take is one E.T. civilization in our galaxy to have reached technical sophistication several million years ago. This civilization could send little green explorers out in flying saucers, or build self-replicating robot probes. Either way, assuming the travelers only go v<.1c and supposing that it takes 100,000 years from the time the travelers arrive on the new world to the time a new robot or people vehicle is sent out (a very conservative estimate), the original civilization will have the entire galaxy populated in a little over ten million years.
Consider that the earth is about 4.5 billion years old, and the galaxy itself over ten billion years old. If, in fact, the conditions for the development of technical civilizations in our galaxy really are favorable enough for there to be some E.T.'s around sending radio broadcasts then why hasn't at least one flying saucer made its way to earth by now? Why isn't there at least one robot probe in our vicinity which has detected us?
I am skeptical of the premise of radio SETI, in other words. It's hard to understand the view that there are several advanced E.T. societies around transmitting messages of peace and good will but none have yet managed to show up in our neck of the woods in person or through their robot surrogates. I'm more willing to believe that we are the only technical civilization ever to exist in our galaxy than I am in that hypothesis.
It could have happened many times. But just not recently or while SETI is being operated. They may have passed through the solar system itself just before we got radio, and won't be back until after earth is destroyed in a mysterious bright flash.
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And what powers these probes. Can we build a complex gadget that works for a 100 years much less 10,000. And who would fund such an endeavor.
Consider that the earth is about 4.5 billion years old, and the galaxy itself over ten billion years old. If, in fact, the conditions for the development of technical civilizations in our galaxy really are favorable enough for there to be some E.T.'s around sending radio broadcasts then why hasn't at least one flying saucer made its way to earth by now? Why isn't there at least one robot probe in our vicinity which has detected us?
Its a really long way out there. We haven't even really let ourselves be known yet. What would even bring a "flying saucer" this way.
I am skeptical of the premise of radio SETI, in other words. It's hard to understand the view that there are several advanced E.T. societies around transmitting messages of peace and good will but none have yet managed to show up in our neck of the woods in person or through their robot surrogates. I'm more willing to believe that we are the only technical civilization ever to exist in our galaxy than I am in that hypothesis.
The search I am involved in does not look for any radio signals purposely beamed at us. I am looking for another race that has developed far enough down the technological road to have developed radio like we have. There appears to be only 4 fundamental forces in all of nature; Strong Force, Weak Force, Gravity, and Electromagnetism EM. Both the strong force and Weak force are confined to the nucleus of the atom. Gravity requires prodigious amounts of energy to manipulate, so the only one that is practical for long distance communication is EM. In an extremely short period of time, we are using EM across the entire spectrum from basically DC to light. We are now radiating that same spectrum into outer space. In fact at certain frequencies, we are the brightest object in the known heavens. So what we are looking for, is a race that is doing the same thing we are, unintentional radiation of radio wave into outer space in all directions.
Because radio signals are extremely cheap and interstellar travel is extremely expensive, no matter how you figure it. So the fact that radio signals are scarce, at some level, means that interstellar travellers are extremely scarce. If the aliens were here already, chances are that the sky would emit a cacophony of radio signals, which apparently it does not.