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Arecibo (our biggest radio telescope) could communicate with another telescope of the same size at a rate of 1 bit / second up to 1000 light years away.
Does MESchlum or anybody else have a source for the calculation this was based on? What was the frequency of the carrier for the signal?
I have just read through quite a bit of this very old thread. I especially enjoyed the comments of drkitten and euromutt, but there were many other interesting comments.
For what it is worth I am not particularly optimistic about the possibility of SETI detecting an extraterrestial signal created by other life forms.
Scientific American several years back published an article that suggested that life was only possible in a fairly small band in our own galaxy If this is the case then the number of stars that are likely candidates for life is much smaller than expected.
There have also been other theories that suggest that some of the particular features of our solar system (such as Jupiter and the moon) may have played an essential role in the formation of life on earth. So if there is something to those theories then the number of solar systems that life might arise in could be much smaller than expected.
And of course there is the fact that SETI's been listening for quite awhile now which is at least a suggestion that SETI might not succeed at all.
And then there is my own, pessimistic, theory which is that there is a kind of natural law that limits the lifespan of technological civilizations so that the lifespan of a technological civilization that we might communicate with is much smaller than might have been expected. The idea behind my pessimistic theory is that the development of nuclear weapons is an aspect of all technological civilizations at some point in their life and that once nuclear weapons have been developed the destruction of the technological civilizations become inevitable. A possible alternative pessimistic theory is that it isn't necessarily nuclear weapons that do technological civilizations in but rather some other aspect of their technology which eventually destroys them.
Also, for what it is worth, by my definition of science, SETI is absolutely a scientific endeavor. Parasychology investigations can be but often aren't for many of the reasons listed by the previous posters.