Enrico Fermi asked a question that has troubled those searching for signals from extraterrestrial civilizations ever since: if the universe is teeming with advanced civilizations (as some solutions to the famous Drake equation would indicate), were are they? (From the physics arXiv blog via Improbable Research.)
Reginald Smith of the self-established Bouchet-Franklin Institute in Rochester, New York state, says in this paper, submitted to the International Journal of Astrobiology, that something is missing from the calculations: how far a signal from an advanced civilization can travel before it becomes too faint to hear. Factoring that in, he finds that:
“Assuming the average communicating civilization has a lifetime of 1,000 years, ten times longer than Earth has been broadcasting, and has a signal horizon of 1,000 light-years, you need a minimum of over 300 communicating civilization in the galactic neighborhood to reach a minimum density.”
Which means that even if there are a couple of hundred advanced civilizations in our galaxy, it’s quite likely none of them will ever notice the others…and our efforts at searching for extraterrestrial intelligence may be doomed.
(Image: Reginald Smith.)