I heard him lecture on the possibility of intelligent life in the universe, as opposed to our inability to detect any. If there were another planet like earth in the Milky Way, with all the radio waves being propagated throughout this galaxy by us, we should have detected it easily long ago.
So Morrison went through all the probabilities, and concluded that if for some reason each intelligent planet that came along only lasted for less than 10,000 years, there then would not be any other earth-like planet radiating radio waves in this galaxy at this time. In other words, if technology lasts for less than 10,000 years, only one earth at a time would be radiating.
It's easy to imagine why intelligent technological life might not last more than 10,000 years.
1. First reason is that with nuclear weapons, which of course comes with intelligence, like we just left the Garden of Eden, it is likely that each planet would commit nuclear suicide, if not right away, the highest probability, at least within 10,000 years.
2. Second reason is that if a planet were peaceful enough to avoid blowing itself up, it would last more than 10,000 years, like heaven on earth lasting forever. But as soon as it detected the radio waves from another planet, it would turn off its own antennas. You know, every newly intelligent planet must think it's alone in the universe.
3. Third reason is that after a 1000 years or less, better ways to communicate than by radio are discovered.
4. Fourth reason is that god comes to each planet and teaCHES THAT TECHNOLOGY IS EVIL AND THE OCCUPANTS GO BACK TO LIVING AS MUCH AS POSSIBLE LIKE NATIVE AMERICANS.
Opps. Another unintended set of caps. Must come from god. Of course with very advanced technology, mobile homes with solar screens would replace tents.
5. Fifth reason is that the intelligent beings learn to live in dark matter, which may be frictionless, and where they would then be immortal. Nowadays I think death is required to live in dark matter, but that may be overcome some day in the future.