[highpost]

Star Trek may have made us think that Class M planets are abundant, but the probability of detecting intelligent life on any given habitable planet is remote. There may be many Class M planets within our detection range, but the trick is to find one that has an intelligent civilization at precisely this moment in time minus the time it takes for radio signals to reach Earth.

Let’s say that Earth is about 4.5 billion years old and that intelligent life has been externally detectable for about 120 years since radio was invented around 1900. And it’s by no means certain that just because a civilization on a given Class M planet achieves radio signal generation that it will soon achieve warp drive technology and build a fleet of starships. That civilization could simply watch episodes of the Golden Bachelor while consuming all of its available resources and then fade away. Or just blow each other up.

I’m not saying that intelligent life outside of Earth does not or has never existed. We can only detect a small part of the known universe. And we can only detect what’s going on roughly right now because there isn’t a WayBack Machine for interstellar radio signals.

All this requires the combination of several low probability events:

  * A planet must be within detectable range of Earth.
  * A civilization must have developed.
  * The civilization needs to survive for a meaningful period of time. One century is not meaningful.
  * The civilization must be visible essentially right now.

The combination of those events yields a very low probability.

I’m not saying that the search for intelligent life on other planets isn’t interesting or worthwhile, but I do think that Elon Musk should stop wasting his time on space travel and start spending it on global warming. That will give us the best chance of extending our run as an intelligent civilization.