Extraterrestrial Intelligence


  • The main questions: Are we alone or is there intelligent life elsewhere?
  • Need to ask first: How could we find out if it is out and there? How can we communicate?

Where Could Intelligent Life Possibly Develop?

  • First conditions: Existence of extrasolar planets (we now know there are lots of those); Environments suitable for life (life in general, we haven't found those yet, but we have found planets with atmospheres, and there are ideas for how to go further).
  • Additional conditions: In addition to life existing on a planet, what is the likelihood that it develops into intelligent forms and civilizations?
  • How many civilizations might exist in our galaxy? Use the Drake equation to estimate it theoretically; Optimistic result: As many as the average lifetime of a civilization expressed in years; Carl Sagan estimated about 1 million in our galaxy, one every 50 pc!

  What about Communications and Contact?

  • Detecting signals – SETI: Some radio telescopes are listening (What was the 1977 "Wow!" signal?); Our best bet is around 18-21 cm waves; Project Phoenix was ended without a signal, but there are other searches; An optical SETI telescope has started operating at Harvard, looking for brief flashes of light.
  • How can we reach out? Interstellar travel? Takes far too long. Send out probes? Already done (Pioneer 10, Voyager); Send radio waves? In 1974 we broadcast a radio message to space, and we're waiting; Also, we may be contributing to future life elsewhere by leaking out our own, panspermia-style.
  • Contact? No real evidence yet of extraterrestrial presence on Earth (despite some relatively widespread beliefs).

 Summary: SETI could succeed tomorrow, or it may be an endeavor for multiple generations: We are a very young technology in a very old galaxy; Our own leakage radiation outshines the Sun at many frequencies, and we are detectable to others; When our use of the spectrum becomes more efficient, it will be time to consider deliberate transmissions and the really tough questions: Who will speak for Earth? What will they say?

So far, though, the conclusion is: "We live in a quiet neighborhood" (Peter Backus, Seti Institute).

page by luca bombelli <bombelli at olemiss.edu>, modified 29 sep 2012

"This porridge is too hot," Goldilocks exclaimed.
So she tasted the porridge from the second bowl.
"This porridge is too cold."
So she tasted the last bowl of porridge.
"Ahhh, this porridge is just right!" she said happily.
And she ate it all up.

"Goldilocks and the 3 Bears" children's story