Chapter 18 The Search for Extra- terrestrial Life

What do you think? What do people who search for extraterrestrial intelligence look for?

Our planet is special to us, but is not unique in its possibilities for life What are the elements necessary for life? C A R B O N –organic molecules that have carbon and... –hydrogen –nitrogen –oxygen –sulfur –phosphorus –ethyl alcohol –formaldehyde –methyl cyanoacetylene –acetaldehyde

Miller-Urey Experiment showed that numerous organic compound necessary for life can be synthesized from gases present in Earth’s early atmosphere.

SETI uses radio telescopes to eavesdrop on radio/TV communications from other civilizations SETI - Search for Extraterrestrial Intelligence High Resolution Microwave Background Survey Now, primarily funded through private donations Radio waves travel at the speed of light

T HE W ATER H OLE : The Best Place to Listen

The Drake equation predicts how many civilizations are in the Milky Way N = R * f p n e f l f i f c L R * = rate at which solar-type stars form in the galaxy f p = fraction of stars that have planets n e = number of planets per stay system suitable for life f l = fraction of those habitable planets on which life actually arises f i = fraction of those life forms that evolve into intelligent species f c = fraction of those species that develop adequate technology and then choose to send messages out into space L = lifetime of that technologically advanced civilization

We have been sending signals and spaceprobes into space for a century TV signals broadcast since the 1930s Frank Drake sent a message directed at the great globular cluster in Hercules which is 30,000 light years away Voyager spacecraft now leaving our solar system launched in the 1980s carry human memorabilia

Plaque on Voyager Space Probes

What did you think? What do people who search for extraterrestrial intelligence look for? They search for radio signals from other advanced civilizations.

Self-Check 1: Discuss the Drake Equation and make estimates for the various factors in it. 2: Explain why radio telescopes are used in the search for extraterrestrial signals. 3: Outline the results to date of the SETI program.