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Speaker 1: Welcome to brain Stuff from how Stuff Works dot com

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Speaker 1: where smart Happens. Hi, I'm Marshall Brain with today's question,

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Speaker 1: how does CETI at homework? Let's start with the acronym

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Speaker 1: first ST stands for the Search for extraterrestrial intelligence. This

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Speaker 1: search uses large radio telescopes. With these telescopes, scientists involved

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Speaker 1: in cet hope to detect radio signals that are leaking

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Speaker 1: from other intelligent civilizations or that other civilizations have specifically

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Speaker 1: aimed at us. The basic principles of CETI rely on

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Speaker 1: three assumed facts. First, there must be some other intelligent

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Speaker 1: life forms out there. The Milky Way galaxy alone contains

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Speaker 1: billions of stars like our own son, and the universe

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Speaker 1: contains billions of galaxies. If intelligent life can evolve in

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Speaker 1: one place, then presumably it can evolve in many other

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Speaker 1: places as well. Second, any intelligent civilization would discover radio

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Speaker 1: waves and begin leaking them into space. Humans, as an

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Speaker 1: intelligent life form, discovered radio waves fairly early in our development,

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Speaker 1: and we've been leaking radio signals in significant quantities for

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Speaker 1: much of the twentieth century. We leak signals and everything

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Speaker 1: from AM and FM radio broadcast to TV broadcast to

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Speaker 1: all sorts of satellite and radar broadcasts. Every time you

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Speaker 1: open your garage door, you leak a small radio signal

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Speaker 1: into space. Third, any intelligent civilization would realize that there

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Speaker 1: might be other intelligent civilizations, and it might try to

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Speaker 1: send high powered radio signals right at us. Humans have

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Speaker 1: in fact tried this in several different ways. If you

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Speaker 1: can find a copy of Carl Sagan's book entitled Murmurs

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Speaker 1: of Earth, it offers a great introduction to what we've tried.

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Speaker 1: If either the first or the second assumption is invalid,

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Speaker 1: then CT is a hopeless waste of time. If they

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Speaker 1: both turn out to be true, however, that it's only

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Speaker 1: a matter of time before we detect something. The problem

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Speaker 1: with SET is that it requires massive computational resources. SET

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Speaker 1: is listening to a huge number of frequencies. Then the

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Speaker 1: computer has to look at each frequency separately and try

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Speaker 1: to decide if it's carrying an intelligent signal as opposed

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Speaker 1: to noise. To give you an idea of the scope

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Speaker 1: of the problem, the antenna used by Setti at home

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Speaker 1: records thirty five gigabytes of data every day. It takes

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Speaker 1: millions of hours of computation time just to process one

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Speaker 1: day's worth of data. Buying that amount of computational power

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Speaker 1: would be incredibly expensive, so Seti at Home comes up

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Speaker 1: with an ingenious way to create that computing power out

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Speaker 1: of thin air. When your computer is idle, it displays

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Speaker 1: a screen saver. In most cases, a computer displaying its

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Speaker 1: screensaver is doing absolutely nothing. All the computing power available

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Speaker 1: when your machine is being wasted, So Citty at Home

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Speaker 1: created its own screensaver, which you install on your machine.

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Speaker 1: With the setting at Home screensaver installed, your computer actually

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Speaker 1: processes set data while it's idle. The screensaver downloads a

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Speaker 1: packet of data containing a work unit of radio signals

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Speaker 1: and then grinds away on them. When it's done, it

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Speaker 1: sends the results back and gets another packet. Do you

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Speaker 1: have any ideas or suggestions for this podcast? If so,

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Speaker 1: please send me an email at podcast at how stuff

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Speaker 1: works dot com. For more on this and thousands of

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Speaker 1: other topics, go to how stuff works dot com