Welcome to brain Stuff from how Stuff Works dot com where smart Happens. Hi, I'm Marshall Brain with today's question, how does CETI at homework? Let's start with the acronym first ST stands for the Search for extraterrestrial intelligence. This search uses large radio telescopes. With these telescopes, scientists involved in cet hope to detect radio signals that are leaking from other intelligent civilizations or that other civilizations have specifically
aimed at us. The basic principles of CETI rely on three assumed facts. First, there must be some other intelligent life forms out there. The Milky Way galaxy alone contains billions of stars like our own son, and the universe contains billions of galaxies. If intelligent life can evolve in one place, then presumably it can evolve in many other places as well. Second, any intelligent civilization would discover radio
waves and begin leaking them into space. Humans, as an intelligent life form, discovered radio waves fairly early in our development, and we've been leaking radio signals in significant quantities for much of the twentieth century. We leak signals and everything from AM and FM radio broadcast to TV broadcast to all sorts of satellite and radar broadcasts. Every time you open your garage door, you leak a small radio signal
into space. Third, any intelligent civilization would realize that there might be other intelligent civilizations, and it might try to send high powered radio signals right at us. Humans have in fact tried this in several different ways. If you can find a copy of Carl Sagan's book entitled Murmurs of Earth, it offers a great introduction to what we've tried. If either the first or the second assumption is invalid,
then CT is a hopeless waste of time. If they both turn out to be true, however, that it's only a matter of time before we detect something. The problem with SET is that it requires massive computational resources. SET is listening to a huge number of frequencies. Then the computer has to look at each frequency separately and try to decide if it's carrying an intelligent signal as opposed to noise. To give you an idea of the scope of the problem, the antenna used by Setti at home
records thirty five gigabytes of data every day. It takes millions of hours of computation time just to process one day's worth of data. Buying that amount of computational power would be incredibly expensive, so Seti at Home comes up with an ingenious way to create that computing power out of thin air. When your computer is idle, it displays a screen saver. In most cases, a computer displaying its
screensaver is doing absolutely nothing. All the computing power available when your machine is being wasted, So Citty at Home created its own screensaver, which you install on your machine. With the setting at Home screensaver installed, your computer actually processes set data while it's idle. The screensaver downloads a packet of data containing a work unit of radio signals and then grinds away on them. When it's done, it sends the results back and gets another packet. Do you
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