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Chapter 28: Problem 9

Why are most searches for extraterrestrial intelligence made using radio telescopes? Why are most of these carried out at frequencies between \(10^{3} \mathrm{MHz}\) and \(10^{4} \mathrm{MHz}\) ?

Short Answer

Expert verified
Radio telescopes are used for searches for extraterrestrial intelligence mainly because they can efficiently detect and analyze signals in the radio frequency portion of the electromagnetic spectrum where most cosmic signals are found, and it is least affected by noise. The frequency range between \(10^{3} MHz\) and \(10^{4} MHz\) is typically chosen because it includes the 'water hole', a range believed to be universally recognized as optimal for signal transmission, and less absorbed by Earth's atmosphere.

Step by step solution

01

Purpose of Radio Telescopes

Radio telescopes are used because they have the ability to detect and interpret in the radio frequency portion of the electromagnetic spectrum where most of the signals from the universe are found. This range is where the background noise is the least, allowing for the detection of weak signals. Radio waves are also not easily blocked or refracted, unlike other forms of electromagnetic waves.
02

The Chosen Frequency Range

The frequency range between \(10^{3} MHz\) and \(10^{4} MHz\) is typically chosen for extraterrestrial searches because it includes the 'water hole'. The water hole is a specific range of frequencies that are less absorbed by the Earth's atmosphere, and also given its name due to the presence of signals from hydrogen and hydroxyl ions. Scientists believe that a technologically advanced civilization would choose this range to communicate as it could be universally recognized as optimal for signal transmission.
03

Combining the reasoning

In summary, the use of radio telescopes and the specific frequency range are both determined by the goal of increasing the chances of successfully detecting potential signals from extraterrestrial intelligence, while minimizing interference from natural and manmade noises.

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