Why Do Astronomers Search for Signals of Extraterrestrial Intelligence at a Wavelength

question 13

Multiple Choice

Why do astronomers search for signals of extraterrestrial intelligence at a wavelength of 21 centimeters?

• A) At 21 centimeters there is very little contamination from other material in the galaxy.
• B) Hydrogen emits radiation at 21 centimeters.
• C) Oxygen emits radiation at 21 centimeters.
• D) Greenhouse gases emit radiation at 21 centimeters.

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