By measuring the Doppler shift of the 21-centimeter line, what fundamental property of gas clouds can scientists calculate?

Answer

The radial velocity of the gas clouds.

Measuring the Doppler shift in the radiation allows scientists to determine how fast the gas clouds are moving toward or away from the observer, which is their radial velocity.

By measuring the Doppler shift of the 21-centimeter line, what fundamental property of gas clouds can scientists calculate?

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