The light from a distant cloud of gas and dust looks distinctly red to the naked eye. When a spectrum is taken, it is found that many wavelengths that would normally be expected to be in the middle of the spectrum have been shifted into the long-wavelength end of the spectrum. Thus, the red color in this situation is due to

Question

The light from a distant cloud of gas and dust looks distinctly red to the naked eye. When a spectrum is taken, it is found that many wavelengths that would normally be expected to be in the middle of the spectrum have been shifted into the long-wavelength end of the spectrum. Thus, the red color in this situation is due to

Quizplus · Accepted Answer

The red color is due to the Doppler effect, specifically redshift, indicating the cloud is moving away from the observer.

The Light from a Distant Cloud of Gas and Dust