Astronomers use doppler shifts to calculate precisely how fast stars and other astronomical objects move toward or away from earth. for example the spectral lines emitted by hydrogen gas in distant galaxies which is normally found at a wavelength of 21 centimeters on earth, might be observed at 21.1 centimeters instead. what would this difference indicate to astronomers?

Galaxy is moving away from Earth.

Explanation:

Doppler shifts in the spectrum indicate about the motion of celestial bodies. Doppler effect is the apparent change in wavelength or frequency when there is relative motion between the source and the observer. Red-shifted light indicates that celestial body is moving away and blue-shifted light indicates that it is moving closer.

When astronomers observe a wavelength of 21 cm to be shifted to 21.1 cm - it means the light is red-shifted because the apparent wavelength is longer. Thus, astronomers can conclude that from the difference in the wavelengths that the galaxy is moving away from the Earth.

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