Ascientist is studying the light emitted by several celestial objects. he records the shifts in each object's spectral lines (in nm). based on these measurements, determine whether each object is moving toward or away from earth.

It will be closer to the Earth if the spectral lines are longer.

Explanation:

In space, scientists can determined if a celestial object is moving toward the Earth if the wavelength is longer, that is, if is moving to the red side of the visible light spectrum.

On the other hand, when a celestial object is getting away from Earth, the spectral line is shorter, that is, the wavelength is smaller in nm, and in the visible light spectrum is moving to the blue side.

This is how scientist can determine the expansion of the universe by the footprint of each star (the spectral line) and the length of the same.

Hope this info is useful.

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