Question

What would most likely cause the future acceleration of the expansion of the universe?
radiation from the Sun
the existence of background radiation
the continued existence of dark energy
light shifts identified by the Doppler effect

Answer 1

Answer:

An increase (or decrease) in the frequency of sound, light, or other waves as the source and observer move towards (or away from) each other. The effect causes the sudden change in pitch noticeable in a passing siren, as well as the red shift seen by astronomers.

Explanation:

The characteristic sound of a motorcycle buzzing by is an example of the Doppler effect. The Doppler effect is an alteration in the observed frequency of a sound due to motion of either the source or the observer. Although less familiar, this effect is easily noticed for a stationary source and moving observer.

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