Exam-style question
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What can be inferred about the motion of a galaxy if its light exhibits a significant redshift?.
- A.It is moving towards the Earth
- B.It is moving away from the Earth
- C.It is stationary relative to the Earth
- D.It is orbiting another galaxy
Model answer
What a good answer should say
- It is moving away from the Earth
Explanation
Why this works
The evidence of a significant redshift indicates that the light waves are stretched, which shows that the galaxy is receding from the observer. This implies that the universe is expanding, leading to the conclusion that the galaxy is moving away from the Earth.
Common mistake
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