Exam-style question
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What does the y-intercept of a velocity-distance graph represent?.
- A.The velocity of the closest galaxy
- B.The velocity of the furthest galaxy
- C.The expansion rate of the universe
- D.The current velocity of the observer
Model answer
What a good answer should say
- The velocity of the closest galaxy
Explanation
Why this works
The evidence from the y-intercept of a velocity-distance graph shows the velocity of galaxies when they are at a distance of zero. This indicates the velocity of the closest galaxy to the observer.
The implication is that it provides a reference point for understanding the movement of other galaxies, leading to the conclusion that it helps in measuring the overall expansion of the universe.
Common mistake
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