Question

what do we mean when we say that the universe is expanding? question 9 options: A. within galaxies, average distances between star systems are increasing with time and the galaxies and galaxy clusters are, in general, receding from each other. B. everything in the universe is gradually growing in size. C. the average distance between galaxies is increasing with time. D. the statement is not meant to be literal; rather, it means that our knowledge of the universe is growing.

Answer 1

The concept of an expanding universe refers to the increasing distances between galaxies and within galaxies over time, not individual celestial bodies growing in size. This is observed by the motion of distant galaxies moving away from us.

Step-by-step explanation:

When we say that the universe is expanding, we refer to option A and C: within galaxies, average distances between star systems are increasing with time and the galaxies and galaxy clusters are, in general, receding from each other; and the average distance between galaxies is increasing with time. This isn't to suggest individual stars and planets themselves are expanding, but rather the vast cosmic spaces in between are. This idea comes from observations of distant galaxies moving away from us in all directions, indicating that the universe has been expanding since the Big Bang.

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