Concept explainers
Explain why it only appears that we are at the center of expansion of the universe and why an observer in another galaxy would see the same relative motion of all but the closest galaxies away from her.
The appearance of our galaxy at the center of the expansion of the universe and an observer would see the same relative motion from another galaxy.
Explanation of Solution
Introduction:
Universe is expanding from everywhere and it has no center of expansion. Materials expand from a center in a conventional explosion while Big Bang was an ordinary explosion as there was no time and space before it. Since, the entire universe is expanding not from a center point.
According to Hubble's law, the expansion of the universe is uniformly at all places and the galaxies which were farther away, those were faster receding that's why it appears that we are at the center of the expansion.
Consider an example of a balloon analogy to explain the expansion of the universe. Consider some dots on the surface of the balloon. When air is blown inside it, the balloon expands in all direction and the distance between the dots increases from the point under consideration as a center. Similarly, the universe is expanding uniformly as there is no center of expansion.
From the above, it is clear that an observer can see themselves as stationary at any point on the universe and the other objects appears moving away in space uniformly in all the directions that's why an observer would see the same relative motion from another galaxy.
Conclusion:
Therefore, the universe is expanding uniformly in all the directions as there is no center of expansion that's why an observer would see the same relative motion from another galaxy.
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