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What Does the Expansion of the Universe Look Like from an Galaxy on the Edge of the Known Universe?

-- | May 20, 2016

Question: If you were to project yourself instantly to the edge of the known universe, (knowing that the universe is expanding at or near the speed of light from this perspective) and you were to take a telescope and look towards our galaxy, should you not see our galaxy moving at the same speed as we we see the galaxies from our perspective from here? Since everything moving is measured from our perspective, how can we surmise that we, moving at “x” speed from this point of view is not really moving at or near the speed of light looking from the edge of the universes point of view? — Louis

Answer: The answer to this question rests on the tricky nature of the expansion of the universe. A simple model that is not strictly correct but is a good enough approximation is that everything in the universe is moving away from everything else. In other words, think of it as space being created between all objects everywhere, thus looking like everything moving away from everything else. Therefore, as soon as you go to the edge of the known universe, you go to a place that is at rest in the observer’s reference frame, just like the reference frame that we sit in here on Earth. You would see the same universal expansion at the far-away galaxy as you see here in our own Milky Way galaxy.

Jeff Mangum

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