Our Universe is huge. In each and every direction on the sky, powerful telescopes observe galaxies whose light took more than 10 billion years to arrive at Earth. But wait - if we receive such ancient light from two opposite directions, and if the Big Bang happened just' 13.8 billion years ago, does that mean that the Universe is expanding faster than light? And wouldn't that violate Albert Einstein's theory of relativity, which says that the speed of light is an absolute limit? The answer may surprise you. But first, we need to take a closer look at the expansion of the Universe.
As described in the previous instalment of this series, we know that the Universe is expanding because galaxies appear to speed away from each other - their mutual distances are continuously increasing. But we also saw that cosmic expansion shouldn't be pictured as galaxies racing through empty space at incredibly high velocities. Instead, it is empty space itself that expands, pushing the galaxies ever further away from each other.
This story is from the February 2023 edition of BBC Sky at Night Magazine.
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This story is from the February 2023 edition of BBC Sky at Night Magazine.
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