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How Did The Universe Expand To 46 Billion Light-Years In Just 13.8 Billion Years?

5 Mar 2019, 15:01 UTC
How Did The Universe Expand To 46 Billion Light-Years In Just 13.8 Billion Years? C. Faucher-Giguère, A. Lidz, and L. Hernquist, Science 319, 5859 (47)

If the Universe is 13.8 billion years old, and the speed of light is truly our cosmic speed limit, how far away should we be able to see? The answer seems obvious: 13.8 billion light-years, since a light-year is the distance light can travel in a year, and nothing can go faster than that.

Unfortunately, like a great many answers that seem obvious when you apply your logical common sense to them, that’s not how things actually work. In reality, if you were to look at the most distant thing of all you can possibly see, and ask “how far away is it,” the answer is much farther than that: 46 billion light-years. That might sound impossible, but it’s not. You just have to expand your way of thinking.

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