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How many light years is the universe?

Ashley Howard

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Amanda Johnson on November 1, 2018

If one is assuming the Big Bang theory is in essence true, then just take the age of the Known Universe, and multiply the result by two. You can see, the fastest way that anything could have been spotted out since the Big Bang is the speed of light, so that if the Known Universe is 15 billion years, it would be 30 billion light years wide. The problem with this response is that it ignores the expansion of space. If, indeed, it is true that, IN the ABSENCE OF EXPANSION, a photon that started traveling very close to the start of the Big Bang and then continued traveling for 15 billion years travel of 15 billion light-years. The situation changes with expansion, however. The 15 billion light-years that the photon would have travelled, over time, expanded to more than 45 billion light-years. Therefore, that infinitesmally small part of our Universe that we can see is actually about 46 billion light-years in radius.

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