If we know approximately how long it’s been since the Big Bang, and we know approximately how fast the universe expands/has been expanding, why can’t we get a good estimate on how big the non-observable universe is? Or more specifically, why can’t we figure out the radius on how far matter has spread out since the Big Bang?
In: Planetary Science
Because as far as we know (and this is extremely theoretical), the big bang didn’t happen in any one place, but everywhere at once. It’s just that “everywhere” approaches being a single point, because the more you look into the past, the closer everything is (so if you picture two galaxies, no matter the distance, they would be in the same place near the big bang).
Wether all truly comes from a point or not is an open question, but since as far as we know the big bang happened everywhere, we cannot use it to determine the size of the universe, which has no center.
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