It’s based on the expansion rate of the universe, known as the Hubble Constant. If you know how fast it is expanding, it’s simple to calculate how long it took for things to travel as far as they have, based on their distance from us. The earth doesn’t have to be at the center of it all, since all points are expanding away equally from all others. Theoretically.
It’s based on the expansion rate of the universe, known as the Hubble Constant ... Theoretically
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As long as the Hubble Constant was always the same. Of which there is no proof, and will be none, until a time machine is invented so these people can go billions of years back in time to prove the Constant was always constant.
I would say that there is MUCH “Theoretically” involved in these calculations.
The Hubble theories are swiss cheese at this point.
New discoveries of massive “early” galaxies means we really need to rethink a lot of previous views on this topic.