Re:If the universe is 13.8B years old, how can we see 46B li...
by NeedMoreTea on Saturday December 07, 2019 @10:23PM
(#21734165)
Sure, but the high school, pop science and TV explanations of relativity and the universe rarely consider anything apart from the two trains travelling toward each other, nearing C, with an observer aboard one train. People can grasp that relatively easily, along with doppler explanations of red shift. Every decent attempt to take a step or two further is to be approved. :)
When tracks start moving as well it gets mind bending, and no longer intuitive. Now we have multiple scenarios where the combination of track movement (universe expansion), and train movement result in it being "obvious" you have to exceed C somewhere, which we're told is impossible. Otherwise how can the distances end up where they are. It's between these two points most non-physicists stop as it starts to feel deeply contradictory.
https://en.wikipedia.org/wiki/Hubble%27s_law
"(...) the notion of the universe expanding at a calculable rate was first derived from the general relativity equations in 1922 by Alexander Friedmann"
The space expands. It's been known for a long time.
We might not know why exactly this happens and there is still some discussion about ultimate fate of the universe although prevalent theory is that it will expand at an ever faster rate until every molecule will be torn from each other and matter will no longer be able to form.