On Wed, Jan 22, 2020 at 12:48 AM Alan Grayson <[email protected]> wrote:
*> **I strongly disagree that finite rates of expansion will result in an > open universe. I believe it will be a closed hyper-sphere, but I am open to > being wrong. AG * If empty space has a residual intrinsic energy of any value greater than zero, which General Relativity allows for and Quantum Mechanics demands, then the expansion of the universe will accelerate. If the universe is accelerating then it is open regardless of what its spatial shape is, regardless of how many degrees the angles of a triangle add up to (please remember the term "spatial shape" is not equivalent with the term "spacetime shape"). And when you ask "How big is the universe?" you need to know exactly what you're really asking. You have nothing outside of the universe to compare it to so one answer would be "The universe is as big as the universe", but you may find that unsatisfying. What you really want to know is if the universe is open or closed, you want to know "If you keep going in one direction will you head out for infinity and keep getting further and further from your starting point for eternity, OR will you eventually hit some sort of wall or eventually start getting closer to your starting point ?" Today we have very good evidence the universe is accelerating and thus open. Independently we have moderately good evidence that Inflation occured. And we have pretty good evidence the universe is spatially pretty flat. We'll never be able to observationally prove it has exactly zero spatial curvature but if all you want to know is how big the universe is, that is to say if all you want to know is if it's open or closed, then how many degrees the angles of a triangle add up to is not important. John K Clark -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAJPayv2k1cXdRr38NVyja9eA7F9q9j24o_eDc_hW%2BMDJd-bXMQ%40mail.gmail.com.
