On Monday, December 24, 2018 at 8:25:11 PM UTC, agrays...@gmail.com wrote: > > > > On Monday, December 24, 2018 at 6:40:03 AM UTC, Brent wrote: >> >> >> >> On 12/23/2018 8:22 PM, agrays...@gmail.com wrote: >> >> >> >> On Monday, December 24, 2018 at 3:50:33 AM UTC, Brent wrote: >>> >>> >>> >>> On 12/23/2018 4:47 PM, agrays...@gmail.com wrote: >>> >>> *If by "flat", you mean mathematically flat, like a plane extending >>> infinitely in all directions, as opposed to asymptotically flat like a huge >>> and expanding sphere, you have to reconcile an infinitesimally tiny >>> universe at the time of the BB, and simultaneously an infinitely large >>> universe extending infinitely in all directions. AG* >>> >>> >>> All that's "infinitesimally tiny" is the visible universe. You must >>> know that the Friedmann equation just defines the dynamics of a scale >>> factor, not a size. >>> >> >> *Are you claiming the visible universe at the BB was infinitesimally >> tiny, but the non visible part was infinitely large (mathematically flat), >> or huge (asymptotically flat)? AG * >> >> >> Right. Although we can't be sure whether it is actually flat or just >> very big. >> >> Brent >> > > *OK. Agreed. We seemed to disagree on this in the past, but maybe we > miscommunicated. AG* >
Here's what Ned Wright wrote. Is the Universe really infinite or just really big? We have observations that say that the radius of curvature of the Universe is bigger than 70 billion light years. But the observations allow for either a positive or negative curvature, and this range includes the flat Universe with infinite radius of curvature. The negatively curved space is also infinite in volume even though it is curved. So we know empirically that the volume of the Universe is more than 20 times bigger than volume of the observable Universe. Since we can only look at small piece of an object that has a large radius of curvature, it looks flat. The simplest mathematical model for computing the observed properties of the Universe is then flat Euclidean space. This model is infinite, but what we know about the Universe is that it is really big <http://www.astro.ucla.edu/~wright/HGTTG.html>. <http://www.astro.ucla.edu/~wright/cosmology_faq.html#top> *It is misleading. He's referring to the VISIBLE universe and concludes it might be infinite in spatial extent. Impossible due to its finite age. I wrote him about this, but never received a reply. AG* -- 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 everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
