On Mon, Dec 24, 2018 at 6:28 PM <[email protected]> wrote: > > > On Monday, December 24, 2018 at 9:47:52 PM UTC, Jason wrote: >> >> >> >> On Mon, Dec 24, 2018 at 4:04 PM <[email protected]> wrote: >> >>> >>> >>> On Monday, December 24, 2018 at 8:25:11 PM UTC, [email protected] >>> wrote: >>>> >>>> >>>> >>>> On Monday, December 24, 2018 at 6:40:03 AM UTC, Brent wrote: >>>>> >>>>> >>>>> >>>>> On 12/23/2018 8:22 PM, [email protected] wrote: >>>>> >>>>> >>>>> >>>>> On Monday, December 24, 2018 at 3:50:33 AM UTC, Brent wrote: >>>>>> >>>>>> >>>>>> >>>>>> On 12/23/2018 4:47 PM, [email protected] 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* >>> >>> >>> >> It's only impossible if you believe the believe the big bang occurred >> only at a point, rather than everywhere. >> >> Consider that every point in space sees everything else around it flying >> away from it, such that if you rewound time, everything would return to a >> single point centered at that location. But this is true for every point in >> space, so the implication is that the BigBang didn't happen at one >> particular location long in the past, but at every point, including the >> period at the end of this sentence. >> > > *You seem inclined to extreme hypotheses for which there is no data. AG * > >> >> This is the default "standard" model used used by cosmologists, it's called the concordance model, or the Lambda-CDM model. There is significant data for it.
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