On Sunday, December 23, 2018 at 10:38:00 PM UTC, Bruce wrote: > > On Mon, Dec 24, 2018 at 1:38 AM John Clark <[email protected] > <javascript:>> wrote: > >> On Sat, Dec 22, 2018 at 11:32 PM Bruce Kellett <[email protected] >> <javascript:>> wrote: >> >> *> The point is that inflation only solves the problem given certain >>> initial conditions. We have no independent knowledge of those initial >>> conditions, * >> >> >> From observations I think we do have a little knowledge about what those >> initial conditions must have been, they could not have been fractal and >> infinitely complex as Penrose postulated because then the universe would >> also have started out in a condition of maximum possible entropy and could >> not have evolved to be in the much lower entropy state we see today. >> >> > *so it could well be that the initial condition was that everything >>> was always at a uniform temperature,* >> >> >> It's not just temperature, the initial conditions would also be that >> spacetime was uniformly flat. Today the observed density of >> matter/energy in the universe is very close to what would be needed to >> achieve overall spacetime flatness; for this to be true today the early >> universe must have been closer than one part in 10^62 to that >> critical density point. Coincidence? Maybe, but I doubt it. >> >> >>> > *and there was no need for something, such as inflation, to render >>> the CMB uniform everywhere.* >> >> >> So inflation can't fix things if the universe started out with infinite >> complexity and entropy, but nothing else could either and yet the universe >> we see today is not in a maximum entropy state. And inflation is not needed >> if the initial conditions were at a uniform temperature and the mass/energy >> density was within one part in 10^62 of the critical point. >> > > Flatness is explained if the unknown parameter k in the FRW solution is > set to zero. The the universe is always flat, no need to fine tune. Setting > k = 1 or k = -1 is just as fine-tuned or not as k=0. >
*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* > > > >> It would seem to me that if two theories can explain observations then >> the one with the simpler initial conditions is the superior. >> > > The trouble is that inflation is not a simple theory. Where does the > inflation potential come from? (Do you even know what it is? Why don't we > see the inflaton?)The slow roll parameters have to be fine-tuned to a > remarkable degree to get agreement with observation, etc, etc. All you > have to do without inflation is have smooth initial conditions with k=0 -- > very much simpler..... > > Bruce > -- 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 post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
