On Monday, December 24, 2018 at 9:35:05 PM UTC, Bruce wrote: > > On Tue, Dec 25, 2018 at 4:43 AM John Clark <[email protected] > <javascript:>> wrote: > >> On Sun, Dec 23, 2018 at 5:38 PM Bruce Kellett <[email protected] >> <javascript:>> wrote: >> >> *> 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.* >>> >> >> There are an infinite number of ways space could have been curved but you >> picked one particular way (no curvature at all) for your initial conditions >> and did so for no particular reason other than to make the theory fit the >> facts that you already knew. Inflation explains why spacetime curvature >> could have any finite value whatsoever when the universe first came into >> existence and it would still look flat today even with our most sensitive >> instruments. It didn't have to start out with spacetime being zero or >> anything close to it, and that doesn't sound fined-tuned to me. >> >> And the same thing is true of temperature, why are things at the same >> temperature when there was no time for them to come into thermal >> equilibrium? Inflation explains why, your explanation is they just did. >> Inflation says that 10^-35 seconds after the start of the universe and it >> had doubled in size about a hundred times (and 10^35 seconds is a long >> long time compared to the Planck Time of 10^-43 seconds) the difference in >> temperature in our part of the universe would be almost zero but not >> precisely zero due to random quantum variations, and quantum theory allows >> you to calculate the intensity and size of what those temperature >> variations should have been. And you can also calculate what those >> temperature variations would evolve into after the universe has been >> expanding for 380,000 years, and what we calculate and what we see are the >> same. >> >> That's also how we know that at the very largest scale the universe is >> in general flat. They did this by looking at the oldest thing we can >> see, the Cosmic Microwave Background Radiation (CMBR) formed just 380,000 >> years after the Big Bang. So if we look at a map of that background >> radiation the largest structure we could see on it would be 380,000 light >> years across, spots larger than that wouldn't have had enough time to form >> because nothing, not even gravity can move faster than light, a larger lump >> wouldn't even have enough time to know it was a lump. >> >> So how large would an object 13.8 billion light years away appear to us >> if it's size was 380,000 light years across? The answer is one degree of >> arc, but ONLY if the universe is flat. If it's not flat and parallel lines >> converge or diverge then the image of the largest structures we can see in >> the CMBR could appear to be larger or smaller than one degree depending on >> how the image was distorted, and that would depend on if the universe is >> positively or negatively curved. But we see no distortion at all, in this >> way the WMAP and Planck satellite proved that the universe is in general >> flat, or at least isn't curved much, over a distance of 13.8 billion light >> years if the universe curves at all it is less than one part in 100,000. >> >> >>> >> 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?* >>> >> >> From the same place gravitational potential does I suppose, but inflation >> would be simpler, in General Relativity gravity needs a tensor field but >> inflation only needs a scalar field. >> >> >>> > *Why don't we see the inflaton?* >>> >> >> Maybe we do see it, maybe the acceleration of the universe we see today >> is the inflation field at work having undergone a phase change when the >> universe was 10^-35 sec old and switched into a much lower gear. Or maybe >> not. Andrei Linde thinks the inflation field decayes away like radioactive >> half life, and after the decay the universe expanded at a much much more >> leisurely pace. But for that idea to work Guth's the inflation field had to >> expand faster than it decayed, Linde called it "Eternal Inflation". Linde >> showed that for every volume in which the inflation field decays away 2 >> other volumes don't decay. So one universe becomes 3, the field decays in >> one universe but not in the other 2, then both of those two universes >> splits in 3 again and the inflation field decays away in two of them but >> doesn't decay in the other 4. And it goes on like this forever creating a >> multiverse. >> >> If any of this is true we may be able to prove it because Eternal >> Inflation would create gravitational waves with super long wavelengths that >> would produce very slight changes in the polarization of the cosmic >> microwave background radiation that we should be able to detect before >> long, assuming they exist. >> > > You seem to be convinced by inflation theory. I am a lot more sceptical > because I see problems that you brush away contemptuously. Why has the > inflation not been seen at LHC? If it decayed into ordinary matter, it must > couple to ordinary matter, and so can be produced in high energy > collisions. But no evidence for any such particle has been found. Inflation > does not solve the horizon problem, either. At the end of the inflationary > period, the temperature was absolute zero everywhere -- no fluctuations. > The hot big bang came from the reheating phase where the inflation field > decayed into ordinary matter. As a quantum process, this would have > occurred randomly everywhere, so there would have been no uniformity in > temperate at all. >
Do you have a typo at end? Did you intend to write "... so there would have been no NON uniformity in temperature at all." AG > 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.
