On Mon, Mar 18, 2019 at 6:36 AM <agrayson2...@gmail.com> wrote: > On Sunday, March 17, 2019 at 12:12:58 PM UTC-6, Brent wrote: >> >> On 3/17/2019 4:50 AM, agrays...@gmail.com wrote: >> >> On Sunday, March 17, 2019 at 3:05:14 AM UTC-6, agrays...@gmail.com >> wrote: >>> >>> >>> >>> On Sunday, March 17, 2019 at 2:49:43 AM UTC-6, Bruce wrote: >>>> >>>> On Sun, Mar 17, 2019 at 7:38 PM <agrays...@gmail.com> wrote: >>>> >>>>> >>>>> >>>>> On Thursday, March 14, 2019 at 8:27:58 PM UTC-6, agrays...@gmail.com >>>>> wrote: >>>>>> >>>>>> IIUC, the combined mass of an electron and proton is larger than the >>>>>> hydrogen atom they form at recombination time. Thus, I would expect a >>>>>> very >>>>>> narrow pulse of energy as a result when recombination occurs. This >>>>>> apparently being the case, why does the CMBR have a black body >>>>>> distribution >>>>>> and not a pulse with a very narrow spread? TIA, AG >>>>>> >>>>> >>>>> Is this a really dumb question and the reason for zero replies; or is >>>>> it because no one here has the answer? Or maybe just no interest in >>>>> another >>>>> puzzle? AG >>>>> >>>> >>>> Dumb question. CMB is thermal radiation, not the recombination energy. >>>> It reflects the temperature at the time the universe became transparent to >>>> radiation of all wavelengths -- because the electron-proton plasma >>>> recombined to form less reactive hydrogen. >>>> >>>> Bruce >>>> >>> >>> But the recombination energy must be part of the mix at recombination >>> time and this is never mentioned in the texts I have read. I suppose this >>> is another dumb question. AG >>> >> >> What this thread shows is that I don't understand the CMBR. Maybe no one >> does. ISTM that the universe was cooling *prior* to recombination time >> and therefore must have had a thermal spectrum *independent* of the >> recombination. Yet the going assumption, AFAICT, is that the CMBR *comes >> into existence* at recombination time, but is independent of the >> physical recombination which is never included or mentioned as part of the >> observed spectrum. Can anyone explain what is actually going on in this >> model? TIA, AG >> >> >> Your mistake is assuming that this recombination is one big jump from >> complete dissociation to bound hydrogen atom. A hydrogen atom has lots of >> energy states and, as the plasma cooled due to expansion, there would be a >> continuous shift of energy from the proton/electron to the gamma rays. >> >> Brent >> > > In fact, hydrogen has a countably infinite set of energy states, which I > forgot. Is it correct to say that these recombination states form the > thermal signature which is observed (in which case Bruce's explanation is > misleading)? AG >
No, that is not a correct thing to say. Recombination occurs when the average thermal energy of particles in the plasma was below the dissociation energy of hydrogen, which, as I recall, is around 14 eV. But the radiation we see as CMB now is the blackbody radiation from this initial plasma. Energy contributions from the recombination of hydrogen atoms are present, but just form part of the thermal spectrum -- because not all recombinations take a proton and an electron directly from the unbound state to the lowest energy state (14.? eV). There is a range as electrons cascade down, and many of these transitions are of much lower energy -- red-shafted to invisibility now. 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 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.
