On Saturday, December 30, 2017 at 8:33:17 PM UTC-6, [email protected] wrote: > > > > On Saturday, December 30, 2017 at 2:40:22 PM UTC-7, Lawrence Crowell wrote: >> >> On Saturday, December 30, 2017 at 2:28:52 PM UTC-6, [email protected] >> wrote: >>> >>> >>> >>> On Saturday, December 30, 2017 at 1:03:58 PM UTC-7, Lawrence Crowell >>> wrote: >>>> >>>> On Friday, December 29, 2017 at 8:45:41 PM UTC-6, [email protected] >>>> wrote: >>>>> >>>>> >>>>> >>>>> On Friday, December 29, 2017 at 6:59:22 AM UTC-7, Lawrence Crowell >>>>> wrote: >>>>>> >>>>>> The cosmological constant is Λ ~ 10^{-52}cm^{-2} and the scale factor >>>>>> evolves as >>>>>> >>>>>> a(t) = a_0 exp(t sqrt{Λc^2/3}). >>>>>> >>>>>> The factor sqrt{Λc^2/3} ~ 10^{-18}sec^{-1}. For a billion years this >>>>>> is t ~ 3x10^{16} sec and so sqrt{Λc^2/3}t ~ .03 and the scale factor >>>>>> increases by 1.03. The CMB microwave background will be expanded by a >>>>>> small >>>>>> change. In 10 billion years this is t ~ 3x10^{17}sec and so >>>>>> sqrt{Λc^2/3}t ~ >>>>>> .3 and the scale factor expands by 1.4. At 100 billion and a trillion >>>>>> the >>>>>> scale factor expands by 20 and in a trillion years by 10^{13}. This >>>>>> means >>>>>> the CMB peak wavelength will be about 10^{10}m. That is not quite the >>>>>> length of the cosmos, but in 10 trillion years the expansion factor is >>>>>> close to ~ 10^{800} which means the wavelength at this point is larger >>>>>> than >>>>>> the cosmological horizon scale. At that point the CMB will be removed >>>>>> from >>>>>> the view of any observer. The time where wavelength becomes longer than >>>>>> the >>>>>> cosmological horizon occurs in about 2 trillion years. >>>>>> >>>>>> LC >>>>>> >>>>> >>>>> *Does the CMB just keep getting progressively redder as the cosmos >>>>> expands, or does it actually "wink out", meaning CMB photons which we >>>>> might >>>>> eventually observe, begin their journey beyond our horizon? Since no new >>>>> ones are being created, and the original ones are within our immediate >>>>> neighborhood, like Andromeda, I don't see how they can wink out. AG * >>>>> >>>> >>>> Think of a cube with sides length L. This is a region that permits >>>> wavelengths of λ = L/2, L, 3L/2, ...as standing waves. By this as one >>>> photon of those wavelength leaves another enters. So we can think of space >>>> as having properties similar to a resonance cavity. As space expands this >>>> box expands, which means the permitted standing waves have longer >>>> wavelength. So as space expands electromagnetic waves within it also >>>> becomes stretched. This is the red shifting of light. >>>> >>>> Local clusters of galaxies that are gravitationally bound will not have >>>> this issue. These galaxies will remain in relative close proximity. If it >>>> were not for the fact Andromeda and the Milky Way are going to coalesce in >>>> about 4 billion years Andromeda would be observable from this galaxy far >>>> into the future in wavelengths of light emitted by stars. The other >>>> galaxy, >>>> M33 or Triangulum, the smaller of the three large galaxies in the local >>>> group, may orbit around this newly formed Androway or Milkomeda galaxy for >>>> a nearly indefinite time into the future. >>>> >>>> LC >>>> >>> >>> *So you agree with Brent that the CMB will grow redder as the universe >>> expands, but will never "wink out" as will be the case for galaxies not >>> gravitationally bound to the MW? The key difference is contained in the >>> concept of photons entering the box as others leave, and I suppose this >>> follows from the omnidirectional nature of the CMB. Correct? AG* >>> >> >> Once the wavelength of CMB radiation has expanded beyond any possible >> quarter wave stack size it it no longer detectable. Once it has expanded to >> a scale larger than the cosmological horizon it is absolutely impossible to >> detect. In that case we can say the CMB has winked out. This will happen in >> a finite time in the future, though two trillion years is 144 times the age >> of the universe now and almost eternity compared to our lifetimes. In the >> extreme time frame beyond from 10^{30} to 10^{110} years there will only be >> supermassive black holes. The cosmological horizon does emit Hawking-Gibbon >> radiation that is analogous to Hawking radiation. This radiation will >> perturb black holes, and potentially a civilization or collective of >> intelligent life that lives around such a SMBH using its angular momentum >> as energy might be able to detect this perturbation. The SMBH might not >> decay quite as it would in a pure vacuum. This might be the detection of >> the cosmological horizon. I will refrain from much comment on the >> plausibility of such civilizations. >> >> The box argument in part works because of the isotropy of the CMB >> radiation. >> >> LC >> > > *What is a quarter wave stack? I get the key point. TY. Since the CMB is > ubiquitous and isotropic, it can't be treated like a source which becomes > located beyond the cosmic horizon. AG * >
An organ pipe is a quarter wave stack. It has open and closed, or Newman and Dirichlet, boundary conditions on either end. That way it is resonant with a wavelength by being a quarter of a wavelength in dimension. LC -- 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.
