On Sunday, December 31, 2017 at 8:10:39 PM UTC-6, agrays...@gmail.com wrote:
>
>
>
> On Sunday, December 31, 2017 at 7:25:53 AM UTC-7, Lawrence Crowell wrote:
>>
>> On Saturday, December 30, 2017 at 8:33:17 PM UTC-6, agrays...@gmail.com
>> 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, agrays...@gmail.com
>>>> 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, agrays...@gmail.com
>>>>>> 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
>>
>
> *Standing waves in an expanding box is a plausible model for analyzing the
> evolution of the CMB, but in reality the photons comprising the CMB don't
> bounce off a barrier, but keep moving away from the source event, some
> 380,000 years after the BB. How would you overcome this deficiency in your
> model? TIA, AG*
>
>From an operational perspective they are equivalent. In any case the
expansion of space expands waves in it.
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 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.
