On Saturday, May 23, 2020 at 4:32:05 PM UTC-5, Lawrence Crowell wrote:
>
> On Friday, May 22, 2020 at 8:30:10 PM UTC-5, Alan Grayson wrote:
>>
>>
>>
>> On Tuesday, May 19, 2020 at 11:18:15 PM UTC-6, Alan Grayson wrote:
>>>
>>>
>>>
>>> On Tuesday, May 19, 2020 at 6:26:08 PM UTC-6, Lawrence Crowell wrote:
>>>>
>>>> You cannot of course circumnavigate the spatial manifold of the
>>>> universe. Anything beyond the cosmological horizon moves away faster than
>>>> you can ever catch up. It is a bit like the part in the movie The Shining
>>>> with Jack Nicholson where the hotel hallway expanded faster than he could
>>>> run. If we could though observe this, say analogous to Jack Nicholson in
>>>> the film, there would be optical effects. The spatial manifold could be a
>>>> k
>>>> = 1 closed or k = -1 hyperbolic or the dodecahedral tessellated universe
>>>> of
>>>> Poincaré. Yet so far data is not forthcoming.
>>>>
>>>> A Planck energy of quanta, say a UV graviton, could have causal
>>>> influence on us is it expands to the cosmological horizon or near so. The
>>>> B-modes of inflation, which are still being pursued, represent Planck
>>>> units
>>>> redshifted to some appreciable scale comparable to the cosmological
>>>> horizon. This is a z factor z = 10^{10}ly/ℓ_p = 6.3×10^{60}, where taking
>>>> the nat-log of this and multiplying by the horizon scale 1.3×10^{10}ly we
>>>> get 1.8×10^{12}ly. The furthest out anything can have traversed at the
>>>> speed of light to reach is from that distance and from the earliest near
>>>> Planck time in the universe. What this means is the source or emitter of
>>>> this graviton was early on close to our region and the source is not that
>>>> incredible distance away.
>>>>
>>>> LC
>>>>
>>>
>>> Is this estimate reasonable, also from
>>>
>>> https://www.forbes.com/sites/startswithabang/2020/05/19/would-a-long-journey-through-the-universe-bring-us-back-to-our-starting-point/#fe376fef6c50
>>>
>>>
>>> The appearance of different angular sized of fluctuations in the CMB
>>> results in different spatial curvature scenarios. Presently, the
>>> Universe appears to be flat, but we have only measured down to about the
>>> 0.4% level. At a more precise level, we may discover some level of
>>> intrinsic curvature, after all, but what we've observed is enough to tell
>>> us that if the Universe is curved, it's only curved on scales that are
>>> ~(250)^3 times (or more than 15 million times) larger than our
>>> presently-observable Universe is.
>>>
>>> AG
>>>
>>
>> What I'm asking is whether, based on current measurements, if the
>> universe is curved, can we conclude that the universe is *15 million
>> times larger* than our presently observable universe? TIA, AG
>>
>
> Without data there is nothing we can conclude. The spatial surface of the
> universe appears to be flat or without curvature that is 300 or so larger
> than the cosmological horizon distance. That is about 4 trillion light
> years, or about 2 times the possible distance any causal connection from
> inflation could reach us, Beyond that we know absolutely nothing. Unless
> some sensitive optical work is done with CMB imaging that can push this
> further we may never know.
>
> In the end physics and observable cosmology is local, and we are
> approaching certain limits due to our locality as observers. If we measure
> much further out and closer to inflation and the initial quantum event we
> will only push out about 1.8 trillion light years. It is unclear if any ray
> tracing measurement of gravitons or neutrinos from this earliest moment of
> the observable universe.
>
> LC
>
I watched the following a few days ago that is related to this topic.
LC
https://youtu.be/e1dOnqCu9pQ
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