[ExI] Dark mass = FTL baryons?

[John Clark]

On Sun, Aug 20, 2017  Stuart LaForge <avant at sollegro.com> wrote:

>
>> ​>​
>> You can't go to infinity in all directions, the past is a specific finite
>> ​
>> ​n​
>> umber, 13.8 billion years, the future is unknown and could well be
>> ​
>> infinite but almost certainly  is not equal to the past, it is not 13.8
>> ​
>> billion years.
>
>
> ​> ​
> Well I would say at the scale of about 3 billion lightyears, structures
> stop being apparent and the universe becomes of sufficiently homogenous
> density for my calculation to be valid.


​In the past direction 3 billion years ago things were a little closer
together than they are now but otherwise stuff looked more or less the same
as now, but go back much further and that is not the case. 6 billion yeas
ago the universe was decelerating not accelerating as it is now, and 12
billion years ago stars were much bigger and galaxies were much smaller and
more irregular than now, and 380,000 years after the Big Bang when the
cosmic ​microwave background radiation was emitted that we can still see
the universe was a billion timed denser than it is now.

That doesn't sound very homogeneous and that's just in the past direction.
What will the universe look like in 12 billion years? The past direction is
finite, is the future direction finite too? Nobody knows.

>
>> ​>​
>> If you include the entire "contents of the 4-D ball" you'd be including
>> ​
>> events outside our past lightcone that can not influence any observation
>> we
>> ​
>> make, so that can't explain the observations we can make of Dark Matter or
>> ​
>> Dark energy.
>
>
> ​> ​
> Blackhole singularities are outside our light cone as well, hidden behind
> event horizons to protect causality, yet they nonetheless influence the
> shape of space-time


​The singularity at the center of a Black Hole is outside the light cone
but the event horizon and the intense gravitational field there is not, it
can influence things far away but, like everything else, only at the speed
of light. Physics can't say what the Singularity is doing but it doesn't
need to if you're only interested in things outside the event horizon.  ​


> ​> ​
> I claim the same privilege for superluminal space-noodles of dark matter.
> ​ [...]
> The dark matter is superluminal relative to our rest frame.


Whatever Dark Matter is one thing we know for sure is it's not
​
superluminal
​,
in fact it's very slow; recent studies show it's less than 54 meters per
second
​
.So I guess you could say 120 mph is the speed of dark:

https://arxiv.org/abs/1309.6971


> ​> ​
> They can gravitationally warp space-time and according to GR, that's just
> geometry. To say gravity is subject to causality is like saying an
> elephant's trunk causes its ass.
>

​Even gravity can't cause thing to change at arbitrary distances
instantaneously, if it could gravitational waves could not exist. If you
suddenly pushed the sun sideways the Earth would not change its orbit in
the slightest for about 8 minutes because even gravity and the spacetime
distortions it causes is limited to the speed of light. ​

John K Clark






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