
Astronomers Indirectly Spot Neutrinos Released 1 Second After the Big Bang - srikar
https://www.scientificamerican.com/article/astronomers-indirectly-spot-neutrinos-released-just-1-second-after-the-birth-of-the-universe/
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bognition
So how exactly does the timing of this work out. If the neutrinos were kicked
off at the big bang and have been traveling at nearly the speed of light since
then, how is it that we are further away from the epicenter of the big bang
than the neutrinos?

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fennecfoxen
"Epicenter"? No, no, it doesn't work that way: the Big Bang was everywhere all
at once. It's just that "everywhere" had much less empty space in between it
at the time.

The way it works is that neutrinos were made everywhere, including some places
which, after adjusting for cosmic inflation, are ~13.7 giga-light-years away,
therefore the speed-of-light neutrinos produced there will arrive at the Earth
approximately Now.

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PhilWright
If the Big Bang happened everywhere at the same time then does that mean the
universe was infinitely big at the start? Every time I watch a science program
about the big bang they say that everything was contained in an area smaller
than an atom? Surely both cannot be true.

I don't have a physics background, so forgive a naïve question.

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pdonis
_> If the Big Bang happened everywhere at the same time then does that mean
the universe was infinitely big at the start?_

Not necessarily; there are models with a spatially infinite universe and
models with a spatially finite universe. In our best current model, the
universe is spatially infinite; but there is enough wiggle room in the data
that a spatially finite (but very, very large) model is still possible (though
unlikely).

 _> Every time I watch a science program about the big bang they say that
everything was contained in an area smaller than an atom?_

They are talking about the observable universe, not the entire universe.
Unfortunately, many pop science treatments don't make the distinction clear.

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TeMPOraL
So correct me if I'm wrong, but it seems that in a model of a spatially finite
universe there obviously has to be a centre, right?

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pessimist
Consider the surface of a sphere. It is finite but has no centre.

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TeMPOraL
Oh, I forgot about those cases. Thanks! But are those types of models the only
finite universe models currently considered? What about just bog standard
"surface of a circle", aka. space in a sphere? After all, Olbers' paradox gets
resolved by the speed of light and the expansion of the universe.

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TheOtherHobbes
The "sphere" has more than the usual three dimensions, so the "surface" is
really our four dimensional space/time.

From the point of view of _any_ observer in our universe, space/time
accelerates away equally in all directions - just like a grid on a ball that's
inflating spreads out over time.

But the grid has more than two dimensions.

You may be wondering what's "inside" the "sphere." Whatever is there can't be
reached from the universe, no matter which direction you travel in. It's
literally in a different dimension.

But that's almost completely meaningless as a statement. No one has any idea
how the "sphere" really works.

In our universe we can take it for granted that space/time defines a system
for measuring shapes and distances.

Outside of the "surface" of the universe, there's no way to know how shapes or
distances work, or whether there even needs to be something on the "inside" \-
it's possible the "sphere" only exists as a mathematical template, because
it's the only way space/time can hang together, and it's some kind of weird
emergent thing that has to happen. (Insert further idle speculation here.)

This is all really, really hard to imagine. Brains evolved for swinging
through trees can't visualise it without math. Brains with math are still very
much struggling with it.

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reptation
Does anyone know of strong proofs of galaxy red shifts being due to
relativistic Doppler effect? It seems like almost everything in Cosmology
depends on this being true.

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ProAm
Im not sure what you are asking, this is really proven. Are you asking about a
differing theory??

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reptation
I work down the hall from this guy and he's really convincing:
[http://www.ccsenet.org/journal/index.php/apr/article/viewFil...](http://www.ccsenet.org/journal/index.php/apr/article/viewFile/25856/15981)

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pdonis
People can be really convincing and still be wrong. As far as I can tell on a
quick skim, this theory (that the redshifts are due to differential scattering
of starlight) is one that was ruled out several decades ago by cosmologists.
Also, his "fundamental inconsistencies of the Big Bang Theory" would be better
titled "fundamental misunderstandings on the author's part". The cosmology FAQ
I linked to upthread discusses a number of these misunderstandings.

