Inflationary vs deflationary phase of Big Bang

[BIGphysician]

TL;DR Summary

Shape of the big bang? And universe?

Hi I'm a medical doctor, this is just a hobby my uncle got me interested in as a kid. If the universe is acceleration and galaxies are moving further apart, we assume the universe as a whole is expanding as a result. It's also projected to my understanding that eventually the universe will contact and a cycle of matter and force creation will be recycled four the next big bang.

How do we know that we aren't accelerating towards a singular contraction point rather than away from one (deflating vs inflating). Every galaxy is moving away from every other at the same rate and distance?

What's the shape of the universe? If it's an expanding sphere with a centrally located origin of force, galaxies originating from different relative locations at the singularity would result in different relative distances?

 

[PeroK]

Is that what your uncle told you?

 

[berkeman]

Welcome to PF, doctor.

Have a look at some of the PF Insights articles about the Big Bang and related issues, to see if they help with your understanding:

https://www.physicsforums.com/insights/?s=big+bang

 

[BIGphysician]

Is that what your uncle told you?

Something like that, he wrote a several thousand page primer on quantum mechanics but it's over my head, what's your view of the meta physics

 

[Ibix]

If the universe is acceleration and galaxies are moving further apart, we assume the universe as a whole is expanding as a result.

No, we don't assume - we can see distant galaxies moving away in all directions. It's also a fairly straightforward implication of feeding the cosmological principle into Einstein's Field Equations.

It's also projected to my understanding that eventually the universe will contact

Assuming you mean "contract" here, maybe. Our best estimates don't rule out an eternally expanding universe.

and a cycle of matter and force creation will be recycled four the next big bang.

That's highly speculative. Penrose thinks so, but it's not anywhere near a fully fleshed out theory, let alone generally accepted.

How do we know that we aren't accelerating towards a singular contraction point rather than away from one (deflating vs inflating).

I don't even know how that would make sense.

Every galaxy is moving away from every other at the same rate and distance?

No. For any pair of galacies a given distance apart they are moving further apart at the same rate (more or less, excluding gravitationally bound ones). That does not mean all galaxies are moving apart at the same rate.

What's the shape of the universe?

Infinite in extent, would be our best guess. Even in the case of a closed universe, though, there is no center.

 

[PeterDonis]

what's your view of the meta physics

This is a forum about physics, not metaphysics.

 

[Vanadium 50]

what's your view of the meta physics

Probably not too different than your view of "metamedicine".

 

[phinds]

If the universe is acceleration and galaxies are moving further apart, we assume the universe as a whole is expanding as a result.

Assuming you mean accelerating and not acceleration (which in your sentence would not make sense) then you have it backwards. The universe is expanding due to something we do not understand the cause of. We call it "dark energy" and BECAUSE of dark energy, the galaxies that are not locally bound are moving away from each other.

If two galaxies are a billion light years apart and are receding from each other at, say X miles per hour, then two galaxies that are two billion light years apart are receding from each other at 2X. Expansion is a rate based on distance, not a set speed.

 

[Jaime Rudas]

The universe is expanding due to something we do not understand the cause of. We call it "dark energy" and BECAUSE of dark energy, the galaxies that are not locally bound are moving away from each other.

Are you talking about expansion or accelerating expansion?

 

[phinds]

Are you talking about expansion or accelerating expansion?

Good catch. Thank you.

Obviously I was talking about, and should have SAID I was talking about, the acceleration of expansion.

@BIGphysician the current expansion of the universe is a result of the ORIGINAL expansion of the universe. Dark energy has cause that expansion to accelerate. It was believed until fairly recently that the expansion of the universe would either slow down and reach a steady state or even reverse and collapse backwards.

It was discovered in the first actual evidence either way that, much to scientists surprise, the universe's expansion was accelerating. This was so unexpected that the data was at first suspected, but found to be correct.

 

[Jaime Rudas]

It was discovered in the first actual evidence either way that, much to scientists surprise, the universe's expansion was accelerating. This was so unexpected that the data was at first suspected, but found to be correct.

Yes, although it seems that it wasn't an unexpected surprise for everyone:
https://tritonstation.com/2019/01/2...learned-to-stop-worrying-and-love-the-lambda/