Undergrad Post Big Bang Gravity

[Hyku]

TL;DR

How did gravity compress the mass of the post Big Bang universe?

If gravity is caused by the warping of spacetime - how did gravity compress the mass of the post Big Bang universe? Does said compression indicate the force of gravity exists independent of space time? Was Newtonian gravity responsible for the compression? On the other hand, if spacetime was the main causal factor of the formation of the universe - when did it come into existence?

Thanks.

Hyku (Curious layman)

 

[PeterDonis]

how did gravity compress the mass of the post Big Bang universe?

What makes you think this happened?

 

[Hyku]

The "battle" between gravity and pressure.

 

[Ibix]

The "battle" between gravity and pressure.

Our current models suggest that the universe started in a dense state. Gravity didn't have anything to do with making it that way.

Was Newtonian gravity responsible for the compression?

Newtonian gravity isn't a separate effect; it's what you get from general relativity when the field strength is weak and everything is moving much slower than light.

On the other hand, if spacetime was the main causal factor of the formation of the universe - when did it come into existence?

I don't understand what you are asking here.

 

[Hyku]

It seems that my lay assumption "How did gravity compress the mass of the post Big Bang universe?" is incorrect. Thanks for your clarification. Regarding spacetime - what is it made of, and how does it support all the mass in the universe?

Thanks

 

[Vanadium 50]

Spacetime is made up of spacetime.

 

[Ibix]

Regarding spacetime - what is it made of, and how does it support all the mass in the universe?

It's the lowest level thing there is in classical models of gravity. So it just is, it isn't made up of anything as far as we know. A working theory of quantum gravity may one day provide more answers, but we don't have one yet.

 

[PeterDonis]

The "battle" between gravity and pressure.

There is no such thing in the universe as a whole. This "battle" you describe only exists in a system in hydrostatic equilibrium. The universe as a whole is not in hydrostatic equilibrium.

 

[PeterDonis]

Regarding spacetime - what is it made of

It's not "made of" anything. In our current model of the universe, "spacetime" is a fundamental thing; it's not "made of" anything else.

how does it support all the mass in the universe?

It doesn't; the universe as a whole is not in hydrostatic equilibrium, so there is no "support" to begin with.

 

[Hyku]

So, because the mass is in constant motion - it does not "fall"?
Does spacetime have the same velocity as said mass?
How does mass curve spacetime?
It seems that the "spacetime is like a sheet of rubber" analogy is fallacious?

Wow! The structure of the universe is counterintuitive. Yet, compared to the quantum world, it must be the equivalent of studying grade 10 algebra.

I am in humble shrub mode.

 

[PeterDonis]

So, because the mass is in constant motion - it does not "fall"?

No. The matter in the universe as a whole does not "fall" because there is nowhere for it to "fall" to. There is no "center". The universe is homogeneous and isotropic.

Does spacetime have the same velocity as said mass?

The question doesn't make sense. Spacetime has no "velocity".

How does mass curve spacetime?

Through the Einstein Field Equation, as any basic textbook on GR will tell you.

It seems that the "spacetime is like a sheet of rubber" analogy is fallacious?

It is certainly very limited, as plenty of previous PF threads will tell you. In particular, it does not work for the universe as a whole.

 

[Hyku]

Thanks guys.