Once flat always flat and reverse?

[sanctus]

just to be sure if today the universe is flat (not important if it really is so don't discuss this) it doesn't imply it has always been flat right? I think so because the different energy densities (matter, radiation,...) can evolve in time as well as the critical density itself.

Thanks for any confirmation or anti-confirmation of this.

[coldcreation]

just to be sure if today the universe is flat (not important if it really is so don't discuss this) it doesn't imply it has always been flat right? I think so because the different energy densities (matter, radiation,...) can evolve in time as well as the critical density itself.

Thanks for any confirmation or anti-confirmation of this.

 

 

 

You are correct Sanctus, according to big bang cosmology.

 

It has been shown that the linear velocity field (velocity increasing directly with distance from any arbitrary point in the field), or the velocity-to-distance ratio (the Hubble constant) gives rise to a singular problem for modern cosmology.

 

Consider an expanding universe where an observer sees galaxies twice as far from another moving twice as fast. When the velocity vectors are reversed, galaxies twice as far approach at twice the speed. All galaxies are in a free-fall towards the observer (and it make no difference where the observer is), so all galaxies in the manifold reach the observer at the same time t = 0.

 

But that’s not all. In current language, they all end up at the same point in space. Though, space becomes meaningless because there are no more coordinates, no distance between points, all of space is wrapped up inside the singularity - so too is the entire material universe.

 

This, technically, would be called infinite curvature, since all things would end up at the origin, ie., the same place, when the clocks are reversed.

 

There is something wonderful about time-travel in big bang cosmology that makes the fairytale vision more real than most fantastical writings; the mingling with passing charades of outrageous forces, dark matter, phantom energy made luminous.

 

But it’s not the sort of place you’d want to slip off á deux for a long weekend while the in-laws are baby-sitting.

 

 

Chin chin, santé

 

CC

[LaurieAG]

Consider an expanding universe where an observer sees galaxies twice as far from another moving twice as fast. When the velocity vectors are reversed, galaxies twice as far approach at twice the speed. All galaxies are in a free-fall towards the observer (and it make no difference where the observer is), so all galaxies in the manifold reach the observer at the same time t = 0.

 

Hello CC,

 

Considering that the two galaxies are moving away from each other, shouldn't they move towards each other (regardless of where the observer is) when their vectors are reversed?

 

Put another way, if you had extensive astronomical data on the positions of the two galaxies over a long period of time (by observation or extrapolation), and you reversed the order of time, surely the galaxies would move closer to each other if the observer maintained a fixed position relative to the start point? If the observers original position at time t = 0 was the same as that of the two galaxies then what you say would be true.

 

While there are ways that could be used to determine if things are one way or the other, we may have to wait for a long time to get the astronomical data, and extrapolation of existing data based on this type of reasoning would just create a self fulfilling prophecy!

 

Or we could try making 360 degree observations from a fixed point relative to our galactic center and see what happens when we reverse the time line.

[coldcreation]

 

Consider an expanding universe where an observer sees galaxies twice as far from another moving twice as fast. When the velocity vectors are reversed, galaxies twice as far approach at twice the speed. All galaxies are in a free-fall towards the observer (and it make no difference where the observer is), so all galaxies in the manifold reach the observer at the same time t = 0.

 

 

Hello CC,

 

Considering that the two galaxies are moving away from each other, shouldn't they move towards each other (regardless of where the observer is) when their vectors are reversed?

 

Put another way, if you had extensive astronomical data on the positions of the two galaxies over a long period of time (by observation or extrapolation), and you reversed the order of time, surely the galaxies would move closer to each other...

 

I'm pretty sure that's what I wrote.

 

... if the observer maintained a fixed position relative to the start point? If the observers original position at time t = 0 was the same as that of the two galaxies then what you say would be true.

 

While there are ways that could be used to determine if things are one way or the other, we may have to wait for a long time to get the astronomical data, and extrapolation of existing data based on this type of reasoning would just create a self fulfilling prophecy!

 

Or we could try making 360 degree observations from a fixed point relative to our galactic center and see what happens when we reverse the time line.

 

I really don't understand the rest of your post. What is your question? There are no observers at t = 0 (that is the big bang itself).

 

Note too that I did not make up this idea. It follows directly from Hubble's law when you reverse the clocks. It is a consequence of the standard model, something to which I personally am opposed. So the fulfilling prophecy you wrote about seems to apply more to the mainstream (I don't know because I can't understand what you are saying).

 

To tell you the truth, I don't even understand what this thread is about. The title makes no sense to me.

 

I think Sanctus wanted the "anti-confirmation" that if the universe is flat today it would (or wouldn't rather) always be flat.

 

Is that correct Sanctus?

 

CC

[sanctus]

Yes I agree the title can be confusing because when I wrote it I was thinking with always pointing to the future and reverse meant in the past.

 

The question was exactly how you interpreted it: Supose the universe is shown to be flat today, what does this imply on its flatness in the future and past? And my answer of which I seeked confirmation (or "anti-confirmation") was that it doesn't imply that it was always and will always be flat (although I'm not so sure about this anymore now)

[LaurieAG]

Hello CC,

 

I really don't understand the rest of your post. What is your question? There are no observers at t = 0 (that is the big bang itself).

 

Note too that I did not make up this idea. It follows directly from Hubble's law when you reverse the clocks. It is a consequence of the standard model, something to which I personally am opposed. So the fulfilling prophecy you wrote about seems to apply more to the mainstream (I don't know because I can't understand what you are saying).

 

As far as I am aware, if you reverse the clocks, our solar system has orbited around our galactic center around 20 times since the 'big bang'. While simplistically this idea, as a consequence of the standard model, may seem appealing, there is a lot missing in going from point A (the Big Bang at t = 0) to point B (the present).

 

I think Sanctus wanted the "anti-confirmation" that if the universe is flat today it would (or wouldn't rather) always be flat.

Is that correct Sanctus?

CC

 

If the universe was always flat we would have to consider the big bang in a similar way to how we regard other extremely large universal explosions. i.e. expansion doesn't exist in current terms because the bang is just redistributing (finite) matter around an existing (possibly infinite in the larger scale) area instead of creating it's own area during its expansion.

 

We can observe almost unlimited examples of matter contracting and expanding (and exploding) in the universe, as independant observers, so why should we regard the 'biggest bang' as being any different?

[LaurieAG]

Hello Sanctus,

 

The question was exactly how you interpreted it: Supose the universe is shown to be flat today, what does this imply on its flatness in the future and past? And my answer of which I seeked confirmation (or "anti-confirmation") was that it doesn't imply that it was always and will always be flat (although I'm not so sure about this anymore now)

 

If the universe is flat today, and it comprises of large amounts of mass separated by areas of less mass with cold vacuum between the masses, surely the 'big bang' point at (near) singularity would be surrounded by a perfect (almost) vacuum, which has no mass?

 

That's my point, if the speed of light in a vacuum is constant, a perfect vacuum contains no mass (or exotic particles/anti-particles etc), and light will flow in a straight line without interference from any mass, why should a universe containing a theoretical 'big bang' be expected to behave any differently from any other theoretical singularity (black hole) contained in the same universe?