# Question from a fool about the big bang

#### zengin

I have no education in any of this material, only questions. this looked like a good place to ask :). So what im wondering is if half way through the big bang's cycle (when the universe halts and then reverses) if i was on a solar system on the edge of the halted universe where would the light be going as it breached the edge of existance? If indeed the big bang is true and the universe expands and collapses, is it possible that information exists from the previous bang in this way? Im sure this post is full of logic and spelling errors (please excuse them)

#### mgb_phys

Homework Helper
Firstly it's not guaranteed that the universe will collapse - it depends on the exact amount of mass in the universe.
Secondly there is no reason to believe that there is a cycle - in fact you could argue that any question about what happend before the big bang is meaningless since there was no time.

The improtant point is that the universe itself is expanding, so there is no edge to be on. It's difficult to explain but imagine a map being drawn on a rubber sheet and the sheet being stretched is a better picture than an empty black space with stars expanding out from the centre.
So no solar system is at the edge and you wouldn't notice the expansion/contraction other than by looking at the relative speed of distance galaxies.

#### Alex48674

Also the universe is supposedly infinite in size, so there is no edge.

#### mgb_phys

Homework Helper
No the universe is finite in size but has no edge!
Think of it like the Earth - it's defintely finite but there isn't an edge

#### cristo

Staff Emeritus
Also the universe is supposedly infinite in size, so there is no edge.
No the universe is finite in size but has no edge!
I'm afraid I don't agree with mgb here: there is no general consensus on whether the universe is finite or infinite. Therefore I don't think it was fair to shoot down Alex's point. However, I do agree with the points made earlier that there is no boundary to the universe: this is a general consensus.

mgb_phys said:
Think of it like the Earth - it's defintely finite but there isn't an edge
This might be a little confusing, so it should be pointed out that what mgb means here is to think of the surface of the Earth. This is indeed finite but boundary-less.

#### sLeeping_bEauti

Also the universe is supposedly infinite in size, so there is no edge.
I dont agree with this, even in the terms of it being like earth with no boudries because we dont know whether its curved or not just that it's expanding and if it is expanding there must be an edge thats moving foward hasnt there?

Thats not very clear but you no what i mean....

also if we took into account what Zengin said about watching it from another solar system, would it be the same effect as a black hole, im just wondering because when a massive star collapses in on itself it can create one then i would think a whole universe would, and if thats true, in anyway, would that mean that the light you would see from another solar system would never change like a person watching from outside an event horizon?

katii x

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#### cristo

Staff Emeritus
I dont agree with this, even in the terms of it being like earth with no boudries because we dont know whether its curved or not just that it's expanding and if it is expanding there must be an edge thats moving foward hasnt there?
No. Whether the universe is finite or infinite it does not have a boundary; that is, it has no edge. A good way to think of the former case is to imagine the surface of a sphere, and imagine us being 2d people living on the surface: this is a finite universe with no boundary. It seems that you may be thinking about this but a little confused. It is important to not think of the whole sphere, but only the surface of the sphere in this analogy.

#### russ_watters

Mentor
And, of course, the sphere in that analogy can be expanding...

#### sLeeping_bEauti

No. Whether the universe is finite or infinite it does not have a boundary; that is, it has no edge. A good way to think of the former case is to imagine the surface of a sphere, and imagine us being 2d people living on the surface: this is a finite universe with no boundary. It seems that you may be thinking about this but a little confused. It is important to not think of the whole sphere, but only the surface of the sphere in this analogy.
So what you mean is that if you were to run around it forever you would never have to stop because there are no edges...yea i see that now, i was thinking in a different sense.
Is it confirmed that the universe is this way? (spherical i mean), and if so how did they prove that?
x

#### yenchin

As mentioned, the universe could be either infinite or finite, we have not prove either case.

#### cristo

Staff Emeritus
And, of course, the sphere in that analogy can be expanding...
Yes, sorry, I forgot to include that point!

Is it confirmed that the universe is this way? (spherical i mean), and if so how did they prove that?
x
No, we don't know what the topology of the universe is; this is just an example of how a surface can be finite yet unbound. There are three different classes the universe couls fall into: closed, flat and open. Cosmologists distinguish between the cases through the energy density parameter $\Omega$ which is defined as the ratio $\rho/\rho_{crit}$. Here, $\rho$ is the energy density of the universe and $\rho_{crit}$ is what we call the critical energy density of the universe; that is, the energy density that a flat universe would have. If the universe is any more dense than the critical energy density, then it will be closed, and any less it will be open.

Currently, the value we have for omega is (about) $1.02 \pm 0.02$.

#### sma11fry

Missing the point

we try hard to describe our universe in terms of what we see on earth, and what we can relate to.
If every dimension were folded like a topological doughnut where the inside touches the outside through a plane (imagine a cone where the inside curves round to touch the outside, matter on one side is anti-matter on the other Time travelling forward is time travelling backwards on the other, you can see the example of matter being drawn into a blackhole and thrown out about its centre, but the curvature of the rotation is undefined. The fabric of this dimensional plane is what we are refering to as dark matter, or the ether of space, energy on one side is matter on the other, We see matter and anti-mater appear rhymically between the two states, we describe string theory to define these two points, but then we ask why is gravity so small compared to the other forces in nature. Simply the reason is they are in equilibrium, every mass is balanced by a mass on the other side of the plane. Visible mass is vibrating, Invisible or impercievable mass is still. Light is transmitted through dark matter in the same way balls on an office toy vibrate. The first ball falls on the mass of balls, the ball at the far end bounces off. Gravity likewise uses the same medium, dark matter pulls and pushes like hydrolics, transmitting light and gravity, magnetism and in theory electrical energy, because dark matter is in natures graphite, we can transmit or move energy along from dark matter to dark matter like a three dimentional cimenma screeen. Only our energy moves, the fabric, or lack of it ( a vacuum) are only an entity or abscence of a congelled energy packet, an oscillation that appears as a structure but is infact a Pattern . Another analogy the nail board, where the shape of an object is made by the excitation of the nolonger dark matter.

Or am I talking crap? You choose!

#### sma11fry

I missed one detail, Matter and energy don't coexist simultaneously, they oscillate, energy matter energy matter, like remnance we only see changes, or objects hitting targets, not how they appeared, the action of seeing light changes it.

#### Chronos

Gold Member
Perhaps we could all agree the universe is observationally finite. Nothing beyond that is terribly important in my mind.

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