[CorneliusDalvert (OP)]

As I understand it our universe is pretty energetic even the vacuum on space still has high energy radiation whizzing through it and quantum foam bubbling away so why isn't the time space of our universe just expanding to fill a void ?

[Bill S]

Consider, perhaps, that if the Universe is all there is, it is just expanding.  The addition of "into nothing" confuses the issue, because it suggests that "nothing" is something into which the Universe could expand.

[timey]

That's an interesting and thought provoking perspective on 'nothing' at the other end of the scale there Bill! 

[Bill S]

So, where do you stand on this one, Vikki?

[Diogo_Afonso_Leitao]

You can see the expansion of the universe not as objects being being pushed apart, but as the very own fabric of spacetime expanding. This makes the expansion easier to understand.

[ProjectSailor]

The thought that it is expanding shows that it is not infinite.. and therefore there must be something external to the universe.

I feel we are tying ourselves down by saying there is nothing 'outside' the universe. for reasons above there is evidence that there is 'something' outside the universe even if that is void.

When we discuss universe are we discussing the observable universe? which should be everything created in our big bang.. and the question would then be.. could our universe be a bubble in the void with other unobservable bubbles from other big bangs?

The problem with these ideas are.. since they are unobservable they are disprovable and hence you can never confirm nor deny the existence of anything outside of the observable universe.

[evan_au]

It is my view that the universe is infinite, and time goes from infinity to infinity

How do you explain the Cosmic Microwave Background, which has a current temperature around 2.7K, and a redshift of z≈1000?
- If the universe were much older, the CMBR would have a higher redshift, and a lower temperature.
- If the universe were infinitely old, you should see no evidence of CMBR.

[CorneliusDalvert (OP)]

Hi Bill S Why can't a 3 dimensional space contain nothing ? Could't the energy in our universe be compared to a form of pressure which is rushing out to fill an area of no pressure ? The steady increase in expansion could be caused by the increasing surface area of the "bubble" of our universe ,more surface more effect , just an idea or am I way off the mark ? If I've moved into moron country please feel free to tell me Also in terms of small scale nothing , isn't that what the planck length does , below that size energy has no practical effect so it may as well be nothing ?

[Bill S]

Why can't a 3 dimensional space contain nothing ?

What would stop the sides from meeting in the middle?

Could't the energy in our universe be compared to a form of pressure which is rushing out to fill an area of no pressure ?

In that model, wouldn’t the expansion of the Universe slow, or even stop, as the “pressure” rushed out?

If I've moved into moron country please feel free to tell

I’m poorly equipped to make that sort of judgement. []

Also in terms of small scale nothing , isn't that what the planck length does , below that size energy has no practical effect so it may as well be nothing ?

That’s an interesting way to look at it, but I doubt that the Planck length has any more influence on smaller scale objects than (eg) an inch has on the material being measured.

Saying that “below that size energy has no practical effect so it may as well be nothing” is similar to saying “this thing is so big it may as well be considered infinite.  That may work in many situations, but is only an approximation.

[evan_au]

matter and  antimatter repel

That is a hypothesis that you cannot back up.

Some physicists at CERN hope that this year, they will be able to produce enough low-temperature anti-hydrogen to accurately measure the force of gravitational attraction between matter (the Earth) and anti-matter (the anti-hydrogen).

By the way, most physicists expect that matter & anti-matter will attract. Some have suggested in the past that they might attract less, but we should know sometime this year.

[stevaneq]

I find the concept of the universe expanding into nothing difficult to comprehend as "expansion" suggests the universe is moving outwards and this suggests the universe has an "edge". I don't believe anyone has come up with
a solid and accepted"universe edge theory" but please correct me if I am wrong. Maybe the answers cannot be found in 3 dimensional concept of the universe but lie in the discovery of "other dimensions" which science may reveal in due course...

[timey]

So, where do you stand on this one, Vikki?

Well Bill,  I can see the possibility that it is by means of the gravity field that time occurs, and that between the occurrence of these 2 phenomenon, the dimensions of geometry emerge.

Therefore, under this remit, it is the gravity field that expands the dimensions of time and space.

Where there is no time, existence cannot exist.  How can we describe non-existence?  Can we call it 'nothing'?

[guest39538]

As I understand it our universe is pretty energetic even the vacuum on space still has high energy radiation whizzing through it and quantum foam bubbling away so why isn't the time space of our universe just expanding to fill a void ?

I think most scientists now agree that the visual Universe is just that, not finite but unseen by observation due to light stretching at distance and decreasing its magnitude giving us the inability to see in that zone from our zone.  Likewise can be assumed for objects beyond that boundary, that by time the light reflects from the object and reaches our eyes , there is not enough intensity of the carrier signal to see the object and also there is the inherent distance property of matter vanishing by vanishing point to sight.  A lot of scientists now conceive a multi-verse is beyond our vision boundary, although again this is just speculation of the beyond.  I do not think expanding into nothing is an appropriate term, I would say the visual Universe is inflating into the Unknown, which would be a factual answer with no speculation of the unknown.

[CorneliusDalvert (OP)]

Hi Bill re: What would stop the sides meeting ... I don't quite understand the question , surely volume has no prerequisite to what it contains ? re : In that model ,..Yes it would if the "pressure " could equalize however as it appears that space (not just our universe ) is potentially infinite that inflation ( thanks Thebox ) could continue until all the energy in our universe was spread pretty thin re: small scale everything has a practical limit , water stops being water when you get to  hydrogen and oxygen atoms , when an energy can't effect anything does it have a value of any significance ? I thought that's what the planck length implied below this size no measurable value ? Again if my knuckles are dragging on the floor throw me a banana and I'll be happy

[PmbPhy]

The thought that it is expanding shows that it is not infinite.. and therefore there must be something external to the universe.

That is not at all the case. An infinite universe can still expand. Think of it like this: consider an infinite flat plane which has a grid on in. At t = 0 the distance between a grid line and the next grid line is 1 meter. As time increases that distance increases. So the universe started off as being infinite and then it became even "more infinite". This is very valid concept in mathematics and as well in physics.

[Bill S]

  An infinite universe can still expand. Think of it like this: consider an infinite flat plane which has a grid on in. At t = 0 the distance between a grid line and the next grid line is 1 meter. As time increases that distance increases.

What you say is true of an unbounded space, but to apply it to infinity is at best a misuse of mathematics, and at worst "fairy-tale physics".  Apart from the mathematical approximations that we call infinities, infinity is so far outside the scope of our understanding that to apply to it the rules of our 3+1 dimensional Universe is just speculation.

So the universe started off as being infinite and then it became even "more infinite".

That makes no more sense than saying something started as being perfect, and became "more perfect".

[Bill S]

What would stop the sides meeting ... I don't quite understand the question

By definition a 3 dimensional space is finite.  To be in any way meaningful, if this space "contains nothing", you must be contrasting it with "something" outside.  I was thinking of "something" exerting greater pressure than "nothing".  However, it's probably simpler than that because if the sides are not touching, there is space between them.

[Bill S]

Therefore, under this remit, it is the gravity field that expands the dimensions of time and space.

Where there is no time, existence cannot exist.  How can we describe non-existence?  Can we call it 'nothing'?

Surely, if there is gravity there would have to be matter/energy to cause the gravity to exist.  If there is matter/energy there has to be space for it to emerge/exist in, and time to allow this to happen.  Gravity could do nothing unless time already existed.

[PmbPhy]

What you say is true of an unbounded space, but to apply it to infinity is at best a misuse of mathematics, and at worst "fairy-tale physics".

That is quite wrong. You've always had problems with the concept of infinity and this is another trouble spot for you. Any mathematician or physicist knows this to be quite correct and what it precisely means and it's correct.

That makes no more sense than saying something started as being perfect, and became "more perfect".

Bill - I have no desire to force you to correct misconceptions that people have. I'm only here to answer questions and point out mistakes that people make. After I do my best at that and they simply refuse to disagree with what the physics tells us, i.e. what cosmologists know to be the case and teach in their classes, I simply let it go at that.

All that I'm going to do at this point is to recommend that you download the following text on calculus

Calculus: Concepts and Contexts by James Stewart: http://bookos-z1.org/book/2428040/4cccc0

Turn to the section on infinity and read it very carefully. Good luck.

[timey]

Therefore, under this remit, it is the gravity field that expands the dimensions of time and space.

Where there is no time, existence cannot exist.  How can we describe non-existence?  Can we call it 'nothing'?

Surely, if there is gravity there would have to be matter/energy to cause the gravity to exist.  If there is matter/energy there has to be space for it to emerge/exist in, and time to allow this to happen.  Gravity could do nothing unless time already existed.

What you say is true Bill.  That's why I'm so keen to define the state of non existence, or 'nothing'.
As a mathematical enterprise within quantum mechanics, I suspect that this 'state' could perhaps be calculated, (under the correct remit),  to contain traces of an 'energy', possibly kinetic, that might initiate a quantum fluctuation, that carries mass, and would initiate the resulting gravity field, time, and the geometric dimensions of space , in the microscopic, """simultaneously""" as a reaction.  That this emergence of a fluctuation and it's associated physical effects would be an inevitability of the pre conditions of non-existence.
With regards to an expansion of these physical effects, these fluctuations would have to result in virtual particles that had 'the time' in which to take on the characteristics of real particles.
... This Bill, (chuckle) is of course highly speculative to say the least!