Everything's expanding... well no, actually.

[R300will]

Slightly late to the game on this but i was on my honeymoon, about the hubble deep field view and that none of those galaxies are moving and the space between them isn't expanding. Isn't the deep field how we got the whole red shift thing and that the universe was expanding in the first place?

By 'new space being created' isn't that kind of like expansion because it slots inbetween the other 'units of space' and pushes the rest out? or is this too simple to work in real life?

[Gene Vincent]

R300will said:

Slightly late to the game on this but i was on my honeymoon, about the hubble deep field view and that none of those galaxies are moving and the space between them isn't expanding. Isn't the deep field how we got the whole red shift thing and that the universe was expanding in the first place?

By 'new space being created' isn't that kind of like expansion because it slots inbetween the other 'units of space' and pushes the rest out? or is this too simple to work in real life?

Welcome, you have misread that particular bit, the objects in the image are not in themselves expanding, but the space between them is sufficiently large to allow expansion to occur.

Your second paragraph is correct.

[SpudLink]

Sorry, I'm neither a mathematician nor a cosmologist. Let me see if I understand this concept.

In principle, if our solar system were alone in space, far from any galaxy, it would have it's own measurable GEB. However the GEB of a star would be greater than the distance between stars, therefore the stars in a galaxy have a collective GEB based on the galactic mass. This means that there is no measurable GEB for any individual body within the galactic GEB.

Is that about right?

[Gene Vincent]

In essence, yes.

[EliseNick]

Gene Vincent said:

Our solar system contributes to our galaxies overall mass and its overall gravity.

There is not a threshold regarding mass, there is a threshold regarding isolation.

Our local group has a centre of its gravitational mass about half-way between our Milky Way and Andromeda, the GEB for our local group is an oblate spheroid.

The Virgo cluster gravitational centre is about 18Mpc from our own, so there is about 11Mpc between our respective GEBs, that area of space is subject to expansion by the method previously outlined.

As a rule of thumb there needs to be a minimum of 4.3Mpc between massive bodies for expansion to occur, but it is hugely variable, for example the Virgo Cluster has components that are particularly fast moving which does change the maths.

The Virgo Super Cluster does not have a GEB, it is too widespread and the individual parts of the Super Cluster are sufficiently far apart for its component parts to each have their own, other Super Clusters are populated more densely and in that case the Super cluster will have a combined GEB that will be irregular in shape due to many nodes within it.

OK, I finally get this. I think you're saying metric expansion doesn't lead to expansion of gravitationally bound objects. I don't think that's controversial at all.

Somewhere you say the GEB is "the point where gravity and Cosmological expansion are equal". (So it is a surface in space then.) Be careful when making dimensionally incompatible quantities equal.

Edited by EliseNick on Saturday 25th August 19:57

[Gene Vincent]

EliseNick said:

OK, I finally get this. I think you're saying metric expansion doesn't lead to expansion of gravitationally bound objects. I don't think that's controversial at all.

Somewhere you say the GEB is "the point where gravity and Cosmological expansion are equal". (So it is a surface in space then.) Be careful when making dimensionally incompatible quantities equal.

Edited by EliseNick on Saturday 25th August 19:57

Cool.

I know where you are coming from on the apparent incompatible quantities (or rather properties I think you mean) but I have been embroiled in QFT theory for a few years now and as you get deeper into this particular branch of mathematics you realise that at root in QFT everything is the same.

For example for most people apples and pears are quite different, to a physicist, they are barely any difference atomically... for a physicist he might baulk at my mixing various bits of particle theory, energies, gravity etc, each having very unique spin/iso-spin, properties etc, but for me they are barely different at all, they are all simply the interaction of probabilities within fields of probabilities, as you mine into the maths of QFT things lose much of their distinction.

[Gene Vincent]

Anyway, join in the discussions, a good mind is always appreciated.

[mebe]

Dumb question time, if expansion is causing galaxies to appear to recede at speeds >c I assume you have to take the view that "it's OK they're not really moving hence all sorts of speed of light rules aren't broken" - puzzles me how can we see them at all?

[R300will]

Gene Vincent said:

R300will said:

Slightly late to the game on this but i was on my honeymoon, about the hubble deep field view and that none of those galaxies are moving and the space between them isn't expanding. Isn't the deep field how we got the whole red shift thing and that the universe was expanding in the first place?

By 'new space being created' isn't that kind of like expansion because it slots inbetween the other 'units of space' and pushes the rest out? or is this too simple to work in real life?

Welcome, you have misread that particular bit, the objects in the image are not in themselves expanding, but the space between them is sufficiently large to allow expansion to occur.

Your second paragraph is correct.

Ah right that makes more sense. If gravity acting within things like stars stops them expanding then it will be the same for the space within atoms as well because the weak, strong and electromagnetic forces are far stronger than gravity anyway. So my question would be what effect will only some parts of space being 'allowed' to expand have on the whole scheme of things?

Or is space expanding everywhere anyway, but the atoms and therefore stars etc with some decent force of attraction just not moving with it so everything stays in balance?

[Gene Vincent]

mebe said:

Dumb question time, if expansion is causing galaxies to appear to recede at speeds >c I assume you have to take the view that "it's OK they're not really moving hence all sorts of speed of light rules aren't broken" - puzzles me how can we see them at all?

They've been around a long time.

Think of it in this way, a Jet Aircraft travelling faster than the speed of sound (mach 1) doesn't fall silent after passing through that barrier, what really happens is the sound becomes disassociated with we receive.

When a Jet approaches at above mach 1 the image will pass in front of you in silence and then a little time later the roar of it engine hits you.

That is in light terms 'Blue Shift'

After the Jet has passed in front of you it might be well out of sight yet the roar continues miles behind in its wake.

That is in light terms 'Red Shift'

The Jet is long gone, but the sound it made lingers as a trace of the trajectory it made.

[Gene Vincent]

R300will said:

So my question would be what effect will only some parts of space being 'allowed' to expand have on the whole scheme of things?

Or is space expanding everywhere anyway, but the atoms and therefore stars etc with some decent force of attraction just not moving with it so everything stays in balance?

In answer to your question, that is what is happening and has happened in this Cosmos since the Inflationary period ended and the elements that formed the stars and Galaxies started to coalesce, this is why the red shift is greater the further into space (and therefore back in time) there were fewer massive bodies with extensive GEBs.

Space is not expanding everywhere, it only expands when there is 4.3mpc between massive bodies.

There is however rather a lot of that sort of empty space.

[dodgyviper]

If space itself is being created but the cosmos has a finite quotient of energy, what is the mechanism of this process? I.e. The act of creation is a change of state/motion, so what drives this change?

[Gene Vincent]

dodgyviper said:

If space itself is being created but the cosmos has a finite quotient of energy, what is the mechanism of this process? I.e. The act of creation is a change of state/motion, so what drives this change?

I've started a thread on causality that addresses this matter.

[mattnunn]

Horizons last night dealt with this in a quite easilly digestable way, it's probably on the I player, there was ping pong balls in jars and stuff like that...

[MiseryStreak]

Thanks for the heads up, have to watch that.

I thought of another stupid question, Gene:

If, hypothetically speaking, a star existed on its own, outside of any galaxy or galaxy cluster's GEB, what would the effect of the unrestrained cosmological expansion have on this star? Would new space be created between the stars constituent fermions, or would the new space only be created outside of the star's own GEB? If the second possibility is true, how big would this GEB be for a type G2 star of one solar mass, for instance?

What I'm really asking is does any gravity present prevent cosmological expansion? So would a lone baryon have its own GEB too?

[Gene Vincent]

Bedazzled said:

Interesting topic, but I'm baffled by how 'new nothing' can push other space away to create the expansion. How does this square with the standard model, where the fundamental forces are manifest via force carrier particles?

Think of it as vacuum energy and no mystery persists.

[Gene Vincent]

MiseryStreak said:

...If, hypothetically speaking, a star existed on its own, outside of any galaxy or galaxy cluster's GEB, what would the effect of the unrestrained cosmological expansion have on this star? Would new space be created between the stars constituent fermions, or would the new space only be created outside of the star's own GEB? If the second possibility is true, how big would this GEB be for a type G2 star of one solar mass, for instance?

What I'm really asking is does any gravity present prevent cosmological expansion? So would a lone baryon have its own GEB too?

The expansion is weak, really weak, so any mass overcomes it.

If you think about it, this is a good thing. Otherwise atomic particles would expand themselves.

So, yes a singleton star has a GEB, (but they don't often occur) but please don't confuse a singleton with a star like my own.

There are mathematical issues with part of this regarding isolation.

But for the purposes of clear thought, the simple rule is that the expansion is very weak but it is on such a massive scale that it can appear to move huge masses, but it doesn't actually move them at all, the fundamentals of space itself expands, the apparent movement is a side effect of looking.

[MiseryStreak]

Gene Vincent said:

The expansion is weak, really weak, so any mass overcomes it.

If you think about it, this is a good thing. Otherwise atomic particles would expand themselves.

So, yes a singleton star has a GEB, (but they don't often occur) but please don't confuse a singleton with a star like my own.

There are mathematical issues with part of this regarding isolation.

But for the purposes of clear thought, the simple rule is that the expansion is very weak but it is on such a massive scale that it can appear to move huge masses, but it doesn't actually move them at all, the fundamentals of space itself expands, the apparent movement is a side effect of looking.

OK, great. So there is no expansion of space (no creation of new nothing) anywhere near anything of mass. So there will never be any way of directly measuring the creation of new space experimentally, as any apparatus of any mass will negate the effect. All we can do is observe the fact that massive objects appear to be moving away from each other, but no movement or inertia is actually taking place, there is just new space being created between regions of matter.

This is very interesting because I always held the childish notion that the expansion of the cosmos was the result of the explosive force of the Big Bang, that everything was quite literally flying apart from that initial explosion.

Second silly question:

If you placed two massless gluons a measured distance apart in the expansion zone between galaxies, left them there a while (a while being enough time to allow some expansion to occur) then came back and measured them again, would the measured distance be greater?

If the answer is yes, then doesn't that mean that for all intents and purposes movement has occurred, regardless of the cause of the increased distance between the two massless particles?

If the answer is no, then how can we define the expansion, the observed distances becoming greater, when the measured distances between objects remains the same?

[Gene Vincent]

The 'Big Bang' was neither big nor was it a bang...

But we see spontaneity in mass but it returns to nothing, the rate of the spontaneous production of matter and it s return equals the amount of spontaneous production of new space.

I don't understand your question, it doesn't make sense to me, sorry, I'll have another look when I've eaten...

[MiseryStreak]

Bedazzled said:

MiseryStreak said:

So there is no expansion of space (no creation of new nothing) anywhere near anything of mass.

How can expansion be selective about where it occurs? The underlying creation process must happen everywhere but is [currently] overcome by gravity and atomic forces which bind matter together.

It's not being selective, it is trying to expand everywhere but can't where there is a certain amount of gravity. What you just said I think?
You've raised another interesting point though, as gravity overcomes the expansion, then the strong force must do also, at very small scales obviously.

Gene Vincent said:

I don't understand your question, it doesn't make sense to me, sorry, I'll have another look when I've eaten...

I was trying to use another hypothetical experiment to determine whether the expansion of space is directly measurable, rather than just through observations of distant objects. And if it is then understand why this isn't classed as movement under our current definition. I understand that two objects haven't moved themselves, as new space has been created between them, but whatever the process for the increase of distance between two objects, if it has increased then how can it not be classed as movement? Mathematically, semantically or otherwise. Something (possibly everything) has moved.