Everything's expanding... well no, actually.
Discussion
BenM77 said:
Instead of space expanding, might it be infinite ?
Could the expansion you see just be gaps created by galaxy's travelling through space at different speeds ?
Tell me if I'm wrong, but isn't it the case the all galaxies are moving further away from each other? Like peas floating on the surface of a lake, and the lake is ever expanding. There are some moving towards each other and colliding, but on balance, the space they sit in is getting bigger. The speed the galaxies can move within that space is limited by the known laws of physics, but the space between them is expanding faster then anything can move within space. Could the expansion you see just be gaps created by galaxy's travelling through space at different speeds ?
Observations show that galaxies are moving apart faster than the laws of physics allow, so that leaves 'expanding space' as solution we are discussing?
SpudLink said:
BenM77 said:
Instead of space expanding, might it be infinite ?
Could the expansion you see just be gaps created by galaxy's travelling through space at different speeds ?
Tell me if I'm wrong, but isn't it the case the all galaxies are moving further away from each other? Like peas floating on the surface of a lake, and the lake is ever expanding. There are some moving towards each other and colliding, but on balance, the space they sit in is getting bigger. The speed the galaxies can move within that space is limited by the known laws of physics, but the space between them is expanding faster then anything can move within space. Could the expansion you see just be gaps created by galaxy's travelling through space at different speeds ?
Observations show that galaxies are moving apart faster than the laws of physics allow, so that leaves 'expanding space' as solution we are discussing?
It really is fascinating, I was thinking of the big bang theory with everything moving away from one point.
The way I see it the GEB (never heard of that term before either) is just like an event horizon for EM radiation. Gravity has an infinite range that's an inverse square to distance (in newtonian mechanics anyway). There is no boundary to any mass' gravitational influence, but there is a point where that gravity is equaled by cosmological expansion.
So, instead of the event horizon marking the extent to which a black hole prevents light escaping, the GEB marks the extent to which the gravitational source prevents space expanding.
So gravity, in a significant enough quantity, bends EM radiation back on itself and holds back cosmological expansion, as well as slowing time. It's certainly got a lot on its plate.
So, instead of the event horizon marking the extent to which a black hole prevents light escaping, the GEB marks the extent to which the gravitational source prevents space expanding.
So gravity, in a significant enough quantity, bends EM radiation back on itself and holds back cosmological expansion, as well as slowing time. It's certainly got a lot on its plate.
Edited by MiseryStreak on Friday 24th August 14:52
MiseryStreak said:
The way I see it the GEB (never heard of that term before either) is just like an event horizon for EM radiation. Gravity has an infinite range that's an inverse square to distance (in newtonian mechanics anyway). There is no boundary to any mass' gravitational influence, but there is a point where that gravity is equaled by cosmological expansion.
So, instead of the event horizon marking the extent to which a black hole prevents light escaping, the GEB marks the extent to which the gravitational source prevents space expanding.
So gravity, in a significant enough quantity, bends EM radiation back on itself and holds back cosmological expansion, as well as slowing time. It's certainly got a lot on its plate.
On the money MS, right on the money.So, instead of the event horizon marking the extent to which a black hole prevents light escaping, the GEB marks the extent to which the gravitational source prevents space expanding.
So gravity, in a significant enough quantity, bends EM radiation back on itself and holds back cosmological expansion, as well as slowing time. It's certainly got a lot on its plate.
Edited by MiseryStreak on Friday 24th August 14:52
EliseNick said:
Gene Vincent said:
EliseNick said:
Gene Vincent said:
On the money MS, right on the money.
Can you write down an equation defining the GEB for a given mass distribution?But if you identify yourself as the employer who is paying for this work and an E-mail address I'll happily send it you... even though you should really be reading what I'm sending you already!
Gene Vincent said:
EliseNick said:
Gene Vincent said:
EliseNick said:
Gene Vincent said:
On the money MS, right on the money.
Can you write down an equation defining the GEB for a given mass distribution?But if you identify yourself as the employer who is paying for this work and an E-mail address I'll happily send it you... even though you should really be reading what I'm sending you already!
OK, let's try to explain in simple terms why we appear to see Galaxies moving away from us at velocities greater than 'c'.
As we have seen items of mass have their own gravitational cohesion, they have sufficient gravity to remain 'whole' whilst empty space beyond that influence can allow the empty space to expand, this expansion is nothing more than new space.
The best way to see this is to for the moment to consider space as 'nothing' (it is full of Quantum Fields, but ignore that for a few moments) and although this sounds like a bit of 'word play' but nothingcanpropagate faster than light.
Now those fields... the immediate thought is well 'they' have to fill that void and surely that has to obey the speed of light rule, well, no they don't, fields are simply probabilities and empty space is a zero probability area.
As we have seen items of mass have their own gravitational cohesion, they have sufficient gravity to remain 'whole' whilst empty space beyond that influence can allow the empty space to expand, this expansion is nothing more than new space.
The best way to see this is to for the moment to consider space as 'nothing' (it is full of Quantum Fields, but ignore that for a few moments) and although this sounds like a bit of 'word play' but nothingcanpropagate faster than light.
Now those fields... the immediate thought is well 'they' have to fill that void and surely that has to obey the speed of light rule, well, no they don't, fields are simply probabilities and empty space is a zero probability area.
Also reading through this thread and others I think there may be a bit of confusion regarding the inflationary period.
The important thing to remember, or realise if you didn't before, is that during the inflationary period there was not a Cosmos as we see it now.
There were no stars or galaxies and much of the 'material' that made such things still not separated to form such things.
This 'soup' didn't have a 'speed limit' imposed on it as our 'older' Cosmos does, so for a short time there were the conditions to spread out at any velocity it could muster and that is what happened.
So all the material that makes this Cosmos was thrown out at what we call superluminal velocities in a short bust of inflation.
It was only when the dilution was right that the stars and Galaxies formed that we see to day and they slowed from this velocity as a result.
This is why the Cosmos is about 93blys across, but we see only about 13.7blys of it, we are 'playing catch-up'.
The inflation spread the bits that can make stars and galaxies further than we can see because that was done when there was no speed of light around, since that time we do have the speed of light to contend with and this is dictated by the amount of time this limit has been in place.
I hope this clears up some vagaries in your minds.
The important thing to remember, or realise if you didn't before, is that during the inflationary period there was not a Cosmos as we see it now.
There were no stars or galaxies and much of the 'material' that made such things still not separated to form such things.
This 'soup' didn't have a 'speed limit' imposed on it as our 'older' Cosmos does, so for a short time there were the conditions to spread out at any velocity it could muster and that is what happened.
So all the material that makes this Cosmos was thrown out at what we call superluminal velocities in a short bust of inflation.
It was only when the dilution was right that the stars and Galaxies formed that we see to day and they slowed from this velocity as a result.
This is why the Cosmos is about 93blys across, but we see only about 13.7blys of it, we are 'playing catch-up'.
The inflation spread the bits that can make stars and galaxies further than we can see because that was done when there was no speed of light around, since that time we do have the speed of light to contend with and this is dictated by the amount of time this limit has been in place.
I hope this clears up some vagaries in your minds.
EliseNick said:
You're not going to give me a straight answer at all, are you?
You have asked two questions.You received a 'Yes' to one and a 'No' to the other, now... not wishing to belittle you in any way but... as far as I know, and feel free to correct me if this is not the case, that's about as straight a pair of answers the English language allows.
Questions I have asked to which I still don't understand the answer (aside from asking for an equation for the GEB):
Why does the Sun not have one, but a galaxy does? Is there some threshold mass?
So is it a distance? Or a volume?
Suppose I could flick a switch and make our galaxy's GEB glow bright orange. What would I see if I stood on Earth and looked into the sky? If I was in the Andromeda Galaxy? If I was in the Virgo Cluster?
Why does the Sun not have one, but a galaxy does? Is there some threshold mass?
So is it a distance? Or a volume?
Suppose I could flick a switch and make our galaxy's GEB glow bright orange. What would I see if I stood on Earth and looked into the sky? If I was in the Andromeda Galaxy? If I was in the Virgo Cluster?
EliseNick said:
Why does the Sun not have one, but a galaxy does? Is there some threshold mass?
So is it a distance? Or a volume?
Suppose I could flick a switch and make our galaxy's GEB glow bright orange. What would I see if I stood on Earth and looked into the sky? If I was in the Andromeda Galaxy? If I was in the Virgo Cluster?
Our solar system contributes to our galaxies overall mass and its overall gravity.So is it a distance? Or a volume?
Suppose I could flick a switch and make our galaxy's GEB glow bright orange. What would I see if I stood on Earth and looked into the sky? If I was in the Andromeda Galaxy? If I was in the Virgo Cluster?
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.
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