Everything's expanding... well no, actually.
Discussion
We read, see and hear that the Cosmos/Universe is expanding... well, only parts of it are actually.
Is this well known here?
In the light of how much some here didn't know/realise about 'time', before I proceed it would be good to know who understands why not all the Cosmos/Universe is getting bigger.
Over to you...
Is this well known here?
In the light of how much some here didn't know/realise about 'time', before I proceed it would be good to know who understands why not all the Cosmos/Universe is getting bigger.
Over to you...
Marf said:
Can I phone a friend?
Apologies, my first response was facetious. Yes, I understand the concept.
Perhaps rather than just stating something which most people hold to be "true" and then saying "aha! you're wrong!" you could post up a link to the research/article that is asserting that the universe is not expanding uniformly which we can then use as the basis for the discussion?
I did that with the 'Time' thread and it want 'all aghast' on me and thought this might be a better less assertive approach...Apologies, my first response was facetious. Yes, I understand the concept.
Perhaps rather than just stating something which most people hold to be "true" and then saying "aha! you're wrong!" you could post up a link to the research/article that is asserting that the universe is not expanding uniformly which we can then use as the basis for the discussion?
OK... New post coming up setting out how it is...
We will hardly pass a week by without being told that the Cosmos is expanding, we are often given analogies using balloons and all sorts of other minds-eye ways to envision this expansion.
Well the truth is that not all of the Cosmos is expanding at all.
In fact everything we can see... isn't.
Right out in that Deep Field picture from the Hubble Telescope every thing in that picture is not expanding.
Another fact about this expansion is that lots and lots of 'empty space' isn't either.
...and I'm not talking about Dark Matter or Dark Energy, we can forget them for the moment, they play no part in this explanation, we have to add and subtract them later, but first you need to know the basics and the basics are that the Cosmos overall is expanding, but all that I've outlined above isn't.
To save me writing something that is already well understood, do the majority understand that what I have written so far is correct and do you understand the 'mechanism' that causes this effect?
Well the truth is that not all of the Cosmos is expanding at all.
In fact everything we can see... isn't.
Right out in that Deep Field picture from the Hubble Telescope every thing in that picture is not expanding.
Another fact about this expansion is that lots and lots of 'empty space' isn't either.
...and I'm not talking about Dark Matter or Dark Energy, we can forget them for the moment, they play no part in this explanation, we have to add and subtract them later, but first you need to know the basics and the basics are that the Cosmos overall is expanding, but all that I've outlined above isn't.
To save me writing something that is already well understood, do the majority understand that what I have written so far is correct and do you understand the 'mechanism' that causes this effect?
FarmyardPants said:
My personal theory is that the regions of spacetime that aren't expanding are those occupied by particles of mass. Since no two particles of mass can occupy the same point in ST, the mass acts as a "hole" which in a sense displaces ST causing a local distortion that we perceive as gravitation. But for this idea to make any sense ST must be expanding (or trying/failing to expand in areas occupied by mass), and possibly expanding at an ever increasing rate (I haven't thought it through, not having the time, inclination or background).
Still, we can all have our ideas. Having read the "Time" thread, I expect to be branded an uneducated idiot, how I should read more about the subject and how much you enjoy reading posts from people who clearly have no clue about the subject.
Ok, over to you GV, tell it like it is and let the Education by Arrogance commence!
First, not knowing and wanting to know does not mean you are an uneducated idiot, in fact it is the exact opposite and I applaud all such noble intentions, I only decry those that know a bit but refuse to learn more.Still, we can all have our ideas. Having read the "Time" thread, I expect to be branded an uneducated idiot, how I should read more about the subject and how much you enjoy reading posts from people who clearly have no clue about the subject.
Ok, over to you GV, tell it like it is and let the Education by Arrogance commence!
Edited by FarmyardPants on Wednesday 22 August 14:53
So, your approach has nothing but respect from me.
It's a subtle difference but easily missed.
You are surprisingly close to being right, indeed no mass is expanding in this Cosmos at all and the reason is startlingly simple, it is Gravity.
Most people will know that mass concentrates gravity at its centre and the greater the mass the greater the gravitation that permeates from it and it is these gravity wells and all contained within them that does not expand, there is an 'event horizon' surrounding every Galaxy in the Cosmos, that event horizon is correctly called a Gravitational Extent Boundary and is the point where gravity and Cosmological expansion are equal... the extent of some Galaxies GEB is enormous.
So it is not the items in space that are expanding, it is the space between their GEBs.
A Black Hole Stars event horizon is huge compared to the size of the star within and the Black Hole Stars GEB is even larger by a substantial magnitude.
The expansion of the Cosmos 'pushes and pulls' these large GEBs along with it and because they are an area of stability within the motion we call the effect a phase shift or more commonly Red or Blue Shift. Red Shift is something moving away, Blue is approaching.
If you view this in your minds eye very carefully you see why we see almost exclusively Red Shift and not a lot of Blue.
Locally (in Cosmological terms) our own Galaxy is being approached by the Andromeda Galaxy, we see a blue shift in its signature.
Japsteeze said:
I dont think its very well understood at all, otherwise you wouldnt go your week without being told about the universe expanding.
I don't really understand what you mean when you say everything we see is not expanding? Red-shift, is it all a lie!?
Read my previous post and it all makes sense.I don't really understand what you mean when you say everything we see is not expanding? Red-shift, is it all a lie!?
It is very well understood, exactly in fact.
Japsteeze said:
Ah I see what you were saying. I understand that objects are moving further apart, and it is not that everything is expanding. I was thinking that at the very start you were saying that galaxies etc are not moving futher apart, and disputing Hubble's law.
To think about heterogeneous expansion of space with gravity cancelling it in areas of significant enough mass, I imagine a ballon expanding (space) with taped sections of it (mass) holding that section together while the rest of space (baloon) expands.
That is it. you have the correct image, bits of space remain 'glued together', that 'glue' is gravity.To think about heterogeneous expansion of space with gravity cancelling it in areas of significant enough mass, I imagine a ballon expanding (space) with taped sections of it (mass) holding that section together while the rest of space (baloon) expands.
FarmyardPants said:
GR gives a good explanation of the effects of gravity but I have yet to read a convincing theory as to the cause of it, probably because accepted theory is that it is a fundamental force (as evidenced by the fact that scientists often ask why it is so weak compared with the other forces) and as such it is not considered to be 'caused' by anything. I like to think that gravity is a side effect of something else, which is why I look this from the other perspective.
As an aside, is the size of an event horizon as seen by an observer not a function of how far away the observer is from said BH? I guess no such thing applies to the GEB.
The 'hashed' explanation is that gravity is an effect of the four-momenta.As an aside, is the size of an event horizon as seen by an observer not a function of how far away the observer is from said BH? I guess no such thing applies to the GEB.
It does work... up to a point but it is not a fulsome explanation yet.
The idea that gravity is a fundamental force is losing ground to a QFT based explanation..
A 'side-effect' is a very good place to hold your thinking as it is more likely that it is.
I'll run another thread on Event Horizons and some of the least realised aspects of what they really show about the fundamental aspects of Gravity.
It will be a long one though as I'll have to cover the (now dwindling) alternatives.
BenM77 said:
Interesting thread, so is it still believed that our galaxy is moving away from the big bang ?
We might be.But that local Andromeda blue-shift could mean that we are either in stasis or moving toward it and this might mean we have 'countered' our own 'personal' expansion from the BB.
BenM77 said:
I have seen the explanation that looks like we are the centre of the big bang but are not, perhaps blue shift and red shift could help work where the centre is ? This will probably sound very dumb
Not in the least dumb.In maths we have the 'Cosmological Principle' and this simply states that the Cosmos looks the same from everywhere, not the position of the stars, but the recession of the stars from your viewpoint (Isotropy and Homogeneity) it's a bold statement to make but it has recently been reinforced by the detailed understanding of the CMBR (Cosmic Microwave Background Radiation)
We can safely take the CP as being correct.
Observation can't tell us enough to be conclusive that the Cosmos is either infinite and expanding/contracting or that it is simply finite and expanding, we need maths...
We have to use Einsteins GR to do this and the results are at first sight inconclusive, thanks to GR being perhaps the most tested of all the theories we've ever had it could be either... but there is a little final issue when you take the maths apart in detail, if the Cosmos were infinite then not only would every point be the same viewpoint as far as expansion is concerned but it means that each observers local cluster point cannot move and this detail is what kills the possibility of the Cosmos being infinite. Our local cluster moves!
BTW, a further nail in coffin of time having a substantive existence all of its own is that if you apply the CP to all four dimensions, you get no big bang, it applies only to the space bit of spacetime.
Bedazzled said:
From what I've read everything is expanding, but objects which are bound either gravitationally or atomically 'bounce back' into their natural position, at least while those forces are stronger than the force of expansion. So for example the planets in our solar system adjust their orbit to compensate for expansion; but expansion occurs locally all the same.
If the force of expansion continues to increase then it could theoretically overcome gravity causing gravitationally bound objects fly apart, or even overcome atomic forces causing atoms to fly apart (according to Lawrence Krauss, in his famous "a universe from nothing" presentation). It's a moot point unless we get to the bottom of what causes expansion in the first place, and what is likely to happen to the magnitude of the repulsive force in the future.
The intriguing mystery for me is how such a force could cause the dramatic inflationary period after the big bang, and how at this very moment distant galaxies with redshifts greater than 1.4 are moving away from us faster than light.
Gravity is the most pervasive of all the parts that make up the Cosmos, there is no 'bounce back' just constant check-mate.If the force of expansion continues to increase then it could theoretically overcome gravity causing gravitationally bound objects fly apart, or even overcome atomic forces causing atoms to fly apart (according to Lawrence Krauss, in his famous "a universe from nothing" presentation). It's a moot point unless we get to the bottom of what causes expansion in the first place, and what is likely to happen to the magnitude of the repulsive force in the future.
The intriguing mystery for me is how such a force could cause the dramatic inflationary period after the big bang, and how at this very moment distant galaxies with redshifts greater than 1.4 are moving away from us faster than light.
The increase in the force of expansion will most likely be self-immolating in that the increased distances between objects will allow this to happen without any adverse effect.
A sort of 8pi^2 equilibrium.
They WERE moving apart at faster than light, they won't be now, the inflationary period was a very long time ago.
Edited by Gene Vincent on Wednesday 22 August 20:42
Bedazzled said:
Gene Vincent said:
There WERE moving apart at faster than light, they won't be now, the inflationary period was a very long time ago.
Have a play around with the cosmos calculator here (I'm using omega=0.27, lamda=0.7, hubble=70). The light reaching us from a galaxy with a redshift of 1.4 was emitted 4.6 billion years after the big bang; well after the inflationary period which lasted only a fraction of a second. We've observed galaxies with redshifts of 8.6 which are moving away from us at over twice the speed of light.But my guess is that the '70' is todays Hubble Constant (actually 71 if so) but the 'constant' is no such thing, in the past, into which you are looking, it was markedly different.
Plus does the link calculate all three main shift mechanisms?
I don't trust 'applications' from whatever source, I'll do the maths myself, I feel happier.
Sorry, been working.
I think there might be a fundamental misunderstanding of this entire expansion concept.
So, to get us back on track I'll briefly re-iterate what we know happens as related in this thread.
1/. The Cosmos is expanding.
2/. There are bits of this Cosmos we can see and although they are in the sway of the overall expansion mechanism, they themselves, thanks to their own gravity, don't expand.
3/. These visible entities also have extensive gravity fields and these extend hugely beyond their visible extent.
Thus far we've kept things simple.
Now we have the hard bit.
The reality is that although the expansion is quantified and the truth is the expansion of space has no speed.
You have to accept that the best manner in which to think of the expansion of space is as the creation of new empty space.
That is what an Expanding Cosmos really does.
I know you've all grown up with first the 'universe' expanded at the speed of light, then you were told there was this 'inflationary' period and we went back to the speed of light thing, well it's not correct, the inflationary bit is (but even that doesn't work quite as you might believe) but we didn't go back to the speed of light expansion.
The Cosmos today, as we speak is expanding far faster than the speed of light.
I know... this is a bitter thing to find out, but I'm not Mary Poppins, you're getting no spoonful of sugar from me.
Empty space... out there between the GEBs 'new' space is produced, in varying amounts, 1 or 2 parts per million and instantly too.
This is enough to cause the entire Cosmos (remembering the GEBs don't in themselves) to expand in size faster than light... but nothing is actually moving.
Someone much smarter than me, and much nicer too, once said something like "if you think you understand something fundamental in this Cosmos, then you simply haven't understood at all"
The above will test your powers of understanding to the limit.
I think there might be a fundamental misunderstanding of this entire expansion concept.
So, to get us back on track I'll briefly re-iterate what we know happens as related in this thread.
1/. The Cosmos is expanding.
2/. There are bits of this Cosmos we can see and although they are in the sway of the overall expansion mechanism, they themselves, thanks to their own gravity, don't expand.
3/. These visible entities also have extensive gravity fields and these extend hugely beyond their visible extent.
Thus far we've kept things simple.
Now we have the hard bit.
The reality is that although the expansion is quantified and the truth is the expansion of space has no speed.
You have to accept that the best manner in which to think of the expansion of space is as the creation of new empty space.
That is what an Expanding Cosmos really does.
I know you've all grown up with first the 'universe' expanded at the speed of light, then you were told there was this 'inflationary' period and we went back to the speed of light thing, well it's not correct, the inflationary bit is (but even that doesn't work quite as you might believe) but we didn't go back to the speed of light expansion.
The Cosmos today, as we speak is expanding far faster than the speed of light.
I know... this is a bitter thing to find out, but I'm not Mary Poppins, you're getting no spoonful of sugar from me.
Empty space... out there between the GEBs 'new' space is produced, in varying amounts, 1 or 2 parts per million and instantly too.
This is enough to cause the entire Cosmos (remembering the GEBs don't in themselves) to expand in size faster than light... but nothing is actually moving.
Someone much smarter than me, and much nicer too, once said something like "if you think you understand something fundamental in this Cosmos, then you simply haven't understood at all"
The above will test your powers of understanding to the limit.
Edited by Gene Vincent on Thursday 23 August 20:03
EliseNick said:
What is a "Gravitational Extent Boundary"? It obviously doesn't look like a conventional event horizon. Google just sent me... back to this thread! When you say "correctly called a GEB", correct in what sense?
The Suns 'local' GEB has within it our planet and the others... but it extends out much further than that.EliseNick said:
What is a "Gravitational Extent Boundary"? It obviously doesn't look like a conventional event horizon. Google just sent me... back to this thread! When you say "correctly called a GEB", correct in what sense?
I thought I'd explained the phenomena earlier."Most people will know that mass concentrates gravity at its centre and the greater the mass the greater the gravitation that permeates from it and it is these gravity wells and all contained within them that does not expand, there is an 'event horizon' surrounding every Galaxy in the Cosmos, that event horizon is correctly called a Gravitational Extent Boundary and is the point where gravity and Cosmological expansion are equal... the extent of some Galaxies GEB is enormous."
Forget the Sun analogy as in reality it doesn't really have a GEB in the terms we are using in this thread.
For a moment I thought I'd not explained this...
EliseNick said:
Gene Vincent said:
I thought I'd explained the phenomena earlier.
"Most people will know that mass concentrates gravity at its centre and the greater the mass the greater the gravitation that permeates from it and it is these gravity wells and all contained within them that does not expand, there is an 'event horizon' surrounding every Galaxy in the Cosmos, that event horizon is correctly called a Gravitational Extent Boundary and is the point where gravity and Cosmological expansion are equal... the extent of some Galaxies GEB is enormous."
Forget the Sun analogy as in reality it doesn't really have a GEB in the terms we are using in this thread.
For a moment I thought I'd not explained this...
Why does the Sun not have one, but a galaxy does? Is there some threshold mass?"Most people will know that mass concentrates gravity at its centre and the greater the mass the greater the gravitation that permeates from it and it is these gravity wells and all contained within them that does not expand, there is an 'event horizon' surrounding every Galaxy in the Cosmos, that event horizon is correctly called a Gravitational Extent Boundary and is the point where gravity and Cosmological expansion are equal... the extent of some Galaxies GEB is enormous."
Forget the Sun analogy as in reality it doesn't really have a GEB in the terms we are using in this thread.
For a moment I thought I'd not explained this...
Can you write down an equation defining the surface you are terming the GEB for a given mass distribution?
Our star is part of a greater gravitational mass.
It's not a surface, it is an extent of influence.
Somewhere on here I have given a figure for the minimum distance between massive objects for the influence of gravity to diminish to a point where expansion can act.
I'll take a look tomorrow or find my notes at work and post it up again.
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!
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