Loaf of bread analogy

[SpeedFreek]

Yes, quite right.

I probably should have said that the universe having an "edge" where the galaxies stop and there is nothing beyond, is considered to be the least likely scenario. It is at the bottom, in terms of the list of probabilities, as it would violate the cosmological principle.

 

[ZenGalacticore]

Hey man I'm no physicist or cosmologist. I'm fairly good at business math and algebra, but...

I was just throwing out a creative/spatial -left handers are the only people in their right minds- kind of thought out there!

I don't know if we'll ever be able to prove through inference, much less observe, extra-dimensions beyond the three of space and the fourth of time. Well, I take that back. I think we can safely infer that our familiar three-dimensional spatial universe is probably warped into a fourth spatial dimension of some as yet undefinable kind. (Plus time).

Seriously. If Hawking and all those other really smart guys and gals out there really figure out-mathematically- what happened before the 'big bang' and WHY it happened, well, then we will be even more perplexed about what caused that "event" and what happened before or "outside" of "It".

"It" just really blows the mind!!! "It" really does! :lol: Why is there 'anything'?

 

[SpeedFreek]

Oh, I completely agree with you on that point, and the points in your previous post.

I was just trying to point out that there is a difference between the universe residing in a higher unseen dimension, and our universe having an unseen "edge" in the dimensions we know. I think we were talking at crossed purposes.

 

[FlatEarth]

You keep confusing expansion, which was one of the initial conditions of the Big Bang, with accelerating expansion, which requires a separate cause. I am talking about the acceleration of that expansion, which is the reason dark energy is required.

Well, actually I am not confused at all, but I understand why you would say that. I believe you have the classical rules of cosmology so ingrained that you are having trouble understanding what I am saying. Let me summarize my thoughts in bullet fashion because they do get lost in these lengthy exchanges.

1. Expansion of space-time was initiated at the BB and continues unabated.
2. Expansion of space-time accelerates and has always accelerated. This is the key factor that I believe current theory has wrong.
3. The expansion of space-time is not driven by a force, but is analogous to gravity which is a distortion of space-time and not a force.
4. Matter initially expanded at about the same rate as space-time, but gravity and other forces emerged which caused matter to expand at a slower rate, and allowed stars and galaxies to form.
5. Galaxies continued to expand away from each other, and the effects of gravity gradually decreased as the distance separating them increased.
6. And finally, galaxies began to separate at accelerating rates that more closely align with the ever accelerating expansion rate of space-time as the effects of gravity faded.
7. There is no dark energy, and no need for a cosmological constant!

Observations and equations without the cosmological constant support this conclusion!

I see where you are going wrong now - you misunderstand what accelerating expansion means. Do you think it is the fact that the further away a galaxy is, the faster it is receding, means the expansion is accelerating? If so, you are incorrect!

I must tell you this gave me a chuckle. I arrived at the understanding that more distant galaxies recede at higher rates on my own, thank you very much! This is obviously not the same as accelerating expansion. :roll:

The "geometric" centre of the 3-Torus is in a different dimension! All we are concerned about is the three-dimensional surface of that torus, which has no edge or centre. Wrap my grid model from above onto the surface of that 3-Torus and hopefully you will see what I mean. No part of our universe is in the hole in the centre of the Torus - it is a four dimensional shape!

I stand corrected. Let's just say I believe the universe is more like an expanding bubble that is finite, where space-time curves, wraps, and warps at the outer limit. A universe with a center.

 

[SpeedFreek]

There is a very good reason why those "classical rules of cosmology" are so ingrained.

I apologise for explaining things you already knew, and assuming you were making the same mistake I have seen a lot of others make, but the reason I was having trouble understanding what you were saying is because what you were saying made no sense to me. I now understand your argument. You see space-time as something separate from the mass/energy of the universe, rather than being defined by them. Yours is a rather strange interpretation of general relativity, to say the least!

How can you define space-time, except using the coordinate positions of the objects that reside within it?

To avoid another "wall of text" post on my part, let's look at one of the points you made, for starters. Points 1 & 2 are simple assertions, so:

3. The expansion of space-time is not driven by a force, but is analogous to gravity which is a distortion of space-time and not a force.

Gravity is the name given to how the mass/energy of the universe stresses, or distorts, space-time. It is an unseen "pseudo-force", but we know what causes it - the contents of the universe. What we do not know is how that "pseudo-force" is transmitted, hence the search for the graviton, for evidence of the Higgs ocean and suchlike. But it is the stress-energy tensor of general relativity that is describing what gravity does.

Constant or decelerating expansion or even the contraction of the universe are the natural consequences of the mass-energy density of the universe, nothing more is required, unless the expansion is accelerating.

Basically, your idea violates general relativity, which can accurately describe our observations (with the addition of dark matter/energy). I was under the impression that you misunderstood modern theoretical physics, but it seems you simply think that general relativity is wrong, even though it describes so much of what we see very well indeed.

So, what is it in this universe that causes space-time to expand and yet is decoupled from mass or energy? Whatever it is, it has to reside within our universe, in order to have an effect on our universe. What should we be looking for as a cause for your constantly accelerating expansion?

Or to put it another way - in an empty universe, what would be expanding? And what would be accelerating that expansion?

 

[FlatEarth]

There is a very good reason why those "classical rules of cosmology" are so ingrained.

I do think it is very difficult for those who have invested years in learning "the rules" and use them on a day-to-day basis to consider that long accepted beliefs could be incorrect. I agree they indeed should be ingrained and honored, but when observations indicate an anomaly, it's time to reexamine them. It's in this spirit that the idea of dark energy arose, and this is an alternative to that.

You see space-time as something separate from the mass/energy of the universe, rather than being defined by them. Yours is a rather strange interpretation of general relativity, to say the least!

I like to think of this idea as unconventional versus strange, but I believe a fresh view of the universe is in order due to the latest observations.

How can you define space-time, except using the coordinate positions of the objects that reside within it?

Yes, the decoupling of space-time from matter-energy means space-time cannot be measured in its entirety, but it is defined by the portion we can measure. We've already touched on this subject by agreeing that the universe is far larger than what we can see, so it becomes a moot point.

Constant or decelerating expansion or even the contraction of the universe are the natural consequences of the mass-energy density of the universe, nothing more is required, unless the expansion is accelerating.

Basically, your idea violates general relativity, which can accurately describe our observations (with the addition of dark matter/energy). I was under the impression that you misunderstood modern theoretical physics, but it seems you simply think that general relativity is wrong, even though it describes so much of what we see very well indeed.

This idea supports your statement up to the "unless the expansion is accelerating" part. The acceleration is not attributable to an actual force, but only to the accelerating expansion of space-time. With this in mind, the tenants of general relativity are honored. Better yet, there is no need for a cosmological constant.

So, what is it in this universe that causes space-time to expand and yet is decoupled from mass or energy? Whatever it is, it has to reside within our universe, in order to have an effect on our universe. What should we be looking for as a cause for your constantly accelerating expansion?

Or to put it another way - in an empty universe, what would be expanding? And what would be accelerating that expansion?

That's the million dollar question. What caused the Big Bang in the first place? Whatever caused it, it created all the matter-energy there is along with space-time. This idea suggests that the accelerating expansion of space-time is merely a property or characteristic of space-time, and is not fueled by a force.

 

[SpeedFreek]

This idea supports your statement up to the "unless the expansion is accelerating" part. The acceleration is not attributable to an actual force, but only to the accelerating expansion of space-time. With this in mind, the tenants of general relativity are honored. Better yet, there is no need for a cosmological constant.

But General Relativity is not honoured, as there is no mechanism in GR to accelerate the rate of expansion! If you wish to introduce some new property into the equations that accelerates the rate of expansion, you are essentially adding a cosmological constant, or quintessence, depending on how you do it.

The question is still open as to whether that which accelerates the rate of expansion has been there all along, or has emerged later in the history of the universe, but in order to describe what we see, it cannot be equivalent to that which caused the expansion in the first place.

I am beginning to think that you consider space-time to be something real, rather than an abstract concept used to convey the dynamical nature of the universe. A lot of popular literature seems to describe it as such, when it is no such thing. It is simply a convenient way to paint the picture.

If you want to give space-time special properties of its own, you have to define them and include them in the equations. There is no property for expansion itself as it is simply a coordinate result that emerges from the currently favoured solution to Einsteins field equations.

 

[FlatEarth]

But General Relativity is not honoured, as there is no mechanism in GR to accelerate the rate of expansion! If you wish to introduce some new property into the equations that accelerates the rate of expansion, you are essentially adding a cosmological constant, or quintessence, depending on how you do it.

To the contrary, the way I see it GR is honored. The universe behaved exactly as described by GR until the effects of distance reduced the attraction of the galaxies to each other, at which time acceleration of space-time presided. Remember, space-time is not a force and will not appear in the equation as a force. The equation remains unchanged.

The question is still open as to whether that which accelerates the rate of expansion has been there all along, or has emerged later in the history of the universe, but in order to describe what we see, it cannot be equivalent to that which caused the expansion in the first place.

It seems more correct to say the properties of space-time are unchanging rather than vary due to unknown forces, but there is no way to say for sure. Contrary to what you said, I believe a mature universe that is expanding at an accelerating rate is more fantastic than the initial inflationary epoch. Imagine the implications of such a phenomenon.

I am beginning to think that you consider space-time to be something real, rather than an abstract concept used to convey the dynamical nature of the universe. A lot of popular literature seems to describe it as such, when it is no such thing. It is simply a convenient way to paint the picture.

If you want to give space-time special properties of its own, you have to define them and include them in the equations. There is no property for expansion itself as it is simply a coordinate result that emerges from the currently favoured solution to Einsteins field equations.

Space-time is real in the sense it gives the universe three dimensions plus time. Theoretically there could be space-time with no matter, and certainly we have observed areas of the universe that are essentially empty.

I'm not sure I understood your last statement because it seems like a contradiction. If there is no property for expansion itself, why would the expansion properties in this idea need to be incorporated? You seem to be fixed on the idea that galaxies are moving apart due to a force acting on them, but remember they are not actually moving (or accelerating). Space is expanding around them.

 

[SpeedFreek]

You might find this paper interesting...

Expanding Space: the Root of all Evil?

While it remains the staple of virtually all cosmological teaching, the concept of expanding space in explaining the increasing separation of galaxies has recently come under fire as a dangerous idea whose application leads to the development of confusion and the establishment of misconceptions. In this paper, we develop a notion of expanding space that is completely valid as a framework for the description of the evolution of the universe and whose application allows an intuitive understanding of the influence of universal expansion. We also demonstrate how arguments against the concept in general have failed thus far, as they imbue expanding space with physical properties not consistent with the expectations of general relativity.

 

[SpeedFreek]

But General Relativity is not honoured, as there is no mechanism in GR to accelerate the rate of expansion! If you wish to introduce some new property into the equations that accelerates the rate of expansion, you are essentially adding a cosmological constant, or quintessence, depending on how you do it.

To the contrary, the way I see it GR is honored. The universe behaved exactly as described by GR until the effects of distance reduced the attraction of the galaxies to each other, at which time acceleration of space-time presided.

Yes, that is how it is generally thought of. But the emergent acceleration that came with the reduced gravitational "density" is something in the order of hundreds of magnitudes too small to have driven the initial expansion.

The question is still open as to whether that which accelerates the rate of expansion has been there all along, or has emerged later in the history of the universe, but in order to describe what we see, it cannot be equivalent to that which caused the expansion in the first place.

It seems more correct to say the properties of space-time are unchanging rather than vary due to unknown forces, but there is no way to say for sure. Contrary to what you said, I believe a mature universe that is expanding at an accelerating rate is more fantastic than the initial inflationary epoch. Imagine the implications of such a phenomenon.

As long as dark energy is a constant and we are not dealing with a "force" that increases in time, the only implications are that all the galaxies outside of our supercluster will disappear from view. Only with a "phantom energy" that increases with time do we face a "big-rip" scenario, where atoms are eventually ripped apart, and the evidence so far seems to be on against that scenario.

I am beginning to think that you consider space-time to be something real, rather than an abstract concept used to convey the dynamical nature of the universe. A lot of popular literature seems to describe it as such, when it is no such thing. It is simply a convenient way to paint the picture.

If you want to give space-time special properties of its own, you have to define them and include them in the equations. There is no property for expansion itself as it is simply a coordinate result that emerges from the currently favoured solution to Einsteins field equations.

Space-time is real in the sense it gives the universe three dimensions plus time. Theoretically there could be space-time with no matter, and certainly we have observed areas of the universe that are essentially empty.

I'm not sure I understood your last statement because it seems like a contradiction. If there is no property for expansion itself, why would the expansion properties in this idea need to be incorporated? You seem to be fixed on the idea that galaxies are moving apart due to a force acting on them, but remember they are not actually moving (or accelerating). Space is expanding around them.

I hope you have had a look at that paper I posted above. Space-time only describes the four dimensions of the universe and the relationship between events, it doesn't define them. The notion of "expanding space" is useful, but don't be misled into thinking it somehow causes cosmological distances to increase, it can better thought of as the measured result.

I find it strange how you are so against a cosmological constant, which is essentially a background effect that pervades all of space, but are happy to attribute the accelerating expansion of the universe to "space-time" instead..

But the bottom line is that all our observations tell us that the acceleration of the expansion is not due to the same thing that caused the expansion in the first place.

 

[FlatEarth]

Yes, that is how it is generally thought of. But the emergent acceleration that came with the reduced gravitational "density" is something in the order of hundreds of magnitudes too small to have driven the initial expansion.

I am not proposing an alternate explanation to the initial expansion, so that is why I'm at a loss to reply to this comment. Perhaps I made an earlier statement that made you think I was, but that is not my intention. That is why I say GR is honored.

As long as dark energy is a constant and we are not dealing with a "force" that increases in time, the only implications are that all the galaxies outside of our supercluster will disappear from view. Only with a "phantom energy" that increases with time do we face a "big-rip" scenario, where atoms are eventually ripped apart, and the evidence so far seems to be on against that scenario.

The concept of the Big Rip is intriguing. I know how this sounds, but before I heard of it, I imagined a similar fate of the universe. How could it keep expanding with no consequence? It was unnerving to hear this theory from cosmologists, to tell the truth.

I hope you have had a look at that paper I posted above. Space-time only describes the four dimensions of the universe and the relationship between events, it doesn't define them. The notion of "expanding space" is useful, but don't be misled into thinking it somehow causes cosmological distances to increase, it can better thought of as the measured result.

I did look at the paper and thanks for posting the link.
Without expanding space, all galaxies would be converging, so how can it be said it is only the measured result? It is the result! As I mentioned in an earlier post, GR predicts that space can exist without matter! Space rules.

I find it strange how you are so against a cosmological constant, which is essentially a background effect that pervades all of space, but are happy to attribute the accelerating expansion of the universe to "space-time" instead.

I understand it better, thanks to you, but I have misgivings about adding a new background force to explain the latest observations. We must actually define the force and find the source: and more than likely it will be a search down a long dead end road.
On the other hand, I believe an evolved understanding of space-time with ever-accelerating properties of expansion can explain current observations without adding a theoretical background force. It is a more elegant solution.

But the bottom line is that all our observations tell us that the acceleration of the expansion is not due to the same thing that caused the expansion in the first place.

Whether driven by a background force or caused solely by the effects of expanding space-time, the observations are the same. As stated earlier, this idea does not propose a change what caused the expansion in the first place.

 

[SpeedFreek]

I am not proposing an alternate explanation to the initial expansion, so that is why I'm at a loss to reply to this comment. Perhaps I made an earlier statement that made you think I was, but that is not my intention. That is why I say GR is honored.

I was under the impression that your suggestion was that the expansion of "space-time" has been accelerating all along, but it was only when everything was far apart enough for the acceleration to beat the gravitational density that the objects in the universe started to accelerate apart.

My point is that space-time is only actually defined by the stuff within it, so it has not been accelerating all along - earlier in the history of the universe, the rate at which distances increased was slowing down.

However, with a negative "energy" that has been in the background all along, the expansion of space over time would only accelerate when the gravitational density was low enough to allow it.

The concept of the Big Rip is intriguing. I know how this sounds, but before I heard of it, I imagined a similar fate of the universe. How could it keep expanding with no consequence? It was unnerving to hear this theory from cosmologists, to tell the truth.

The Big Rip would require "phantom (dark) energy", where its value increases over time, rather than stays constant or decreases, so it is a very unlikely scenario. There is no observational evidence so far that the acceleration is caused by anything other than an effect that is constant, or decreasing.

I did look at the paper and thanks for posting the link.
Without expanding space, all galaxies would be converging, so how can it be said it is only the measured result? It is the result! As I mentioned in an earlier post, GR predicts that space can exist without matter! Space rules.

The expansion of the universe does indeed act as if space expands, but it is not necessarily a property of space itself that causes the increase in cosmological distances, over time.

Does the light from distant galaxies get gradually redshifted as it travels, or is the redshift only an apparent effect caused by the difference in the scale of the universe between the time the light was emitted and finally detected? In this case, as we are all "lodged" within the expanding universe, the end result is the same, but is there a property of expanding space that actually stretches light as it travels?

Space might be able to exist without matter, but how can it expand if there is nothing by which to measure that expansion?

I believe an evolved understanding of space-time with ever-accelerating properties of expansion can explain current observations without adding a theoretical background force. It is a more elegant solution.

You are adding a new theoretical ever-accelerating property to space-time instead! And in order for matter to couple/decouple with this new property of yours (to allow the expansion of the universe to decelerate as has been observed), you also need a new mechanism to show how the two sides interact. Gravity cannot be the answer in your scenario, as it is already the answer to the mainstream view of why the expansion of the universe decelerated for 9 billion years. If you want to think in terms of expanding space, then the expansion of space was decelerating for a very long time.

All you are doing is swapping dark-energy (which is simply a placeholder for "that which causes the rate at which distances increase to accelerate") for accelerating and expanding space-time, which makes no sense as you can only define space-time by the events that occur within it! So you are adding a whole new level of complication into the equations - space-time that somehow exists at a totally separate level from the objects that populate it!

:mrgreen:

 

[FlatEarth]

I was under the impression that your suggestion was that the expansion of "space-time" has been accelerating all along, but it was only when everything was far apart enough for the acceleration to beat the gravitational density that the objects in the universe started to accelerate apart.

You are correct when saying my idea is that space-time was always expanding at an accelerating rate.

My point is that space-time is only actually defined by the stuff within it, so it has not been accelerating all along - earlier in the history of the universe, the rate at which distances increased was slowing down.

I understand your point, but despite the paper which supports it, I believe it is not correct. I believe space-time is not defined by matter, but can exist without it. So in my view, the expansion of matter and the expansion of space-time can and do have differing rates of expansion.

However, with a negative "energy" that has been in the background all along, the expansion of space over time would only accelerate when the gravitational density was low enough to allow it.

This is exactly the same effect that I believe was caused by accelerating space-time instead of a "negative" energy in the background. The results are the same, only the cosmological constant is not needed.

The Big Rip would require "phantom (dark) energy", where its value increases over time, rather than stays constant or decreases, so it is a very unlikely scenario. There is no observational evidence so far that the acceleration is caused by anything other than an effect that is constant, or decreasing.

I don't have a strong opinion on this, but a possibility with the accelerating space-time idea is that are we are going to be ripped to shreds eventually! :!:

You are adding a new theoretical ever-accelerating property to space-time instead! And in order for matter to couple/decouple with this new property of yours (to allow the expansion of the universe to decelerate as has been observed), you also need a new mechanism to show how the two sides interact.

This is true, I am changing the properties of space-time by saying it expands independently from matter and is expanding at an ever accelerating rate. I don't understand your point of requiring a new mechanism, however. They interact as we have always understood them to. For example, our local group of galaxies are gravitationally bound to each other and will never fly apart despite the expansion of space, regardless of the rate of expansion. The decoupling of space-time and matter is happening right in our own galactic back yard!

Gravity cannot be the answer in your scenario, as it is already the answer to the mainstream view of why the expansion of the universe decelerated for 9 billion years. If you want to think in terms of expanding space, then the expansion of space was decelerating for a very long time.

No one owns the rights to gravity! The mainstream view is not totally incorrect, but I am saying it is inventing a new force when there is another explanation that does not. I find a new force idea more difficult to rationalize than a revised view of space-time.

All you are doing is swapping dark-energy (which is simply a placeholder for "that which causes the rate at which distances increase to accelerate") for accelerating and expanding space-time, which makes no sense as you can only define space-time by the events that occur within it! So you are adding a whole new level of complication into the equations - space-time that somehow exists at a totally separate level from the objects that populate it!

And this is where we will never see eye to eye. You maintain that space cannot exist without matter, and I believe that to be incorrect. If I understand what you are saying, GR only describes space-time where matter is present, and that sounds reasonable. That means the addition of a larger, expanding, and essentially empty volume of space-time is not predicted by GR, but i believe it is not counter to it, because space-time is not comprised of matter or energy.

:mrgreen:

You are starting to look like the Hulk! Watch out for those gamma rays!

 

[SpeedFreek]

I understand your point, but despite the paper which supports it, I believe it is not correct. I believe space-time is not defined by matter, but can exist without it. So in my view, the expansion of matter and the expansion of space-time can and do have differing rates of expansion.

Not just that one paper - the scientific consensus built up over the past century supports my point. That paper was just illustrating why the notion of "expanding space" itself might mislead people into attributing space itself with properties it might not possess, which is exactly what you seem to be doing with your idea. Rather than an energy that resides within space, you attribute the acceleration of the expansion to space itself.

You believe that space and time can exist without matter? What is time, then, if it is not the duration of events in space? How can there be an event in an empty universe?

You are adding a new theoretical ever-accelerating property to space-time instead! And in order for matter to couple/decouple with this new property of yours (to allow the expansion of the universe to decelerate as has been observed), you also need a new mechanism to show how the two sides interact.

This is true, I am changing the properties of space-time by saying it expands independently from matter and is expanding at an ever accelerating rate. I don't understand your point of requiring a new mechanism, however. They interact as we have always understood them to. For example, our local group of galaxies are gravitationally bound to each other and will never fly apart despite the expansion of space, regardless of the rate of expansion. The decoupling of space-time and matter is happening right in our own galactic back yard!

I'm sorry but what you are describing is not space-time, it is something else entirely, and requires new properties and a new mechanism in order for the effects of those properties to "communicate" with the contents of the universe.

Gravity cannot be the answer in your scenario, as it is already the answer to the mainstream view of why the expansion of the universe decelerated for 9 billion years. If you want to think in terms of expanding space, then the expansion of space was decelerating for a very long time.

No one owns the rights to gravity! The mainstream view is not totally incorrect, but I am saying it is inventing a new force when there is another explanation that does not. I find a new force idea more difficult to rationalize than a revised view of space-time.

You are inventing a new "force" with your alternate explanation, but you are attributing the properties of that "force" to space-time. What you cannot seem to understand is that space-time is simply how we describe events in space and time!

And this is where we will never see eye to eye. You maintain that space cannot exist without matter, and I believe that to be incorrect. If I understand what you are saying, GR only describes space-time where matter is present, and that sounds reasonable. That means the addition of a larger, expanding, and essentially empty volume of space-time is not predicted by GR, but i believe it is not counter to it, because space-time is not comprised of matter or energy.

I don't think I said that space cannot exist without matter - I would have to ask Minkowski about that one! What I said is that space cannot expand without something in that space in order to measure that expansion. You seem to be confused between space and space-time. One is the gaps between the objects in the universe and the other is how we choose to define those gaps in a universe where space and time are dynamic.

 

[FlatEarth]

SpeedFreek, it is clear we will never agree on this idea so I think it is time to end the exchange. I thank you for giving the idea your consideration and the effort you put forth to indoctrinate me to the dark side.

I do fully understand the points you have made, and although you use information that is widely accepted in the scientific community some of it seems incorrect to me. We have entered into a circular exchange that will have no conclusion, so it's time to stop!

Thanks to MeteorWayne for letting us diverge from the original topic.

Flat