What is the fabric of space made of

[brainstorm]

My point is that light (in whatever form you choose to envision it) redshifts with universal expansion, which is true for all EM radiation, and in a sense, matter.

How so with matter? And what does this suggest about the conservation of energy and matter?

 

[nismaratwork]

How so with matter? And what does this suggest about the conservation of energy and matter?

Here is an explanation, and in my view and a decent refutation of what I'm talking about: http://www.astro.ucla.edu/~wright/tiredlit.htm

Of course, the balloon analogy has its limitations, and there is no explanation as to how or why this effect does not take place. This is why I said "We're talking about a scale that is not open to this kind of analysis."

 

[brainstorm]

Here is an explanation, and in my view and a decent refutation of what I'm talking about: http://www.astro.ucla.edu/~wright/tiredlit.htm

Of course, the balloon analogy has its limitations, and there is no explanation as to how or why this effect does not take place. This is why I said "We're talking about a scale that is not open to this kind of analysis."

Nice link. Thanks. But you completely ignored the questions in my post: 1) What did you mean when you said that matter, in a sense, redshifts with universal expansion; and
2) What is implied about the disappearance or appearance of matter/energy at any scale?

 

[nismaratwork]

Nice link. Thanks. But you completely ignored the questions in my post: 1) What did you mean when you said that matter, in a sense, redshifts with universal expansion; and
2) What is implied about the disappearance or appearance of matter/energy at any scale?

Saying that matter redshifts was incorrect on my part, and misleading. Matter eventually will reduce to radiation, which will redshift. The argument that light may redshift is a very old one, so I'm sorry that I assumed your familiarity. http://en.wikipedia.org/wiki/Tired_light

I'm not arguing that this is correct, but it is puzzling. On one had the universe seems to be expanding, radiation redshifts, but the effects of this loss are not observed. Dark Energy or vacuum expectation energy doesn't match or make up for the apparent loss. although neutrino pair creation has been put forth. Many take the view that conservation of energy doesn't apply to the universe as a whole, and until there is a way to confirm its symmetries (or not) it will probably remain a mystery.

 

[brainstorm]

Ok, you just mean that matter can undergo redshift once it is converted into radiation.

I'm not arguing that this is correct, but it is puzzling. On one had the universe seems to be expanding, radiation redshifts, but the effects of this loss are not observed.

In the link you posted, it said that redshift doesn't reduce the energy of radiation, it just dilates the waves such that it takes more time for the same amount of energy to reach a destination point. So, unless I am understanding something wrong, no energy is lost - it's just delivered at a slower rate over a longer period of time.

Dark Energy or vacuum expectation energy doesn't match or make up for the apparent loss. although neutrino pair creation has been put forth.

How exactly is the loss apparent?

Many take the view that conservation of energy doesn't apply to the universe as a whole, and until there is a way to confirm its symmetries (or not) it will probably remain a mystery.

Regardless of what "many" or few take as a view, it's ultimately the reasons behind what they think that matters, not their conclusive opinions. Everything theoretical ultimately remains a mystery. The issue is what can be reasoned despite fundamental unanswerability, and how.

One thing I don't understand is whether you agree that any matter/energy lost or gained at the level of "the universe" has to be lost or gained in some sub-set of it. So unless there is a specific mechanism for matter/energy to be lost or gained, conservation law is logical. The question I would be asking is what happens to radio-waves when they red-shift? Is their a lower limit to radiation frequency or does everything exist amid photons so old that their frequency has long since surpassed measurability?

This raises another question, which is why gamma rays are the upper-limit of EM frequency? I wonder if it is possible that yet higher frequencies begin behaving as material particles with the ability to slow down, for some reason. I only wonder this because gamma rays are supposedly the size of an atomic nucleus and the amount of energy expressed in them is growing exponentially; and because I wonder where the bridge between energy and matter (in that direction) takes place.

 

[Dmitry67]

So unless there is a specific mechanism for matter/energy to be lost or gained, conservation law is logical.

No

I can give an example: you stand in front of the building (1000'000kg). It has 0 kinetic energy. Now you run towards it at 10m/sec. In your frame of reference (where you are at rest), kinetic energy of the building is now huge. Where did this energy come from? :)

Of course, you would say: this is not fair! When you started to run, you changed your frame, so you just can't compare energy of the building in 2 different frames!

Now the Universe. There is no frame which can cover the whole Universe. In Cosmology there is a pseudo-frame ('all universe at time t') but it is not a valid physical frame because if you draw this frame, you would see that it is not a flat surface in spacetime but it is curved!

 

[nismaratwork]

No

I can give an example: you stand in front of the building (1000'000kg). It has 0 kinetic energy. Now you run towards it at 10m/sec. In your frame of reference (where you are at rest), kinetic energy of the building is now huge. Where did this energy come from? :)

Of course, you would say: this is not fair! When you started to run, you changed your frame, so you just can't compare energy of the building in 2 different frames!

Now the Universe. There is no frame which can cover the whole Universe. In Cosmology there is a pseudo-frame ('all universe at time t') but it is not a valid physical frame because if you draw this frame, you would see that it is not a flat surface in spacetime but it is curved!

A curve which changes from t₁ to t₂ , whence Noether's Theorem becomes an issue.

 

[brainstorm]

No

I can give an example: you stand in front of the building (1000'000kg). It has 0 kinetic energy. Now you run towards it at 10m/sec. In your frame of reference (where you are at rest), kinetic energy of the building is now huge. Where did this energy come from? :)

Of course, you would say: this is not fair! When you started to run, you changed your frame, so you just can't compare energy of the building in 2 different frames!

Now the Universe. There is no frame which can cover the whole Universe. In Cosmology there is a pseudo-frame ('all universe at time t') but it is not a valid physical frame because if you draw this frame, you would see that it is not a flat surface in spacetime but it is curved!

Framing is an epistemological issue. In your process of running toward the building, you convert a certain amount of energy into momentum, which is conserved during your collision with the building. No energy is lost or gained during that process. The only reason you are able to suggest it is possible is by confounding your analysis by using framing to change the descriptions of what is going on. Running toward the building doesn't increase the KE of the building the same as would pushing the building over. And besides, the KE only matters once it gets expressed through transference to something else. Prior to collision, the KE expressed is just a build up of dynamic potential to transfer energy to another carrier, isn't it?

If no energy is created or destroyed at the micro-level of empirically observable matter-energy, how could it occur at a more complex level or larger scale?

 

[nismaratwork]

Framing is an epistemological issue. In your process of running toward the building, you convert a certain amount of energy into momentum, which is conserved during your collision with the building. No energy is lost or gained during that process. The only reason you are able to suggest it is possible is by confounding your analysis by using framing to change the descriptions of what is going on. Running toward the building doesn't increase the KE of the building the same as would pushing the building over. And besides, the KE only matters once it gets expressed through transference to something else. Prior to collision, the KE expressed is just a build up of dynamic potential to transfer energy to another carrier, isn't it?

If no energy is created or destroyed at the micro-level of empirically observable matter-energy, how could it occur at a more complex level or larger scale?

It's a principle that just doesn't apply; energy cannot be created, yet here we are. At the scale of the universe as a whole, it's not that the notion is invalid, it just does not apply to it.

 

[brainstorm]

It's a principle that just doesn't apply; energy cannot be created, yet here we are. At the scale of the universe as a whole, it's not that the notion is invalid, it just does not apply to it.

Implicit deus ex machina is not an interesting scientific proposition. I am interested in what process(es) could convert energy into matter and how/when this may occur naturally. I suspect either something to do with black hole gravity, ultra high energy radiation, or both. I would also like to establish whether radiation can ever permanently escape gravitational fields. If it can't, then it would seem that energy inevitably gets converted into matter, which inevitably gets coagulated into a body with sufficient gravitation to result in nuclear fusion, converting the matter back into energy. This would, I think, establish the universe as a perpetual system of matter-energy conversions, which could also mean that it has no beginning or end. The big bang is suggested to be an absolute beginning, but technically I don't think BBT addresses what happened prior to the amalgamation of the energy/matter that began expanding in the first place. It may have been due to the convergence of a prior universe of dynamic matter-energy into a singularity with the propensity to expand. I think the key to theorizing this would involve finding some mechanism whereby black holes can destabilize or otherwise generate radiation. The only theory of this I know is that of Hawking radiation, but could that process be significant enough to result in big-bang levels of energy-expansion?

 

[nismaratwork]

Implicit deus ex machina is not an interesting scientific proposition. I am interested in what process(es) could convert energy into matter and how/when this may occur naturally. I suspect either something to do with black hole gravity, ultra high energy radiation, or both. I would also like to establish whether radiation can ever permanently escape gravitational fields. If it can't, then it would seem that energy inevitably gets converted into matter, which inevitably gets coagulated into a body with sufficient gravitation to result in nuclear fusion, converting the matter back into energy. This would, I think, establish the universe as a perpetual system of matter-energy conversions, which could also mean that it has no beginning or end. The big bang is suggested to be an absolute beginning, but technically I don't think BBT addresses what happened prior to the amalgamation of the energy/matter that began expanding in the first place. It may have been due to the convergence of a prior universe of dynamic matter-energy into a singularity with the propensity to expand. I think the key to theorizing this would involve finding some mechanism whereby black holes can destabilize or otherwise generate radiation. The only theory of this I know is that of Hawking radiation, but could that process be significant enough to result in big-bang levels of energy-expansion?

You are, in a different area, making my point: there is no theory to cover the period "before" there was a "before (before BB), and conservation of energy doesn't apply to the universe as a whole, only its subsystems. You can show how energy is conserved in a given system, but not for the entire universe, which logically should be losing energy, but empirically seems not to be. How matter is created from energy is spelled out in E=Mc², but the conditions for that are no longer present (in any part of the universe that I know of).

 

[brainstorm]

You are, in a different area, making my point: there is no theory to cover the period "before" there was a "before (before BB), and conservation of energy doesn't apply to the universe as a whole, only its subsystems. You can show how energy is conserved in a given system, but not for the entire universe, which logically should be losing energy, but empirically seems not to be. How matter is created from energy is spelled out in E=Mc², but the conditions for that are no longer present (in any part of the universe that I know of).

What empirical observation supports the idea that the entire universe is losing energy? The only thing I can imagine you mean is that red-shift eventually results in total dissipation of EM wave energy, but I asked you in another post why EM waves can't continue expanding beyond the radio spectrum?

Also, you casually say that no conditions for converting energy into matter still exist anywhere in the universe, but what do you think about black holes? When gravitation exceeds the ability of EM radiation to move translocally, it seems logical to me that it would have to become localized, probably through some form of loop of radiant energy bent in on itself.

Also, what about the possibility of higher frequency EM emissions than gamma rays? Could it be that some level of fusion reactions generate such ultra-high frequency emissions and that these contain so much energy in so small a volume of spacetime that they bend-in on themselves due to their own attractive force? In this sense, some stars may emit particles in addition to other frequencies of EM radiation.

Still, if anything is to account for conversion of sub-gamma wavelengths, I think it would have to be black holes. And, likewise, you didn't respond to the question of whether you think radiation can escape gravitation indefinitely or whether it eventually has to traverse gravity-field topography until it reaches a black hole.

edit: I just realized after posting that if the nascent particles of matter generated by powerful stars have the capacity to absorb other forms of radiant energy, they could act as germinal particles, like snow balls collecting free energy to grow into electrons. In this sense, a powerful star could emit such particles into space where their path would intersect with other radiation traveling in a non-parallel direction, and as such they would end up incorporating that energy into their loop-structure. This almost sounds like it could be a form of "dark matter."

Could this be tested by comparing the mass and composition of large stars to the total energy of their emissions? If the energy of the star's radiation was less than expected, would that suggest it was generating something other than radiation, like elementary particles or "dark matter?"

 

[apeiron]

You can show how energy is conserved in a given system, but not for the entire universe, which logically should be losing energy, but empirically seems not to be.

Perhaps it is indeed better to start with the empirlcal here? We observe the universe to be largely flat, homogenous, isotropic, and so can impute a conservation principle at work.

Then what seems to be in exact balance is cooling and expansion. So there is a fundamental equilibrium between energy and spacetime. The universe is a dissipative structure which is its own heat sink. Radiation spreads and cool. An initial thick hot point runs down a gradient of dissipation to become a thin cold void.

Of course, dark energy is the new complication - both necessary because there was not enough energy/matter/gravity to balance the observed expansion rate, and a complication as it seems to throw in an extra little persistent acceleration, implying an open thermodynamic story.

So on the whole, the universe looks like a closed story - a gradient simply being run down from a hot point to a cold void, a phase transition we are seeing from the inside. But there is still a small nagging openness. I think this will be due in the end to a marginal QM uncertainty as various people have speculated.

 

[brainstorm]

Perhaps it is indeed better to start with the empirlcal here? We observe the universe to be largely flat, homogenous, isotropic, and so can impute a conservation principle at work.

I don't think you can call the universe an empirically observable entity. The universe is a theoretical superset of everything that exists. As such it is an extrapolation of what is imagined to exist in the same way as the set of all observable matter-energy phenomena, which is theoretically a subset of the universe in its imagined entirety. In short, empirically observable occurrences can only be a subset of the total set of everything theorized to exist as part of "the universe," so the universe can't be empirically circumscribable.

This is poorly written so here's an example: Presumably there are stars/galaxies in existence beyond the Hubble horizon where stars have red-shifted beyond visibility. Still, they are presumed to exist as part of the universe despite having become empirically unobservable. Therefore, only the subset of empirically observable phenomena are empirically observable, not the the universe as a whole, which includes the unobservable stars/galaxies too.

Then what seems to be in exact balance is cooling and expansion. So there is a fundamental equilibrium between energy and spacetime. The universe is a dissipative structure which is its own heat sink. Radiation spreads and cool. An initial thick hot point runs down a gradient of dissipation to become a thin cold void.

So you think energy is dissipating into nothingness? What makes you think it is not simply transferring or transforming into new expressions? This is why I asked you if you think radiation can proceed indefinitely away from all gravity fields? I don't think it can/does.

 

[nismaratwork]

Perhaps it is indeed better to start with the empirlcal here? We observe the universe to be largely flat, homogenous, isotropic, and so can impute a conservation principle at work.

Then what seems to be in exact balance is cooling and expansion. So there is a fundamental equilibrium between energy and spacetime. The universe is a dissipative structure which is its own heat sink. Radiation spreads and cool. An initial thick hot point runs down a gradient of dissipation to become a thin cold void.

Of course, dark energy is the new complication - both necessary because there was not enough energy/matter/gravity to balance the observed expansion rate, and a complication as it seems to throw in an extra little persistent acceleration, implying an open thermodynamic story.

So on the whole, the universe looks like a closed story - a gradient simply being run down from a hot point to a cold void, a phase transition we are seeing from the inside. But there is still a small nagging openness. I think this will be due in the end to a marginal QM uncertainty as various people have speculated.

I disagree, first, because I can't imagine a way of defining the symmetries needed to invoke Noether's Theorem for the universe as an entity, and because Brainstorm is right; how is it empirically observable as a whole? We see only a small slice of it, and we know that; for the rest... ? How do you formulate a conservation law for something that is ill defined in the sense needed for such a thing?

 

[brainstorm]

I disagree, first, because I can't imagine a way of defining the symmetries needed to invoke Noether's Theorem for the universe as an entity, and because Brainstorm is right; how is it empirically observable as a whole? We see only a small slice of it, and we know that; for the rest... ? How do you formulate a conservation law for something that is ill defined in the sense needed for such a thing?

You can just postulate that the unobservable parts of the universe behave similarly to the observable parts and tentatively assume that if matter-energy is being conserved in all observable/fathomable mechanisms present that it would be conserved in the unobservable parts too. You just have to acknowledge that your assumption is tentative and state your assumptions so that they can be subject to critique.

The big question that would tip the scale for me in either direction is whether energy can red-shift beyond radio-waves or if it somehow just disappears at lower frequencies. On the other hand, if the combined rate of expansion between two galaxies exceeds the speed of light, then light is ultimately surpassed by the expansion of space. Or maybe it would be more accurate to say that its dilation converges with the dilation of space itself. In that case, is that energy really lost or has it simply merged with the energy of universal expansion, adding to the rate of expansion the way a drop of water in a pond causes ripples that eventually flatten out and raise the overall water-level of the pond?

 

[apeiron]

This is poorly written so here's an example: Presumably there are stars/galaxies in existence beyond the Hubble horizon where stars have red-shifted beyond visibility. Still, they are presumed to exist as part of the universe despite having become empirically unobservable. Therefore, only the subset of empirically observable phenomena are empirically observable, not the the universe as a whole, which includes the unobservable stars/galaxies too.

I don't see the problem here. We start with what we observe (an equilbrium as far as we can see) and then extrapolate over the event horizon. We can't know for sure what lies over the horizon. but our extrapolations can still be logical.

So yes, there would be a supraluminal expanse of universe beyond our current event horizon - based on logical extrapolation. And we can also make guesses about what came before the big bang on the same basis.

So you think energy is dissipating into nothingness? What makes you think it is not simply transferring or transforming into new expressions? This is why I asked you if you think radiation can proceed indefinitely away from all gravity fields? I don't think it can/does.

Well we know that if the universe contained just radiation, then there would not be sufficient gravity to create the flat balance we observe. Even throwing in dark matter, only got things up to around 30%. So dark energy, or something like, was needed to balance the books, providing the missing 70%. So I think that is a basic misconception you have here.

A good introduction to this in general is...
http://www.mso.anu.edu.au/~charley/papers/LineweaverChap_6.pdf

See especially the diagram on p71 to answer your query about the minimum possible wavelength of photons.

The general view I am expressing is that energy is being turned into spacetime in essence. That is the phase transition taking place. This is hard to see if you are imagining energy as stuff (substance) and space as a stage or framework (form), but if you frame both as geometry (positive or open vs negative or closed curvature), then it becomes easier to appreciate how the two might be related.

 

[apeiron]

I disagree, first, because I can't imagine a way of defining the symmetries needed to invoke Noether's Theorem for the universe as an entity, and because Brainstorm is right; how is it empirically observable as a whole? We see only a small slice of it, and we know that; for the rest... ? How do you formulate a conservation law for something that is ill defined in the sense needed for such a thing?

Hah, if we observe the universe (as far as the eye can see) to be flat, homogenous, isotropic, then it has scale symmetry - no scale of observation is preferred. So what conservation principle does that imply here, given Noether's Theorem?

I think that does tell us that expansion is following a conservation principle. Cooling is possible because the heat is creating its own heat sink.

But you would be right. Conventional ways of imagining cooling~expansion don't really add up. Something is missing.

For me, it is the lack of a proper model of development - a notion of vagueness. Conventional notions of development are monadic - things progress in only one direction, and so that is not a symmetry. But vagueness is the basis of a dyadic philosophy where things develop because you have things going in two complementary directions - towards the local and the global. You have in fact a foundational asymmetry (that arises out of a vagueness, the foundational symmetry).

And this is why it then seems so natural to relate energy and spacetime so directly. They are two faces of the same coin. They may look very different of course (they are asymmetric and complementary), but that difference is precisely what develops.

During the big bang, the difference between the two was vague - so symmetric that you could not tell them apart. The kind of state described as a quantum foam in loop quantum gravity where the energy fluctuations are as large as the metric. At the heat death, all the local fluctuations will have been smoothed away as far as possible. In effect, the roiling energy will have become stretched out to make a thin cold fabric of infinitely large spacetime.

All that energy of the big bang would have indeed gone somewhere - into creating the void. Again, this picture is too simple because dark energy is now another piece of the puzzle. But as the baseline story of a closed system (and dissipative structure theory is about the self-organisation of closed systems) it still makes sense to me.

 

[brainstorm]

I don't see the problem here. We start with what we observe (an equilbrium as far as we can see) and then extrapolate over the event horizon. We can't know for sure what lies over the horizon. but our extrapolations can still be logical.

So yes, there would be a supraluminal expanse of universe beyond our current event horizon - based on logical extrapolation. And we can also make guesses about what came before the big bang on the same basis.

This is what I was saying. It IS possible to THEORIZE the behavior of the universe as a whole through tentative extrapolations from observables. However, the other poster was suggesting that empirical observation of the universe as a whole could serve as a starting point for theorizing. I don't see how this is possible if the universe only exists at the theoretical level of extrapolation and is not empirically circumscribable.

Well we know that if the universe contained just radiation, then there would not be sufficient gravity to create the flat balance we observe. Even throwing in dark matter, only got things up to around 30%. So dark energy, or something like, was needed to balance the books, providing the missing 70%. So I think that is a basic misconception you have here.

I don't understand what is meant by "observed flat balance." Do you know of a link that explains the logic of what is observed and what is extrapolated from that and how? The only thing I've read has to do with galaxies rotating at an apparent speed faster than C, but I forget how this is logically brought to bear on estimations of their mass/gravitation.

A good introduction to this in general is...
http://www.mso.anu.edu.au/~charley/papers/LineweaverChap_6.pdf

See especially the diagram on p71 to answer your query about the minimum possible wavelength of photons.

I looked at the picture. I did not see how it related to the minimum possible wavelength of photons. Maybe my brain hit its minimum wavelength:)

The general view I am expressing is that energy is being turned into spacetime in essence. That is the phase transition taking place. This is hard to see if you are imagining energy as stuff (substance) and space as a stage or framework (form), but if you frame both as geometry (positive or open vs negative or closed curvature), then it becomes easier to appreciate how the two might be related.

This sounds similar to the lines along which I have been thinking. Would you care to elaborate - if necessary in PM if you are concerned about being harassed about independent thought?

 

[apeiron]

I'm sure my comments above are pretty opaque, so let me try to give a little more perspective.

The conventional way of looking at things is Newtonian - the universe as a static eternal back drop. And this stage has atomistic contents - a bunch of particles.

Modern cosmology challenges this basic picture in so many ways. And a new core mental picture could be emerging - at least you can see the gist of things in the writings of Davies and Lineweaver. I've read a ton of different people, but I keep coming back to their current work as lighting the path ahead.

See
http://www.ctnsstars.org/conferences/papers/The%20physics%20of%20downward%20causation.pdf
http://www.mso.anu.edu.au/~charley/papers/DavisDaviesLineweaver.pdf
and really many of the papers on
http://www.mso.anu.edu.au/~charley/publications.html

In brief, they are taking a self-organising system view. They are taking the observed facts about the universe, such as its scale flatness, its expansion, its light cone coherence, and making them basic rather than add-ons.

The Newtonian universe is static, so expansion and a direction of change have to be added as secondary features. Likewise it is empty, so contents like energy have to be added.

This is all very primitive modelling, and so we want to start with a model that is inherently dynamic, inherently full of potential (potential energy and potential spacetime), etc.

Now the beautiful idea at the heart of the Davies/Lineweaver work (it is not their idea as such, many are thinking along the same general lines, they just express it most clearly IMHO) is that the description of the universe can be boiled down to blackbody photons radiated by event horizons. A de sitter space view.

It is a spherical co-ordinates type view (and I remember nismaratwork may have had an enthusiasm for that). Instead of spacetime as a static frame, it is defined in terms of lightcones - comoving volumes bounded by event horizons. So an inherently dynamic view. And event horizons have now been brought into the fold of thermodynamic/entropic modelling. So the boundaries of spacetime are inherently in dynamic equilibrium with the contents. Energy is being related to spacetime in a direct fashion. Closure, in energy conservation terms, is being defined (in a way it was not in an open, unbounded, Newtonian universe).

The event horizon approach also unites the description of the local and the global. The global scale is set by lightcones and comoving volumes. The local by the thermodynamics of black holes.

We know the universe is expanding, which is puzzling because it seems like an action in a single direction, a violation of conservation. Some force must be continually pushing it larger.

And then we look at the contents of the universe, such as photons, and say something must be stretching them - like the expansion of space.

But an inherently dynamic view of the universe puts these kinds of things back together as a single action of separation - symmetry breaking. Energy spreads out to expand spacetime, and the growth of spacetime cools energy (spreads it about). Two faces of the same coin.

Again, you then need an ontology of development that makes this an actual change in state, rather than an apparent tautology, a simple circularity. It certainly sounds circular to say that photons are spreading the spacetime they are in, and spacetime is spreading the photons it contains. Which is why a notion like vagueness becomes essential because you do get back actual change - a change from a vague potential to a crisply dichotomised outcome.

But regardless, current cosmology - taking Davies and Lineweaver as examples - is learning to take a dynamic and self-organising approach to imagining the universe. It is quite unlike the Newtonian thinking that is still the standard issue mental model.

 

[brainstorm]

But an inherently dynamic view of the universe puts these kinds of things back together as a single action of separation - symmetry breaking. Energy spreads out to expand spacetime, and the growth of spacetime cools energy (spreads it about). Two faces of the same coin.

But cooling doesn't mean disappearance. It just means an increase in the ratio of time to energy.

Again, you then need an ontology of development that makes this an actual change in state, rather than an apparent tautology, a simple circularity. It certainly sounds circular to say that photons are spreading the spacetime they are in, and spacetime is spreading the photons it contains. Which is why a notion like vagueness becomes essential because you do get back actual change - a change from a vague potential to a crisply dichotomised outcome.

Yes, I am also interested in the relationship between EM waves and space fabric itself, but this is because I see spacetime as nothing more than energetic relations between material objects. So spacetime seems to be nothing more than energy mitigated by gravitational attraction. When the energy is expressed as momentum of massive bodies, this is more obvious than when you're looking at EM waves themselves flattening out, because if they eventually fail to reach a target, how did they create spacetime? I believe the answer may lie in the way a rocket in space generates thrust without pushing against except what it is emitting. Stars may generate space by pushing against the photons they emit - but I have heard counterarguments against this too.

The rest of your post sounded like pure buzz. I'm not saying that that's all it is. Just the way you throw all those words and concepts out like that without explicating concrete reasoning for any of gives it the appearance of buzz. You may not have the patience and care to break individual concepts down into detailed reasoning/logic.

 

[apeiron]

But cooling doesn't mean disappearance. It just means an increase in the ratio of time to energy.

Something does disappear - or more correctly, gets minimised. And that is the general entropic gradient. The heat disappears into the production of the space leaving a heat death.

You seem to want to say that energy cannot be destroyed, so it must get transformed into something (like material in the form of black holes). Yet the citations I provided show how ultimately (in the universe as we now observe it) black holes will be embedded in a spacetime fabric so cold they must evaporate - radiate away that localised energy. So eventually, all radiation becomes part of the flat fabric. The blackbody radiation of event horizons in a de sitter spacetime.

this is more obvious than when you're looking at EM waves themselves flattening out, because if they eventually fail to reach a target, how did they create spacetime?

That is the point of the Lineweaver/Davies work - the beautiful idea of holographic bounds. The event horizons of spacetime are the "target" that gets reached by radiation.

I believe the answer may lie in the way a rocket in space generates thrust without pushing against except what it is emitting. Stars may generate space by pushing against the photons they emit - but I have heard counterarguments against this too.

OK, we are back to Newtonian viewpoints which are simply going to lead you in false directions. The idea of back-reaction may have some uses, but not in the way you are suggesting here.

Certainly, even if there was some contribution by stars in the fashion you imagine, it would have to be a vanishingly small component of the cosmic action. If all the entropy contained in all the stars was immediately converted to CMB radiation, it would add only 1 per cent to the universe's total.

This is why reading http://www.mso.anu.edu.au/~charley/papers/LineweaverChap_6.pdf would be good. It addresses these basic questions.

The rest of your post sounded like pure buzz. I'm not saying that that's all it is. Just the way you throw all those words and concepts out like that without explicating concrete reasoning for any of gives it the appearance of buzz. You may not have the patience and care to break individual concepts down into detailed reasoning/logic.

From my point of view, I show quite a bit of patience breaking down both what I think, and what also other people think .

Davies and Lineweaver are both very clear communicators. So perhaps you will suffer less buzz if you just read them.

 

[brainstorm]

Something does disappear - or more correctly, gets minimised. And that is the general entropic gradient. The heat disappears into the production of the space leaving a heat death.

And by "production of space" do you mean something other than increasing distance between surrounding objects? If not, wouldn't the increase in distance translate into a propulsion? E.g. if a car on a long carpet would stay in place and use its wheels to bunch up the carpet behind it and just assume that the carpet could be floating on a liquid, then as the bunched folds of the carpet expanded, the car would be propelled forward along with the part of the carpet it was sitting on. So the expansion of the folds in the carpet could be seen as entropy but also as propulsion at the same time. So if the dissipation of EM waves results in increasing distance between the point of emission and the destination, has energy been lost or converted into distance/space?

You seem to want to say that energy cannot be destroyed, so it must get transformed into something (like material in the form of black holes). Yet the citations I provided show how ultimately (in the universe as we now observe it) black holes will be embedded in a spacetime fabric so cold they must evaporate - radiate away that localised energy. So eventually, all radiation becomes part of the flat fabric. The blackbody radiation of event horizons in a de sitter spacetime.

Ok, so if black holes evaporate into radiation, then their mass eventually gets converted into spatial expansion - if the idea of EM waves expanding into distance/space is correct. Still, the distance/space between particles and waves is only relevant as long as these are gravitationally connected. What happens to the energy of distance/space when the objects it separates have evaporated into pure energy? Can it really just vanish or mustn't it transfer to the spatial relations among other objects/particles?

My guess would be the cold-matter of the universe would eventually begin converging once radiation-production has ceased. I am guessing Hawking radiation would not be enough to maintain positive expansion. In that case, the remaining black holes would begin accelerating toward each other due to their gravity and the amount of energy they generated en route to each other would correlate with the amount of distance between them, which would theoretically convert that distance/space back into radiation, no? Possibly such a convergence would result in a big-bang as all the black holes would approach C together in mutual orbit.

OK, we are back to Newtonian viewpoints which are simply going to lead you in false directions. The idea of back-reaction may have some uses, but not in the way you are suggesting here.

Ironically, the idea that EM radiation becomes space/distance is like an Einsteinian "spacetime fabric" way of explaining propulsion. It's just that the source of the energy doesn't "go anywhere" except away from its surroundings, right?

[/quote]Certainly, even if there was some contribution by stars in the fashion you imagine, it would have to be a vanishingly small component of the cosmic action. If all the entropy contained in all the stars was immediately converted to CMB radiation, it would add only 1 per cent to the universe's total.[/quote]
So what is the rest?

From my point of view, I show quite a bit of patience breaking down both what I think, and what also other people think .

Thank you for your gracious patience :)

 

[apeiron]

Ok, so if black holes evaporate into radiation, then their mass eventually gets converted into spatial expansion - if the idea of EM waves expanding into distance/space is correct. Still, the distance/space between particles and waves is only relevant as long as these are gravitationally connected. What happens to the energy of distance/space when the objects it separates have evaporated into pure energy? Can it really just vanish or mustn't it transfer to the spatial relations among other objects/particles?

No, the cites I provided explain that in a realm of pure radiation - a relativistic gas - the photons span event horizons. Now this does start to look like a virtual sizzle of interaction. All we have left is the self-interaction of the vacuum. But it continues to have a pressure, it continues to expand, it continues to have the same essential dissipative structure.

My guess would be the cold-matter of the universe would eventually begin converging once radiation-production has ceased. I am guessing Hawking radiation would not be enough to maintain positive expansion. In that case, the remaining black holes would begin accelerating toward each other due to their gravity and the amount of energy they generated en route to each other would correlate with the amount of distance between them, which would theoretically convert that distance/space back into radiation, no? Possibly such a convergence would result in a big-bang as all the black holes would approach C together in mutual orbit.

A recollapse is possible but the current evidence suggests not only is there enough material in various forms to keep the universe expanding in unbroken inertial fashion, but there is a weak dark energy acceleration on top of things.

But yes, a recollapse would mean a reconcentration that made things hot again. Or hot, small and once more vague, I would say.

Ironically, the idea that EM radiation becomes space/distance is like an Einsteinian "spacetime fabric" way of explaining propulsion. It's just that the source of the energy doesn't "go anywhere" except away from its surroundings, right?

I am suggesting it goes into its surroundings, into creating its surroundings.

So what is the rest?

The papers explain this. It is the CMB. When the big bang cooled sufficiently, anti-matter and matter could condense out. But almost all of it immediately annihilated to create the spreading/cooling CMB. A tiny fraction of matter remained. Which will eventually get swept up into black holes and radiated away too.

 

[brainstorm]

All we have left is the self-interaction of the vacuum. But it continues to have a pressure, it continues to expand, it continues to have the same essential dissipative structure.

Dissipative in what sense? That decreasing pressure draws particles/energy from higher pressure surroundings?

I am suggesting it goes into its surroundings, into creating its surroundings.

By "surroundings," I meant energetic matter and EM waves. What did you mean?

When the big bang cooled sufficiently, anti-matter and matter could condense out. But almost all of it immediately annihilated to create the spreading/cooling CMB. A tiny fraction of matter remained. Which will eventually get swept up into black holes and radiated away too.

So most of the energy of the initial big bang went into expansionary motion then? Would you agree that spatial separation between matter is a form of potential energy? Or do you think potential energy simply dissipates as objects move into ever weaker orbits in a gravitational field?

 

[apeiron]

So most of the energy of the initial big bang went into expansionary motion then? Would you agree that spatial separation between matter is a form of potential energy? Or do you think potential energy simply dissipates as objects move into ever weaker orbits in a gravitational field?

Of course matter is a temporary added complication to the basic picture. I am talking about the basic picture - which is just a bath of radiation spanning event horizons in comoving volumes. Or rather, that is what Davies and Lineweaver are talking about.

So there would be no localised gravitational potentials as the CMB is so evenly spread.

 

[brainstorm]

Of course matter is a temporary added complication to the basic picture. I am talking about the basic picture - which is just a bath of radiation spanning event horizons in comoving volumes. Or rather, that is what Davies and Lineweaver are talking about.

So there would be no localised gravitational potentials as the CMB is so evenly spread.

I'm confused. As far as I know there is no existence of "space" except as separation between points of matter despite their gravitational attraction for each other. Even massless energy is supposed to trace the contours of spacetime as defined by gravitational field topography. What defines the event horizons and comoving volumes except energized matter? If massless energy itself can stake off gravitational topography, how does that occur? How can photons exert gravitation without mass?

 

[Dmitry67]

If massless energy itself can stake off gravitational topography, how does that occur? How can photons exert gravitation without mass?

Again, Mass is not a source of gravity
Stress energy tensor is.

 

[robheus]

What are thoughts "made of"?

Space is merely a concept to differentiate different locations of objects in three dimensions.

In the theory of relativity space should be thought of a space-time and space-time itself does not have independend existence from matter/energy.

So, you could say that space-time is the mode of existence of matter/energy.

Space-time is not "made" of something else, yet space-time is never completely empty of matter/energy.

So, physical space is not just abstract mathetamatical geometry, where there is space-time there is matter/energy and vice versa.

 

[brainstorm]

So, physical space is not just abstract mathetamatical geometry, where there is space-time there is matter/energy and vice versa.

Good post. I think you could look at space as the vacuum inside a closed, de-pressurized container. The walls of the container are impelled to collapse into each other except the tensile strength prevents them from doing so. However, since there is no container-wall around the Earth, sun, galaxies, etc., the force pulling objects and particles apart has to be dynamic energy, from the big bang or just their motion relative to each other or however you describe it. Gravity is interesting, though, in that it relaxes as things move farther away from each other, so the "vacuum" elasticity relaxes as distances increase. So as gravity approaches zero, it seems like space could simply transcend gravitational relations, but how could gravitational attraction between two objects ever reach absolute zero? If it can't, then how could space-time ever exist in the absence of matter-energy?