It may sound disingenuous and that's fine, but I get that. And thank you for it. I don't argue for the sake of argument any more, and have not done so for years. I will ruminate some more and see what digestive gases produce. Gravity, or the place where inflation might overcome it, is something I want to think more about. Thank you all who took the time.

New space is being added everywhere. — Pfhorrest

Is there space inside objects like planets? If so, do we see an increase in the size of the planets over time?

I am not at all certain of what you think to have implicated any disingenuousness on your part; my purpose was only to illustrate the specifics of that cosmology we are now reflecting upon, and thereby to contribute in some way to the broader part of its discussion. In these efforts of mine, I was motivated by nothing else than to inform, to teach, and while I do on occasion pursue argument for its own sake, this doesn't apply in the present case. But even if it did, to inform would have still been my foremost aim in doing so.

On an unrelated note, I seem to have made several errors, albeit minor ones in my initial response to your query, and while this is an expected thing, especially when using a mobile-device, I don't wish to give off the impression of illiteracy. Thus, they have since been rectified, even if in appeal to little more than my own semantic perfectionism.

Thanks, it's all good. I took you assistance in the spirit you intended. My implication was a defensive response to another teacher who wasn't so interested in my enlightenment.

I assumed as much after having glanced over parts of your earlier exchange, despite having chosen simply to overlook it. But, you shouldn't feel yourself to be at fault for the reason that the other party who was of involvement has a known habit of commenting on a thread, only to cause an undue tension. His writings seldom demonstrate much of an insight either, even in those few instances for which he makes a genuine effort to bring something of value to the discussion; I myself can attest firsthand to this pattern he has shown, though I don't feel his behaviors warrant such attention at all.

I suppose the time has thus come to move on.

Agreed.

Which is why preliminary definitions are useful.

Is there space inside objects like planets? If so, do we see an increase in the size of the planets over time? — SimpleUser

There is space yes, but we don’t see small things (where even a galaxy is “small” for these purposes) expand because on small scales the forces holding those things together completely dwarf the force of expansion. It’s only on huge intergalactic scales that there is enough space relative to matter that the expansion of space outpaces the attraction of matter to itself.

There is space yes, but we don’t see small things (where even a galaxy is “small” for these purposes) expand because on small scales the forces holding those things together completely dwarf the force of expansion. — Pfhorrest

I know it is trite, and cliché, to bring up the pot-smoking stories of our universe on the head of someone else's pin, or a universe on the head of our pin, but they sure come to mind in consideration of the space between the atoms of our Earth, so great as to allow a neutrino to whip on through, unimpeded by the tug of gravity holding those atoms together, or the space that is, by some other force, pushing them apart. How can that be? All while the giant and clumsy photon can barely pass through my green house panels, only to get locked up in the flimsy leaf of a fern, captured and forced into servitude of photosynthesis. And this, after lightyears of travel across the universe. What an ignominious ending. Or maybe not. Maybe a wonderful beginning. Jeesh! Another toke, bro. LOL!

To the OP

If we first assume the universe started with a Big Bang, then there should have been a shock-wave extending out from the center. — Don Wade

The big bang theory does not posit an explosion into space from some point in that space. Any simple description on the web will tell you this. The expansion of the universe is not a speed, and is measured in different units. Pfhorrest seems to know the physics.

Science tells us that the shock-wave could not move faster than the speed of light. Did it?

Science says no such thing. It makes no mention of a shock wave, which is something you get from say a star exploding in space. The universe isn't an object in space like a star.

the diameter of the universe is about 90 billion light years — T Clark

The diameter of the visible part of the universe is about that. That volume includes all the material that can possibly ever have had a causal effect on us today. It doesn't mean we can see that far. Any light that has ever reached Earth up until the present has never been further from us than a proper distance of under 6 billion light years. Measured that way, the size of the visible universe is under a 6 BLY radius. We can only see these really distant galaxies because they were much closer than that distance back when they emitted the light that we're seeing now.

Which is why preliminary definitions are useful. — tim wood

Indeed, definitions are fine so long as they are not definitive...

That is precisely the argument which I had sought to make earlier; while the so called light-cone of the universe is available to us, this applies only in part, and even under the assumption that a far greater portion of which could be sighted through some technological means, those photonic emissions made by the corresponding point-source are at such a distance that their image may not even reach us across the entire lifespan of the universe so as to thereby preclude their reaching us outright. Under all circumstances then, and unless the rate of expansion slows considerably enough to no longer appear superluminal, such images will be forever confined to the immediate wake of expansion.

The universe isn't an object in space like a star. — noAxioms

Then what is the universe? That is, something other than it started with a big bang. Does the universe exist in space, or does space exist in the universe? Which came first, space, or the universe?

I like it! Gotta keep a sence of humor.

Under all circumstances then, and unless the rate of expansion slows considerably enough to no longer appear superluminal — Vessuvius

Again, the expansion rate is expressed in different units and thus is not a speed and cannot be meaningfully compared using a word like 'superluminal'.

Then what is the universe? That is, something other than it started with a big bang. — Don Wade

A reasonable definition, but still dependent on serveral assumptions such as your chosen interpretation of QM. An MWI guy for instance might say that the universe is the one universal wave function. Any follower of a realist interpretation (MWI being one of them) might say that the universe is all that is. I learn towards the RQM side, but I'm hesitant to say the universe is all that I measure since that confines it to the visible universe, and it needs to be meaningful to talk about more distant things, however much those things don't relate to us.

Does the universe exist in space

No model supports that. It is a naive interpretation that is quickly falsified.

or does space exist in the universe?

Time as well since it is the same thing. Few can get their heads around time being part of the universe rather than the universe existing in time, which reduces its ontology to that of a mere object.

Which came first, space, or the universe?

Great example of trying to think of the universe as being contained by time. The universe is not an object. Spacetime is part of the structure that is the universe.

With respect, your question appears to me a rather senseless one. The available evidence indicates that it began as a tightly bound singularity, of such density, and extremes of temperature, and so well-compressed that the traditional constituents of matter cannot be spoken of, at least not in a meaningful way when examining this state. Only during the Planck Era, having lasted for a duration of approximately 10^-43 seconds beginning after the start of expansion, when the forces of gravitation began to separate from the electromagnetic and nuclear forces with which they were formerly unified, did temperatures start to reduce enough to permit the formation of matter as we generally understand it. Though, even in this case, fully-defined atoms began to emerge only during the Inflationary Epoch at which temperatures reduced overall by a factor of nearly 100,000, and which itself had succeeded another transitory phase whereby the separation of gravity as a distinct force was completed. It was during the Inflationary Epoch that the seeds of the universe's large scale structure were sown on account of the Quantum Fluctuations which in the immediate moments when expansion first initiated, caused certain discrepancies in the distribution of matter, and thus a differing level of destiny across unique regions, to emerge, which were then amplified proportionally in their scale as the metric of space rapidly changed to accommodate something much larger.

It is thence a rather misleading characterization to say that the universe "started" with the Big Bang, as it always existed beforehand, just in a state so unlike anything we can conceive that one cannot speak of it meaningfully.

You seem to have misconstrued my words; I know it to be the case that the rate of expansion is expressed in units separate from that of more traditional ideas of velocity, but as seen from the perspective of a fixed observer, relative to some far off position which is of so large a scale as to make the effects of such expansion dominate, for all intents and purposes it does appear to the observer as though a superluminal velocity is attained.

Do notice how I qualified my statement with likening its chosen object only as appearance, rather than an absolute. As my argument certainly wasn't that this reference frame is somehow privileged, or the only one of merit. The purpose for which I cited it was instead to highlight how ideas of causality are meaningless in these cases because the light-cone of the observer is forever prevented from accessing the image of such distant point-sources, and nothing more.

but as seen from the perspective of a fixed observer, relative to some far off point which is of so large a scale as to make the effects of such expansion dominate, for all intents and purposes it does appear to the observer as though a superluminal velocity is attained. — Vessuvius

The rate of increase in proper separation of a sufficiently distant (and visible) galaxy does indeed increase at a rate greater than c, but this still isn't superluminal since the light emitted by that galaxy in a direction away from us is moving away from us even faster. Nothing is outrunning any local light as you know.
The speeds expressed are relative to a non-inertial coordinate system and relativity theory doesn't forbid object or light from moving at speeds above c relative to a different kind of coordinate system, so none of this is particularly contradictory with anything.

Minkowski spacetime does contradict the geometry of the universe. Given Minkowski spacetime, light will eventually get from any location to any other. There are no event horizons. Not so with our universe, so Minkowski spacetime (typically assumed by any naive description of bang happening at a location and filling pre-existing empty space) cannot describe our universe.

Do notice how I qualified my statement with likening its chosen object only as appearance, rather than an absolute.

I did, but there's not much appearance to it. We see redshift and brightness, both of which approach infinity and zero respecitively with subluminal local motion, and from that glean the speed. If we wait long enough, we see the object get smaller over time, but not so much that it appears to move super fast. Take GN-z11 which at redshift z=11 is the most distant galaxy know. Yet it subtends an angle that places it only about 3 billion light years away, making it appear to move quite slowly actually. Speed from appearances is a calculation relative to a model and a coordinate system, not something that can be directly measured just by looking at it.
I think that under a Minkowski inertial frame, the most distant object visible would appear almost 7 billion light years away. I mapped the universe to such a coordinate system as best I could once. It almost works if expansion is uniform and not accelerating, but there's simply no way to work dark energy into it.

As my argument certainly wasn't that this reference frame is somehow privileged, or the only one of merit.

Good grief, I never caught a suggestion of that in your posts.

The purpose for which I cited it was instead to highlight how ideas of causality are meaningless in these cases because the light-cone of the observer is forever prevented from accessing the image of such distant point-sources, and nothing more.

You're talking about objects outside the visible universe? A few will become visible as that radius expands, but most never will. As a non-realist, I cannot say that any of those objects specifically exist relative to us, but someone positing an objective state of the entire universe would say that these distant objects do exist, any one of which is receding from us at an arbitrarily high rate.

It is thence a rather misleading characterization to say that the universe "started" with the Big Bang, as it always existed beforehand, just in a state so unlike anything we can conceive that one cannot speak of it meaningfully. — Vessuvius

I admire your effort in expressing your thoughts. I'm trying to grasp the the image, but there seems to be a "leap-of-faith" in the transition of events as you progress from a "tightly bound singularity". Maybe I'm missing it when you state "one cannot speak of it meaningfully". I'm looking for a continuous cause and effect but I'm just not visualizing it - and, maybe that's what you were pointing out?

I am aware of how on a practical level the degree of redshift of a point-source as experienced by a distant observer increases to infinity in correspondence with a like decrease in its observed energy. I am aware as well, of how because we are restricted in our ability to observe only any portion of the universe, and that one cannot physically catch sight of such superluminal motion, for the reason that the local photonic-emissions, such as you yourself noted, are receding from the observer's position at an even faster rate. It is in likely consequence of this physical inability, that notions of proper causality breakdown, and therefore are deprived of all application when examining these sorts of instances; and, while I cannot attest to the deficiencies of Minkowski Spacetime that you alluded to, nor the degree of redshift experienced in select cases, my purpose was to show why this sighting of so-distant an object is forbidden, such that it resolves into contradiction when one assumes its exercise of a causal influence on things within the context of the observer's respective light-cone.

Notwithstanding our dispute over the aptness of "Superluminal" as a descriptor, at least as pertaining to the current discussion, I am in agreement with and thus recognize as true, every concern you raised. In fact, on several occasions I myself made the same points, with an example of this being that we may never even have the opportunity to observe certain signals because to ever reach us, they must cross a greater distance than the duration over which the universe exists, or is otherwise expected to before it reaches a state of maximum Entropy, will allow for.

I assure you there applies no leap of faith when one restricts analysis to moments after the Big Bang occurred, rather than before; this is because of the latter's inability to be either modelled or conceptualized with our current methods, and that in such a state, every means available to us collapses on its head. Only insofar as we conceive of a Unified Field Theory, in which all the forces of matter and causal interaction are treated as one, and able to thereby be quantized on the smallest of scales, can we hope to move forward in our analysis of its earliest stage of development, when there was found only the associated singularity.

Context of argument, is of more relevance than anything else, herein.

I do have one example against a 'bang from a location in otherwise empty space' which is that if such a thing occurred, all the mass of the universe would be compressed into a small space and would form a black hole, preventing any explosion (and shock wave) into said empty space.

On the other hand, an expansion of arbitrarily high compression of mass/energy (as posited by the BBT) would still involve a reasonably uniform distribution of mass and energy over all of spacetime, not at all meeting the stress energy tensor conditions of a black hole.

I think there is reason to note that while the conditions of that stress-energy tensor which is characteristic of a Black Hole are left unsatisfied in the case of a mass subject to an arbitrarily high-degree of compression, at least insofar as it is allowed to expand so as to not again revert into a singularity, certain discontinuities do emerge because of fluctuations in how it is distributed on the Quantum Scale; this, being a consequence of the Exclusion Principle, which induces a repulsion at the inter-atomic distance between any number of Fermions such that they are forced to occupy unique states and thereby be set at some distance from each other. Following a period of expansion, these fluctuations are amplified in scale according to how far the underlying metric of space has been lengthened. This same effect is responsible, so far as we know, for the large-scale structure of the universe and why in particular, bodies of mass tend to congregate in so-called Cosmic Filaments which extend in size to several dozen megaparsecs on average and themselves consist in hundreds of unique galactic-clusters. While the corresponding 'gaps' which emerged during the initial stages of expansion are now accounted for by 'Voids' of equal size to the aforementioned filaments, but consisting instead largely of empty-space.

As T Clark suggests, we should acknowledge proven undisputed evidence, and then distinguish it from theory and speculation. All are fine so long as we recognise what each element represents.

Science is confident about the minimum size of the universe today in absolute terms. It is also confident about what the speed of light can achieve in normal circumstances today. Clearly the maths which T Clark pointed out is self explanatory if you believe in the Big Bang. The universe must, in absolute terms, have expanded faster than the recognised maximum speed of light.

As I have pointed out in other threads, the principle that 'the speed of light was the maximum that could ever be achieved', was and remains speculation. It's not been a bad supposition for our limited circumstances and for our development of such things as atomic energy, but that doesn't have to extend to the cosmos.
When the evidence clearly says that, in certain conditions, it must be possible to travel faster than the speed of light in absolute terms, then we are fools to ignore it.

Indeed, in this respect, relativity is open to too many variables to provide a comment on this - when by its nature, any 'absolute factor' must take precedence over relative readings. The width of the universe is such an absolute - and a figure that wasn't available to Einstein.

The inflation of space was a notion dreamt up purely to preserve the notion of a fixed value for the speed of light as currently measured. It has no evidence to support it and only exists to preserve doctrine over substance.

The conversations on this thread have also blurred a number of other factors.

There is a difference between:- material moving outwards; a shock wave; and space itself expanding.

I feel that in normal language, suggestions of a shock wave would need some medium in which to generate the wave, (as others have suggested). You may argue that Dark Energy might constitute that wave, but Dark Energy is just theory and has no physical evidence to support it either. So it may not be correct - and I give an example of a simple alternate theory below.

However, for the moment, I'd like to set the context for all potential explanations. The 9 year results of the WMAP programme clearly stated that the dimensional lines run straight and are not bent as far as we can tell. Therefore by implication, they run to infinity and so space itself may genuinely be infinite.

Whether that means that space is 'something' rather than emptiness is hard to fathom. Finipolscie speculated that space may represent the framework for existence - quite apart from any material or energy that might occupy it.

His logic was along the following lines :-

If you were on the leading edge of the expanding material from the Big Bang and could see a location ahead of you which you can identify and move towards, then that space must exist in some form. He also pointed out various ideas that say there are a small number of core factors in existence which shape everything else. I think he said there were 6 - which he likened to settings on the 'control panel which governed the rules of existence'.

I have found other authors who make the same point. There 6 parameters, and each of them could, theoretically, have had any of a whole range of settings - each potentially resulting in very different manifestations of the universe..... but why they settled on the settings that they did, is unknown.

However we are also unsure of what makes existence conform to those settings, and therefore we speculate about a framework for existence, although we don't know how it might be imposed. It is this which suggests that space may be more than simply 'location' - and not just the material or unidentified Dark Energy which may occupy it.

The idea of Dark Energy was entirely driven by the finding that the redshift was increasing - from which people assumed that the expansion was accelerating. However, there is no need for Dark Energy if the original Bang-Crunch model of the universe is applied fully.

Think about it. The increasing redshift could just mean that we have entered the crunch part of the cycle in which case, Gravity would be causing that acceleration - there would be no need for Dark Energy.

The inflation of space was a notion dreamt up purely to preserve the notion of a fixed value for the speed of light as currently measured. It has no evidence to support it and only exists to preserve doctrine over substance. — Gary Enfield

What you're asserting then, is that the near entirety of Inflationary Cosmology, as physicists apprehend it today, is a facade.

Indeed, in this respect, relativity is open to too many variables to provide a comment on this - when by its nature, any 'absolute factor' must take precedence over relative readings. The width of the universe is such an absolute - and a figure that wasn't available to Einstein. — Gary Enfield

Relativity, despite what its name suggests, is not a triumph of 'relative' readings over 'absolute' ones; despite that you haven't elaborated on what they even entail for you. Einstein geometrically interpreted the universe with a four-dimensional Lorentzian Manifold, whose metric tensor varies with time (again, the tensor equivalent of cosmological inflation). You can't straddle between two, antithetical narratives. Either abnegate General Relativity, and be a proponent of nonstandard ideas - or accept it, with all its known implications (inclusive of an expanding universe - wherein observed, absolute distances on a fabric can exhibit velocity differentials superior to c, without the material on that fabric ever defying SR in localized regions).

Hi Aryamoy Mitra

What you're asserting then, is that the near entirety of Inflationary Cosmology, as physicists apprehend it today, is a facade. — Aryamoy Mitra

I am saying, very clearly, that Inflationary Cosmology was specifically proposed to preserve the notion of a fixed speed for light. It may be true, but it lacks any real evidence.

When it was pointed out that objects in space were not inflating, (which they should if space itself was inflating), then a 2nd round of gobbledygook emerged to try and justify the nonsense, despite the simple evidence. You are arguing for doctrine of substance - because you have no actual evidence for inflation as opposed to the basic implication of faster than light travel.

You can't straddle between two, antithetical narratives. Either abnegate General Relativity, and be a proponent of nonstandard ideas - or accept it, — Aryamoy Mitra

I think I can just about guess what this jargon means - but you seem to be suggesting that I am jumping around between theories, when I am not. I am simply saying that the evidence of distance divided by time - when applied to absolute and agreed values, trumps vague notions based on doctrine over real substance.

As I said before. I acknowledge that your preferred theory may one day be given substance, but it hasn't yet - and the historical fact remains - it was dreamt up to preserve a fixed C

I think I can just about guess what this jargon means - but you seem to be suggesting that I am jumping around between theories, when I am not. I am simply saying that the evidence of distance divided by time - when applied to absolute and agreed values, trumps vague notions based on doctrine over real substance. — Gary Enfield

$Ds/Dt$ can parameterize unchanged spatial distances, on a Minkowski metric - not on a varying one.

As I said before. I acknowledge that your preferred theory may one day be given substance, but it hasn't yet - and the historical fact remains - it was dreamt up to preserve a fixed C — Gary Enfield

I'm not contending that fixing C was one of SR's postulates; all I'm stating is that there exists a valid and demonstrable interpretation of cosmological inflation, that is consistent with that postulate.

For what it's worth, this isn't merely a preferred theory; it's what the majority of Physicists will attest to (not an appeal to authority, but a testament to its perceived credence).

unsatisfied in the case of a mass subject to an arbitrarily high-degree of compression — Vessuvius

Unsatisfied in the case of uniform distribution everywhere. The level of compression has nothing to do with it. The current density of the universe (about 6 protons per cubic meter) is enough to prevent expansion if it was that mass expanding into empty space. None of the material would have sufficient recession speed to exceed the escape velocity of the bounded mass that comprised the occupied part of the universe.

I am curious as to how the current density would have any influence on either the physical possibility of expansion, or the degree to which it occurs. In what way then are these two factors correlated, in particular, or otherwise based upon a mutual relationship of causality?

Science is confident about the minimum size of the universe today in absolute terms. It is also confident about what the speed of light can achieve in normal circumstances today. Clearly the maths which T Clark pointed out is self explanatory if you believe in the Big Bang. The universe must, in absolute terms, have expanded faster than the recognised maximum speed of light. — Gary Enfield

Gary, I really like your post! In my opinion, It reflects a lot of insight.