Time, Gravitation, Acceleration, and their effects. Or wibbly wobbly timey wimey.

[Val]

... I've heard the metaphor of being like you're running on a track and the track is stretching as you run, but because the track is simply "space" it doesn't count as matter breaking lightspeed. But if it's literally "nothing" that is doing this, how is it expanding? Or a better question would be, exactly WHAT is expanding?

Edited August 23, 2015 by Val
Missing words

[theend3r]

I read this very interesting thought experiment somewhere that tries to explain space.

Imagine yourself as an astronaut floating in space. Now you start yourself spinning like a ballet dancer. When you spread your arms you can feel the centrifugal force pulling at your hands. Now we remove all matter, light and energy in the whole universe, except you. So the universe is now completely dark and only consists of empty space and you spinning like a top. You would still feel the centrifugal pull on your hands if you spread your arms. But there is nothing else in the universe that you could be spinning relative to. Except, you are spinning relative to space.

Space is something.

It is that exact same space that governs the speed of light.

http://boards.straightdope.com/sdmb/showthread.php?t=500974

[rtxoff]

I read this very interesting thought experiment somewhere that tries to explain space.

Imagine yourself as an astronaut floating in space. Now you start yourself spinning like a ballet dancer. When you spread your arms you can feel the centrifugal force pulling at your hands. Now we remove all matter, light and energy in the whole universe, except you. So the universe is now completely dark and only consists of empty space and you spinning like a top. You would still feel the centrifugal pull on your hands if you spread your arms. But there is nothing else in the universe that you could be spinning relative to. Except, you are spinning relative to space.

Space is something.

It is that exact same space that governs the speed of light.

The thing is that space can only be something because there is matter and vice versa. An astronaut which is a whole universe might follow entirely different physical rules as we have them in our universe. Space without matter is pointless.

There must be something to be able to measure distances between or have an spatial orientation to something else. I am also going as that far saying that an astronaut being an universe can't rotate as described simply because there is nothing else he could rotate relative to (not even space).

[K^2]

You would still feel the centrifugal pull on your hands if you spread your arms. But there is nothing else in the universe that you could be spinning relative to. Except, you are spinning relative to space.

[PB666]

It has been said that this is the very reason that Einstein was hesitant about publishing General Relativity. It seemed wrong to him that one can experience acceleration even if you remove any matter that can be a source of reference. It is a violation of Mach Principle. And there are still a lot of people unhappy about it.

But there is no such thing as an empty space, really. Remove all matter, and you are still left with fields. That's what vacuum really is. A bunch of interacting and self-interacting fields in their ground state. I'll be first one to admit that it's weird that you cannot measure velocity relative to these fields, while you can measure absolute acceleration. But such are the underlying symmetries.

There is an underlying assumption here that we know what all the fields are. There maybe a field by which you could measure velocity against, a static wave that expands, stretches and appends itself from the initial inflatron. You can measure angular momentum with light, since angular momentum creates inertia you really can't measure it against graviational waves. I should point out that empty space may create a outlet for the introducion quantum singulaties as some of the multiverse theories posit.

I don't think its odd that space is made up of a fabricy kind of field. Sort of reminds me of the wizrd of Oz, looking behind the facade then old reality no longer makes sense and all we see are blips in the fabric. But I don't think humans are there yet, because if we can tamper with the most basal properties of space time (space and time) we have to assume that uncertainty works at this level also, and if we can register its existence, then we havealso the same ability to manipulate in uncertain ways. If the predictions are correct space-time is expanding, warped yes, but those warped areas are expanding away from other similarly warped areas at an increasingly faster rate, which means even black holes cannot cease the acceleration of Space time. So at some level our known energy manipulates space-time, but at another level our known sources of energy are insuuficient to explain all its motion, which implies a more deeply rooted space-time behavior is present. Manipulating space-time at this level may have unforeseen conquences. if we can cause quantum scale spikes at GeV to TeV range and still somehow miss this then I wonder how much energy such a field contain, but then you think about the energy pouring into the inflatron, if only a small fraction of this resulted in inertially relevant energy, how much dark energy must have poured into space time to create the inflatron itself, and its apparently still out there working. If you see the field then I would estimate that everything else in it looks rather trivial. The fact that space-time began accelerating again warns Us that its properties are not clear. That ther are deeper and more powerful forces working

It would be humorous however if the EM drive and it dialectric radiowave resonator was capable of surfing it. Unlikely.

Edited August 23, 2015 by PB666

[K^2]

There is an underlying assumption here that we know what all the fields are. There maybe a field by which you could measure velocity against, a static wave that expands, stretches and appends itself from the initial inflatron.

No, that is completely wrong. We don't know what all the fields are, but we do know the local symmetries they must obey. Poincare symmetry group is one of them. That's all the information we need to say that it's impossible to measure velocity relative to a ground state of any of these fields. Now, if you have excitation in these fields, and these excitations are massive (either due to mass of the fields, or due to self-interaction), then you can measure velocity relative to them. But since these excitations are otherwise known as matter, that shouldn't be a surprise.

If there exists a field that does not satisfy that particular local symmetry, then conservation laws are wrong. See discussion in EMDrive thread on just how improbable that is. The only reason I don't use the word "impossible," is on technicalities. But for all practical purposes, it is.

[PB666]

No, that is completely wrong. We don't know what all the fields are, but we do know the local symmetries they must obey. Poincare symmetry group is one of them. That's all the information we need to say that it's impossible to measure velocity relative to a ground state of any of these fields. Now, if you have excitation in these fields, and these excitations are massive (either due to mass of the fields, or due to self-interaction), then you can measure velocity relative to them. But since these excitations are otherwise known as matter, that shouldn't be a surprise.

If there exists a field that does not satisfy that particular local symmetry, then conservation laws are wrong. See discussion in EMDrive thread on just how improbable that is. The only reason I don't use the word "impossible," is on technicalities. But for all practical purposes, it is.

This sounds like a challenge, but as i mentioned if such a field existed it might be difficult to measure with it or against it meaningful way, this will probably be one of the Universes deeply held secrets. I don't believe EMD is exploiting such a field although it would be humorous if it was because such a feably designed device is some how digging into to root of space time and slapping it about a bit. Also scarey however if true somene could find away to stretch space-time and place planets in more distant orbits. Or move earth to a higher orbit to deal with climate change.

There is always the potential of a lower layer. Poincair group isometries are special relativity, which means at plancks scale they may not be strictly obeyed. But even without this, i could see this as a layer that was active during inflation and is pretty much in a passive state now ........ que sera, sera.

You forget, we don't know what caused the Universe to accelerate its expansion. The current evidence suugest it is not repulsion in galaxies, and the pressure of gases between galaxies is two low to explain this which leaves, inevitably, space-time itself, that which was inflated. So yeah the may be limiting anchoring of something a wobbly tidal like feild that expands, stops, accelerates. The density of matter in space falls too low and it somehow increases the separation between itself and others. It could be quantum gravity itself that keeps it from accelerating and when Q G falls too low it begins inflating again.

[K^2]

Poincair group isometries are special relativity, which means at plancks scale they may not be strictly obeyed.

General. Specifically, Poincare Group is the gauge symmetry of the gravitational field. It's the reason we have space-time curvature.

You forget, we don't know what caused the Universe to accelerate its expansion.

I do not forget. It's irrelevant. We don't know what the source of that expansion is, but we can measure acceleration, which means we can estimate the curvature, which means we can derrive the stress-energy tensor that's driving the expansion. Think of it as early electrodynamics. We have not yet discovered an electron, but we can understand electric charge.

Knowing which field it is, spcifically, that carries this particular charge is irrelevant. It'd be nice to know, because it might help us expand the standard model. But it doesn't change anything about our understanding of General Relativity and how relative velocity vs relative acceleration work. Because that's down to symmetries. And these are in perfect agreement with accelerated expansion.

[PB666]

Knowing which field it is, spcifically, that carries this particular charge is irrelevant. It'd be nice to know, because it might help us expand the standard model. But it doesn't change anything about our understanding of General Relativity and how relative velocity vs relative acceleration work. Because that's down to symmetries. And these are in perfect agreement with accelerated expansion.

You are wrong, while it does not prove that there is a wobbly static field in space-time it does tell us something fundemental about space time, because if we can verify that it is not due to repulsion of galaxies, then space time itself has a structure, if that were the case the FTL travel, Warp fields, And Time travel backwards would be impossible, things like wormholes would also be impossible. And since we have not observed any of these relativistically speaking then I would argue that space does have structure and this is what is causing the observed acceleration. The next step is to assert that each quantum unit of space has a fixed coordinate at a given time, this is more speculative.

Think about it, two galaxies whose origin in the inflaton is 20' span that had been receding from each other for 10 billion years at one rate, then they begin receding at a second rate. Either gravity has changed, and this is not sufficient to explain the inflation or some other behavior is operating. The galaxies are two far apart to be explained by any other field except purturbations in space-time iitself. Its in escapable that something much more fundemental than our current understanding is at work, since it is niether explained by relativity or QM it needs niether abide by them. The tensor may not be felt after all. How good is your model of acceleration, and after having read several recent papers on gravity each group is getting a different result for G, sometimes better equipment is giving more anomolous results. Tell these folks why we don't have an accurate assessment of G past 6-7 digits. If you can explain that and also the behavior of quantum gravity, then I would be more willing to concretize my beliefs like you have.

Other issues on Poincare will be dealt with later.

[Findthepin1]

Earth is moving around the Sun at 30km/s. The sun is moving around the galaxy at 230km/s. The galaxy is moving toward a ludicrously massive object called the Great Attractor at 626km/s. So at any given moment, the Earth is moving at a minimum speed of 366km/s, or 0.122% c. Why don't we see any time dilation here?

[K^2]

You are wrong, while it does not prove that there is a wobbly static field in space-time it does tell us something fundemental about space time, because if we can verify that it is not due to repulsion of galaxies, then space time itself has a structure

Woah. Does not follow. At all. All it tells us is that whatever carries that dark energy charge^* is spread throughout the universe, rather than being concentrated only at galaxies. This does not imply any new structure to the space-time. Only that there is a (probably) unknown field that interacts with gravirty differently than ordinary matter. Which would follow from the charge.

^* I keep using the word "charge". I should clarify that I mean a conserved charge of the relevant symmetry. E.g. the charge of the U(1) symmetry is the electrical charge. Since we are talking about Poincare symmetry, the conserved charge is the stress-energy tensor. Specifically, if I recall correctly, dark energy appears as a pressure term. Which isn't exactly the same thing as conventional gas-in-a-container kind of pressure, but there are parallels, hence the name.

So at any given moment, the Earth is moving at a minimum speed of 366km/s, or 0.122% c. Why don't we see any time dilation here?

Time dilation is relative. Relative to Great Attractor, Earth is time-dilated. Relative to us, it's the Great Attractor that's time dilated. If that's confusing, look up Twin Paradox on Wikipedia.

Edited August 24, 2015 by K^2

[PB666]

Woah. Does not follow. At all. All it tells us is that whatever carries that dark energy charge^* is spread throughout the universe, rather than being concentrated only at galaxies. This does not imply any new structure to the space-time. Only that there is a (probably) unknown field that interacts with gravirty differently than ordinary matter. Which would follow from the charge.

The latest study I linked here says the effect of dark energy is not observed between particles within galaxies, it appears to only occur between galaxies at great distances. So yeah it implies that space-time is restructuring itself between galaxies. I don't think that gravity is sufficiently powerful enough to explain the expansion, if you can show otherwise, I might believe it. Gravity shifts (lowering G) could result in a differential slow down, not an expansion, and expansion has to be an effect above and beyond gravity or reductions in gravity, or have you know a gravity to create and anti-gravity well? The alternative is that inflation of space-time was always there, but as the universe expanded the extent of gravitational attraction has faded over distance, that F = G M1M2/r2 or time. I don't think this is sufficiently powerful explanation either, but if substantial amount of energy has been lost in the universe due to conversion to energy that is no longer gravitational . . . . .

I should clarify that I mean a conserved charge of the relevant symmetry. E.g. the charge of the U(1) symmetry is the electrical charge. Since we are talking about Poincare symmetry, the conserved charge is the stress-energy tensor. Specifically, if I recall correctly, dark energy appears as a pressure term.

key work being appears. This were my thoughts initially but I have been changing my mind, mainly because there is no strong evidence for this and the trend of evidence counters this, and there is no leverage for pressure effects (at least not in galaxies). Acceleration of space-time is also with its sets of problems, but then it is without precedence.

So lets go through the pros and cons.

Lets say something is interfering with action of gravity across great distances.

1. We start out with space-time expanding at a rate set forth by inflation

2. The particles in that sea are attracted to each other by gravity, as a consequence they begin slowing relative to each other and to space-time (assuming that particles add energy and thus would have more gravity than vacuumless space). Light on the other hand slows down much more slowly and its momentum would change less.

3. What we have is the opposite, that particles are accelerating relative to space time, but relative to each other (in close proximity) they behave as if gravity is a dominant force, so that only at great distances is this acceleration of any importance.

Next lets argue its a pressure, what type of pressure might it be, hydrogen (that is matter) or dark matter? We know the temperature of hydrogen between galaxies, there is not enough hydrogen of high enough energy to amount to squat. Dark matter flux would be noticible (see below). That would have to have come from another inflation which would have inflated faster than the first, if it passed around galaxies the galaxies would have lensed its presence and you would see a peculiar gravitational lensing on one side, the same side of all galaxies that changed with the curvature of space time granted by the inflatron. Ok so if its electrostatic pressure, then the plasma ejected by GBHs would be deflected either one direction or the next. If it were neutrinos, we would all be dead.

Can't really be pressure, can't really be gravity. Either its a new unknown field that pulses everthing with inflation, or space time itself is inflating, either way we can't tell the difference.

So lets go into Poincare, 10 part group isometries, the full symmetry of special relativity. These include the special transformative relationships in space, including rotation and time effects. The light equation follows that speed of light is equal in all directions indifferent point in the direction of earth turning and direction of revolution or the receding directions.

This means that there is no relative position or time better than any other position or time, a corner stone of relativity and which should not be doubted and taken as absolute but below planck's time interval. With a fixed velocity for C that never varies, and that we have never seen vary in a vacuum, C defines Planck's velocity and given Planck's time defines Plank's unit of length. Within the space of planck's time and length, C can vary. So basically if there was a spatial coordinate system in the universe, it could not be operating at the quantum level or any level above (relativistic or classic physics), which means it would have to be physics that operates so basally that even quantum mechanics is subservient to it. Transformations would have to occur inside the planck's scale. It could even be a fluctuation of the planck's scale in different parts of the Universe, ripples of QM. It could be anything that is two small for us to observe in any meaningful way. IOW the observed inflation could be a ripple through the universe that disturbed QM and may have cause a faster replication of a small amount of vacuum space. There is out there a theory that claims that if space gets empty enough of matter and light, that on response may be to inflate, of course in that theory a new universe would spring forth as big-bang post-singularity.

So the problem basically is, if manifestation of dark-energy is in space time, then the increases in red-shifting due to acceleration has also to be manifested in the propogation of field through quantum time and space, the perturbations are then corrected and we cannot observe the inconsistency of the inflation event. For example, light from a more distant galaxy is traveling through an area as space-time has accelerated its expansion, so how should that effect the wavelength? Theoretically it should not affect the wavelength, and we should not see increased redshifting, but we do, so that this would have to be corrected in the manifestation of the basal level into quantum level. Or the time spent crossing the inflationary event is so small compared to time spent traveling across post-inflated space, that we don't detect that there was a meaningful blue shift. In this case the Universe could be substantially older than the estimates. Alternatively as it is traveling through an area, then space cannot inflate, the photon essentially blocks inflation and therefore it maintains a frequency consistent with its origin and shift of speed. There is not going to be many volumes of space where this condition would be valid, except the smallest units of space. Which then implies that space must have a unit.

So what if its a new unknown field. Ok so what if it is, and what if that field propagates in a lower level of physics, a special level that interacts only with QM. Then we have a new set of metrics, probably of a statistic nature, that are then used to specifically explain how quantum mechanical phenomena are generated. Its not particularly an issue of contradicting relativity, it would remain intact for all intents and purposes, its more of an issue of trying to fit a very local specific energy pattern into the concept of dark energy. The other thing is that there is a basic assumption that its frame of reference would be material, but it could actually be expanding away from us at near the speed of light, and the third stipulation that it has to have been consistent, in other words once the field is turned on or up, its stays on or up. However it could be sporadic. The only thing that really fits is instability in space-time whose result is an apparent acceleration.

Which isn't exactly the same thing as conventional gas-in-a-container kind of pressure, but there are parallels, hence the name..

pV = NRT. The pressure is created by the action of vibrational energy on atoms and molecules. The vibrational energy cannot interact at distances were dark energy is observed acting, and even fields could not operate since they would need to exceed the speed of light. The energy could be pouring into space-time itself, not into matter. We may be observing an increase in potential kinetic energy differences, but the things we are measuring kinetic energy differences with are traveling so far away, it would be a physical impossibility for the two objects ever to translate relative to each other. At 5 billion light years in light age and accelerating away from each other, light from these places leaving now may never reach us, thus it may be consistent that no pressure need be involved. This all could be a sign that the universe is beginning to fracture, possibly into a multiverse, with the specific arrival of domains that have not inflated recently and others that have inflated moreso, and will inflate even more as they spread apart.