Gravity Works Like This

[Undefined]

Morning, Grumpy.

RC



Did the fact that ancient Greeks thought the sun was a Chariot of the Gods(bet you wondered where that name originated)have any effect on the accuracy of their calendar? Spacetime has been confirmed by direct observation and extremely precise measurement. Whether or not it is the final word, it accurately describes and predicts the real behavior of the real Universe without relying on ad hoc abominations like epicycles. So we will keep using it until a better, even more complete understanding evolves, just like we kept using Newton(and still do except in extreme conditions)until Relativity evolved.

Farsight



That is time's definition, an artificial construct to measure a real thing, time. All mathematical descriptions are maps of a very real territory, or we would'nt bother drawing them.

You guys have no shame. The idiocy of what you post has been exposed and you don't even know enough about the subject to know that, you learn nothing and deny all presented data. Trolls.

Grumpy

Mate, why do you persist with all these irrelevant philosophical soliloquies and 'non-explanations' instead of listening to the science presented to you in real empirical terms not just more of your impressions based on abstract interpretations of observations?

Get once and for all that observation, measurement, calculation and prediction based on abstractions may be and has been useful, but in no way do they EXPLAIN the underlying reality in terms of entities/mechanisms. That is what EINSTEIN was trying to do in his later years by trying to marry Quantum Mechanics with the GR concepts. But he failed, because his PARTIAL abstract math model and the the PARTIAL math model of QM cannot either in concert or separately ever become a COMPLETE reality model. Obviously, else the professional Relativists and QMers would have come up with the complete reality (not abstract math only construct) model of the universal physics, including GRAVITY without all the multi-universe and 'brane/String and other math-turbative desperations in lieu of actual understanding the reality itself instead of going further and further away from it via math abstractions which Einstein himself saw the encroaching and misleading incomprehensibility potential of way back when!

You haven't even acknowledged Sir Roger Penrose's explanation of what 'time' is and is not in reality terms. Nor have you acknowledged Sean Carroll et al's real experimental tests that prove reality energy-space at its fundamental level is flat Euclidean and extending to infinity beyond observable universal volume.....which makes the BB 'beginning' and other "non-Euclidean' interpretations/hypotheses of energy-space a non-starter and highly suggests that all observations purporting to 'support' BB, Inflation, expansion etc 'geometries' have been MISINTERPRETED to 'fit' the BB biased 'theories', not facts indicating eternal and infinite universal processing energy-space extent fundamentally.

Grumpy, as a friend in both science and humanity, I urge you to stop the waffling and presenting abstraction and philosophy 'overlays' and 'interpretations' and 'impressions' of what you think it all means. Go back a re-read all that you've been told lately in more REAL EMPIRICALLY BASED terms and understandings/distinctions, and try to read them without old blinkers on. Just folloow the real things and drop the UNreal things you have accepted AS 'real'. Then you might want to come back and apologize to at least Maxila for unfairly treating him so nastily without any real justification at all in reality. as distinct from your biases which have led you into arrogant dismissals and personal insults of fairly put points and the persons putting them. Don't keep killing the messenger because you don't 'get' the real message that is evolving in the mainstream TOO even as we speak.

Try to have no hard feelings, Grumpy, Maxila, everyone....life's too short! Good luck and enjoy your future discussions!

 

[PhysBang]

That wasn't the point of my referring to Epicycles construct. The point is that Epicycles was a mathematical model ONLY, and explained NOTHING of the mechanisms and physics in reality terms, only in maths model construct terms.

Sure. And you speak in gross ignorance.

First, epicycles weren't merely a mathematical model, they were capturing observations. Additionally, their use revealed physical relationships that could be used to turn these observations into evidence.

And Newtonian Gravity was also a mathematical construct ONLY (it even ABSTRACTLY/MATHEMATICALLY inherently conjured up visions of "Instantaneous Gravitational Action at a Distance!").

So it wasn't correct in any way?

And even Einsteinian maths 'spacetime' construct has only abstraction 'explanations/interpretations' which don't identify the Gravity mechanism in reality terms, only abstract geometric terms as part of the math construct itself, not reality extant in entity/mechanisms terms.

What would "reality terms" look like? Is this a language of the divine?

OK? Stop with the trolling personal/evasion tactics and 'cheerleading each other' in same. Just either address and refute the new points raised in reality terms/context or just ADMIT that all you have so far is 'abstraction math construct' interpretations and assumptions which even Einstein began to bemoan when he said that "the mathematicians invaded my theory such that I no longer understand it".

I addressed your points: you are speaking ignorance and in uselessness.

You and your fellow trolls will bring dishonor to the physicist mainstream profession if you keep using troll evasion/personal/semantics etc tactics/excuses because, as Grumpy might put it: "Got nothing?"

You might assume that you have a point, but if you never learn anything about the science, then you can't enter into a discussion about it.

At least the REAL mainstream physicists are starting to catch up with this 'crank' (see my post #296 re "energy-space" to Russ for indication of that as recent as TODAY).

It is not the sign of a sane mind to take the use of the same sequence of letters (not even in the right order) to mean exactly the same thing.

 

[PhysBang]

Mate, why do you persist with all these irrelevant philosophical soliloquies and 'non-explanations' instead of listening to the science presented to you in real empirical terms not just more of your impressions based on abstract interpretations of observations?

Pot, kettle, black.

 

[Undefined]

Pot, kettle, black.

Easy for trolls to post such inane self-justifying one-liners. If you can't answer on the science points made then you are just posting self-justifying 'noise'.

So can you answer on the science points instead of continuing personal/opinion disparagements based on your own misunderstandings and abstract impressions? Thanks.

 

[Undefined]

Sure. And you speak in gross ignorance.

First, epicycles weren't merely a mathematical model, they were capturing observations. Additionally, their use revealed physical relationships that could be used to turn these observations into evidence.

So it wasn't correct in any way?


What would "reality terms" look like? Is this a language of the divine?

I addressed your points: you are speaking ignorance and in uselessness.

You might assume that you have a point, but if you never learn anything about the science, then you can't enter into a discussion about it.

It is not the sign of a sane mind to take the use of the same sequence of letters (not even in the right order) to mean exactly the same thing.

What do you think MODELS do, other than 'capture observations'? Are you for real, mate?

No-one ever disputed that's what models DO. The question is the INTERPRETATIONS from that model as to what the actual underlying reality entities/mechanisms might BE.

The point is that NO purely mathematical model OF the 'captured observations' can ever become a complete representation of the whole reality in entity/mechanism terms. Hence why Relativity, QM and String/Brane etc etc abstractions from maths have, even after so many DECADES, still not even explained the GRAVITY enigma (to them and in their abstract models).

Mate, if RE-THINKING everything you know is good enough for Sir Roger Penrose, Sean Carrol et al, it should be good enough for you and Grumpy et al. Yes?

Or do you all rate yourselves as 'superior' in knowledge and intellectual capabilities than Sir Roger and many other mainstream mathematical-physicists who ARE rethinking everything because of such 'cranks' as me and others who keep pointing out things previously 'swept under the 'carpet of evasion' tactics/attitudes which you STILL try on even though many mainstreamers have STOPPED such tactics/evasions (to their great credit. Kudos!).

Good luck.

 

[Undefined]

Farsight, you started the thread, but you seem to have assumed that everyone should just agree with you!

That's not the case as far as I and my slight disagreeing perspectives go in some of the 'details' and 'conslusions' which Farsight presents, OnlyMe. I actually try to understand and identify WHAT 'details' I and Farsight are not yet 'congruent' on. I and he can discuss the 'reality evience/implications' and go from there. No 'broad brush' impressions and attitudes on either 'side' there at least. So please speak for yourself, mate!

 

[Undefined]

Can you explain what this means in terms of the accepted mathematics of quantum mechanics? Can you demonstrate that a photon has the proper spin properties of a graviton?

If you can't demonstrate this, then why shouldn't we dismiss your claim out of hand as merely fantasy?

If someone has never learned the mathematics of GR, can they be said to have the same idea of GR as Einstein had?


Again, can you point to where Einstein included this idea in his exact mathematical formulation of GR? Or are you just lying about this?

The GRAVITON is a hypothetical particle, hence any 'properties' are assumed/attributed from equally hypothetical perspective/assumptions. So no-one can yet actually know what 'spin properties' such a still-hypothetical 'particle/entity' might/should have, except only in their own abstract hypothetical 'construct'. Which, until the 'graviton' is found to actually exist in reality physics, means any further speculation on hypothetical is neither here nor there and signifies nothing at all, from EITHER 'side' in the discussion.

 

[PhysBang]

Mate, if RE-THINKING everything you know is good enough for Sir Roger Penrose, Sean Carrol et al, it should be good enough for you and Grumpy et al. Yes?

You think me ignorant. You demonstrate that you are. You think that I never re-think things. You demonstrate that you don't even think once about this topic. I'm not sure what you seek to do with your high-school level of philosophy, but it's not going to add anything to our understanding of science or anything else.

 

[PhysBang]

The GRAVITON is a hypothetical particle, hence any 'properties' are assumed/attributed from equally hypothetical perspective/assumptions. So no-one can yet actually know what 'spin properties' such a still-hypothetical 'particle/entity' might/should have, except only in their own abstract hypothetical 'construct'. Which, until the 'graviton' is found to actually exist in reality physics, means any further speculation on hypothetical is neither here nor there and signifies nothing at all, from EITHER 'side' in the discussion.

That's a very interesting position to take in ignorance. Yet many scientists present good reasons to say that gravitons have a specific spin.

If someone wants to make claims, then they should back up these claims.

 

[Undefined]

That's a very interesting position to take in ignorance. Yet many scientists present good reasons to say that gravitons have a specific spin.

If someone wants to make claims, then they should back up these claims.

Hypothetical 'reasons' by any chance? Until they can prove the existence of a hypothetical 'particle' that is itself the speculative entity of a hypothetical construct that cannot YET even explain the mechanism for gravity and the coupling mechanism between mass/energy and energy-space that produces the observed gravitational phenomena, how can you sit there with a straight face saying things like that and then pretend to 'tell the cranks off' abot their own speculations (which in some cases are actually based in reality and not speculative fantasies pure and simple like that!). Get a grip on reality, PhysBang. Other mainstream scientists are starting to, maybe you should also if you wish to continue pretending to 'speak for mainstream', hey?

 

[Undefined]

You think me ignorant. You demonstrate that you are. You think that I never re-think things. You demonstrate that you don't even think once about this topic. I'm not sure what you seek to do with your high-school level of philosophy, but it's not going to add anything to our understanding of science or anything else.

Then why are you and Grumpy et al here ignoring what Sir Roger and Sean Carroll et al have been doing that puts your old hat insistences/interpretations into proper perspective as no longer true or supportable given the new reality re-think practically 'forced' on mainstreamers by the reality-based re-thinking observations/perspectives of some 'cranks' for some time now?

 

[PhysBang]

Then why are you and Grumpy et al here ignoring what Sir Roger and Sean Carroll et al have been doing that puts your old hat insistences/interpretations into proper perspective as no longer true or supportable given the new reality re-think practically 'forced' on mainstreamers by the reality-based re-thinking observations/perspectives of some 'cranks' for some time now?

You are fantasizing what I'm doing in the same way that you are fantasizing about physics. I am ignoring nothing. And, having met Carroll, I am quite confident that he would be horrified that you think anything he wrote is support for your claims.

 

[Grumpy]

Special Relativity

"Special relativity is a theory of the structure of spacetime. It was introduced in Einstein's 1905 paper "On the Electrodynamics of Moving Bodies" (for the contributions of many other physicists see History of special relativity). Special relativity is based on two postulates which are contradictory in classical mechanics:
The laws of physics are the same for all observers in uniform motion relative to one another (principle of relativity).
The speed of light in a vacuum is the same for all observers, regardless of their relative motion or of the motion of the light source.
The resultant theory copes with experiment better than classical mechanics, e.g. in the Michelson–Morley experiment that supports postulate 2, but also has many surprising consequences. Some of these are:
Relativity of simultaneity: Two events, simultaneous for one observer, may not be simultaneous for another observer if the observers are in relative motion.
Time dilation: Moving clocks are measured to tick more slowly than an observer's "stationary" clock.
Relativistic mass
Length contraction: Objects are measured to be shortened in the direction that they are moving with respect to the observer.
Mass–energy equivalence: E = mc2, energy and mass are equivalent and transmutable.
Maximum speed is finite: No physical object, message or field line can travel faster than the speed of light in a vacuum.
The defining feature of special relativity is the replacement of the Galilean transformations of classical mechanics by the Lorentz transformations. (See Maxwell's equations of electromagnetism)."

http://en.wikipedia.org/wiki/Theory_of_relativity

I copied that from Wiki(shameless plagiarism), but if you look back over my posts in this thread, Wiki could have copied that from my posts.

General Relativity

"General relativity is a theory of gravitation developed by Einstein in the years 1907–1915. The development of general relativity began with the equivalence principle, under which the states of accelerated motion and being at rest in a gravitational field (for example when standing on the surface of the Earth) are physically identical. The upshot of this is that free fall is inertial motion: an object in free fall is falling because that is how objects move when there is no force being exerted on them, instead of this being due to the force of gravity as is the case in classical mechanics. This is incompatible with classical mechanics and special relativity because in those theories inertially moving objects cannot accelerate with respect to each other, but objects in free fall do so. To resolve this difficulty Einstein first proposed that spacetime is curved. In 1915, he devised the Einstein field equations which relate the curvature of spacetime with the mass, energy, and momentum within it.
Some of the consequences of general relativity are:
Clocks run more slowly in deeper gravitational wells. This is called gravitational time dilation.
Orbits precess in a way unexpected in Newton's theory of gravity. (This has been observed in the orbit of Mercury and in binary pulsars).
Rays of light bend in the presence of a gravitational field.
Rotating masses "drag along" the spacetime around them; a phenomenon termed "frame-dragging".
The universe is expanding, and the far parts of it are moving away from us faster than the speed of light.*
Technically, general relativity is a theory of gravitation whose defining feature is its use of the Einstein field equations. The solutions of the field equations are metric tensors which define the topology of the spacetime and how objects move inertially."

Same source.

*As I have pointed out Einstein knew that a static Universe would collapse, he thought the Universe was probably static, he added a "negative field" that kept the Universe static(or at least from collapsing in short order)and called it the Cosmological Constant. Amazingly, it shares many characteristic with what we know about Dark Energy(what little we know, I should say). Einstein did not know that the Universe was expanding until over 30 years after publishing GR. He never knew that his "biggest mistake" could turn out to be his most amazing "prediction" of all.

Near word for word what I have been posting, so let's not have anyone else trying to tell us that Einstein said or wrote anything other than this in his theory(whatever he said that didn't survive scrutiny to make it into his finished work). And I do know Relativity better than the cranks do.

Grumpy

 

[OnlyMe]

The problem with the first sentence above is, that you left out, "suggested or assumed to be fact or truth... Anything just being accepted, is not the same as having been proven.

The constant speed of light was well established fact long before Einstein used it as his postulate, so my definition is the one that pertains in this case. It was not just a postulate in Relativity, it was a well evidenced fact.

The speed of light was and has been measured to be constant both before Einstein introduced SR and since... But all of those measurements, were conducted in a locally consistent inertial frame of reference here on earth. The postulate was not that the speed of light is locally constant, it was and is that it is universally constant in all inertial frames. Thai is within the context of SR.

We, as in the royal we not meaning myself, have never measured the speed of light in any inertial frame other than one associated with a lab here on earth. So even though we know that every measurement made here on earth returns a constant speed of light, extending that to inertial frames sufficiently removed from the labs here on earth, remains a postulate. In addition all of our measurements have been for the two way speed of light. We again accept as postulate that the one way speed of light is equivalent to the two way speed of light we have accurately measured.

While a variable speed of light would play havoc with how GR is conceptually projected as a description of reality, it would have no real effect on GR beyond that.

Wrong, the theory depends on c being constant, all other properties are relative to that value. You cannot sustain Relativity absent constant c. It is one of only two postulates and the other is the interconnection of properties to keep c constant. Gr depends on c just like SR does.

GR, though SR served in some ways as a foundation, does not depend on SR. SR is essentially a weak field approximation of GR in a similar way as do Newton's field equations.

As you say above, if c is constant all other properties are relative to the constancy of c. As I said earlier, if c is variable it would mean that many if not all other involved properties could be constant.

By the way, on the issue of a constant or variable speed of light (within the context of GR), I do not know the answer. All I can say is that it remains an un-proven postulate, that works.

That, too is false, it has been shown to be true. Lightspeed is always c. That is a fact.

Again, it is a fact that has been proven only in a local inertial frame of reference. Do you have some reference to a measurement of the speed of light that has been carried out somewhere other than a lab here on earth?

The universally constant aspect of the postulate remains a postulate and theoretical. It has not been proven...

In this whole discussion too many important fundamental issues remain assumed! No one has really addressed definitions in a manner that any consensus could be reached. What is mass and inertia? Are they inherent characteristics? Is gravitation an inherent characteristic of mass or is it (gravitation), together with mass and inertia, all emergent?

Mass curves spacetime, curved spacetime is gravity. Mass is condensed energy, energy and mass are equivalent by the ratio of c squared. Inertia is the energy of mass in motion AND it's resistance to acceleration. Yes all these things are properties of spacetime and the energy it contains. We do not know all the details but these things we do know.

"Curved spacetime is gravity." If it were that simple there would not be so many people working hard to come up with a model for quantum gravity. You see QM sees space as flat and time as separate from space.

Old school relativity was based on mass and inertia as inherent characteristics of charged particles.

No, it was based on constant c, it didn't deal with particles at all, charged or not. Photons are not particles. I sense you know nothing about Relativity, either. What's happened to our school systems?

Yes, yes.., GR does not deal with particles. I added that because QM is where all of the current focus on understanding mass and inertia is at these days and QM deals with matter at the level of particles.

Mass and inertia were unstated assumed fundamental characteristics of matter, in the case of both SR and GR. Einstein never had to be define either because at the time there was no suggestion that they might one day be found to be emergent rather than inherent characteristics. And no they have not yet been proven emergent but that seems the track things are on.

Just because a theoretical model works even as well as GR has, does not mean it is a complete and true description of reality.

It is the only one we have that explains the way we see the Universe behave, ALL OF IT, we will keep treating it as a real picture of reality until it is shown to be false, just like we did with Newton. It has shown that it is accurate to a ridiculous degree, it cannot be denied as an extremely accurate model of reality. It probably isn't complete but the alternative is to say "Duh, I don't know." No other theory even comes close, especially those that deny facts up front(c).

Grumpy

Grumpy, I have not intended any of my comments to be personal. Though it seems from some of your response you have taken them as such. For the most part the way you present your understanding of GR is consistent with what I was taught in the late sixties and how I conceptually understood it to be, up to somewhere between five to seven years ago.., when I began to try and understand some of what has been being done with quantum gravity. Somewhere in there I encountered a conceptual shift, and things I was once certain to be one way, I am no longer so certain of. That does not mean that I have any less confidence in GR than I ever did. What it means is that conceptually GR took on a more general landscape, as I have become more and more convinced (though that may be too strong a word) that mass, inertia and gravity are emergent quantum phenomena, where GR describes the classical dynamics.

Please don't take anything I say personally.

 

[Undefined]

You are fantasizing what I'm doing in the same way that you are fantasizing about physics. I am ignoring nothing. And, having met Carroll, I am quite confident that he would be horrified that you think anything he wrote is support for your claims.

So, let's get you straight, PhysBang. Sean et al have confirmed (via triangulation on CMB map features, and the 'angles' added only to 180 degrees to 3 decimal places accuracy) that universal energy-space is Euclidean flat to infinity beyond observable universal volume, and you still carry on here as if that hasn't happened, just because you want to keep 'cranks' in their place?

What sort of 'scientist' are you? Does Carroll know who you are and that you are still peddling BBang Inflation/Expansion etc scenarios in lieu of more recent understandings from him and others that space is flat to INFINITY and no BBang 'beginning' scenario or 'non-Euclidean' math/abstraction overlay 'shape' to the 'universe' etc produces that flatness to infinity? Does he know you've 'met him'? Does 'meeting him automatically give you license to 'speak for him' rather than let his work speak for him?

Face it, his work and the re-thinking of Sir Roger and other mainstreamers are now coming back to the obvious OCCAM's understanding that A-Priori only a pre-existing, eternally processing, infinite energy-space extent/evolution over eons across many 'observational volumes' of localized dynamics in the larger background can produce the CMB without all the ad hoc fixes and 'expansion' and theoretical abstractions/interpretations of what is already readily explicable and interpretable in reality terms by Occam's understanding already pointed out.

Get up to speed, PhysBang, even the mainstreamers are now leaving you and your 'personality-based' arguments of old hat impressions from abstraction behind while they catch up to the reality 'crank'. Good luck.

 

[Grumpy]

OnlyMe

The speed of light was and has been measured to be constant both before Einstein introduced SR and since... But all of those measurements, were conducted in a locally consistent inertial frame of reference here on earth

All of them? Experiments measuring lightspeed have been made on carousels, in aircraft, hung from balloons and launched into space. Clocks in freefall tick faster or slower depending on height and orbital speed, in LEO their speed more than offsets their lessened time dilation, at geosynchronous it's probably the other way round(it's complicated, the math is accurate, however), those hung from balloons tick faster(less gravity, no speed, basically), those in aircraft tick slower(speed and small difference in gravity gradient)as do those on carousels(higher acceleration). I'm sure there are several experiments that have been done on the space station or Skylab or Mir. Not to mention the signals we've sent back and forth to Voyager and other space probes. What about GPS. Without knowing these effects precisely and compensating for them, they would direct you into a drainage ditch instead of into the 7/11 parking lot a block away. Lightspeed is constant, Relativity is the way the Universe is seen to work.

The postulate was not that the speed of light is locally constant, it was and is that it is universally constant in all inertial frames. Thai is within the context of SR.

It is also true in GR, lightspeed is constant, it is spacetime curvature that keeps it that way as the coordinate speed slows due to time dilation. Like my diagrams illustrate. Lightspeed did not suddenly start changing between the time Einstein published SR and GR, it is always measured to be exactly c in space or in a gravity field. GR extended the principle to ALL frames, inertial or accelerated. That relationship is shown by the Einstein Field Equations, but you are on your own wading through them.

We, as in the royal we not meaning myself, have never measured the speed of light in any inertial frame other than one associated with a lab here on earth. So even though we know that every measurement made here on earth returns a constant speed of light, extending that to inertial frames sufficiently removed from the labs here on earth, remains a postulate. In addition all of our measurements have been for the two way speed of light. We again accept as postulate that the one way speed of light is equivalent to the two way speed of light we have accurately measured.

That is so not true, we can even measure lightspeed in distant galaxies, given the right configurations or events. One recent one tracked the light from a nova as it illuminated shells of previously ejected dust and gas, timing it as the wave front expanded over more than a year. Want to guess what value they got? Like I said, in Cosmology our clocks are huge. And the Michelson-Morley experiments showed light travels at exactly c in all directions relative to acceleration or orbital movement. Their search for an ether ended up supporting Relativity.

GR, though SR served in some ways as a foundation, does not depend on SR. SR is essentially a weak field approximation of GR in a similar way as do Newton's field equations.

No, SR is a special case in Relativity, both SR and GR are part of the whole theory. After GR was published Einstein called them just Relativity in his later revisions. Both SR and GR are valid. SR is about Relativity in inertial frames, GR is about Relativity in accelerated frames.

Again, it is a fact that has been proven only in a local inertial frame of reference. Do you have some reference to a measurement of the speed of light that has been carried out somewhere other than a lab here on earth?

I'll look one up, but they are numerous, as I already explained. GPS does it every day, for one. Each satellite has it's own frame in relation to the receiver and to each other. They require careful calculation and adjustments in timing in order to be accurate.

"Curved spacetime is gravity." If it were that simple there would not be so many people working hard to come up with a model for quantum gravity. You see QM sees space as flat and time as separate from space.

Curved spacetime is gravity. Quantum gravity is only relevant at Planck lengths and the first few femtoseconds of time. But spacetime is gravity, whatever it quantisizes to at that level(probably the Higgs Bosun).

Yes, yes.., GR does not deal with particles. I added that because QM is where all of the current focus on understanding mass and inertia is at these days and QM deals with matter at the level of particles.

But the Quantum is another realm. In the macro the Universe is Relative. We don't yet know how the two will be reconciled, but there is no reason to think it will affect Relativity much.

Mass and inertia were unstated assumed fundamental characteristics of matter, in the case of both SR and GR.

Why do you call it assumed? Mass and inertia are MEASURED AND DEFINED characteristics of matter. That mass and inertia is in the field equations. As well as the energy calculations of speed(remember mass gain?). We assume nothing, even the postulates of Relativity are established fact.

Einstein never had to be define either because at the time there was no suggestion that they might one day be found to be emergent rather than inherent characteristics.

You don't know the first thing about what Relativity says, either, evidently.

Grumpy

 

[OnlyMe]

All of them? Experiments measuring lightspeed have been made on carousels, in aircraft, hung from balloons and launched into space.

Accurate measurements of the speed of light, in vacuum, can only be made for the two way speed of light and in a lab where distance can be measured independent of light. Measured on a carrousel, plane or ballon, sure it is possible, but those would all represent essentially flat spacetime, as far as accuracy of measurement is concerned. And the whole experimental package with clock would have be in that same inertial frame.

If you can find a reference where that kind of measurement has been made on a space station, I would be interested. I am sure if anyone had sent that kind of gear up on a satellite it would have been news I would not have missed.

Clocks in freefall tick faster or slower depending on height and orbital speed, in LEO their speed more than offsets their lessened time dilation, at geosynchronous it's probably the other way round(it's complicated, the math is accurate, however), those hung from balloons tick faster(less gravity, no speed, basically), those in aircraft tick slower(speed and small difference in gravity gradient)as do those on carousels(higher acceleration). I'm sure there are several experiments that have been done on the space station or Skylab or Mir. Not to mention the signals we've sent back and forth to Voyager and other space probes. What about GPS. Without knowing these effects precisely and compensating for them, they would direct you into a drainage ditch instead of into the 7/11 parking lot a block away. Lightspeed is constant, Relativity is the way the Universe is seen to work.

It is also true in GR, lightspeed is constant, it is spacetime curvature that keeps it that way as the coordinate speed slows due to time dilation. Like my diagrams illustrate. Lightspeed did not suddenly start changing between the time Einstein published SR and GR, it is always measured to be exactly c in space or in a gravity field. GR extended the principle to ALL frames, inertial or accelerated. That relationship is shown by the Einstein Field Equations, but you are on your own wading through them.

That is so not true, we can even measure lightspeed in distant galaxies, given the right configurations or events. One recent one tracked the light from a nova as it illuminated shells of previously ejected dust and gas, timing it as the wave front expanded over more than a year. Want to guess what value they got? Like I said, in Cosmology our clocks are huge. And the Michelson-Morley experiments showed light travels at exactly c in all directions relative to acceleration or orbital movement. Their search for an ether ended up supporting Relativity.

No, SR is a special case in Relativity, both SR and GR are part of the whole theory. After GR was published Einstein called them just Relativity in his later revisions. Both SR and GR are valid. SR is about Relativity in inertial frames, GR is about Relativity in accelerated frames.

I'll look one up, but they are numerous, as I already explained. GPS does it every day, for one. Each satellite has it's own frame in relation to the receiver and to each other. They require careful calculation and adjustments in timing in order to be accurate.

Curved spacetime is gravity. Quantum gravity is only relevant at Planck lengths and the first few femtoseconds of time. But spacetime is gravity, whatever it quantisizes to at that level(probably the Higgs Bosun).

But the Quantum is another realm. In the macro the Universe is Relative. We don't yet know how the two will be reconciled, but there is no reason to think it will affect Relativity much.

Why do you call it assumed? Mass and inertia are MEASURED AND DEFINED characteristics of matter. That mass and inertia is in the field equations. As well as the energy calculations of speed(remember mass gain?). We assume nothing, even the postulates of Relativity are established fact.

You don't know the first thing about what Relativity says, either, evidently.

Grumpy

The rest of this strays from the issue of the measured constancy of the speed of light and seems more like a defense of SR and GR than anything else. You obviously believe that relativity stands or falls on this issue (I do not!) and from your last statement, a personal attack, it would seem you are vested in this and taking any difference of interpretation as a personal threat. So I will let it rest here.

Still if you do have a reference to a controlled two way speed of light measurement, conducted other than in our local frame of reference, I would be interested.

 

[Farsight]

...In this whole discussion too many important fundamental issues remain assumed! No one has really addressed definitions in a manner that any consensus could be reached. What is mass and inertia? ...

That's an easy one. Really. But one for another thread.

Yes, but MOTION is a consequence of energy dynamical processing of energy-space itself from one location/interaction to another and another. The evolution of dynamical energy imbalances between locations and their environment of energy-space and other 'features' processing in/of that energy-space are what drives the motion.

Hence motion itself is not an independent 'entity' as such; much as time' is not an independent entity. While motion precedes time in the heirarchy of observables (the former is an observable, the latter is a derivative abstract from that motional observable), in no way is motion itself anything more than the observed consequences of energy-space itself processing in/across that energy-space context/dynamics from location to location.

I trust my rushed posting is still sufficient to clarify/distinguish between observable motion OF the energy-space entity per se, mate?

Yes. I do know what you mean, and I don't disagree. The thing is, without motion, you can't be sure that space / energy is actually there. You can't measure any time, or any distance. It's hard to tell the difference between something and nothing.


All: can I ask you all to read the OP and comment upon how gravity works. If you don't agree with what I've said, say why you think light curves and an electron falls down.

 

[PhysBang]

So, let's get you straight, PhysBang. Sean et al have confirmed (via triangulation on CMB map features, and the 'angles' added only to 180 degrees to 3 decimal places accuracy) that universal energy-space is Euclidean flat to infinity beyond observable universal volume, and you still carry on here as if that hasn't happened, just because you want to keep 'cranks' in their place?

Carroll is not, as far as I know, a member of a cosmology observation team. He does very good theoretical work, however. So to say that he has "confirmed" anything is a little strange.

However, yes, the overall geometry of the observable universe as a whole does seem, after a great deal of investigation, to be "flat". Yet this conclusion is only possible after doing a lot of research that a) assumes that GR is very, very accurate, b) takes a great deal of spacetime curvature at smaller scales into account.

It is not rational to take the results of contemporary cosmology as evidence that GR is incorrect without doing some serious work on the specifics of the science.

you are still peddling BBang Inflation/Expansion etc scenarios in lieu of more recent understandings from him and others that space is flat to INFINITY and no BBang 'beginning' scenario or 'non-Euclidean' math/abstraction overlay 'shape' to the 'universe' etc produces that flatness to infinity?

A) You are imagining what I support. B) Carroll supports the standard cosmological model, the "big bang" theory; this theory doesn't necessarily include a beginning.

Does he know you've 'met him'? Does 'meeting him automatically give you license to 'speak for him' rather than let his work speak for him?

I do not speak for him. I merely read what he wrote (as you do not seem to have done) and I am able to judge how horrified he would be at the way you are misrepresenting his work.

 

[PhysBang]

If you don't agree with what I've said, say why you think light curves and an electron falls down.

People have said this many, many times: there is an established scientific literature on gravity that has observed both.

E.g., http://www.nature.com/nature/journal/v220/n5166/abs/220436a0.html

One cannot merely fantasize physics: without a way to go from supposed explanation of physics to a physics application, one has no explanation.