Equivalence Principle vs Second Law of Thermodynamics

[Alan Grayson]

IMO the former is approximate, and latter is exact. It seems to me that the qualifier "local" when describing the EP hides a multiple of sins. An observer can be in the vicinity of a very weak gravity field, or near a hugely intense gravity field, and get contrary detections of tidal forces depending on the accuracy of the measurement devices used, and the length of the enclosure to observe two test masses in free fall. In both cases we can find gravity indistinguishable from acceleration, OR distinguishable, depending on the design of the experiment. In the case of the 2nd law, I am not aware of any situation where it is violated. 

As for GR, even if we assume geodesic motion in free fall is a postulate of the theory, a nagging question remains; if a test particle is released from a state of spatial rest (due to an external force ceasing to be applied); why does it start of move in a theory where no forces exist? 

AG

[John Clark]

On Fri, Jun 20, 2025 at 3:44 AM Alan Grayson <agrays...@gmail.com> wrote:

 > if a test particle is released from a state of spatial rest (due to an external force ceasing to be applied); why does it start of move in a theory where no forces exist? 

I think you're trapped in an infinite loop. If you keep asking the exact same question then you will keep getting the exact same answer. So I suggest you reread what the previous answers were.

John K Clark    See what's on my new list at  Extropolis

til

[Alan Grayson]

I'll do that, but as I recall you posted a weak argument which depended on the equivalence of gravitational and inertial mass, so the consequences immediately followed, AG

[Alan Grayson]

Here, in part, is what you wrote earlier to answer to my question; what causes a test particle it to begin spatial motion when initially being spatially at rest, after a restraining force is removed:

> I fail to see how the EP implies geodesic motion. If true, the proof must be exceedingly subtle.

I'll try one more time. If you are in freefall then you experience no gravity, so from your perspective your local spacetime is flat and things move in a path that is the shortest distance between two points, a Euclidean straight line. But from my perspective standing on the Earth's surface you are being affected by gravity and are moving through spacetime that is curved and non-Euclidean. The Equivalence Principle says both points of view are equally valid, but the only way that could be true is if I see you moving in a path that is the shortest distance between two points in 4D non-Euclidean space, and that is a geodesic.

> If we assume mass/energy somehow causes a distortion in spacetime gemetry, and we hold a test mass spatially at rest in a gravity field, the question "why does it move"

If you are holding an object and standing motionless on the Earth's surface then you and the object are still following a path through 4D non-Euclidean spacetime because both of you are still moving through time, but that path is NOT a geodesic because a force is being applied to the bottom of your feet. When you release the object its spacetime path suddenly changes to that of a geodesic while your path remains non-geodesic. And things on different spacetime paths is the definition of "movement".

*******************

I don't understand how your text answers my question. I highlighted your claim above. What causes the "sudden" change you refer to above. Are you invoking magic? You seem to claim that 4D curvature is the cause, as if it replaces an external force called gravity. Maybe you don't understand my question or won't admit you don't know the answer. AG

[John Clark]

On Fri, Jun 20, 2025 at 8:17 AM Alan Grayson <agrays...@gmail.com> wrote:

 

If you are holding an object and standing motionless on the Earth's surface then you and the object are still following a path through 4D non-Euclidean spacetime because both of you are still moving through time, but that path is NOT a geodesic because a force is being applied to the bottom of your feet. When you release the object its spacetime path suddenly changes to that of a geodesic while your path remains non-geodesic. And things on different spacetime paths is the definition of "movement".

*******************

> I don't understand how your text answers my question. I highlighted your claim above. What causes the "sudden" change you refer to above.

YOU were the cause because you suddenly release your hold on the object, so the force on the object suddenly stopped, so the path of the object through 4D spacetime suddenly changed to a geodesic path, BUT you remained on a non-geodesic path because you were still experiencing a force on the bottom of your feet, so the distance between your fingers and the object suddenly started to increase. 

If you were in freefall (that is to say if there was no force being applied to the bottom of your feet) and released your grip on the object then the distance between your fingers and the object would NOT increase. 

 

> Are you invoking magic?

 

No because I don't think you're Harry Potter  

 

> You seem to claim that 4D curvature is the cause, as if it replaces an external force called gravity.

I don't claim that, Einstein claimed that in 1915, and every experiment and observation after that has failed to prove that Einstein was wrong. As far as we can tell gravity is geometry. 

 

> Maybe you don't understand my question or won't admit you don't know the answer. AG

I don't know the ULTIMATE answer to ANYTHING because without exception questions either go on forever or terminate in a brute fact.  

John K Clark    See what's on my new list at  Extropolis

-_=

[Alan Grayson]

I'd like an interim answer, and what Wheeler says -- that space tells matter how to move -- is woefully inaccurate. AG  

John K Clark    See what's on my new list at  Extropolis

I think I know the answer. I posted it earlier but you never confirmed or disconfirmed. I think the geodesic equations must have space and time dependent on each other, sort of like the LT does. When the object is released, its proper time continues to increase, forcing its spatial components to change. This IS "the cause" of the spatial motion from being spatially at rest due to the external force. When it moves, it does so on a geodesic path due to the postulate in GR, that free fall motion is geodesic. AG  

-_=

[John Clark]

On Fri, Jun 20, 2025 at 9:08 AM Alan Grayson <agrays...@gmail.com> wrote:

>> I don't know the ULTIMATE answer to ANYTHING because without exception questions either go on forever or terminate in a brute fact.  

> I'd like an interim answer,

And I have already done that. Several times in fact.  

 > what Wheeler says -- that space tells matter how to move -- is woefully inaccurate. AG  

The correct Wheeler quote is "Matter tells spacetime how to curve. Spacetime tells matter how to move". I can't think of a better 12 word summary of General Relativity than that. But before you receive your PhD in General Relativity you'd probably need to go into a little more detail.  

 

> I think the geodesic equations must have space and time dependent on each other,

Of course space and time are related to each other, that's why Wheeler talks about "spacetime", and Wheeler brings up the matter of matter. You didn't. I think Wheeler made very good use of 12 words.  

 John K Clark    See what's on my new list at  Extropolis

du8

 

 

[Alan Grayson]

What Wheeler says is BS for the masses. Surprised you can see it, or the issue I have raised. AG 

du8

 

 

[Alan Grayson]

What Wheeler says is BS for the masses. Surprised you can't see it, or the issue I have raised. And because I used the word "space" instead of "spacetime" you found fertile grounds to avoid understanding what I was writing. So, once again I see you as a class of would-be scientists who will never advance our understanding of physical reality. AG 

d

[John Clark]

On Fri, Jun 20, 2025 at 10:01 AM Alan Grayson <agrays...@gmail.com> wrote:

>> The correct Wheeler quote is "Matter tells spacetime how to curve. Spacetime tells matter how to move". I can't think of a better 12 word summary of General Relativity than that.

> What Wheeler says is BS for the masses. Surprised you can't see it, or the issue I have raised.

Are you also surprised that none of Wheeler's physicist colleagues can see the "issue" you have raised either? What exactly is the "issue" by the way? I thought you said the word "local" resolved your confusion.

John K Clark    See what's on my new list at  Extropolis

r4v

[Alan Grayson]

I changed my mind when I realized that separate observers in different enclosures, with different measuring devices, could reach different conclusions about finding tidal forces, or not, and conclude gravity is indistinguishable from acceleration, or not. I have no idea what Wheeler's colleagues think about this issue, nor does it really matter. The facts speak for themselves for anyone willing to accept them. Moreover, I think it leaves a lot of unresolved issues to claim that geometry alone xplains motion for free falling objects, without specifying exactly how geometry interacts with material objects. GR tells us how to calculate that effect, but as far as I can tell, offers no explanation of the physical interaction. At the end of the day, you seem to support the "shut up and calculate" school of thought, or philosophy.  AG  

[Alan Grayson]

I concede that if two test masses are dropped and observed for short enough distances, no tidal forces will be observed, and the observer will affirm the EP regardless of the accuracy of the measuring device used. But what this shows is not surprising and not grounds for the claim to have discovered some new, deep principle. Your opinion is what? AG 

[John Clark]

On Fri, Jun 20, 2025 at 4:19 PM Alan Grayson <agrays...@gmail.com> wrote:

>>> What Wheeler says is BS for the masses. Surprised you can't see it, or the issue I have raised.

>> Are you also surprised that none of Wheeler's physicist colleagues can see the "issue" you have raised either? What exactly is the "issue" by the way? I thought you said the word "local" resolved your confusion.

> I changed my mind

You must've changed your mind and become re-confused just a few minutes ago. I wonder what your opinion will be a few minutes from now.  

 

> when I realized that separate observers in different enclosures, with different measuring devices, could reach different conclusions about finding tidal forces,

If the enclosure was large enough, you would be able to detect tidal forces.  Do you really believe that Einstein and his colleagues weren't able to figure that out? It's also true that the tidal force near a supermassive black hole would be very low, title forces wouldn't be strong enough to start tearing your body apart until after you have passed the event horizon.

>I have no idea what Wheeler's colleagues think about this issue, nor does it really matter.

Because you know far more about General Relativity than all the professors who have spent their entire careers studying it?

 

 > I think it leaves a lot of unresolved issues to claim that geometry alone xplains motion for free falling objects, without specifying exactly how geometry interacts with material objects.

But Einstein's field equation of General Relativity does exactly that! The equation is: 

G_μν = (8πG/c⁴)T_μν

Left of the equal sign is the Einstein Tensor which describes the shape of spacetime which is geometry. And right of the equal sign is the Stress-Energy Tensor which describes the matter density, the energy density, the pressure, the stress, the tension. and the momentum flux; which are all material things. And "specifying exactly how geometry interacts with material objects" is what you asked for!

If I had to summarize what that equation is saying in just 12 words I would say "Matter tells spacetime how to curve. Spacetime tells matter how to move". 

 > At the end of the day, you seem to support the "shut up and calculate" school of thought, or philosophy.  AG  

Speaking of philosophy, can you tell me of one new philosophical problem that General Relativity introduced that Newtonian physics didn't already have? I can't think of one. 

John K Clark    See what's on my new list at  Extropolis

efq

[Brent Meeker]

The second law only holds without exception for systems with infinitely many degrees of freedom.  Once you realize heat energy is the motion of atoms it is seen as an approximation and statistical mechanics is more fundamental. 

Brent

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[Brent Meeker]

The sudden change is that he releases the object.  He stops applying force to it that was preventing it from following a geodesic.  Your question, "Why does it move." ignores that motion is relative and spacetime is 4D.  It wasn't moving relative to the person holding the test mass because he was applying a force to it.  But both were moving along the time axis...just not on a geodesic.  There is no gravitational force in general relativity.  There are forces required to keep from following geodesic curves which are followed by all bodies that do not have forces acting on them.  We think of ourselves as standing still on the surface of the Earth and of falling bodies as being accelerated by a gravitational force.  But the falling body actually has no force action on it.  It is traveling as “straight” as path as possible through spacetime.  In contrast, the ground is pushing up on our feet and is preventing us from following a “straight” (geodesic) path through spacetime.  Here’s an example of a girl throwing up a ball and catching it.  This is from Lewis Carroll Epstein’s excellent little book, “Relativity Visualized”.  I highly recommend it.  The shape of spacetime near a massive sphere is the geometric figure known as the psuedo-sphere.  Circumferential distance around the pseudo-sphere corresponds to proper time and axial distance corresponds to radial  (up/down) spacial distance.  Then you have to remember that in relativity the shortest, straightest path between two events is the *longest,* not shortest, duration between them. This because in the metric spatial interval appears with a negative sign.



While the ball is in the air, no force is acting on it. But if we could see the surface defined by proper time around a circumference and height along an axis, we would see that this surface near the Earth has a trumpet like shape called a psuedo-sphere. We can approximate a segment of this surface by a cone. And having done so, we can unroll the cone so as to draw a “straight” (geodesic) path on it showing the path of the ball. Then when we roll the cone back up we see that from the girl’s viewpoint (taking the ground as stationary) the ball has followed a parabola in spacetime. But in a sense it is the girl who has been accelerating upward while the ball went straight. She has the force of the ground pushing up on her so that she isn’t following a geodesic. In relativity, because of the sign difference between time and distance, the straightest, geodesic path is the longest, instead of the shortest as in Euclidean space. So the girl who followed the curved path aged less than the ball. The dashes in the lines represent the ticks of an ideal clock. It ticks twenty time along each path, but because of the curvature of the girls path, her clock is behind the balls clock when she catches it. This is the time dilation.

Brent

[Alan Grayson]

On Friday, June 20, 2025 at 3:32:22 PM UTC-6 John Clark wrote:

On Fri, Jun 20, 2025 at 4:19 PM Alan Grayson <agrays...@gmail.com> wrote:

>>> What Wheeler says is BS for the masses. Surprised you can't see it, or the issue I have raised.

>> Are you also surprised that none of Wheeler's physicist colleagues can see the "issue" you have raised either? What exactly is the "issue" by the way? I thought you said the word "local" resolved your confusion.

> I changed my mind

You must've changed your mind and become re-confused just a few minutes ago. I wonder what your opinion will be a few minutes from now.  

 

> when I realized that separate observers in different enclosures, with different measuring devices, could reach different conclusions about finding tidal forces,

If the enclosure was large enough, you would be able to detect tidal forces.  

But you still need accurate measurements (depending on the magnitude of the tidal forces), a fact you earlier denied. AG

 

Do you really believe that Einstein and his colleagues weren't able to figure that out?

I haven't made any such claim. I suppose they were/are very happy with GR and the fact that the EP motivated Einstein to develop it, so I doubt they would have been troubled by the fact the P in EP is an overstatement of what it is. AG 

 

It's also true that the tidal force near a supermassive black hole would be very low, title forces wouldn't be strong enough to start tearing your body apart until after you have passed the event horizon.

>I have no idea what Wheeler's colleagues think about this issue, nor does it really matter.

Because you know far more about General Relativity than all the professors who have spent their entire careers studying it?

More abuse from you. Maybe you're not retarded; just abusive? AG 

 

 > I think it leaves a lot of unresolved issues to claim that geometry alone explains motion for free falling objects, without specifying exactly how geometry interacts with material objects.

But Einstein's field equation of General Relativity does exactly that! The equation is: 

G_μν = (8πG/c⁴)T_μν

Left of the equal sign is the Einstein Tensor which describes the shape of spacetime which is geometry. And right of the equal sign is the Stress-Energy Tensor which describes the matter density, the energy density, the pressure, the stress, the tension. and the momentum flux; which are all material things. And "specifying exactly how geometry interacts with material objects" is what you asked for!

The equation does no such thing. It just tells you how to calculate one quality, curvature of spacetime, when you know the other (energy / matter distribution). It doesn't specify any physical process for the calculation it describes. AG 

If I had to summarize what that equation is saying in just 12 words I would say "Matter tells spacetime how to curve. Spacetime tells matter how to move". 

 > At the end of the day, you seem to support the "shut up and calculate" school of thought, or philosophy.  AG  

Speaking of philosophy, can you tell me of one new philosophical problem that General Relativity introduced that Newtonian physics didn't already have? I can't think of one. 

Sure, that's easy; time dilation, length contraction, muon clocks, the fact that spacetime has curvature, etc. Oh, I can anticipate your response. These phenomena have nothing to do with "philosophy". AG 

[John Clark]

On Sat, Jun 21, 2025 at 12:45 AM Alan Grayson <agrays...@gmail.com> wrote:

>> If the enclosure was large enough, you would be able to detect tidal forces.  

> But you still need accurate measurements (depending on the magnitude of the tidal forces), a fact you earlier denied. AG

Huh? I still deny it! It's pretty obvious that if you don't have accurate measurements then you're not gonna be able to tell the difference between gravity produced by a planet or acceleration produced by a rocket regardless of the size of the volume of space you're dealing with. If you don't have accurate measurements an observation will tell you nothing. 

 

• 
  

>>I have no idea what Wheeler's colleagues think about this issue, nor does it really matter.

>> Because you know far more about General Relativity than all the professors who have spent their entire careers studying it?

> More abuse from you.

That was not rhetorical, it was a legitimate question that, given the circumstances, was an entirely reasonable thing to ask. And I'm still waiting for an answer. You said you're not interested in what Physics professors at major universities who have spent their entire careers studying General Relativity have to say on the subject of General Relativity. Why is that? If it's not because you believe you know more about General Relativity than they do then what is the reason? 

 

 > I think it leaves a lot of unresolved issues to claim that geometry alone explains motion for free falling objects, without specifying exactly how geometry interacts with material objects.

But Einstein's field equation of General Relativity does exactly that! The equation is: 

G_μν = (8πG/c⁴)T_μν

Left of the equal sign is the Einstein Tensor which describes the shape of spacetime which is geometry. And right of the equal sign is the Stress-Energy Tensor which describes the matter density, the energy density, the pressure, the stress, the tension. and the momentum flux; which are all material things. And "specifying exactly how geometry interacts with material objects" is what you asked for!

> The equation does no such thing. It just tells you how to calculate one quality, curvature of spacetime, when you know the other (energy / matter distribution).

You said you wanted something "specifying exactly how geometry [the left-hand side of the equation] "interacts with material objects" [the right-hand side of the equation]. Einstein's equation gives you exactly what you asked for. 

 

> It doesn't specify any physical process for the calculation it describes. AG 

Are you equally dissatisfied with Newton's most famous equation F=ma?  What physical process causes force to accelerate mass? Newton didn't say, but he did say what a force could do to a mass.  

>> Speaking of philosophy, can you tell me of one new philosophical problem that General Relativity introduced that Newtonian physics didn't already have? I can't think of one. 

> Sure, that's easy; time dilation, length contraction, muon clocks, the fact that spacetime has curvature, etc. Oh, I can anticipate your response. These phenomena have nothing to do with "philosophy". AG 

No, that's not my response at all!  The phenomena you mention in the above are all new and profound philosophical discoveries, they are also all very odd and non-intuitive. But odd is not the same as paradoxical, so all philosophers came to peace with Relativity by about 1925 except for a few in Germany, and they did so for antisemitic reasons not scientific or philosophical reasons. 

However Quantum Mechanics was an entirely different matter, that really did open up a philosophical can of worms, and even today after more than a century there's no consensus about what it all means. The only thing everybody agrees on is that like it or loathe it Quantum Mechanics works, but I can't think of any modern philosopher who has a problem with relativity.

Actually Einstein solved a major philosophical problem that Newton admitted his theory had. Newton had a big problem with action at a distance. He thought it was crazy that the sun could influence the movement of the Earth, which was millions of miles from it, without influencing anything in between. Newton tried very hard to figure out how forces could operate with no mediating mechanism but he failed. In Newton's book Principia Mathematica, the most important book in scientific history, he made a confession: 

 

"Hitherto I have not been able to discover the cause of those properties of gravity from phenomena, and I frame no hypotheses."

And in a letter to a friend Newton said: 

"That one body may act upon another at a distance through a vacuum, without the mediation of any thing else, by and through which their action and force may be conveyed from one to another, is to me so great an absurdity, that I believe no man, who has in philosophical matters a competent faculty of thinking can ever fall into it."

And in another letter Newton said: 

"Tis unconceivable that inanimate brute matter should (without the mediation of something else which is not material) operate upon & affect other matter without mutual contact, that gravity should be innate inherent & essential to matter so that one body may act upon another at a distance through a vacuum without the mediation of any thing else"

Einstein solved the problem by providing the underlying mediating mechanism Newton was looking for, and it turned out to be spacetime. Einstein could explain exactly how matter affects spacetime and just as important how spacetime affects matter. You might complain that Einstein's explanation is not fundamental enough and you want something even deeper, but to do that we would have to find out what space and time are made of, and nobody knows what that could be, and they may not be made of anything. Space and time may be made of nothing but fundamental stuff, they may exist at the bottom level of reality. 

Or maybe not. Nobody knows.   

  

John K Clark    See what's on my new list at  Extropolis

%+(

[Brent Meeker]

On 6/21/2025 5:52 AM, John Clark wrote:

Einstein solved the problem by providing the underlying mediating mechanism Newton was looking for, and it turned out to be spacetime. Einstein could explain exactly how matter affects spacetime and just as important how spacetime affects matter. You might complain that Einstein's explanation is not fundamental enough and you want something even deeper, but to do that we would have to find out what space and time are made of, and nobody knows what that could be, and they may not be made of anything. Space and time may be made of nothing but fundamental stuff, they may exist at the bottom level of reality. 

Just to confound things further, Einstein originally forumlated general relativity as a tensor field on spacetime similar to an electromagnetic field.  I believe it was pointed out to him that it could also be interpreted as a distortion of spacetime and this had the advantage of automatically making all test particles fall with the same acceleration.  It has now become the standard way to teach it, but Einstein's original approach works just as well.

Brent

[Alan Grayson]

On Saturday, June 21, 2025 at 6:53:00 AM UTC-6 John Clark wrote:

On Sat, Jun 21, 2025 at 12:45 AM Alan Grayson <agrays...@gmail.com> wrote:

>> If the enclosure was large enough, you would be able to detect tidal forces.  

> But you still need accurate measurements (depending on the magnitude of the tidal forces), a fact you earlier denied. AG

Huh? I still deny it! It's pretty obvious that if you don't have accurate measurements then you're not gonna be able to tell the difference between gravity produced by a planet or acceleration produced by a rocket regardless of the size of the volume of space you're dealing with. If you don't have accurate measurements an observation will tell you nothing. 

 

You were quite emphatic as I recall that accurate measurements were irrelevant to detecting tidal forces. Of course, the accuracy necessary to detect tidal forces depends on the experimental situation. If the path of two test masses falling toward the bottom of the enclosure is short, in-accurate measurements will still affirm the EP. Some statements of the EP are not approximations, such as that all objects fall at the same rate under the influence of gravity, but not the equivalence of gravity and acceleration despite the equality of gravitational and inertial MASS. AG

>>I have no idea what Wheeler's colleagues think about this issue, nor does it really matter.

>> Because you know far more about General Relativity than all the professors who have spent their entire careers studying it?

> More abuse from you.

That was not rhetorical, it was a legitimate question that, given the circumstances, was an entirely reasonable thing to ask. And I'm still waiting for an answer. You said you're not interested in what Physics professors at major universities who have spent their entire careers studying General Relativity have to say on the subject of General Relativity. Why is that? If it's not because you believe you know more about General Relativity than they do then what is the reason? 

I never made the claim you allege. I just meant that relativity has some unresolved issues IMO, and that's clear, so I don't need to ask any university professors for their opinions when strong advocates of relativity can be found on this web site and others. For example, an observer measuring the muon's half-life will get one value in the lab and another value when in motion with respect to the muons, while in the frame of the muon no such change is observable. This is the result of the LT, in order to keep light speed frame invariant. But how this can occur remains baffling. Same with time dilation and length contraction. The moving observer sees changes relative to his frame, which we can call APPARENT, yet somehow this is confirmed by measurements, while in the frame of the object being measured, there is no dilation or contraction. 

 

 > I think it leaves a lot of unresolved issues to claim that geometry alone explains motion for free falling objects, without specifying exactly how geometry interacts with material objects.

But Einstein's field equation of General Relativity does exactly that! The equation is: 

G_μν = (8πG/c⁴)T_μν

Left of the equal sign is the Einstein Tensor which describes the shape of spacetime which is geometry. And right of the equal sign is the Stress-Energy Tensor which describes the matter density, the energy density, the pressure, the stress, the tension. and the momentum flux; which are all material things. And "specifying exactly how geometry interacts with material objects" is what you asked for!

> The equation does no such thing. It just tells you how to calculate one quality, curvature of spacetime, when you know the other (energy / matter distribution).

You said you wanted something "specifying exactly how geometry [the left-hand side of the equation] "interacts with material objects" [the right-hand side of the equation]. Einstein's equation gives you exactly what you asked for. 

 

> It doesn't specify any physical process for the calculation it describes. AG 

Are you equally dissatisfied with Newton's most famous equation F=ma?  What physical process causes force to accelerate mass? Newton didn't say, but he did say what a force could do to a mass.  

I reiterate my opinion that Einstein's equation just tells us how to calculate unknowns of interest, but doesn't offer any physical model of exactly how, say, mass/energy results in curvature of spacetime. F=ma needs additional theory to be really understood, and it likely comes from classical E&M, where one body impacting on another produces an acceleration due to local EM fields which are repulsive. IOW, the interaction of the force and the acceleration are local, but in GR there are no forces, so acceleration from spatial rest seems to be an unsolved problem. AG

BTW, Brent was mistaken in his claim that my question, "Why does it move?," doesn't assume 4D spacetime. I referred to spatial rest to mean 3 or the 4 coordinates of spacetime, like when you're sitting on your butt, but time, the 4th dimension, continues to advance. Also, when I used the condition "at rest", I meant at rest on the Earth, or any other frame one might choose. AG

>> Speaking of philosophy, can you tell me of one new philosophical problem that General Relativity introduced that Newtonian physics didn't already have? I can't think of one. 

> Sure, that's easy; time dilation, length contraction, muon clocks, the fact that spacetime has curvature, etc. Oh, I can anticipate your response. These phenomena have nothing to do with "philosophy". AG 

No, that's not my response at all!  The phenomena you mention in the above are all new and profound philosophical discoveries, they are also all very odd and non-intuitive. But odd is not the same as paradoxical, so all philosophers came to peace with Relativity by about 1925 except for a few in Germany, and they did so for antisemitic reasons not scientific or philosophical reasons. 

However Quantum Mechanics was an entirely different matter, that really did open up a philosophical can of worms, and even today after more than a century there's no consensus about what it all means. The only thing everybody agrees on is that like it or loathe it Quantum Mechanics works, but I can't think of any modern philosopher who has a problem with relativity.

Actually Einstein solved a major philosophical problem that Newton admitted his theory had. Newton had a big problem with action at a distance. He thought it was crazy that the sun could influence the movement of the Earth, which was millions of miles from it, without influencing anything in between. Newton tried very hard to figure out how forces could operate with no mediating mechanism but he failed. In Newton's book Principia Mathematica, the most important book in scientific history, he made a confession: 

 

"Hitherto I have not been able to discover the cause of those properties of gravity from phenomena, and I frame no hypotheses."

And in a letter to a friend Newton said: 

"That one body may act upon another at a distance through a vacuum, without the mediation of any thing else, by and through which their action and force may be conveyed from one to another, is to me so great an absurdity, that I believe no man, who has in philosophical matters a competent faculty of thinking can ever fall into it."

And in another letter Newton said: 

"Tis unconceivable that inanimate brute matter should (without the mediation of something else which is not material) operate upon & affect other matter without mutual contact, that gravity should be innate inherent & essential to matter so that one body may act upon another at a distance through a vacuum without the mediation of any thing else"

Einstein solved the problem by providing the underlying mediating mechanism Newton was looking for, and it turned out to be spacetime. Einstein could explain exactly how matter affects spacetime and just as important how spacetime affects matter.

 

The fact that the presence of matter/energy warps spacetime is a POSTULATE of GR, which you can take as brilliant intuition of physical reality, but not as a physical model of how that occurs. AG

 

You might complain that Einstein's explanation is not fundamental enough and you want something even deeper,

Yes, although I definitely appreciate GR, I would like something deeper, but when I say something about the insufficiencies of GR and Relativity in general, I never get a sympathetic hearing, but mostly mockery from the True Believers. AG

[John Clark]

On Sun, Jun 22, 2025 at 1:27 AM Alan Grayson <agrays...@gmail.com> wrote:

>> It's pretty obvious that if you don't have accurate measurements then you're not gonna be able to tell the difference between gravity produced by a planet or acceleration produced by a rocket regardless of the size of the volume of space you're dealing with. If you don't have accurate measurements an observation will tell you nothing. 

 

> You were quite emphatic as I recall that accurate measurements were irrelevant to detecting tidal forces.

What the hell? Accurate measurements are absolutely necessary if you want to detect ANYTHING! If your measurements are lousy then you will not be able to detect tidal forces, and if you can't detect tidal forces then you can't tell the difference between being stationary on the surface of a planet and accelerating in a rocket through empty intergalactic space.    

 > If the path of two test masses falling toward the bottom of the enclosure is short, in-accurate measurements will still affirm the EP.

Correct.  And if you increase the accuracy of your instrument but I reduce the size of the enclosure then the equivalence principle will still be affirmed. The limit of this sequence will be an instrument with perfect 100% accuracy and a volume of zero size (a point), and the equivalence principle will STILL be affirmed.   

 

> Some statements of the EP are not approximations, such as that all objects fall at the same rate under the influence of gravity,

The reason all objects fall at the same rate under the influence of gravity is because gravitational mass and inertial mass are equivalent. And that is the Equivalence Principle. 

>> You said you're not interested in what Physics professors at major universities who have spent their entire careers studying General Relativity have to say on the subject of General Relativity. Why is that? If it's not because you believe you know more about General Relativity than they do then what is the reason? 

 > relativity has some unresolved issues IMO, and that's clear, so I don't need to ask any university professors for their opinions when strong advocates of relativity can be found on this web site

I don't have a PhD in General Relativity from a major university, and I don't think anybody else around here does either, so I pay very close attention to those that do. They know far more than I do about it, and what they say plays a very important part in forming my opinions about what issues are unresolved in General Relativity. However you have used a very different method in forming your opinions, but I can't figure out why.  If it's not because after reading about general relativity for 15 minutes you think you know more about the subject than brilliant people who have spent a lifetime studying the subject, then how did you form your opinions?

 > For example, an observer measuring the muon's half-life will get one value in the lab and another value when in motion with respect to the muons, while in the frame of the muon no such change is observable. This is the result of the LT, in order to keep light speed frame invariant. But how this can occur remains baffling. Same with time dilation and length contraction. 

20 years before Einstein was born Maxwell used his electromagnetic equations to calculate the speed of light, and it agreed perfectly with the experimental  determination  of the speed of light. however those equations did NOT say what that speed was relative to, they just said that was the speed of light.  At the time many thought that was a major flaw in Maxwell's idea, but Einstein thought it was Maxwell's greatest triumph.  

If you believed what Maxwell's equations are telling you and the speed of light really is the same for all observers, then Einstein proved in 1905 that the logical consequence is time dilation and length contraction; if they did NOT occur then there would be a true logical paradox. So if you understand Special Relativity then you shouldn't be baffled, and unlike General Relativity you don't need a firm grasp of 4D non-Euclidean tensor calculus to understand it, high school algebra is sufficient. So you shouldn't be baffled but it's still understandable to be in awe of it all. 

> I reiterate my opinion that Einstein's equation just tells us how to calculate unknowns of interest, but doesn't offer any physical model of exactly how,

You could say exactly the same thing about Newton's equation F=ma, in fact you could say the same thing about ANY equation in physics.  

 

 > F=ma needs additional theory to be really understood, and it likely comes from classical E&M, where one body impacting on another produces an acceleration due to local EM fields which are repulsive.

When you touch a marble with your finger, why is a force applied to the marble? To really get to the bottom of that question you need more than classical physics, you need Quantum Mechanics. It's not because of electromagnetism which can be attractive or repulsive or zero if there is no electrical charge, and atoms have no electrical charge, and both your finger and the marble are made of atoms. 

The real reason is because atoms have electrons in their outer layer, and electrons are fermions (that is to say they have half-integer spin) and so must obey the Pauli Exclusion Principle which says that two fermions cannot be in the same quantum state. On the other hand bosons such as photons (that have integer spin) do NOT need to obey the  Pauli Exclusion Principle, in fact in some circumstances they prefer to be at the same quantum state. In 1917 Einstein used that fact to discover the principle of Stimulated Emission, which is the operating principle behind the LASER, which is an acronym that stands for Light Amplification through Stimulated Emission of Radiation.

But why is the Pauli Exclusion Principle true? Because Quantum Mechanics demands that it be true. What demands that Quantum Mechanics be true? I don't know. 

> when you're sitting on your butt, but time, the 4th dimension, continues to advance. Also, when I used the condition "at rest", I meant at rest on the Earth, or any other frame one might choose. AG

On a space-time diagram you are always moving at a constant speed, the speed of light.  When you're sitting on your butt all your speed is in the time dimension, but when you get up and start walking a small part of your speed is in a spatial dimension, so your speed in the time dimension decreases slightly. And that is called time dilation.  

John K Clark    See what's on my new list at  Extropolis

da;

[Alan Grayson]

On Sunday, June 22, 2025 at 6:57:09 AM UTC-6 John Clark wrote:

On Sun, Jun 22, 2025 at 1:27 AM Alan Grayson <agrays...@gmail.com> wrote:

>> It's pretty obvious that if you don't have accurate measurements then you're not gonna be able to tell the difference between gravity produced by a planet or acceleration produced by a rocket regardless of the size of the volume of space you're dealing with. If you don't have accurate measurements an observation will tell you nothing. 

 

> You were quite emphatic as I recall that accurate measurements were irrelevant to detecting tidal forces.

What the hell? Accurate measurements are absolutely necessary if you want to detect ANYTHING! If your measurements are lousy then you will not be able to detect tidal forces, and if you can't detect tidal forces then you can't tell the difference between being stationary on the surface of a planet and accelerating in a rocket through empty intergalactic space.   

 

In a recent post, here's where you claimed accurate measurements were irrelevant to detecting tidal forces:

>> The sensitivity of the instrument is not the issue, no matter how sensitive it is if you pick a small enough region of space it will not be able to tell the difference,

> Indeed, it IS the issue. The enclosed observer must drop two test masses and determine any tendency for them to converge. So if the region is small enough, and the measurements sufficiently approximate, tidal forces, if they exist, won't be detected. AG 

There is a limit on the precision that any real instrument can have because it will always produce an error, let's call it Ω, that is greater than zero. So no matter how small Ω is, I can always produce a finite region of space in which your instrument cannot detect a difference between gravitational mass and inertial mass. And regardless of how large a volume of space you're interested in, provided it's not infinite, I can produce a large but finite sphere of matter that produces a gravitational field that your instrument cannot distinguish from acceleration. 

So, in this scenario, the experiment can be done so that tidal forces will not be detected and one can conclude the EP holds. But this is obviously contrived, and depends on NOT having a definite idea what "local" means. AG 

 > If the path of two test masses falling toward the bottom of the enclosure is short, in-accurate measurements will still affirm the EP.

Correct.  And if you increase the accuracy of your instrument but I reduce the size of the enclosure then the equivalence principle will still be affirmed. The limit of this sequence will be an instrument with perfect 100% accuracy and a volume of zero size (a point), and the equivalence principle will STILL be affirmed.   

 

> Some statements of the EP are not approximations, such as that all objects fall at the same rate under the influence of gravity,

The reason all objects fall at the same rate under the influence of gravity is because gravitational mass and inertial mass are equivalent. And that is the Equivalence Principle. 

I'm not sure EXACTLY how this conclusion is reached. AG 

>> You said you're not interested in what Physics professors at major universities who have spent their entire careers studying General Relativity have to say on the subject of General Relativity. Why is that?

I never made that claim. You're putting words in my mouth! University professors are usually too busy to deal with issues I raise, so I go to other allegedly knowledgeable individuals, such as Brent, who has a Ph'D in physics from the University of Texas at Austin, one of the foremost universities with a focus in physics. AG 

If it's not because you believe you know more about General Relativity than they do then what is the reason? 

 > relativity has some unresolved issues IMO, and that's clear, so I don't need to ask any university professors for their opinions when strong advocates of relativity can be found on this web site

I don't have a PhD in General Relativity from a major university, and I don't think anybody else around here does either, so I pay very close attention to those that do. They know far more than I do about it, and what they say plays a very important part in forming my opinions about what issues are unresolved in General Relativity. However you have used a very different method in forming your opinions, but I can't figure out why.  If it's not because after reading about general relativity for 15 minutes you think you know more about the subject than brilliant people who have spent a lifetime studying the subject, then how did you form your opinions?

 > For example, an observer measuring the muon's half-life will get one value in the lab and another value when in motion with respect to the muons, while in the frame of the muon no such change is observable. This is the result of the LT, in order to keep light speed frame invariant. But how this can occur remains baffling. Same with time dilation and length contraction. 

20 years before Einstein was born Maxwell used his electromagnetic equations to calculate the speed of light, and it agreed perfectly with the experimental  determination  of the speed of light. however those equations did NOT say what that speed was relative to, they just said that was the speed of light.  At the time many thought that was a major flaw in Maxwell's idea, but Einstein thought it was Maxwell's greatest triumph.  

If you believed what Maxwell's equations are telling you and the speed of light really is the same for all observers, then Einstein proved in 1905 that the logical consequence is time dilation and length contraction; if they did NOT occur then there would be a true logical paradox.

While I agree that for the velocity of light to be frame invariant, from a logical pov we get time dilation and length contraction. That's the conclusion of an observer in the rest frame observing a moving clock. But the observer in the frame of the clock, does not measure these phenomena. So what I find baffling, as the muon case shows, is how an apparent observation of an observer at rest wrt a moving clock, translates into real measurable phenomena. AG

 

So if you understand Special Relativity then you shouldn't be baffled, a unlike General Relativity you don't need a firm grasp of 4D non-Euclidean tensor calculus to understand it, high school algebra is sufficient. So you shouldn't be baffled but it's still understandable to be in awe of it all. 

> I reiterate my opinion that Einstein's equation just tells us how to calculate unknowns of interest, but doesn't offer any physical model of exactly how,

You could say exactly the same thing about Newton's equation F=ma, in fact you could say the same thing about ANY equation in physics.  

Yes, I can say that, and I do, but in the case of classical E&M, I'm pretty sure it was known before QM that electrons occupy the outer regions of atoms, so F can be provisionally understood as repulsive field interactions which create a force preventing penetration into a material object. Of course, QM is clearly more exact, but classical E&M provides a physical model for understanding F. AG 

[John Clark]

On Mon, Jun 23, 2025 at 1:13 AM Alan Grayson <agrays...@gmail.com> wrote:

>> Accurate measurements are absolutely necessary if you want to detect ANYTHING! If your measurements are lousy then you will not be able to detect tidal forces, and if you can't detect tidal forces then you can't tell the difference between being stationary on the surface of a planet and accelerating in a rocket through empty intergalactic space.   

> In a recent post, here's where you claimed accurate measurements were irrelevant to detecting tidal forces:

>> "The sensitivity of the instrument is not the issue, no matter how sensitive it is if you pick a small enough region of space it will not be able to tell the difference"

And my remark in the above is 100% consistent with my other remark that "Accurate measurements are absolutely necessary if you want to detect ANYTHING!"

>> "There is a limit on the precision that any real instrument can have because it will always produce an error, let's call it Ω, that is greater than zero. So no matter how small Ω is, I can always produce a finite region of space in which your instrument cannot detect a difference between gravitational mass and inertial mass. And regardless of how large a volume of space you're interested in, provided it's not infinite, I can produce a large but finite sphere of matter that produces a gravitational field that your instrument cannot distinguish from acceleration." 

 

 And my remark in the above is 100% consistent with my other remark that "Accurate measurements are absolutely necessary if you want to detect ANYTHING!

> So, in this scenario, the experiment can be done so that tidal forces will not be detected

Obviously it can be done! It's ridiculously easy to perform lousy experiments that have huge error bars, but such experiments can tell you nothing. More precise experiments are more difficult but they have the potential to tell you that something is not true. Extremely precise measurements have been made but none of them show that the equivalence principle is false.  

 

> and one can conclude the EP holds.

This is physics not mathematics, no experiment can prove that something is correct, but you can prove that something is incorrect. And so far at least the Equivalence Principle has never been proven to be incorrect.  

 

> But this is obviously contrived, and depends on NOT having no definite idea what "local" means. AG 

The operational definition of "local" means that no matter how sensitive your tidal force measuring device is, I can pick a volume of space that is so small that your device cannot detect that tidal force. If your device is infinitely sensitive (such a device would be unphysical, but never mind) then "local" would be a point which has zero volume.     

>>The reason all objects fall at the same rate under the influence of gravity is because gravitational mass and inertial mass are equivalent. And that is the Equivalence Principle. 

> I'm not sure how this conclusion is reached. AG

If you double the gravitational mass of an object falling to the Earth then you double the force it feels from gravity, but if they are equivalent then you have also doubled the inertial mass, so it takes twice as much force to produce the same acceleration. Therefore the rate of acceleration an object has as it falls to the ground is the same regardless of what the mass of that object is.

>> You said you're not interested in what Physics professors at major universities who have spent their entire careers studying General Relativity have to say on the subject of General Relativity. Why is that?

>I never made that claim. You're putting words in mouth!

No I am not! I can provide a quotation, words actually coming out of your mouth, or at least your keyboard:  

"I have no idea what Wheeler's colleagues think about this issue, nor does it really matter."

 

> University professors are usually too busy to deal with issues I raise,

Don't be ridiculous! All the questions you have raised are ones that you'd expect from a high school student being exposed to relativity for the first time, and all your objections have all been answered to the physics community's satisfaction more than a century ago. You're fighting a war that ended a long time ago. You're like Shoichi Yokoi, a Japanese soldier who didn't know World War II was over and so hit in the jungle on the island of Guam until 1972. If you want controversy you'll find plenty of it in Quantum Mechanics but not in relativity, and certainly not in Special Relativity. 

>> 20 years before Einstein was born Maxwell used his electromagnetic equations to calculate the speed of light, and it agreed perfectly with the experimental  determination  of the speed of light. however those equations did NOT say what that speed was relative to, they just said that was the speed of light.  At the time many thought that was a major flaw in Maxwell's idea, but Einstein thought it was Maxwell's greatest triumph. If you believed what Maxwell's equations are telling you and the speed of light really is the same for all observers, then Einstein proved in 1905 that the logical consequence is time dilation and length contraction; if they did NOT occur then there would be a true logical paradox.

> While I agree that for the velocity of light to be frame invariant, from a logical pov we get time dilation and length contraction. That's the conclusion of an observer in the rest frame observing a moving clock. But the observer in the frame of the clock, does not measure these phenomena. So what I find baffling, as the muon case shows, is how an apparent observation of an observer at rest wrt a moving clock, translates into real measurable phenomena. AG

If things were otherwise it would be far worse than baffling. If the speed of light was constant for all observers but time dilation and length contraction were only apparent and not real then you have a full-fledged logical contradiction on your hands, one that existed not in the abstract world of mathematics or formal logic, but one in the actual physical world. We know for a fact that our physical world is mind-bendingly odd, but odd is not the same as paradoxical.

>>> I reiterate my opinion that Einstein's equation just tells us how to calculate unknowns of interest, but doesn't offer any physical model of exactly how,

>> You could say exactly the same thing about Newton's equation F=ma, in fact you could say the same thing about ANY equation in physics.  

> Yes, I can say that, and I do, but in the case of classical E&M, it was known before QM that electrons occupy the outer regions of atoms,

That is incorrect. Quantum Mechanics started with Max Planck in 1900, Rutherford didn't discover that electrons were "orbiting" the nucleus of the atom until 1911. And classical electrodynamics could NOT explain how it could be possible that a negatively charged electron could orbit a positively charged nucleus because an orbiting object is experiencing acceleration do to the fact it is constantly changing directions, and classical electrodynamics says that an accelerating charged object, such as an electron, will emit electromagnetic radiation, lose energy, fall to a lower orbit, and spiral into the nucleus in 10^-11 seconds. Obviously that doesn't happen. So what classical electrodynamics says is not relevant when you're talking about something as small as an atom. As I explained in my previous post, the true reason I can't pass my hand through my desk is because of quantum mechanics, more particularly because of the  Pauli Exclusion Principle.

John K Clark    See what's on my new list at  Extropolis

wsa

[Alan Grayson]

On Monday, June 23, 2025 at 7:23:48 AM UTC-6 John Clark wrote:

On Mon, Jun 23, 2025 at 1:13 AM Alan Grayson <agrays...@gmail.com> wrote:

>> Accurate measurements are absolutely necessary if you want to detect ANYTHING! If your measurements are lousy then you will not be able to detect tidal forces, and if you can't detect tidal forces then you can't tell the difference between being stationary on the surface of a planet and accelerating in a rocket through empty intergalactic space.   

> In a recent post, here's where you claimed accurate measurements were irrelevant to detecting tidal forces:

>> "The sensitivity of the instrument is not the issue, no matter how sensitive it is if you pick a small enough region of space it will not be able to tell the difference"

And my remark in the above is 100% consistent with my other remark that "Accurate measurements are absolutely necessary if you want to detect ANYTHING!"

>> "There is a limit on the precision that any real instrument can have because it will always produce an error, let's call it Ω, that is greater than zero. So no matter how small Ω is, I can always produce a finite region of space in which your instrument cannot detect a difference between gravitational mass and inertial mass. And regardless of how large a volume of space you're interested in, provided it's not infinite, I can produce a large but finite sphere of matter that produces a gravitational field that your instrument cannot distinguish from acceleration." 

 

 And my remark in the above is 100% consistent with my other remark that "Accurate measurements are absolutely necessary if you want to detect ANYTHING!

> So, in this scenario, the experiment can be done so that tidal forces will not be detected

Obviously it can be done! It's ridiculously easy to perform lousy experiments that have huge error bars, but such experiments can tell you nothing. More precise experiments are more difficult but they have the potential to tell you that something is not true. Extremely precise measurements have been made but none of them show that the equivalence principle is false.  

I am not contemplating lousy measurements. If I have great measurements and detect tidal forces, therefore denying the EP, I can easily change the design of the experiment, so tidal forces will not be detected. Thus, affirming the EP. So, what we have here is nothing less than a contrivance to prove what we want to prove; namely, that the EP remains intact. AG

 

> and one can conclude the EP holds.

This is physics not mathematics, no experiment can prove that something is correct, but you can prove that something is incorrect. And so far at least the Equivalence Principle has never been proven to be incorrect.  

 

> But this is obviously contrived, and depends on NOT having no definite idea what "local" means. AG 

The operational definition of "local" means that no matter how sensitive your tidal force measuring device is, I can pick a volume of space that is so small that your device cannot detect that tidal force. If your device is infinitely sensitive (such a device would be unphysical, but never mind) then "local" would be a point which has zero volume.   

Sure, you can always design the experiment to get the result you want. Is this what you call "physics"? AG

>>The reason all objects fall at the same rate under the influence of gravity is because gravitational mass and inertial mass are equivalent. And that is the Equivalence Principle. 

> I'm not sure how this conclusion is reached. AG

If you double the gravitational mass of an object falling to the Earth then you double the force it feels from gravity, but if they are equivalent then you have also doubled the inertial mass, so it takes twice as much force to produce the same acceleration. Therefore the rate of acceleration an object has as it falls to the ground is the same regardless of what the mass of that object is.

>> You said you're not interested in what Physics professors at major universities who have spent their entire careers studying General Relativity have to say on the subject of General Relativity. Why is that?

>I never made that claim. You're putting words in mouth!

No I am not! I can provide a quotation, words actually coming out of your mouth, or at least your keyboard:  

"I have no idea what Wheeler's colleagues think about this issue, nor does it really matter."

 

> University professors are usually too busy to deal with issues I raise,

Don't be ridiculous! All the questions you have raised are ones that you'd expect from a high school student being exposed to relativity for the first time, and all your objections have all been answered to the physics community's satisfaction more than a century ago.

When I was a graduate student, I had no problem with Relativity. I accepted it without reservation. Now that I am more mature in my thinking, I see there are several unresolved issues. I am not averse to discussing these issues with knowledgeable persons, but most, like you, prefer character assassination, rather than trying to see where I am coming from. AG 

You're fighting a war that ended a long time ago. You're like Shoichi Yokoi, a Japanese soldier who didn't know World War II was over and so hit in the jungle on the island of Guam until 1972. If you want controversy you'll find plenty of it in Quantum Mechanics but not in relativity, and certainly not in Special Relativity. 

>> 20 years before Einstein was born Maxwell used his electromagnetic equations to calculate the speed of light, and it agreed perfectly with the experimental  determination  of the speed of light. however those equations did NOT say what that speed was relative to, they just said that was the speed of light.  At the time many thought that was a major flaw in Maxwell's idea, but Einstein thought it was Maxwell's greatest triumph. If you believed what Maxwell's equations are telling you and the speed of light really is the same for all observers, then Einstein proved in 1905 that the logical consequence is time dilation and length contraction; if they did NOT occur then there would be a true logical paradox.

> While I agree that for the velocity of light to be frame invariant, from a logical pov we get time dilation and length contraction. That's the conclusion of an observer in the rest frame observing a moving clock. But the observer in the frame of the clock, does not measure these phenomena. So what I find baffling, as the muon case shows, is how apparent

 

If things were otherwise it would be far worse than baffling.

Things as they are, remain baffling. You just can't admit that you can't answer my questions. For example, how can an observer see a moving clock ticking slower than an observer in the moving frame, which is at rest with the clock in his frame? That is, how can an apparent observation become real, as in the muon case? You can't bury the question by saying that's how Relativity works. AG

.  

If the speed of light was constant for all observers but time dilation and length contraction were only apparent and not real then you have a full-fledged logical contradiction on your hands, one that existed not in the abstract world of mathematics or formal logic, but one in the actual physical world. We know for a fact that our physical world is mind-bendingly odd, but odd is not the same as paradoxical.

>>> I reiterate my opinion that Einstein's equation just tells us how to calculate unknowns of interest, but doesn't offer any physical model of exactly how,

>> You could say exactly the same thing about Newton's equation F=ma, in fact you could say the same thing about ANY equation in physics.  

> Yes, I can say that, and I do, but in the case of classical E&M, it was known before QM that electrons occupy the outer regions of atoms,

That is incorrect. Quantum Mechanics started with Max Planck in 1900, Rutherford didn't discover that electrons were "orbiting" the nucleus of the atom unAAtil 1911.

And in 1911 QM was not in its final form. That would take another 15+ years. Classical E&M gives us more than a clue whey we can't walk through walls. AG

And classical electrodynamics could NOT explain how it could be possible that a negatively charged electron could orbit a positively charged nucleus because an orbiting object is experiencing acceleration do to the fact it is constantly changing directions, and classical electrodynamics says that an accelerating charged object, such as an electron, will emit electromagnetic radiation, lose energy, fall to a lower orbit, and spiral into the nucleus in 10^-11 seconds.

Does QM explain why atoms in motion don't radiate energy? The protons in the nucleus would presumably do that if they accelerate. With someone like you, who indulges in character assassination, I have to be extremely rigorous. Otherwise, I will incur your de-facto wrath. AG

 

Obviously that doesn't happen. So what classical electrodynamics says is not relevant when you're talking about something as small as an atom. As I explained in my previous post, the true reason I can't pass my hand through my desk is because of quantum mechanics, more particularly because of the  Pauli Exclusion Principle.

John K Clark    See what's on my new list at  Extropolis

wsa

 

When you touch a marble with your finger, why is a force applied to the marble? To really get to the bottom of that question you need more than classical physics, you need Quantum Mechanics. It's not because of electromagnetism which can be attractive or repulsive or zero if there is no electrical charge, and atoms have no electrical charge, and both your finger and the marble are made of atoms. 

The real reason is because atoms have electrons in their outer layer, and electrons are fermions (that is to say they have half-integer spin) and so must obey the Pauli Exclusion Principle which says that two fermions cannot be in the same quantum state.

How does Pauli's Exclusion Principle prevent radiation loss due to acceleration? AG

[John Clark]

On Mon, Jun 23, 2025 at 10:32 AM Alan Grayson <agrays...@gmail.com> wrote:

>>> So, in this scenario, the experiment can be done so that tidal forces will not be detected

>> Obviously it can be done! It's ridiculously easy to perform lousy experiments that have huge error bars, but such experiments can tell you nothing. More precise experiments are more difficult but they have the potential to tell you that something is not true. Extremely precise measurements have been made but none of them show that the equivalence principle is false.  

> I am not contemplating lousy measurements. If I have great measurements and detect tidal forces, therefore denying the EP, I can easily change the design of the experiment, so tidal forces will not be detected.

Yes exactly. No matter how good your instrument is, I can ALWAYS find a volume of space that is so small your instrument is not good enough to detect tidal forces, and this fact holds true all the way down to zero volume and a 100% perfect instrument.

 

>>> But this is obviously contrived, and depends on NOT having no definite idea what "local" means. AG 

>> The operational definition of "local" means that no matter how sensitive your tidal force measuring device is, I can pick a volume of space that is so small that your device cannot detect that tidal force. If your device is infinitely sensitive (such a device would be unphysical, but never mind) then "local" would be a point which has zero volume.   

> Sure, you can always design the experiment to get the result you want.

The experiment seems pretty damn fair to me.  You are allowed to use an instrument of arbitrary precision, even one that is absolutely perfect. And I am allowed to use a volume of arbitrary smallness, even one that has zero volume.   

 

> Is this what you call "physics"? AG

No, that's what I call "local".

>>>>The reason all objects fall at the same rate under the influence of gravity is because gravitational mass and inertial mass are equivalent. And that is the Equivalence Principle. 

>>> I'm not sure how this conclusion is reached. AG

>> If you double the gravitational mass of an object falling to the Earth then you double the force it feels from gravity, but if they are equivalent then you have also doubled the inertial mass, so it takes twice as much force to produce the same acceleration. Therefore the rate of acceleration an object has as it falls to the ground is the same regardless of what the mass of that object is.

> Things as they are, remain baffling. You just can't admit that you can't answer my questions. For example, how can an observer see a moving clock ticking slower than an observer in the moving frame, which is at rest with the clock in his frame?

That's the twin "paradox", and if you really want to understand it then take a look at the following video, it's the best intuitive explanation of how it works that I have ever seen, and it proves that it's not a logical paradox at all, it's just odd.  

I Never Understood How To Intuitively Solve The Twin's Paradox ... Until Now!

You might also want to take a look at this: 

I Never Understood How Curved Time Creates Gravity… Until Now!

And this: 

I never understood why black holes slow down time...until now!

This guy has the ability to explain things very clearly. 

>> And classical electrodynamics could NOT explain how it could be possible that a negatively charged electron could orbit a positively charged nucleus because an orbiting object is experiencing acceleration do to the fact it is constantly changing directions, and classical electrodynamics says that an accelerating charged object, such as an electron, will emit electromagnetic radiation, lose energy, fall to a lower orbit, and spiral into the nucleus in 10^-11 seconds.

> Does QM explain why atoms in motion don't radiate energy?

Yes. Because an electron cannot radiate continuously because it is only allowed to be in certain orbits and radiate a certain amount of energy when it changes orbits. Why is that? Because the electron has wavelike properties, and its wavelength is  h/p where h is Planck's constant and p is momentum. And if the electron is in a stable orbit then it must be in a standing wave because otherwise it would interfere with itself, so the circumference of the orbit must contain a whole number of wavelengths. And that causes the energy levels to be quantized. 

>> When you touch a marble with your finger, why is a force applied to the marble? To really get to the bottom of that question you need more than classical physics, you need Quantum Mechanics. It's not because of electromagnetism which can be attractive or repulsive or zero if there is no electrical charge, and atoms have no electrical charge, and both your finger and the marble are made of atoms.  The real reason is because atoms have electrons in their outer layer, and electrons are fermions (that is to say they have half-integer spin) and so must obey the Pauli Exclusion Principle which says that two fermions cannot be in the same quantum state.

> How does Pauli's Exclusion Principle prevent radiation loss due to acceleration? AG

As I have already explained, Pauli's Exclusion Principle is the reason you can't put your hand through your desk or walk through brick walls. Discrete energy levels are the reason electrons don't radiate continuously and spiral into the nucleus. 

 

>> On the other hand bosons such as photons (that have integer spin) do NOT need to obey the  Pauli Exclusion Principle, in fact in some circumstances they prefer to be at the same quantum state. In 1917 Einstein used that fact to discover the principle of Stimulated Emission, which is the operating principle behind the LASER, which is an acronym that stands for Light Amplification through Stimulated Emission of Radiation. But why is the Pauli Exclusion Principle true? Because Quantum Mechanics demands that it be true. What demands that Quantum Mechanics be true? I don't know. 

> when you're sitting on your butt, but time, the 4th dimension, continues to advance. Also, when I used the condition "at rest", I meant at rest on the Earth, or any other frame one might choose. AG

>> On a space-time diagram you are always moving at a constant speed, the speed of light.  When you're sitting on your butt all your speed is in the time dimension, but when you get up and start walking a small part of your speed is in a spatial dimension, so your speed in the time dimension decreases slightly. And that is called time dilation.  

John K Clark    See what's on my new list at  Extropolis

ih7

 

[Alan Grayson]

On Monday, June 23, 2025 at 3:16:50 PM UTC-6 John Clark wrote:

On Mon, Jun 23, 2025 at 10:32 AM Alan Grayson <agrays...@gmail.com> wrote:

>>> So, in this scenario, the experiment can be done so that tidal forces will not be detected

>> Obviously it can be done! It's ridiculously easy to perform lousy experiments that have huge error bars, but such experiments can tell you nothing. More precise experiments are more difficult but they have the potential to tell you that something is not true. Extremely precise measurements have been made but none of them show that the equivalence principle is false.  

> I am not contemplating lousy measurements. If I have great measurements and detect tidal forces, therefore denying the EP, I can easily change the design of the experiment, so tidal forces will not be detected.

Yes exactly. No matter how good your instrument is, I can ALWAYS find a volume of space that is so small your instrument is not good enough to detect tidal forces, and this fact holds true all the way down to zero volume and a 100% perfect instrument.

 

>>> But this is obviously contrived, and depends on NOT having no definite idea what "local" means. AG 

>> The operational definition of "local" means that no matter how sensitive your tidal force measuring device is, I can pick a volume of space that is so small that your device cannot detect that tidal force. If your device is infinitely sensitive (such a device would be unphysical, but never mind) then "local" would be a point which has zero volume.   

> Sure, you can always design the experiment to get the result you want.

The experiment seems pretty damn fair to me.  You are allowed to use an instrument of arbitrary precision, even one that is absolutely perfect. And I am allowed to use a volume of arbitrary smallness, even one that has zero volume.   

 

> Is this what you call "physics"? AG

No, that's what I call "local".

That's what I call BS!  "Local" means that an event in spacetime depends entirely on the local conditions, such as field strengths at that point. It doesn't mean an experiment can be rigged to get some desired result. AG 

>>>>The reason all objects fall at the same rate under the influence of gravity is because gravitational mass and inertial mass are equivalent. And that is the Equivalence Principle. 

>>> I'm not sure how this conclusion is reached. AG

>> If you double the gravitational mass of an object falling to the Earth then you double the force it feels from gravity, but if they are equivalent then you have also doubled the inertial mass, so it takes twice as much force to produce the same acceleration. Therefore the rate of acceleration an object has as it falls to the ground is the same regardless of what the mass of that object is.

That result follows immediately in Newtonian physics, where the mass being accelerated by a gravitational force is in the numerator, and the inertial mass in the denominator cancel each other out. But how is this recapitulated in GR where there is no force of gravity? AG 

> Things as they are, remain baffling. You just can't admit that you can't answer my questions. For example, how can an observer see a moving clock ticking slower than an observer in the moving frame, which is at rest with the clock in his frame?

That's the twin "paradox", and if you really want to understand it then take a look at the following video, it's the best intuitive explanation of how it works that I have ever seen, and it proves that it's not a logical paradox at all, it's just odd.  

Definitely NOT the TP. Generally, time dilation is a symmetric phenomenon, and remains so in the muon case, but in the TP the traveling twin goes through several accelerations to leave and return to meet his resting twin. So NOT symmetric. I don't think it's hard to show that it's the asymmetry which leads to the age disparity when the twins are reunited. It's the false assumption of symmetry that leads to the alleged paradox. AG 

I Never Understood How To Intuitively Solve The Twin's Paradox ... Until Now!

You might also want to take a look at this: 

I Never Understood How Curved Time Creates Gravity… Until Now!

And this: 

I never understood why black holes slow down time...until now!

This guy has the ability to explain things very clearly. 

>> And classical electrodynamics could NOT explain how it could be possible that a negatively charged electron could orbit a positively charged nucleus because an orbiting object is experiencing acceleration do to the fact it is constantly changing directions, and classical electrodynamics says that an accelerating charged object, such as an electron, will emit electromagnetic radiation, lose energy, fall to a lower orbit, and spiral into the nucleus in 10^-11 seconds.

> Does QM explain why atoms in motion don't radiate energy?

Yes. Because an electron cannot radiate continuously because it is only allowed to be in certain orbits and radiate a certain amount of energy when it changes orbits. Why is that? Because the electron has wavelike properties, and its wavelength is  h/p where h is Planck's constant and p is momentum. And if the electron is in a stable orbit then it must be in a standing wave because otherwise it would interfere with itself, so the circumference of the orbit must contain a whole number of wavelengths. And that causes the energy levels to be quantized. 

I was careful to use the word "atoms". When you accelerate from a traffic light which turns green, the PROTONS in the nuclei of your car and body accelerate. Shouldn't protons, being charged particles, radiate energy when accelerated? I've heard on good authority from one of Brent's colleagues, that this is an unsolved problem in classical E&M. AG 

>> When you touch a marble with your finger, why is a force applied to the marble? To really get to the bottom of that question you need more than classical physics, you need Quantum Mechanics. It's not because of electromagnetism which can be attractive or repulsive or zero if there is no electrical charge, and atoms have no electrical charge, and both your finger and the marble are made of atoms.  The real reason is because atoms have electrons in their outer layer, and electrons are fermions (that is to say they have half-integer spin) and so must obey the Pauli Exclusion Principle which says that two fermions cannot be in the same quantum state.

> How does Pauli's Exclusion Principle prevent radiation loss due to acceleration? AG

As I have already explained, Pauli's Exclusion Principle is the reason you can't put your hand through your desk or walk through brick walls. Discrete energy levels are the reason electrons don't radiate continuously and spiral into the nucleus. 

I don't see the connection between the Exclusion Principle and the fact that electrons have discrete energy levels. AG

>> On the other hand bosons such as photons (that have integer spin) do NOT need to obey the  Pauli Exclusion Principle, in fact in some circumstances they prefer to be at the same quantum state. In 1917 Einstein used that fact to discover the principle of Stimulated Emission, which is the operating principle behind the LASER, which is an acronym that stands for Light Amplification through Stimulated Emission of Radiation. But why is the Pauli Exclusion Principle true? Because Quantum Mechanics demands that it be true. What demands that Quantum Mechanics be true? I don't know. 

A

> when you're sitting on your butt, but time, the 4th dimension, continues to advance. Also, when I used the condition "at rest", I meant at rest on the Earth, or any other frame one might choose. AG

>> On a space-time diagram you are always moving at a constant speed, the speed of light.  When you're sitting on your butt all your speed is in the time dimension, but when you get up and start walking a small part of your speed is in a spatial dimension, so your speed in the time dimension decreases slightly. And that is called time dilation.  

[John Clark]

On Mon, Jun 23, 2025 at 10:27 PM Alan Grayson <agrays...@gmail.com> wrote:

 

>>>> The experiment seems pretty damn fair to me.  You are allowed to use an instrument of arbitrary precision, even one that is absolutely perfect. And I am allowed to use a volume of arbitrary smallness, even one that has zero volume.   

 

>>> Is this what you call "physics"? AG

>> No, that's what I call "local".

>That's what I call BS!  "Local" means that an event in spacetime depends entirely on the local conditions

So local means local. Like all tautologies that is true, but I give up on trying to convince you that, for at least 80 years, no physicist on the planet believes the existence of tides means that the Equivalence Principle must be wrong. I convinced you of the truth for about 10 minutes a few posts ago, but then you decided to become re-confused. I no longer believe it's possible for you to remain permanently unconfused on this matter.  

>> If you double the gravitational mass of an object falling to the Earth then you double the force it feels from gravity, but if they are equivalent then you have also doubled the inertial mass, so it takes twice as much force to produce the same acceleration. Therefore the rate of acceleration an object has as it falls to the ground is the same regardless of what the mass of that object is.

> That result follows immediately in Newtonian physics, where the mass being accelerated by a gravitational force is in the numerator, and the inertial mass in the denominator cancel each other out. But how is this recapitulated in GR where there is no force of gravity? AG 

 I Never Understood How Curved Time Creates Gravity… Until Now!

But of course you'll never watch it. 

 

> Generally, time dilation is a symmetric phenomenon,

Yes. And that plus the fact that Special Relativity says there's no absolute reference frame is why time dilation doesn't produce a logical paradox. If 2 spaceships are not accelerating but are approaching each other at 0.8c they will both observe the other's clock is running 60% slower than their own clock as measured in their own reference frame. That's odd but it's no paradox because both are free to say that they are stationary and it's the other guy that's moving at 0.8c, or if they prefer they can say that it's the other guy who is stationary and they are moving at 0.8c. The results are the same regardless of which reference frame they choose to claim to be in, they will both see the others clock at running 60% slower than their own. 

Asking which clock is "really" running slower would be a nonsensical question because no reference frame has been specified; so there is no logical paradox, just an odd situation. The symmetry is broken if one and only one of the spaceships accelerates as in the twin paradox, as you pointed out. 

 

> When you accelerate from a traffic light which turns green, the PROTONS in the nuclei of your car and body accelerate. Shouldn't protons, being charged particles, radiate energy when accelerated?

The amount of energy radiated would be tiny because the rate of acceleration is so small, and that small amount of energy would not affect an atom's stability even slightly because the energy was provided by the car's engine, not by the atom's internal energy.  

>> As I have already explained, Pauli's Exclusion Principle is the reason you can't put your hand through your desk or walk through brick walls. Discrete energy levels are the reason electrons don't radiate continuously and spiral into the nucleus. 

> I don't see the connection between the Exclusion Principle and the fact that electrons have discrete energy levels. AG

I don't recall saying that there was a connection, but now that you mentioned it the Exclusion Principle is why, even though electrons want to be in the lowest energy state, all the electrons in an atom can't be in the atom's lowest energy state. 

 John K Clark    See what's on my new list at  Extropolis

4vv

[Alan Grayson]

On Tuesday, June 24, 2025 at 5:28:55 AM UTC-6 John Clark wrote:

On Mon, Jun 23, 2025 at 10:27 PM Alan Grayson <agrays...@gmail.com> wrote:

 

>>>> The experiment seems pretty damn fair to me.  You are allowed to use an instrument of arbitrary precision, even one that is absolutely perfect. And I am allowed to use a volume of arbitrary smallness, even one that has zero volume.   

 

>>> Is this what you call "physics"? AG

>> No, that's what I call "local".

>That's what I call BS!  "Local" means that an event in spacetime depends entirely on the local conditions

So local means local. Like all tautologies that is true,

It's only a tautology because you truncated my partial definition. Not honest IMO. AG

 

but I give up on trying to convince you that, for at least 80 years, no physicist on the planet believes the existence of tides means that the Equivalence Principle must be wrong. I convinced you of the truth for about 10 minutes a few posts ago, but then you decided to become re-confused. I no longer believe it's possible for you to remain permanently unconfused on this matter.  

I've read the definition of "local" and it's not the one you use. You feel it's kosher to rig an experiment to get what you want to get. Sorry, but I don't go for that BS. What do tides have to do with this? AG 

>> If you double the gravitational mass of an object falling to the Earth then you double the force it feels from gravity, but if they are equivalent then you have also doubled the inertial mass, so it takes twice as much force to produce the same acceleration. Therefore the rate of acceleration an object has as it falls to the ground is the same regardless of what the mass of that object is.

> That result follows immediately in Newtonian physics, where the mass being accelerated by a gravitational force is in the numerator, and the inertial mass in the denominator cancel each other out. But how is this recapitulated in GR where there is no force of gravity? AG 

 I Never Understood How Curved Time Creates Gravity… Until Now!

But of course you'll never watch it. 

Hey ASSHOLE, stop your fucking, abusive mind reading. I do sometimes read links. It depends on the situation. AG 

 

> Generally, time dilation is a symmetric phenomenon,

Yes. And that plus the fact that Special Relativity says there's no absolute reference frame is why time dilation doesn't produce a logical paradox. If 2 spaceships are not accelerating but are approaching each other at 0.8c they will both observe the other's clock is running 60% slower than their own clock as measured in their own reference frame. That's odd but it's no paradox because both are free to say that they are stationary and it's the other guy that's moving at 0.8c, or if they prefer they can say that it's the other guy who is stationary and they are moving at 0.8c. The results are the same regardless of which reference frame they choose to claim to be in, they will both see the others clock at running 60% slower than their own. 

And no dilation for observers in the frame observing the other frame in motion. AG 

Asking which clock is "really" running slower would be a nonsensical question because no reference frame has been specified; so there is no logical paradox, just an odd situation. The symmetry is broken if one and only one of the spaceships accelerates as in the twin paradox, as you pointed out. 

Do you really understand Relativity? There are reference frames specified, such as the frame using the LT. AG 

 

> When you accelerate from a traffic light which turns green, the PROTONS in the nuclei of your car and body accelerate. Shouldn't protons, being charged particles, radiate energy when accelerated?

The amount of energy radiated would be tiny because the rate of acceleration is so small, and that small amount of energy would not affect an atom's stability even slightly because the energy was provided by the car's engine, not by the atom's internal energy.  

But not in the case of planetary bodies, say like asteroids, and yet we don't measure any radiation emitted. AG 

[John Clark]

On Tue, Jun 24, 2025 at 8:35 AM Alan Grayson <agrays...@gmail.com> wrote:

I give up. If you want to continue to believe that every physicist in the world is a fool because they believe the Equivalence Principle is correct even though tides exist then fine, go right ahead. I have come to the conclusion that it's impossible to have an intelligent civilized conversation with you, at least not for long; however promising it may start out as, it's only a matter of time before it degenerates into something like the following:

>"Hey ASSHOLE, stop your fucking, abusive mind reading."

John K Clark 

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[Alan Grayson]

On Tuesday, June 24, 2025 at 9:55:01 AM UTC-6 John Clark wrote:

On Tue, Jun 24, 2025 at 8:35 AM Alan Grayson <agrays...@gmail.com> wrote:

I give up. If you want to continue to believe that every physicist in the world is a fool because they believe the Equivalence Principle is correct

More of your stupid mind-reading. I don't believe what you allege. You have an incurable abusive habit. Nature is too kind to you, so you're totally unaware of it. BTW, no proton radiation from accelerating asteroids. Something to think about. AG 

[Alan Grayson]

On Tuesday, June 24, 2025 at 11:48:15 AM UTC-6 Alan Grayson wrote:

On Tuesday, June 24, 2025 at 9:55:01 AM UTC-6 John Clark wrote:

On Tue, Jun 24, 2025 at 8:35 AM Alan Grayson <agrays...@gmail.com> wrote:

I give up. If you want to continue to believe that every physicist in the world is a fool because they believe the Equivalence Principle is correct

More of your stupid mind-reading. I don't believe what you allege. You have an incurable abusive habit. Nature is too kind to you, so you're totally unaware of it. BTW, no proton radiation from accelerating asteroids. Something to think about. AG 

even though tides exist then fine, go right ahead. I have come to the conclusion that it's impossible to have an intelligent civilized conversation with you, at least not for long; however promising it may start out as, it's only a matter of time before it degenerates into something like the following:

>"Hey ASSHOLE, stop your fucking, abusive mind reading."

John K Clark

You're pathetic, really pathetic. You couldn't resist the temptation to make a snide remark that I wouldn't read your Twin Paradox links, when, as a factual matter, I intend to do just that, and for a specific reason; namely, the question whether the TP can be solved using both SR and GR, or whether only one is necessary -- but which one? I have been aware that there is an on-going controversy over this specific issue. So, since the cause of my anger lies with you, and only you, for your abusive, and presumptuous de-facto claim that you can read my mind, I really tire of your self-serving BS that you find it impossible to conduct a civilized discussion with me. Anyway, since I can think out-of-the-box, I leave you with the question of why charged particles like protons in atomic nuclei, do NOT radiate energy when accelerated. As you know, orbiting asteroids are constantly accelerating, as are all planetary bodies in the solar system, but as far as I know, no detected radiation has been detected from these bodies, other than the usual suspects, such as thermal radiation. AG