Well done, Berndt... Great argument!

Florides' paper, "Einstein’s Equivalence Principle and the Gravitational Red Shift,"*makes a bold attempt to challenge a well-established interpretation of the Equivalence Principle (EP) and its connection to the gravitational redshift. While the paper raises some interesting points, its arguments often seem to miss the mark due to conceptual misunderstandings and

mathematical missteps.

A detailed response reveals several issues that undermine its core conclusions.

1. Misinterpretation of the Equivalence Principle (EP)

Florides' critique hinges on the claim that the Equivalence Principle cannot, by itself, predict the gravitational redshift, which he argues requires the full general theory of relativity. However, this argument appears to rest on a misunderstanding of what the EP actually asserts.

The EP, in its simplest form, states that the effects of gravity are locally indistinguishable from those of acceleration. This is a cornerstone of general relativity and serves as the foundation for many phenomena, including the gravitational redshift. The EP does not claim to provide a *complete* description of gravitational phenomena—it is a principle that guides the formulation of the theory, not a full theory in itself. Florides seems to conflate the EP with general relativity as a whole and criticizes it for not doing the work of a full theory. This confusion weakens the paper's main argument.

Additionally, Florides appears to dismiss the role of the EP in the redshift phenomenon by suggesting that gravitational redshift can only be derived from the full Einstein field equations. This is incorrect. While the field equations provide a more detailed and precise description, the EP, combined with special relativity, can indeed predict the gravitational redshift in a local region. The redshift occurs because clocks at different gravitational potentials run at different rates—a consequence directly derivable from the EP and special relativity.

2. Flawed Understanding of the Doppler Shift

Florides criticizes the standard use of the Doppler shift formula in the derivation of gravitational redshift, specifically in an accelerating frame of reference. He argues that the Doppler formula is not valid for accelerating bodies and thus should not be applied in this context. However, this criticism is based on a misapplication of the physics involved.

In relativity, the Doppler effect is indeed modified for accelerating observers, but the core principle that motion alters the frequency of received light remains valid. Florides’ argument dismisses the fact that in the small, locally flat regions where the EP applies, the effects of acceleration and gravity can be treated as equivalent. The use of the Doppler shift in this context is a reasonable approximation that holds in the weak-field limit and near a small, localized region.

His attempt to provide a “new” Doppler shift formula, based on classical mechanics and the Newtonian addition of velocities, undermines his argument further. General relativity has long shown that classical mechanics cannot accurately describe relativistic phenomena, particularly light propagation. By resorting to Newtonian assumptions, Florides unnecessarily complicates the issue and moves away from the relativistic framework in which gravitational redshift is naturally described.

3. Confusion Between Local and Global Effects

One of the key mistakes in Florides' analysis is his failure to clearly distinguish between local and global effects in general relativity. The EP is a local principle—it holds in a sufficiently small region of spacetime where the effects of curvature can be neglected. Florides seems to argue that because the EP does not account for gravitational redshift in a global sense, it is inadequate. However, this critique misunderstands the scope of the EP.

The EP is not designed to describe large-scale phenomena like the gravitational redshift across vast distances or regions of varying curvature. For such global phenomena, the full framework of general relativity, including the Einstein field equations, is required. Florides’ critique of the EP for failing to predict gravitational redshift globally is misplaced because the EP was never intended to do so. Local experiments in an accelerating frame do, in fact, predict the same redshift effects as gravitational fields, supporting the utility of the EP.

4. Inconsistencies in Mathematical Treatment

Florides' mathematical treatment of the problem, particularly in Section 3, where he derives his "new" Doppler shift formula, contains several conceptual inconsistencies. For instance:

- He argues that both emitter and receiver must undergo constant acceleration for the derivation of the redshift formula, but this is not necessary in the context of the EP. The standard derivation assumes a comparison between local frames at different gravitational potentials, where one frame could be stationary relative to the other. By insisting on both being accelerated, he introduces unnecessary complications.

- His reliance on Newtonian velocity addition is problematic. In relativistic physics, velocities do not simply add in the Newtonian sense, especially when dealing with light. The velocity of light is invariant and not subject to classical addition rules. Florides seems to be aware of this but continues to use classical mechanics for a problem that clearly demands a relativistic approach. This undermines the credibility of his mathematical derivations.

5. Failure to Address Key Counterarguments

The paper does not adequately address the well-established counterarguments to Florides’ claims. For instance, while he acknowledges that the gravitational redshift has been experimentally verified, such as in the Pound-Rebka experiment, he does not sufficiently reconcile his critique with these observations. The experiments confirm the predictions of both the EP and general relativity, and Florides' paper fails to explain why his theoretical objections should override this empirical evidence.

Moreover, the paper does not engage with the broader literature in modern physics that addresses the limitations of classical mechanics in relativistic contexts. Instead, it relies heavily on outdated references and a narrow selection of critiques, such as those by Fock and Synge, without considering the wealth of modern work that supports the utility of the EP in gravitational physics.

6. Philosophical Overreach

Florides concludes with a dramatic statement that the Equivalence Principle should be “buried with honors,” borrowing from Synge’s earlier critique. However, this is an overreach. While philosophical critiques of the EP, such as Synge’s, are valuable, they do not invalidate the vast experimental and theoretical successes of the EP in general relativity. The principle has stood the test of time precisely because it continues to make accurate predictions in a wide range of physical contexts.

Florides’ dismissal of the EP seems more rooted in a philosophical preference for a different approach rather than a substantive critique based on evidence or theory. He dismisses the successes of the EP without offering a more robust alternative, leaving his conclusion somewhat ungrounded.

Florides’ paper presents an ambitious critique of the Equivalence Principle, but it suffers from conceptual misunderstandings, a flawed mathematical approach, and an overreliance on classical mechanics. His arguments against the use of the EP to predict gravitational redshift do not hold up under scrutiny, and his new Doppler shift formula is unnecessary and incorrectly applied in a relativistic context.

While the paper raises interesting questions about the limitations of classical mechanics, it does not succeed in its attempt to dismantle the role of the EP in gravitational physics. The Equivalence Principle remains a cornerstone of modern physics, and the phenomena it predicts, including gravitational redshift, are well-supported both theoretically and experimentally.

In short, Florides’ critique is more a reflection of a misunderstanding of the EP’s role and scope than a substantive challenge to its validity. The paper would benefit from a more nuanced understanding of the interplay between the EP, general relativity, and relativistic physics as a whole.

Of course he's right... show me a single paper that has directly measured gravitational blueshift! You claim redshift is caused by gravity because light moves against an attracting force—wrong, it’s due to time dilation. You also claim that blueshift occurs because light gains energy from gravitational acceleration—if that were true, a light beam traveling from space to the surface of a gravitating body would gain energy, but at the same time it would lose energy as it moves into a region of stronger gravity, resulting in gravitational redshift. Therefore, gravitational blueshift doesn’t exist unless you're observing light emitted by a falling body from below, within a gravitational field.

Marco Einstein said:

• "Berndt starts with an infinite universe (homogeneous mass distribution) with no net Gravitational Force (constant field). Then, he carved a sphere corresponding to our observable universe and used Birkoff's Theorem to neglect the outside matter influence, thus magically generating a radial distribution of mass and a radial gravitational field."

No he doesn't he starts with a dust-sphere having a certain radius and density and of course a certain gravity and thus time dilation and redshift.

And then:

According to the shell theorem you can now put a solid shell around this dust-sphere and nothing would change. The magic is all in your dogmatized mind my "friend"...

@Berndt Barkholz

No he doesn't he starts with a dust-sphere having a certain radius and density and of course a certain gravity and thus time dilation and redshift.

Missing punctuation. C'mon, Berndt

I suppose you meant:

No, he doesn't.

He starts with a dust-sphere having a certain radius and density and of course a certain gravity and thus time dilation and redshift.

You know that you are postulating the shape of the external mass distribution (a spherical shell). If instead of that, we had a cube, that would be incorrect, and you wouldn't be able to use the shell theorem.

If the universe were finite and we were not at the center of it, again, you would be wrong...

I explained to you many times. The configuration where light is being emitted at the surface of a sphere and propagates to the center of the sphere would result in BLUESHIFT.

And then:

According to the shell theorem you can now put a solid shell around this dust-sphere and nothing would change. The magic is all in your dogmatized mind my "friend"...

I already know you are a crackpot. Now I have to add, a persistent crackpot.

What does this nonsense mean : "You know that you are postulating the shape of the external mass distribution (a spherical shell). If instead of that, we had a cube, that would be incorrect, and you wouldn't be able to use the shell theorem."

Stop bragging... you didn't "explain" anything... you postulate and expect me to take your word as the truth ! Being called a crackpot by an obviously dogmatized you is more like an award...

Now explain what your words above mean... what means this nonsense talk about a cube ? ...or are you out of your mind ?

Events like this and there are many of them, can only be explained with gravitational red-shift: https://www.astronews.com/news/artikel/2008/09/0809-020.shtml

It's in German, but a genius like you surely has no problems with that...

An international team of researchers has discovered a mysterious celestial object in the vicinity of a galaxy cluster 8.2 billion light years away in the constellation of Boetes, which resembles no previously known celestial body. The object appeared on February 21, 2006, became 120 times brighter over the course of around a hundred days, and then disappeared again within a similar period of time.

📷 Using the Hubble Space Telescope, astronomers have discovered an object that they do not know what it is. Image : NASA / ESA

The researchers led by Kyle Barbary from the University of California in Berkeley were actually using the Hubble Space Telescope to search for exploding stars, for supernovae in distant galaxy clusters. But what they discovered two and a half years ago in the direction of the galaxy cluster Cl1432.5+3332.8 was clearly not a supernova.

"The light curve is also not consistent with a gravitational lensing event," the astronomers write in their paper on the mysterious object, which will soon be published in the Astrophysical Journal . In such events, the brightness of a distant star is briefly increased by the gravity of an object in the foreground.

Barbary and her colleagues managed to record several spectra of the new star - but this only made the mystery even greater. "The spectrum is not only inconsistent with a supernova spectrum, it does not resemble anything we have in our catalogs." The researchers therefore conclude that it must be a new type of object of a previously unknown nature.

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There is not even any clarity about the distance of the object. The fact that it was in the area of ​​the galaxy cluster Cl1432.5+3332.8 does not mean that it must have physically belonged to it. The astronomers were unable to locate a galaxy in which the star could have been located. Since no movement of the object could be detected in the sky, it must be further than about 130 light years away, say Barbary and her colleagues. On the other hand, the spectrum shows that it could not have been further than 11 billion light years away. Between 130 and 11 billion light years - somewhere between us and the edge of the visible universe.

Well...They don't know what the object is,,, They know that it is between 130 lyr and 11E9 lyr.

There is no bullshit about Gravitational Redshift. There is no information about Lyman forest or lines or redshift.

How could this support your crackpot idea, Berndt?

If Gravitational Redshift could explain the object, they would have told us.

You have no idea what my crackpot observation, is able to show ! I have no theory dummy. What do you think it means when no Lyman forest was found in the spectrum...you are not even able to SEE what this observation of Kyle Barbary actually is showing, but hey... it needs a bit more grey matter than you can present... however you are intelligent enough to react when I forget a komma... bravo "Einstein" !

Then you state that: "If Gravitational Redshift could explain the object, "THEY" would have told us." ...a typical answer of a programmed AI... thinking independent from the program "THEY" do not allow you and as it seems it's not possible for you either !

Learn how to communicate. Don't make excuses for yourself all the time. Take responsibility.

"They" mean authors.

I didn't see any observation because the link you provided had no observation...:)

The bottom line is that if the universe were a sphere and we were at the center, and the CMB had been released at the sphere surface, then the light would be blueshifted... :)

Of course, you don't have a theory. You just push some stupid idea as if it were yours.

With respect to your "crackpot observation", I concluded you don't have any observation. If you were a scientist and had an astronomical observation, you would provide the reference to the paper instead of talking nonsense.

So. Think sphere. Think dusty sphere. The light from the dusty sphere reaching the center is Blueshifted and not redshifted.

Learn some Physics.

Learn how to communicate said little Marco... he doesn't know yet that just as one calls into the forest so it echoes back...