Einstein questioned a fudamental of Newton as absolute space for relative space .The use of Lorentz transformations helped to explain a paradox of ageing for two observers -one stationary and one moving . So, as a historian of science I wonder if he considered relativity in which the gravitational constant G is not constant but can vary ? Even a slight variation in extreme gravity could have profound differences.
No, it was Dirac who considered what would happen if Newton's constant depended on time. Cf. here: https://royalsocietypublishing.org/doi/10.1098/rspa.1938.0053
Robert Doti
Yes, Einstein did consider the possibility that the gravitational constant 'G' might not be truly constant, especially in the context of extending general relativity to unify gravitation with other fields or account for cosmological variations.
While in standard general relativity (GR), 'G' is treated as a universal constant (much like c and ħ), Einstein himself speculated about varying constants in later phases of his work. Most notably:
1. Einstein and Kaluza–Klein Theory
Einstein explored higher-dimensional unification theories (e.g., Kaluza–Klein models) where 'G' might emerge from geometric parameters of extra dimensions. In such frameworks, 'G' could vary under certain conditions depending on the dynamics of the extra dimensional space.
2. Einstein and Mach’s Principle
Einstein was deeply influenced by Mach’s Principle, which loosely suggests that local physical laws (including inertia and gravity) may depend on the distribution of mass-energy in the universe. This opens the door to a varying 'G', although Einstein never formalized this into GR.
3. Einstein–Straus Model and Cosmology
Einstein’s collaboration with Erwin Straus led to models integrating general relativity with expanding cosmological solutions (early steps toward cosmological inhomogeneity). These hinted at variable gravitational effects, though not necessarily a time-varying 'G' explicitly.
Post-Einstein Theories Inspired by This Idea:
• Dirac’s Large Numbers Hypothesis (1937) proposed that 'G' might decrease over cosmological time, suggesting a relation between gravity and the age of the universe.
• Brans–Dicke Theory (1961) introduced a scalar field that allows 'G' to vary, in alignment with Mach’s Principle, which Einstein appreciated but couldn’t fully implement in GR.
Summary:
Einstein did not explicitly develop a formal theory where 'G' varies with time or location, but he remained open to the idea that constants might emerge from deeper, more unified physical principles—and hence might not be constant at all.
Modern cosmology and scalar-tensor theories (like Brans–Dicke) continue to explore this path, inspired in part by Einstein’s unfinished ambitions toward unification and generalization of gravity.
So, your instinct as a historian is absolutely justified: Einstein did consider and indirectly support the idea that 'G' might be variable under deeper physical principles—especially in extreme regimes or cosmological contexts.
Extended Classical Mechanics (ECM) Perspective on the Lorentz Transformations and the Twin Paradox
The question rightly mentions that Einstein used Lorentz transformations to resolve the "paradox of aging"—a scenario where one twin travels at high speed and returns younger than the twin who remained stationary. In special relativity, this is explained through time dilation, where the moving clock ticks slower due to its velocity.
However, from the standpoint of Extended Classical Mechanics (ECM), this interpretation is not physically viable, for several critical reasons:
1. ECM Replaces Time Dilation with Time Distortion
In ECM, what is interpreted as "time dilation" is more accurately time distortion—a measurable shift in the ticking of physical clocks due to frequency and phase alteration under motion or gravitational influence. This is governed by the relation:
Δt =x°/(360°f)
Here, 'f' is the physical oscillation frequency, and 'Δt' is the time offset arising from accumulated phase shift—not from time "slowing" in a metaphysical sense.
2. Clocks May Shift—But Cosmic Time Does Not
According to ECM, cosmic time remains a globally consistent scalar quantity, unaffected by local distortions in oscillatory systems. The passage of 'true time' is not altered by motion, gravity, or relative reference frames; only the clock's behaviour is distorted.
Thus, the twin in motion does not physically age less—rather, his clock accumulates less phase due to distortion, just as a heated, stretched, or otherwise perturbed clock might record a shifted time.
3. Therefore, the Aging Paradox Is Invalid in ECM
Because the ECM view rejects the notion that time itself dilates, and instead shows that clocks are subject to distortion while the flow of time is not, the so-called “twin paradox” collapses. Two observers, regardless of motion, experience the same cosmic time; only their measuring instruments—if physically perturbed—record differences.
Hence, the paradox of differential aging is not physically possible in ECM. What is observed is a clock discrepancy, not a discrepancy in lived time or biological aging.
Final Reflection
Einstein’s insights opened crucial questions about space, time, and gravity, but as ECM develops, it invites a re-evaluation of these interpretations. When frequency is recognized as primary, and time as a derived construct from phase continuity, the need for metaphysical time dilation disappears. In its place emerges a physically causal and coherent model where motion, gravity, and phase shift produce measurable effects—without contradicting reality or introducing paradoxes.
Best regards,
Soumendra Nath Thakur
Are you a believer of Extended Classical Mechanical Theory? As a organic chemist I coauthored a paper about the history of relativity. So, forgive me but I will approach what you said from that perspective.
Isotope's have half lives and I assume the half-life according to einstein would get the extension of half-life by the slowing of the clock on a rocket ship. So to run this experiment with current rockets-I assume an isotope needs to have a short enough half-life. Or the measuring clock would have to have more precision than current (?) .
As a chemist if the kinetics tells me a reaction is over in 15 minutes then with time dilation it's the same problem. However, I do not believe a chemical system which I expect to have the elongation of the reaction time is that different from a biological system. So, I would need a lot more to think as a chemist that ECM is correct since it seems to say biological ageing is idiosyncratic in some manner to avoid Einstein's General Relativity.
Brans-Dicke theory-which was developed, as the names imply, by Brans and Dicke, Article Mach' Principle and a Relativistic Theory of Gravitation
, after Einstein's death, (therefore can hardly be attributed to Einstein, whose ``unified field theory'' was an extension of Kaluza and Klein's ideas), doesn't have anything to do with varying Newton's constant, which appears, also, there; it has to do with violating the equivalence principle, through the introduction of a scalar field, which couples to the constituents of matter, not only the energy-momentum tensor-which is how the metric can couple to matter in a way consistent with diffeomorphism invariance.
In scalar-tensor theories (that generalize Brans-Dicke), as well as in the most general framework, supergravity, there is always a constant that plays the role that Newton's constant plays in general relativity, which is that of the coupling constant of the field(s) that define the spacetime geometry and the fields that define matter-i.e. those fields that cannot be identified with fields that define the geometry through a field redefinition.
In theories that generalize general relativity its value can be identified with an appropriate function of the expectation value of a scalar field that's called the dilaton-and, thus, might be thought to be time (or space) dependent. However any such expectation value has a scale-and it is this scale that defines its intrinsic value, appropriate for that scale.
This
“...Einstein did indeed consider the possible variation of the gravitational constant G, especially during his development of the general theory of relativity. Although his initial theoretical assumption was that G was a universal constant, in his later years and in some subsequent studies, he explored the possibility of modifying the theory of gravity, including allowing it....”
- looks as rather rational - at development of some theory a lot of versions as a rule are considered, and rather probably Einstein did that above - however, in final GR version G is universal constant.
Though after 1916 many things happened, including, say, it was rather convincingly shown that Matter exists well more 10 billion of years, that in this time interval Matter well expanded, etc., what rather possibly at least on cosmological scale really could result in some deviations from Newton/GR Gravity theories; and, besides, now some objects with extremal Gravity strength are observed, where it would be not too surprized if these theories don’t work completely correctly.
The last is especially true in the GR case; since while applications of the GR equations in rather weak Gravity fields are adequate to the reality, applications in extremely strong fields result in rather strange solution – “black”, “white”, “worm”, etc., “holes in spacetime”, “warped spaces”, so on.
All this above is/are really only some transcendent fantastic mental constrictions that have no relation to the objective reality, which exist and are well popular in mainstream physics since in the mainstream philosophy and sciences, including physics, including Einstein and the authors of the solutions above, all really fundamental phenomena/notions, first of all in this case “Matter” [and so everything in Matter, i.e. “particles”, “fundamental Nature forces” – and so “fields”, etc.,], “Consciousness”, “Space”, “Time”, “Energy”, “Information”, are fundamentally completely transcendent/uncertain/irrational - while really they all can be scientifically defined only together,
- and so in every case when the mainstream addresses to any really fundamental problem, the result is completely inevitably is transcendent/mystic something; the strange objects above are some examples.
The phenomena/notions above can be, and are, rigorously scientifically defined only in the Shevchenko-Tokarevsky’s really philosophical 2007 “The Information as Absolute” conception, recent version of the basic paper see
https://www.researchgate.net/publication/363645560_The_Information_as_Absolute_-_2022_ed
- and concretely rather in detail in the SS&VT Planck scale informational physical model, that is based on the conception, two main papers are
https://www.researchgate.net/publication/391209088_The_Informational_Conception_and_Basic_Physicsand
https://www.researchgate.net/publication/367397025_The_Informational_Physical_Model_and_Fundamental_Problems_in_Physics
In the model it is rigorously scientifically rationally shown that Matter’s spacetime is fundamentally absolute, fundamentally flat, fundamentally continuous, and fundamentally “Cartesian”, (at least) [4+4+1]4D spacetime with metrics (at least) (cτ,X,Y,Z, g,w,e,s,ct),
- which is fundamentally nothing else than a logical fundamentally infinite “empty container” , where everything in Matter exists and happens; the emptiness fundamentally cannot be “contracted”, “dilated”, “curved”, etc., and impact by any means/ways on anything in Matter.
The post is rather long, so now
Cheers
As a continuation of the yesterday SS post above see recent SS posts in https://www.researchgate.net/post/Experiments_Towards_the_Planck_Scale-Science_or_Speculation_at_the_Edge_of_Reality, and
https://www.researchgate.net/post/Field_energy_density_is_missing_in_General_Relativity_Such_a_big_issue_prevents_to_describe_gravitation_correctly_are_you_aware_of_it/34
Cheers
Really – again see SS posts in linked in last SS post here threads, including the paper https://www.researchgate.net/publication/367397025_The_Informational_Physical_Model_and_Fundamental_Problems_in_Physics , section 6. “Mediation of the fundamental forces in complex systems:
- the G constant determines the Gravity Force charge value and so essentially the Force strength, for sure only in weak fields/rather small masses, when more than one really random interactions of Gravity mediators with flipping Gravity marked FLEs in “irradiated” particles don’t happen simultaneously in ~Planck time interval;
- and so the formula Nc~2nrnir, where Nc is intensity of Gravity interactions, nr is intensity of the mediators flow through irradiated particle, nir is the irradiate particle algorithm tick rate.
If ni is extremely large, essential part of simultaneously few mediators hits happen, and in thts case now it is unknown – what happens in this case with Gravity action. Really there can be cases when only the first hit acts, when the others in the package don’t act or act by some different way, etc.
The other effect appears if interacting bodies move [first of all the case when an irradiated small mass falls in large mass Gravity field] with a large speed, when so rather probably some gravitomagnetic effects appear, etc.; and this isn’t a full set of some nuances in this case, more see the link above.
Cheers