Compare · The Nature of Space & Time

Thermodynamics of Spacetime vs Verlinde Entropic Gravity

Emergent Spacetime & Gravity· within family

	Thermodynamics of Spacetime Frontier	Verlinde Entropic Gravity Frontier
Proposed	1995	2011 / 2017
Key figures	Ted Jacobson, Thanu Padmanabhan	Erik Verlinde
In one sentence	Jacobson 1995 showed that Einstein's field equation follows from thermodynamic relations on local Rindler horizons, suggesting general relativity is the equation of state of some underlying microscopic degrees of freedom rather than a fundamental law.	Verlinde proposed that gravity is not a fundamental force but an entropic effect arising from changes in information on holographic screens. The 2016 extension to dark matter has been substantially constrained by 2017-2019 weak-lensing and radial-acceleration-relation tests.
Predictions	Any consistent quantum gravity theory must reproduce the same horizon thermodynamics: a horizon entropy proportional to the horizon's area, S = A / (4 G_N), and the Unruh temperature T = a / (2π), the warmth an accelerating observer feels, in classical and semi-classical limits Modifications to the microscopic structure of spacetime (different entropy-area relation, different horizon temperature) imply higher-curvature corrections to Einstein's equation that could appear in strong-gravity regimes Extended gravity theories with torsion give specific modifications to the thermodynamic relations; observational signatures in gravitational waves or cosmology test these	2010 framework: Newton's law of gravity recovered as an entropic force on holographic screens; relativistic generalization should match GR at leading order 2016 dark-matter extension: a specific scale-dependent extra gravitational potential producing MOND-like behavior in galaxies, without dark-matter particles Specific baryonic Tully-Fisher-like relations between baryonic mass and apparent dark mass; deviations from the predicted scaling falsify the dark-matter extension
Where it breaks	Many authors argue this is a reinterpretation rather than a derivation: assuming entropy-area and Unruh temperature already encodes quantum-gravity input, so Einstein's equations may simply be being rewritten in thermodynamic language The microscopic degrees of freedom remain unspecified; the result is compatible with many underlying theories and therefore doesn't discriminate between them It is unclear how to extend the thermodynamic picture beyond near-equilibrium local Rindler horizons to strong quantum or highly dynamical regimes The framework gives no distinctive observable predictions beyond 'GR plus possible higher-curvature corrections from the underlying microscopic theory'	Lelli, McGaugh & Schombert (2017) tested the 2016 prediction against the radial acceleration relation across ~150 SPARC-database galaxies and found inconsistencies with the predicted scaling at low accelerations Tamosiunas et al. (2019) tested the prediction at galaxy-cluster scales and found significant tension with observed lensing profiles The original 2010 entropic derivation has been criticized for assuming too much input (Bekenstein-Hawking entropy-area law, Unruh temperature) to legitimately derive Newton's gravity from first principles The microscopic model of underlying degrees of freedom remains vague; critics see the framework as under-specified compared to explicit dark-matter models No fully relativistic, calculable version of the 2016 dark-matter scheme exists; observational analyses use phenomenological approximations
Key unresolved problem	The missing-atoms problem: the argument recovers Einstein's gravity by treating spacetime like a heat-carrying gas, but it never says what the underlying atoms of spacetime actually are, leaving the microscopic ingredients completely unidentified.	The cluster mismatch: the 2016 version that tries to do away with dark matter predicts how galaxy clusters should bend light, but those predictions miss the real measurements by a wide margin, and no fully worked-out relativistic version exists to fix it.
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Thermodynamics of Spacetime

1995 · Frontier

Verlinde Entropic Gravity

2011 / 2017 · Frontier

Proposed

1995

2011 / 2017

Key figures

Ted Jacobson, Thanu Padmanabhan

Erik Verlinde

In one sentence

Jacobson 1995 showed that Einstein's field equation follows from thermodynamic relations on local Rindler horizons, suggesting general relativity is the equation of state of some underlying microscopic degrees of freedom rather than a fundamental law.

Verlinde proposed that gravity is not a fundamental force but an entropic effect arising from changes in information on holographic screens. The 2016 extension to dark matter has been substantially constrained by 2017-2019 weak-lensing and radial-acceleration-relation tests.

Predictions

Any consistent quantum gravity theory must reproduce the same horizon thermodynamics: a horizon entropy proportional to the horizon's area, S = A / (4 G_N), and the Unruh temperature T = a / (2π), the warmth an accelerating observer feels, in classical and semi-classical limits
Modifications to the microscopic structure of spacetime (different entropy-area relation, different horizon temperature) imply higher-curvature corrections to Einstein's equation that could appear in strong-gravity regimes
Extended gravity theories with torsion give specific modifications to the thermodynamic relations; observational signatures in gravitational waves or cosmology test these

2010 framework: Newton's law of gravity recovered as an entropic force on holographic screens; relativistic generalization should match GR at leading order
2016 dark-matter extension: a specific scale-dependent extra gravitational potential producing MOND-like behavior in galaxies, without dark-matter particles
Specific baryonic Tully-Fisher-like relations between baryonic mass and apparent dark mass; deviations from the predicted scaling falsify the dark-matter extension

Where it breaks

Many authors argue this is a reinterpretation rather than a derivation: assuming entropy-area and Unruh temperature already encodes quantum-gravity input, so Einstein's equations may simply be being rewritten in thermodynamic language
The microscopic degrees of freedom remain unspecified; the result is compatible with many underlying theories and therefore doesn't discriminate between them
It is unclear how to extend the thermodynamic picture beyond near-equilibrium local Rindler horizons to strong quantum or highly dynamical regimes
The framework gives no distinctive observable predictions beyond 'GR plus possible higher-curvature corrections from the underlying microscopic theory'

Lelli, McGaugh & Schombert (2017) tested the 2016 prediction against the radial acceleration relation across ~150 SPARC-database galaxies and found inconsistencies with the predicted scaling at low accelerations
Tamosiunas et al. (2019) tested the prediction at galaxy-cluster scales and found significant tension with observed lensing profiles
The original 2010 entropic derivation has been criticized for assuming too much input (Bekenstein-Hawking entropy-area law, Unruh temperature) to legitimately derive Newton's gravity from first principles
The microscopic model of underlying degrees of freedom remains vague; critics see the framework as under-specified compared to explicit dark-matter models
No fully relativistic, calculable version of the 2016 dark-matter scheme exists; observational analyses use phenomenological approximations

Key unresolved problem

The missing-atoms problem: the argument recovers Einstein's gravity by treating spacetime like a heat-carrying gas, but it never says what the underlying atoms of spacetime actually are, leaving the microscopic ingredients completely unidentified.

The cluster mismatch: the 2016 version that tries to do away with dark matter predicts how galaxy clusters should bend light, but those predictions miss the real measurements by a wide margin, and no fully worked-out relativistic version exists to fix it.

Reader vote

No votes yet