How Much Room Is Left for Exotic Gravity?

Introduction

For claims about antigravity or unconventional propulsion, one of the most important experimental questions is surprisingly simple: does gravity accelerate different kinds of matter differently? If a material could substantially weaken, screen or reverse its coupling to ordinary gravity because of its composition, a sufficiently sensitive comparison with another material should reveal a difference in free fall.

The strongest direct test of this idea is the MICROSCOPE satellite experiment. It compared titanium- and platinum-alloy test masses while they orbited Earth and found no violation of the weak equivalence principle. Its final result constrained the relative difference in their gravitational accelerations to the level of a few parts in 1015.[APS Journals]journals.aps.orgAPS JournalsMission: Final Results of the Test of the Equivalence Principle | Phys. Rev. Lett.September 14, 2022…Published: September 14, 2022

That does not prove that every imaginable modification of gravity is impossible. Some theories can evade this particular test through very short interaction ranges, screening mechanisms or effects that do not depend on material composition. But it leaves extraordinarily little room for a broad and important class of exotic-gravity models in which ordinary materials possess significantly different gravitational responses. In the context of UFO and antigravity claims, this distinction is crucial: speculative gravitational physics remains an active field, but precision free-fall experiments provide no evidence for the large, controllable departures from ordinary gravity that practical gravity cancellation would require.

What the equivalence principle means for antigravity ideas

The weak equivalence principle, also called the universality of free fall, says that objects subjected only to gravity should undergo the same acceleration regardless of their composition or internal structure. It is one of the empirical foundations underlying general relativity. Before MICROSCOPE, rotating torsion-balance experiments had already compared different substances to roughly the part-in-1013 level.[arXiv]arxiv.orgarXiv Torsion-balance tests of the weak equivalence principleTorsion-balance tests of the weak equivalence principleJuly 10, 2012…Published: July 10, 2012

The useful quantity is the Eötvös parameter, usually written η. In simplified form it compares the accelerations a1​ and a2​ of two test bodies:

η≈a1​+a2​2(a1​−a2​)​.

If the two materials fall identically, η=0. A reproducible non-zero value would be profound. Depending on its characteristics, it could indicate that gravitational and inertial mass are not universally equivalent or that an additional force is acting differently on different forms of matter. The MICROSCOPE researchers explicitly described a non-zero differential acceleration as a possible signature of an equivalence-principle violation or a new long-range force.[PubMed]pubmed.ncbi.nlm.nih.govMICROSCOPE Mission: First Results of a Space Test of the Equivalence Principle - PubMedDecember 8, 2017…Published: December 8, 2017

This is why such experiments are relevant to exotic-gravity proposals even though they are not experiments in propulsion. Many proposed extensions of established physics introduce additional scalar or vector fields. If the new field couples differently to different combinations of protons, neutrons, electrons or nuclear binding energy, two chemically different objects acquire slightly different effective gravitational responses. A composition-sensitive free-fall experiment can therefore detect — or constrain — the proposed interaction without having to know how to build a device exploiting it.[APS Journals]journals.aps.orgAPS JournalsMICROSCOPE Mission: First Constraints on the Violation of the Weak Equivalence Principle by a Light Scalar Dilaton | Phys. Re…

That relationship needs an important qualification. An equivalence-principle test is not a universal detector for every conceivable form of antigravity. A hypothetical effect that couples identically to every form of matter would not necessarily produce differential acceleration between titanium and platinum. Nor does MICROSCOPE by itself rule out forces confined to very short distances or models in which additional fields become strongly screened under the experimental conditions. Modern experimental limits therefore exclude regions of theoretical parameter space rather than proving a blanket theorem that no unconventional gravitational phenomenon can exist. Research on screened scalar fields, for example, continues precisely because such models can suppress observable fifth forces in some environments.[arXiv]arxiv.orgarXiv Fifth force induced by a chameleon field on nested cylindersFifth force induced by a chameleon field on nested cylindersApril 17, 2020…Published: April 17, 2020

What MICROSCOPE does rule against, with exceptional sensitivity, is the simpler and highly relevant possibility that ordinary materials possess appreciably different passive responses to Earth’s gravity.

What MICROSCOPE actually measured

MICROSCOPE was a French space mission led by CNES, with an instrument developed by ONERA and contributions from other European institutions. Launched in April 2016, the roughly 300-kilogram satellite placed its equivalence-principle experiment in a near-circular, Sun-synchronous Earth orbit. The reason for going to space was not theatrical: an orbiting experiment can maintain test bodies in effectively continuous free fall while escaping seismic disturbances and several other limitations of terrestrial laboratories.[CNES]cnes.frMicroscope | CNESMicroscope | CNES…

Inside the satellite were extremely sensitive differential electrostatic accelerometers. The critical comparison involved two concentric cylindrical masses made from different materials: titanium alloy and platinum-rhodium alloy. A second sensor used masses of the same composition and served as a reference. The instrument did not simply drop two objects and watch which reached the floor first. Electrostatic control kept the masses positioned relative to the spacecraft, and researchers measured the forces necessary to do so. If titanium and platinum experienced measurably different gravitational accelerations, a characteristic differential signal should appear.[APS Journals]journals.aps.orgAPS JournalsMission: Final Results of the Test of the Equivalence Principle | Phys. Rev. Lett.September 14, 2022…Published: September 14, 2022

The spacecraft itself was designed to minimise disturbances. Microthrusters compensated for nongravitational accelerations acting on the satellite, while the experiment monitored the relative behaviour of the test masses inside it. The mission accumulated about five months of usable science free-fall data during approximately two and a half years of operation; roughly two-thirds involved the different-composition titanium/platinum pair and the remainder the same-composition reference pair.[APS Journals]journals.aps.orgAPS JournalsMission: Final Results of the Test of the Equivalence Principle | Phys. Rev. Lett.September 14, 2022…Published: September 14, 2022

This matters because a measurement at the 10−15 level is fundamentally an exercise in distinguishing physics from apparatus. Residual atmospheric drag, Earth’s gravity gradient, magnetic disturbances, thermal variations and effects originating inside the accelerometer all had to be characterised. The MICROSCOPE team’s systematic-error analysis explicitly divided possible disturbances into external, spacecraft-related and internal instrumental sources.[arXiv]arxiv.orgarXiv MICROSCOPE: systematic errorsarXiv MICROSCOPE: systematic errors

The final analysis also dealt with thermal instability and short-lived instrumental events capable of imitating part of the expected signal. That makes the published number more meaningful than simply saying that the satellite was capable of detecting extremely small accelerations: the reported uncertainty incorporates a detailed assessment of effects that could masquerade as an equivalence-principle violation.[DOI]doi.orgMICROSCOPE Mission: Final Results of the Test of the Equivalence PrincipleMICROSCOPE Mission: Final Results of the Test of the Equivalence Principle

The final result was

η(Ti,Pt)=[−1.5±2.3(stat)±1.5(syst)]×10−15.

In other words, the measured value remained statistically compatible with zero. CNES summarises the final test as confirming universality of free fall at a precision of about 2.7×10−15, roughly 100 times beyond the precision available from earlier terrestrial tests.[APS Journals]journals.aps.orgAPS JournalsMission: Final Results of the Test of the Equivalence Principle | Phys. Rev. Lett.September 14, 2022…Published: September 14, 2022

A useful way to grasp the scale is that the experiment was looking for a fractional difference measured in quadrillionths. It did not find evidence that titanium was gravitationally special relative to platinum at that extraordinary sensitivity.

The null result squeezes many exotic-gravity models

MICROSCOPE was never merely a contest to add more decimal places to an old observation. Equivalence-principle violations occur naturally in numerous attempts to extend established gravitational physics.

One common example is a hypothetical fifth force mediated by a very light particle or scalar field. Ordinary gravity effectively couples universally to mass-energy, whereas a new field might couple to quantities such as baryon number or combinations of baryon and lepton number. Because different elements contain different proportions of protons and neutrons and have different nuclear binding energies, their acceleration in the combined gravitational and fifth-force field need not be exactly equal.[APS Journals]journals.aps.orgAPS JournalsMICROSCOPE Mission: First Constraints on the Violation of the Weak Equivalence Principle by a Light Scalar Dilaton | Phys. Re…

Even MICROSCOPE’s early results substantially tightened some such models. Researchers analysing light scalar or “dilaton” fields reported approximately an order-of-magnitude improvement over previous equivalence-principle constraints for parts of the relevant parameter space. For a sufficiently light mediator — below about 10−12 electronvolts in the model considered — the first MICROSCOPE result placed particularly stringent limits on hypothetical interactions coupled to baryon number or to the difference between baryon and lepton numbers.[APS Journals]journals.aps.orgAPS JournalsMICROSCOPE Mission: First Constraints on the Violation of the Weak Equivalence Principle by a Light Scalar Dilaton | Phys. Re…

Later theoretical analyses have translated the more precise final MICROSCOPE result into still tighter bounds on particular light-scalar couplings. The exact numerical constraint depends heavily on the assumed field, its mass, its interaction range and what “charge” it couples to, so there is no single model-independent number describing all fifth forces.[arXiv]arxiv.orgarXiv Constraining Light Scalar Field with Torsion-Balance Gravity ExperimentsarXiv Constraining Light Scalar Field with Torsion-Balance Gravity Experiments

That model dependence is essential when interpreting statements that MICROSCOPE “rules out exotic gravity”. It does not. Instead, its null result says that any proposed theory predicting a sufficiently large titanium-versus-platinum differential acceleration under the conditions of the experiment is incompatible with observation. A theory can survive only if its predicted violation lies beneath the experimental limit, falls outside the experiment’s relevant length scale or is suppressed by some mechanism.

The latter possibility motivates screening theories such as chameleon-type models. In these theories, an additional scalar interaction may become difficult to observe in dense environments. Researchers have therefore studied explicitly how a chameleon field would behave inside MICROSCOPE’s nested cylindrical apparatus. Such work illustrates why a precision null result narrows rather than terminates the search for new gravitational physics: increasingly elaborate models must be tested using the conditions under which they actually predict an observable signal.[arXiv]arxiv.orgarXiv Fifth force induced by a chameleon field on nested cylindersFifth force induced by a chameleon field on nested cylindersApril 17, 2020…Published: April 17, 2020

The important point for antigravity discussions is the direction in which the evidence has moved. The increasingly sensitive experiment did not uncover a growing anomaly. The permitted composition-dependent effect became smaller.

Why a tiny allowed deviation is not practical gravity control

The difference between an experimental upper limit and a usable effect is easy to lose in discussions of unconventional propulsion.

Suppose, purely for illustration, that an unknown interaction existed immediately below MICROSCOPE’s sensitivity and changed the gravitational acceleration of one material relative to another by roughly one part in 1015. At Earth’s surface, where gravitational acceleration is about 9.8ms−2, that fractional scale corresponds to only about 10−14ms−2 in differential acceleration.

That is not remotely comparable with cancelling Earth’s gravity. Levitation by gravitational cancellation would require an upward or gravity-reducing effect comparable with g itself — an order-unity alteration rather than a quadrillionth-level composition-dependent difference.

There is an even deeper problem. An equivalence-principle violation would demonstrate that two kinds of matter respond slightly differently; it would not demonstrate that anyone could switch the difference on and off. Practical gravity control would require several additional properties that an equivalence-principle anomaly alone would not provide:

Consequently, even the discovery of a statistically convincing 10−15-scale violation would be revolutionary fundamental physics without automatically being propulsion technology.

The gap becomes especially important when evaluating historical antigravity narratives. A laboratory report of a weight anomaly, unusual force or theoretical departure from general relativity cannot be promoted directly into evidence for operational gravity control. The intermediate experimental questions — composition dependence, magnitude, environmental dependence, systematic errors, repeatability and controllability — are precisely the questions that high-precision gravity experiments are designed to separate.

What remains open — and what does not

MICROSCOPE therefore supports a more precise conclusion than either “antigravity is impossible” or “physics still has mysteries, so antigravity remains equally plausible”.

There is genuine theoretical room for physics beyond general relativity. Some attempts to connect gravity with quantum physics predict additional fields, equivalence-principle violations or other departures from Einsteinian gravity. That is why experiments continue to improve. The absence of a MICROSCOPE signal is scientifically valuable precisely because plausible new-physics models predicted that a signal might occur.[ihes.fr]ihes.frPublication of the last results of the MICROSCOPE missionPublication of the last results of the MICROSCOPE mission

There are also experimental regimes that MICROSCOPE did not exhaust. Ground-based torsion balances can probe different interaction ranges and material combinations. A 2024 short-range equivalence-principle experiment, for example, compared copper and lead test bodies using a rotating three-tonne uranium attractor and found a differential acceleration consistent with zero, establishing new constraints on equivalence-principle-violating interactions at shorter ranges.[arXiv]arxiv.orgarXiv Short-range tests of the equivalence principlearXiv Short-range tests of the equivalence principle

Different experiments are therefore complementary rather than interchangeable. A new force can depend on range, composition, environment and its hypothetical mediator. No single titanium-versus-platinum measurement maps every possible modification of gravity.

But the freedom left by that caveat should not be mistaken for positive evidence of gravity manipulation. For the specific class of exotic-gravity ideas in which ordinary substances couple appreciably differently to Earth’s gravitational field, MICROSCOPE is an exceptionally severe constraint. The experiment deliberately placed chemically different masses in prolonged orbital free fall, controlled disturbances capable of creating false signals and searched at approximately the 10−15 level. It found no significant differential acceleration.[APS Journals]journals.aps.orgAPS JournalsMission: Final Results of the Test of the Equivalence Principle | Phys. Rev. Lett.September 14, 2022…Published: September 14, 2022

That result provides an important baseline for the wider subject of UFO and alleged antigravity research. The existence of speculative gravitational theories is real; so is legitimate experimental research seeking deviations from general relativity. Neither fact establishes that a laboratory, inventor or classified programme acquired a method of cancelling gravity. Where a proposed mechanism predicts that matter should fall substantially differently because of its composition, precision experiments have pushed the permissible discrepancy not towards engineering usefulness, but down towards parts in a quadrillion.

Amazon book picks

Further Reading

Books and field guides related to How Much Room Is Left for Exotic Gravity?. Use these as the next step if you want deeper reading beyond the article.

Book

Gravity: An Introduction to Einstein's General Relativity

By James B. Hartle

Einstein's theory of general relativity is a cornerstone of modern physics. It also touches upon a wealth of topics that students find fa...

See on Amazon

Book

Spacetime and Geometry: An Introduction to General Relativity

By Sean M. Carroll

An accessible introductory textbook on general relativity, covering the theory's foundations, mathematical formalism and major applications.

See on Amazon

Book

A First Course in General Relativity

By Bernard Schutz

Second edition of a widely-used textbook providing the first step into general relativity for undergraduate students with minimal mathema...

See on Amazon

Book

Gravitation

By Charles W. Misner, Kip S. Thorne et al.

First published in 1973, Gravitation is a landmark graduate-level textbook that presents Einstein’s general theory of relativity and offe...

See on Amazon

Browse more on Amazon:Gravity: An to Einstein's General Relativity booksSpacetime and Geometry: An to General Relativity booksA First Course in General Relativity

As an Amazon Associate I earn from qualifying purchases.

eBay marketplace picks

Marketplace Samples

Live-tested eBay searches with available results related to this page.

Shop location

UsingUSA USA USAUKCanadaAustraliaIreland

Selected fromspacecraft model oneBay.co.uk.

Related eBay result

Saturn V Rocket Model Kit – Apollo NASA Space Rocket – Detailed Display Model

GBP 42.29 | Free shippingNewSeller: tim 7864 (99.0% positive)Ships from: GB

View listing on eBay

Related eBay result

Monogram 1:72 Scale NASA Space Shuttle Model Kit 5904 ***RARE*** 1987 Kit

GBP 39.65 | Shipping GBP 5.15NewSeller: doodle325 (100.0% positive)Ships from: GB

View listing on eBay

Related eBay result

Space X Starship V3 and Superheavy Booster Model Rocket Kit Various Scales

GBP 279.99 | Free shippingNewSeller: titansproductdesignltd (96.5% positive)Ships from: GB

View listing on eBay

Related eBay result

ORION MPCV Spaceship Spacecraft Artemis Rocket Model - 6inch Collectible UK Made

GBP 56.86 | Shipping GBP 2.94NewSeller: pri-cut-services (100.0% positive)Ships from: GB

View listing on eBay

Browse more oneBay.co.uk

Example items shown for inspiration; availability and pricing can change. Branchoria may earn a commission if you purchase through outbound eBay links.

Endnotes

1. Source: journals.aps.org
Link:https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.129.121102

Published: September 14, 2022

2. Source: cnes.fr
Title: Microscope | CNES
Link:https://cnes.fr/en/projects/microscope

3. Source: arxiv.org
Title: arXiv Torsion-balance tests of the weak equivalence principle
Link:https://arxiv.org/abs/1207.2442

Published: July 10, 2012

4. Source: journals.aps.org
Link:https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.120.141101

5. Source: arxiv.org
Title: arXiv Fifth force induced by a chameleon field on nested cylinders
Link:https://arxiv.org/abs/2004.08403

Published: April 17, 2020

6. Source: journals.aps.org
Link:https://journals.aps.org/prd/abstract/10.1103/3486-4m4t

7. Source: onera.fr
Title: Einstein was right! | ONERA
Link:https://onera.fr/en/news/einstein-was-right

8. Source: arxiv.org
Title: arXiv MICROSCOPE Mission scenario, ground segment and data processing
Link:https://arxiv.org/abs/2201.10841

9. Source: arxiv.org
Title: arXiv MICROSCOPE: systematic errors
Link:https://arxiv.org/abs/2112.10559

10. Source: doi.org
Title: MICROSCOPE Mission: Final Results of the Test of the Equivalence Principle
Link:https://doi.org/10.26092/elib/3988

11. Source: arxiv.org
Link:https://arxiv.org/abs/1712.00483

12. Source: arxiv.org
Title: arXiv Constraining Light Scalar Field with Torsion-Balance Gravity Experiments
Link:https://arxiv.org/abs/2212.06032

13. Source: physics.aps.org
Link:https://physics.aps.org/articles/v15/94

14. Source: ihes.fr
Title: Publication of the last results of the MICROSCOPE mission
Link:https://www.ihes.fr/en/lest-results-microscope/

15. Source: arxiv.org
Title: arXiv Short-range tests of the equivalence principle
Link:https://arxiv.org/abs/2405.10982

16. Source: opera.cnes.fr
Title: fr User Manual — Opera
Link:https://opera.cnes.fr/index.php/User_Manual

17. Source: psimu.cnes.fr
Title: fr Basic Principle — Psimu
Link:https://psimu.cnes.fr/index.php/Basic_Principle

18. Source: doi.org
Link:https://doi.org/10.1007/JHEP06%282026%29039

19. Source: journals.aps.org
Title: 15g1 gklx
Link:https://journals.aps.org/prd/abstract/10.1103/15g1-gklx

20. Source: journals.aps.org
Title: gw1d hbxj
Link:https://journals.aps.org/prd/abstract/10.1103/gw1d-hbxj

21. Source: journals.aps.org
Title: tlqz 713s
Link:https://journals.aps.org/prl/abstract/10.1103/tlqz-713s

22. Source: journals.aps.org
Title: 17wc xxjm
Link:https://journals.aps.org/prd/abstract/10.1103/17wc-xxjm

23. Source: cnes.fr
Link:https://cnes.fr/en/projects/caspex

24. Source: journals.aps.org
Title: 8mc9 6cmr
Link:https://journals.aps.org/prd/abstract/10.1103/8mc9-6cmr

25. Source: cosparhq.cnes.fr
Link:https://cosparhq.cnes.fr/scientific-structure/scientific-commissions/scientific-commission-h-fundamental-physics-in-space/

26. Source: journals.aps.org
Link:https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.134.191003

27. Source: journals.aps.org
Link:https://journals.aps.org/prd/abstract/10.1103/PhysRevD.110.055022

28. Source: doi.org
Link:https://doi.org/10.1103/PhysRevD.110.055022

29. Source: journals.aps.org
Link:https://journals.aps.org/prd/abstract/10.1103/PhysRevD.109.124013

30. Source: doi.org
Link:https://doi.org/10.1140/epjc/s10052-024-12723-8

31. Source: journals.aps.org
Link:https://journals.aps.org/prd/abstract/10.1103/PhysRevD.109.064010

32. Source: journals.aps.org
Link:https://journals.aps.org/prd/abstract/10.1103/PhysRevD.108.095054

33. Source: doi.org
Link:https://doi.org/10.1103/physrevd.108.095054

34. Source: physics.aps.org
Link:https://physics.aps.org/articles/v16/s97

35. Source: journals.aps.org
Link:https://journals.aps.org/prd/abstract/10.1103/PhysRevD.107.024013

36. Source: physics.aps.org
Link:https://physics.aps.org/articles/v15/197

37. Source: physics.aps.org
Link:https://physics.aps.org/articles/v15/192

38. Source: physics.aps.org
Link:https://physics.aps.org/articles/v15/189

39. Source: physics.aps.org
Link:https://physics.aps.org/articles/v15/s141

40. Source: doi.org
Link:https://doi.org/10.1140/epjc/s10052-022-10905-w

41. Source: physics.aps.org
Link:https://physics.aps.org/articles/v15/156

42. Source: journals.aps.org
Link:https://journals.aps.org/prl/issues/129/12

43. Source: aps.org
Link:https://www.aps.org/about/news/2022/09/general-relativitys-weak-equivalence-principle

44. Source: aps.org
Title: New Results for MICROSCOPE Mission | American Physical Society
Link:https://www.aps.org/apsnews/2022/09/microscope-mission-general-relativity

45. Source: physics.aps.org
Title: philippe brax
Link:https://physics.aps.org/authors/philippe_brax

46. Source: physics.aps.org
Link:https://physics.aps.org/articles/v15/95

47. Source: onera.fr
Title: final results of microscope mission achieve record levels of precision
Link:https://onera.fr/en/presse/communiques-presse/final-results-of-microscope-mission-achieve-record-levels-of-precision

48. Source: doi.org
Link:https://doi.org/10.1103/PhysRevLett.129.101102

49. Source: journals.aps.org
Link:https://journals.aps.org/prl/issues/129/2

50. Source: physics.aps.org
Link:https://physics.aps.org/articles/v15/8

51. Source: doi.org
Title: Pulsed production of antihydrogen | Communications Physics
Link:https://doi.org/10.1038%2Fs42005-020-00494-z

52. Source: journals.aps.org
Link:https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.231102

53. Source: journals.aps.org
Link:https://journals.aps.org/prd/abstract/10.1103/PhysRevD.100.084006

54. Source: doi.org
Link:https://doi.org/10.1103%2FPhysRevD.99.055043

55. Source: doi.org
Link:https://doi.org/10.1103%2FPhysRevD.98.042002

56. Source: meetings-archive.aps.org
Link:https://meetings-archive.aps.org/apr/2018/h04/2/

57. Source: journals.aps.org
Link:https://journals.aps.org/prd/abstract/10.1103/PhysRevD.97.055039

58. Source: videotheque.cnes.fr
Link:https://videotheque.cnes.fr/index.php?id_cat=2911&id_doc=36188&rang=1&urlaction=doc

59. Source: physics.aps.org
Link:https://physics.aps.org/articles/v10/s133

60. Source: onera.fr
Link:https://onera.fr/fr/presse/l-onera-livre-au-cnes-l-instrument-d-accelerometrie-ultra-sensible-de-la-mission-microscope

61. Source: onera.fr
Title: a first for a cold atom accelerometer
Link:https://onera.fr/en/news/a-first-for-a-cold-atom-accelerometer

62. Source: journals.aps.org
Link:https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.106.151102

63. Source: journals.aps.org
Link:https://journals.aps.org/prl/recent?page=493

64. Source: link.aps.org
Title: tlqz 713s
Link:https://link.aps.org/doi/10.1103/tlqz-713s

65. Source: journals.aps.org
Title: 1my7 zklj
Link:https://journals.aps.org/prd/abstract/10.1103/1my7-zklj

66. Source: physics.aps.org
Link:https://physics.aps.org/authors/anonymous

67. Source: cmsm-ds.onera.fr
Link:https://cmsm-ds.onera.fr/html/microscope/Publications.html

68. Source: onera.fr
Link:https://onera.fr/fr/recherche-onera

69. Source: onera.fr
Title: Physics Domain
Link:https://onera.fr/en/phy-dphy

70. Source: onera.fr
Title: Domaine Physique
Link:https://onera.fr/fr/phy-dphy

71. Source: onera.fr
Link:https://onera.fr/en/dphy-research-units

72. Source: onera.fr
Link:https://onera.fr/fr/staff/judicael-bedouet

73. Source: onera.fr
Title: onera 70 years 1963 1983 expansion
Link:https://onera.fr/en/history/onera-70-years-1963-1983-expansion

74. Source: onera.fr
Link:https://onera.fr/fr/staff/elise-colin

75. Source: onera.fr
Link:https://onera.fr/en/identity

76. Source: onera.fr
Link:https://onera.fr/en/research/looking-to-the-future

77. Source: onera.fr
Link:https://onera.fr/en/phy-dota/onda-platform

78. Source: cnes.fr
Link:https://cnes.fr/projets/microscope/en-details

79. Source: cnes.fr
Link:https://cnes.fr/projets/microscope

80. Source: cnes.fr
Link:https://cnes.fr/node?page=12

81. Source: recrutement.cnes.fr
Title: fr Emploi CNES
Link:https://recrutement.cnes.fr/fr/annonce/4195923-26-253-dark-matter-detection-with-the-microscope-and-lisa-space-missions-75014-paris

82. Source: cnes.fr
Link:https://cnes.fr/en/projects/carioqa

83. Source: videotheque.cnes.fr
Link:https://videotheque.cnes.fr/index.php?id_cat=400&id_doc=32850&rang=1&urlaction=doc

84. Source: cnes.fr
Link:https://cnes.fr/projets/microscope/segment-sol

85. Source: cnes.fr
Link:https://cnes.fr/projets/carioqa

86. Source: cnes.fr
Title: electric satellites
Link:https://cnes.fr/en/projects/electric-satellites

87. Source: cnes.fr
Link:https://cnes.fr/en/projects/t2l2

88. Source: cnes.fr
Link:https://cnes.fr/en/projects/parasol

89. Source: cnes.fr
Link:https://cnes.fr/projets/microscope/satellite

90. Source: cnes.fr
Link:https://cnes.fr/en/news

91. Source: cnes.fr
Title: Press releases
Link:https://cnes.fr/en/press-releases

92. Source: cnes.fr
Link:https://cnes.fr/en/projects/goce

93. Source: arxiv.org
Link:https://arxiv.org/abs/2102.00022

94. Source: arxiv.org
Link:https://arxiv.org/html/2204.08484v4

95. Source: arxiv.org
Link:https://arxiv.org/pdf/2512.16804

96. Source: arxiv.org
Link:https://arxiv.org/abs/2209.15487

97. Source: space.com
Title: 32812 einstein equivalence principle put to test
Link:https://www.space.com/32812-einstein-equivalence-principle-put-to-test.html

98. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/29286705/

Published: December 8, 2017

99. Source: pmc.ncbi.nlm.nih.gov
Link:https://pmc.ncbi.nlm.nih.gov/articles/PMC10533407/

100. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/37137301/

101. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/36598504/

102. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/36179190/

103. Source: ui.adsabs.harvard.edu
Link:https://ui.adsabs.harvard.edu/abs/2022PhRvL.129l1102T/abstract

104. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/31868496/

105. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/29694146/

106. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/24702346/

107. Source: npl.washington.edu
Title: torsion balances
Link:https://www.npl.washington.edu/eotwash/torsion-balances

108. Source: npl.washington.edu
Title: equivalence principle
Link:https://www.npl.washington.edu/eotwash/equivalence-principle

109. Source: periodicos.capes.gov.br
Link:https://www.periodicos.capes.gov.br/index.php/acervo/buscador.html?id=W2049737160&task=detalhes

110. Source: ouci.dntb.gov.ua
Link:https://ouci.dntb.gov.ua/en/works/leqW0XDl/

111. Source: cosmosage.online
Link:https://cosmosage.online/arxiv/?pid=2205.14134&rank=pid

112. Source: Wikipedia
Title: Fifth force
Link:https://en.wikipedia.org/wiki/Fifth_force

Additional References

113. Source: youtube.com
Link:http://www.youtube.com/watch?v=9SLr5SW7EQo

114. Source: youtube.com
Link:http://www.youtube.com/watch?v=om1GmMjqXVI

115. Source: youtube.com
Link:http://www.youtube.com/watch?v=JF04GJqJa3Y

116. Source: youtube.com
Title: Neil de Grasse Tyson Explains The Equivalence Principle
Link:http://www.youtube.com/watch?v=AB1S5cSWNmI

117. Source: youtube.com
Title: Manuel Rodrigues
Link:http://www.youtube.com/watch?v=V9oUsinoUEE

118. Source: nature.com
Link:https://www.nature.com/articles/s41550-022-01833-6

119. Source: nature.com
Link:https://www.nature.com/articles/s41567-022-01706-9

120. Source: nature.com
Link:https://www.nature.com/articles/s41598-022-09473-6

121. Source: nature.com
Link:https://www.nature.com/articles/s42003-022-03601-8

122. Source: nature.com
Link:https://www.nature.com/articles/s41526-023-00306-y