Developments of the general relativity accuracy test (GReAT): a ground-based experiment to test the weak equivalence principle

General relativity is founded on the experimental fact that in a gravitational field all bodies fall with the same acceleration regardless of their mass and composition. This is the weak equivalence principle, or universality of free fall. Experimental evidence of a violation would require either that general relativity is to be amended or that another force of nature is at play. In 1916 Einstein brought as evidence the torsion balance experiments by Eötvös, to 10-8–10-9. In the 1960s and early 70s, by exploiting the "passive" daily rotation of the Earth, torsion balance tests improved to 10-11 and 10-12. More recently, active rotation of the balance at higher frequencies has reached 10-13. No other experimental tests of general relativity are both so crucial for the theory and so precise and accurate. If a similar differential experiment is performed inside a spacecraft passively stabilized by 1 Hz rotation while orbiting the Earth at ≃ 600 km altitude the test would improve by 4 orders of magnitude, to 10-17, thus probing a totally unexplored field of physics. This is unique to weakly coupled concentric macroscopic test cylinders inside a rapidly rotating spacecraft.

Download Full-text

Testing the weak equivalence principle

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309990688 ◽

2009 ◽

Vol 5 (S261) ◽

pp. 390-401 ◽

Cited By ~ 1

Author(s):

Anna M. Nobili ◽

Gian Luca Comandi ◽

Raffaello Pegna ◽

Donato Bramanti ◽

Suresh Doravari ◽

...

Keyword(s):

General Relativity ◽

Equivalence Principle ◽

Large Scale ◽

Past History ◽

Low Earth Orbit ◽

Small Scale ◽

Current View ◽

Weak Equivalence ◽

Weak Equivalence Principle ◽

The Universe

AbstractThe discovery of Dark Energy and the fact that only about 5% of the mass of the universe can be explained on the basis of the current laws of physics have led to a serious impasse. Based on past history, physics might indeed be on the verge of major discoveries; but the challenge is enormous. The way to tackle it is twofold. On one side, scientists try to perform large scale direct observations and measurements – mostly from space. On the other, they multiply their efforts to put to the most stringent tests ever the physical theories underlying the current view of the physical world, from the very small to the very large. On the extremely small scale very exciting results are expected from one of the most impressive experiments in the history of mankind: the Large Hadron Collider. On the very large scale, the universe is dominated by gravity and the present impasse undoubtedly calls for more powerful tests of General Relativity – the best theory of gravity to date. Experiments testing the Weak Equivalence Principle, on which General Relativity ultimately lies, have the strongest probing power of them all; a breakthrough in sensitivity is possible with the “Galileo Galilei” (GG) satellite experiment to fly in low Earth orbit.

Download Full-text

Satellite Laser-Ranging as a Probe of Fundamental Physics

Scientific Reports ◽

10.1038/s41598-019-52183-9 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 4

Author(s):

Ignazio Ciufolini ◽

Richard Matzner ◽

Antonio Paolozzi ◽

Erricos C. Pavlis ◽

Giampiero Sindoni ◽

...

Keyword(s):

General Relativity ◽

Gravitational Field ◽

Equivalence Principle ◽

Free Fall ◽

Satellite Laser Ranging ◽

Laser Ranging ◽

Weak Equivalence ◽

Fundamental Physics ◽

Weak Equivalence Principle ◽

Gravitational Theories

Abstract Satellite laser-ranging is successfully used in space geodesy, geodynamics and Earth sciences; and to test fundamental physics and specific features of General Relativity. We present a confirmation to approximately one part in a billion of the fundamental weak equivalence principle (“uniqueness of free fall”) in the Earth’s gravitational field, obtained with three laser-ranged satellites, at previously untested range and with previously untested materials. The weak equivalence principle is at the foundation of General Relativity and of most gravitational theories.

Download Full-text

THE EQUIVALENCE PRINCIPLE AS A PROBE FOR HIGHER DIMENSIONS

International Journal of Modern Physics D ◽

10.1142/s0218271805007991 ◽

2005 ◽

Vol 14 (12) ◽

pp. 2315-2318 ◽

Cited By ~ 3

Author(s):

PAUL S. WESSON

Keyword(s):

General Relativity ◽

Equivalence Principle ◽

Particle Physics ◽

Higher Dimensions ◽

Weak Equivalence ◽

Weak Equivalence Principle ◽

Five Dimensions ◽

Geometrical Symmetry ◽

Higher Dimensional

Higher-dimensional theories of the kind which may unify gravitation with particle physics can lead to significant modifications of general relativity. In five dimensions, the vacuum becomes non-standard, and the Weak Equivalence Principle becomes a geometrical symmetry which can be broken, perhaps at a level detectable by new tests in space.

Download Full-text

Testing the Equivalence Principle in space with MICROSCOPE: the data analysis challenge

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314010953 ◽

2014 ◽

Vol 10 (S306) ◽

pp. 382-384 ◽

Cited By ~ 2

Author(s):

Joel Bergé ◽

Quentin Baghi ◽

Sandrine Pires

Keyword(s):

General Relativity ◽

Data Analysis ◽

Missing Data ◽

Equivalence Principle ◽

Colored Noise ◽

Weak Equivalence ◽

Beyond The Standard Model ◽

Weak Equivalence Principle ◽

Upper Limits ◽

The Standard Model

AbstractTheories beyond the Standard Model and General Relativity predict a violation of the Weak Equivalence Principle (WEP) just below the current best experimental upper limits. MICROSCOPE (Micro-Satellite à traînée Compensée pour l'Observation du Principe d'Equivalence) will allow us to lower them by two orders of magnitude, and maybe to detect a WEP violation. However, analyzing the MICROSCOPE data will be challenging, mostly because of missing data and a colored noise burrying the signal of interest. In this communication, we apply an inpainting technique to simulated MICROSCOPE data and show that inpainting will help detect a WEP violation signal.

Download Full-text

FLAVOR-OSCILLATION CLOCKS, CONTINUOUS QUANTUM MEASUREMENTS AND A VIOLATION OF EINSTEIN EQUIVALENCE PRINCIPLE

Modern Physics Letters A ◽

10.1142/s0217732399002662 ◽

1999 ◽

Vol 14 (36) ◽

pp. 2545-2556 ◽

Cited By ~ 7

Author(s):

A. CAMACHO

Keyword(s):

General Relativity ◽

Probability Distribution ◽

Reference Frame ◽

Quantum Measurement ◽

Equivalence Principle ◽

Space Time ◽

Weak Equivalence ◽

Weak Equivalence Principle ◽

Minkowskian Space ◽

Flavor Oscillation

The relation between Einstein equivalence principle and a continuous quantum measurement is analyzed in the context of the recently proposed flavor-oscillation clocks, an idea pioneered by Ahluwalia and Burgard (Gen. Rel. Grav.29, 681(E) (1997)). We will calculate the measurement outputs if a flavor-oscillation clock, which is immersed in a gravitational field, is subject to a continuous quantum measurement. Afterwards, resorting to the weak equivalence principle, we obtain the corresponding quantities in a freely falling reference frame. Finally, comparing this last result with the measurement outputs that would appear in a Minkowskian space–time it will be found that they do not coincide, in other words, we have a violation of Einstein equivalence principle. This violation appears in two different forms, namely: (i) the oscillation frequency in a freely falling reference frame does not match with the case predicted by general relativity, a feature previously obtained by Ahluwalia; (ii) the probability distribution of the measurement outputs, obtained by an observer in a freely falling reference frame, does not coincide with the results that would appear in the case of a Minkowskian space–time. Concerning this last difference, the probability distribution differs in two directions. Firstly, the maximum, as function of the energy of the system (that emerges if we calculate first the probability distribution in the original curved manifold and then, resorting to the weak equivalence principle, we find the corresponding expression in a freely falling reference frame) is shifted with respect to the case in which the system is in a Minkowskian space–time. Secondly, the magnitude of this maximum is not equal to the respective quantity predicted by general relativity. In other words, we obtain two new theoretical results that predict a violation of Einstein equivalence principle, and that could be measured.

Download Full-text