RUDN University Physicists Suggest the Way to Test Einstein's Theory

RUDN University physicists proposed an experiment to test the validity of the general theory of relativity. Unlike other experiments, it can be reproduced many times. The study is published in Acta Astronautica.

The general theory of relativity (GR) is the most successful theory of gravity, it is used in astronomy and cosmonautics. There are several experimental proofs of GR, but most of them are individual observations of rare natural phenomena that cannot be exactly repeated. RUDN University physicists have developed a "standard" space experiment that would allow reproducing observations. To do this, physicists propose to use the effect of a gravity assist—when the path of a body in space alters under the influence of the gravity of the planets.

"Einstein's gravity has a peculiar empiric justification that is based on a few individual observations of natural events, primarily in other star systems and galaxies. These scattered and diverse observations do not constitute a series of strictly repeated experiments. A "standard" experiment with multiple repeated results that convincingly match GR's predictions could fill this gap. we suggest such an experiment that involves a gravity assist maneuver of a space probe near Venus", said Alexander P. Yefremov, Doctor of Physics and Mathematics, the head of the Institute of Gravitation and Cosmology at RUDN University.

Physicists studied a model with the Sun, Venus, Earth, and a space probe. The planets revolve the Sun in almost circular orbits, and the probe follows an elliptical trajectory. The probe (a spherical body with a diameter of about 0.5 m and a mass of 100-200 kg) launches from Earth and falls freely towards Venus. It approaches Venus at a critical distance of a gravity assist maneuver and returns to Earth's orbit again. The essence of the experiment is that the small distortions of the trajectory, which are introduced by GR, are amplified after a gravity assist maneuver. Therefore, these deviations can be easily measured at the endpoint of the trajectory. RUDN University physicists carried out theoretical calculations, and then tested them in a numerical experiment in a computer simulation.

Calculations and simulation showed that the GR corrections affect the path of the probe before approaching Venus just slightly. The deviation at the point of minimum distance to Venus is only 35 km. Although this is a lot compared to the probe itself, on a cosmic scale this is a tiny distance. But after a GA maneuver, this deviation increases many times. The final points of the trajectory, calculated with and without GR edits, differ by 0.7-3.7 million kilometers (depending on the closest point of the probe to Venus). Such a difference is easy to measure from Earth with the available instruments.

"We show that in Newton and Einstein gravity, the probe's final positions, which are reached concurrently, may differ markedly, and an Earth-based observer can definitively measure that difference. In a real experiment, the probe's motion can differ from the "standard flight" format used in this study for convenience. But there is no doubt that existing space technologies can complete this experiment as described in this study", said Prof. Yefremov.

More information:
Alexander P. Yefremov et al, A “space-ball” experiment to specify the nature of gravity in the solar system, Acta Astronautica (2021). DOI: 10.1016/j.actaastro.2021.06.005

Provided by RUDN University