Solar-system tests of the relativistic gravity

TL;DR

This paper reviews the progress and future prospects of solar-system tests of relativistic gravity, highlighting technological advancements and their implications for understanding fundamental physics and cosmology.

Contribution

It provides a comprehensive summary of the historical development, current status, and future improvements in solar-system tests of relativistic gravity using advanced laser and clock technologies.

Findings

Radio and lunar laser ranging have achieved similar accuracy in testing gravity.

Future laser ranging and clock experiments will significantly enhance test precision.

Technological advancements may lead to breakthroughs in gravity and cosmology understanding.

Abstract

In 1859, Le Verrier discovered the Mercury perihelion advance anomaly. This anomaly turned out to be the first relativistic-gravity effect observed. During the 157 years to 2016, the precisions and accuracies of laboratory and space experiments, and of astrophysical and cosmological observations on relativistic gravity have been improved by 3-4 orders of magnitude. The improvements have been mainly from optical observations at first followed by radio observations. The achievements for the past 50 years are from radio Doppler tracking and radio ranging together with lunar laser ranging. At the present, the radio observations and lunar laser ranging experiments are similar in the accuracy of testing relativistic gravity. We review and summarize the present status of solar-system tests of relativistic gravity. With planetary laser ranging, spacecraft laser ranging and interferometric laser ranging (laser Doppler ranging) together with the development of drag-free technology, the optical observations will improve the accuracies by another 3-4 orders of magnitude in both the equivalence principle tests and solar-system dynamics tests of relativistic gravity. Clock tests and atomic interferometry tests of relativistic gravity will reach an ever-increasing precision. These will give crucial clues in both experimental and theoretical aspects of gravity, and may lead to answers to some profound issues in gravity and cosmology.