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Photo: Pixabay although Einstein's general theory of relativity was widely known more than a century ago, the research on it has never stopped. In a recent study, scientists verified the correctness of Einstein's general theory of relativity with extremely high precision.

In this experiment, scientists want to study the weak equivalence principle (weak equivalence principle) in Einstein's general theory of relativity, that is, "without considering interference factors such as air resistance, different objects have the same acceleration of free fall in the same gravitational field, regardless of their mass or material composition." To test the theory, scientists measured the acceleration of different objects in free fall on a French satellite called MICROSCOPE, which was launched in 2016.

During the lunar walk mission of Apollo 15, astronaut David Scott dropped a feather and a geological hammer in the absence of air resistance. Under the action of lunar gravity, two objects fall to the lunar surface with the same acceleration, which is one of the most famous experiments of the weak equivalence principle. In the latest experiment, MICROSCOPE took a similar approach, using two cylinders made of titanium and platinum alloys to perform free-fall experiments in the earth's gravitational field. By applying electrostatic force to the two objects, the satellite can keep their relative positions consistent. If the electrostatic forces required by two objects are different, it means that their accelerations are different, thus violating the weak equivalence principle.

This result proves that the acceleration difference of this pair of objects during free fall is no more than one-1015, which is the result of the research team's work over the past 20 years. This also means that on this scale, they do not find any evidence that violates the principle of weak equivalence.

This experimental result not only defines new constraints for the deviation of the weak equivalence principle, but also means that on this scale, the theory of gravity proposed by Einstein in 1915, that is, general relativity, has no deviation as a whole. Scientists have long tried to find deviations in this theory, because general relativity is the best description of gravity, but it is not compatible with quantum mechanics, the best physical model on a very small scale.

There is no deviation found in the experiment, which means that there is no sign that we need to expand the theory of general relativity to establish a connection with quantum mechanics. "in future theoretical research, we have this new and better constraint, because we now know that the weak equivalence principle must be true on this scale." Gilles M é tris said in a report at the American physical Society. He is a member of the MICROSCOPE team and a scientist at the C ô te d'Azur Observatory Observatory on the Cote d'Azur, France, whose study was published by the American physical Society.

The MICROSCOPE satellite was launched in April 2016 and 2017, and the researchers released preliminary experimental results. They have been analyzing the data since the end of the experiment in 2018. The latest study finds no evidence that the weak equivalence principle fails under the strictest constraints, meaning that this part of general relativity still holds. At the same time, the results of this study also lay a foundation for more accurate experiments in the future.

This is because scientists have summed up some schemes that can be used to improve the experimental equipment. Some potential upgrades include reducing defects in the outer coating of the satellite, thereby reducing the impact of the satellite on acceleration measurements, and replacing the current line system with wireless connections.

Through the above upgrade measures, the satellite is expected to detect whether the experiment will violate the weak equivalence principle with an accuracy of 1 / 1017, and the accuracy will be 100 times that of the current experiment. However, the research team also said that these improvements are still difficult to achieve, that is, in a short period of time, the experiments completed so far will still be the most accurate experiments to verify the weak equivalence principle.

"there will be no more progress in satellite experiments in the next 10 or even 20 years," said Manuel Rodrigues, a member of the MICROSCOPE project and a scientist at the French Academy of Astronautics (ONERA).

The results were published in the journal physical Review KuaiBao (Physical Review Letters) and the special issue of Classics and Quantum Gravity (Classical and Quantum Gravity) on September 14 local time.

Original text link:

Https://www.scientificamerican.com/article/einsteins-greatest-theory-just-passed-its-most-rigorous-test-yet/

This article comes from the official account of Wechat: global Science (ID:huanqiukexue), written by Robert Lea, translated by Zhang Yifei, revised by clefable

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