Posted in physical review messages And a special number of Classic quantum gravity On September 14, the final results of the MICROSCOPE mission measured the acceleration of free-falling objects in an Earth-orbiting satellite. The team found that the acceleration of object pairs varies by no more than one part in 10^15, ruling out any violations of the weak equivalence principle or deviations from the current understanding of general relativity at this level. credit: (c) ONERA
In new studies published in physical review messages And a special number of Classical and quantum gravity On September 14, a team of researchers presented the most accurate test yet of the weak equivalence principle, a key component of general relativity. The report describes the end results of MICROSCOPE MISSION, which tested the principle by measuring the acceleration of free-falling objects in an Earth-orbiting satellite. The team found that the accelerations of the pairs of objects differed by no more than one part in 10 .15th Exclude any violations of the weak equivalence principle or deviations from the current understanding of general relativity at this level.
“We have new and much better constraints for any future theory, because these theories must not be violated Equivalence principle At this level,” says Gilles Mitris, a scientist at the Côte d’Azur Observatory and a member of the MICROSCOPE team.
The general theory of relativity, published by Albert Einstein in 1915, describes how gravity works and its relationship to time and space. But because it does not take into account observations of quantum phenomena, researchers look for deviations from the theory at increasing levels of accuracy and in different situations. Such violations may indicate new interactions or forces that could unite relativity with quantum physics. The weak equivalence principle (WEP) test is one way to search for potential expansions of general relativity.
According to WEP, objects in a gravitational field fall the same way when no other forces act on them, even if they have different masses or compositions. To test the principle, the MICROSCOPE team designed their experiment to measure the Eötvös ratio – which relates the accelerations of two free-falling objects – with extremely high accuracy. If the acceleration of an object differs from another by more than one part in 1015ththe experiment will measure it and detect this WEP violation.
To measure the Eötvös ratio, the researchers monitored the acceleration of test blocks of platinum and titanium alloys as they orbited the Earth in the MICROSCOPE satellite. The experimental instrument uses electricity
To keep pairs of test blocks in the same position relative to each other and to look for possible differences in these forces, which would indicate differences in the acceleration of the objects.
The main challenge for the experiment was finding ways to test the instrument on Earth to ensure it would work as designed in space. “The difficulty is that the instrument we are launching cannot work on the ground,” says Manuel Rodriguez, a scientist at the French Aeronautical Laboratory. ONERA and a member of the MICROSCOPE team. “So it’s kind of a blind test.”
The MICROSCOPE mission tested the weak equivalence principle by measuring the acceleration of free-falling objects on an Earth-orbiting satellite. The researchers found that the acceleration of pairs of objects varies by no more than one part in 10 .15th, exclude any violations of the weak equivalence principle or deviations from the current understanding of general relativity at this level. Final results will be published in physical review messages And a special number of Classical and quantum gravity On the 14th of September. Credit: (c) CNES 2015
Once the machine was ready, the team launched it in 2016. They launched Preliminary results in 2017but they continued to analyze the data, taking into account systemic glitches and uncertainties, after the mission ended in 2018. They eventually found no WEP violation, and placed the most stringent constraints on the principle yet.
The team’s work paves the way for more accurate testing of WEP with satellite trials. Their analysis includes ways to improve the experimental setup, such as reducing cracks in the satellite’s coating that affected accelerometer measurements and replacing wires in the setup with contactless devices. A satellite experiment implementing these upgrades should be able to measure potential violations of WEP at the level of one part in 1017Researchers say. But the MICROSCOPE results will likely remain the most accurate limitation of WEP for a while.
“For at least a decade or maybe two decades, we don’t see any improvement in the space satellite experience,” Rodriguez says.
The MICROSCOPE mission: Final results of the equivalence principle test, physical review messages (2022).
American Physical Society
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