Einstein’s test of general relativity has big implications

The researchers used a satellite orbiting the Earth to do this Very accurate test It is a fundamental premise of Einstein’s general theory of relativity, which is the modern theory of gravitation. The question is whether two different types of mass – gravitational and inertial – are identical. Scientists found that two objects aboard the satellite fell toward Earth at the same rate, to an accuracy of one part in a quadrillion. This successful test of Einstein’s theory has fundamental implications for current cosmological mysteries – for example, the question of the existence of dark matter and dark energy.

deceive the ancients

Gravity is the force that holds the universe together, attracting distant galaxies and guiding them in an eternal cosmic dance. The force of gravity is controlled in part by the distance between two objects, but also by the masses of the objects. An object with a greater mass experiences greater gravity. The technical name for this type of mass is “gravitational mass”.

Mass has another property that one might call inertia. This is the tendency of the organism to resist changes in movement. In other words, bulky things are hard to move: it’s easier to push the bike from car. The technical name for this type of mass is “inertial mass”.

There is no reason a priori Suppose the gravitational mass and the inertial mass are the same. One controls the force of gravity, while the other controls movement. If they were different, then heavy and light objects would fall at different rates, and indeed the philosophers of ancient Greece noted that the hammer and the feather fall differently. Heavy objects seem to fall faster than light ones. We now know that air resistance is the culprit, but that wasn’t evident in the past.

The situation was clarified on 17The tenth In the last century, when Galileo performed a series of experiments using slopes and fields of different masses to show that objects of different masses fall at the same rate. (His often cited experience of dropping balls from the Tower of Pisa was likely fabricated.) In 1971, astronaut David Scott Repeat convincingly Galileo’s experiment on the airless moon, when he dropped a hammer and a feather, and they fell symmetrically. The ancient Greeks were deceived.

dark guess

The assertion that inertial mass and gravitational mass are the same is known as the equivalence principle, and Einstein’s constant equivalence in his theory of gravitation. General relativity successfully predicts how things will fall under most conditions, and is accepted by the scientific community as the best theory of gravity.

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However, “most” conditions do not mean “everything,” and astronomical observations have revealed some perplexing mysteries. For example, galaxies rotate faster than their stars and the gases within them can explain or explain Einstein’s theory of gravity. The most plausible explanation for this discrepancy is the presence of a substance called dark matter – a substance that does not emit light. Another cosmological mystery is the observation that the expansion of the universe is accelerating. To explain this strangeness, scientists have hypothesized that the universe is filled with a disgusting form of gravity called dark energy.

However, these are matters of informed guesswork. We may not fully understand gravity or the laws of motion. Before we have any confidence that dark matter and dark energy are real, we need to validate Einstein’s theory general relativity Very high accuracy. To do this, we need to show that the equivalence principle is true.

While Isaac Newton tested the equivalence principle in the 17th century, modern efforts have been more subtle. In the 20th century, astronomers bounced lasers off the mirrors left by Apollo astronauts on the Moon to prove that the inertial mass and gravitational mass are the same to an accuracy of one part 10 trillion. This achievement was impressive. But the last experience went even further.

General relativity is undergoing another test

A group of researchers invited microscope The collaboration launched a satellite into space in 2016. Titanium and platinum cylinders were on board, and the scientists’ goal was to test the equivalence principle. By placing their devices in space, they isolate the equipment from vibrations and tiny gravitational differences caused by nearby mountains, underground deposits of oil and minerals, and the like. Scientists monitored the location of the cylinders using electric fields. The idea is that if the two objects were rotating differently, they would have to use two different electric fields to keep them in place.

What they found was that the required electric fields were the same, which allowed them to determine that any differences in inertial mass and gravitational mass came down to less than one part in a quadrillion. Essentially, they rigorously validated the equivalence principle.

While this is an expected result from the point of view of general relativity, it has very serious consequences for the study of dark matter and dark energy. While these ideas are popular, some scientists believe that the rotation properties of galaxies can be best explained by new theories of gravity. Many of these alternative theories suggest that the equivalence principle is not entirely perfect.

MicroSCOPE did not show any violation of the equivalence principle. Their results rule out some, but not all, alternative theories of gravity. The researchers are preparing a second experiment, called MicroSCOPE2, which should be about 100 times more accurate than the previous one. If he sees deviations in the equivalence principle, it will give scientists critical direction toward developing new and improved theories of gravity.

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