Einstein wins again: Space satellite confirms weak equivalence theory

Weak equivalence theory—based on Albert Einstein's general theory of relativity—has a long tradition of experimentally testing it.
in great shape , Weak equivalence theory—based on Albert Einstein’s general theory of relativity—has a long tradition of experimentally testing it.


One of the most counter-intuitive assumptions in physics is that all objects fall at the same rate, regardless of mass, aka equivalence principle, It was memorably painted during the 1971 moonwalk by NASA Apollo 15 astronaut David Scott. He dropped A falcon wing and a hammer, and two objects simultaneously smash through the dirt, through a live television feed.

there is a long tradition To experimentally test the weak equivalence principle, which forms the basis of Albert Einstein’s general theory of relativity. After many centuries of testing, the equivalence principle has held strong. and now microscope (MICROSatellite pom l’Observation de Principe d’Equivalence) mission achieved the most accurate test of the equivalence theory to date, Einstein reaffirmed, To recent paper Published in the journal Physical Review Letters. (Additional related papers appear in a special issue of Classical and Quantum Gravity.)

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John Philoponus, the 6th century philosopher, was the first to argue that the velocity with which an object would fall had nothing to do with its weight (mass) and later became a major influence on Galileo Galilei some 900 years later. Gone. Galileo supposedly dropped cannon balls of varying masses from Italy’s famous Leaning Tower of Pisa, but the story is probably apocryphal.

galileo did Roll the balls down inclined planes, making sure the balls roll at a very low speed, which makes it easy to measure their acceleration. The balls were similar in size, but some were made of iron, others of wood, making their masses different. Lacking an accurate clock, Galileo reportedly timed the balls’ travel with his pulse. And like Philoponus, he found that no matter what the inclination, the balls would travel at the same rate of acceleration.

Galileo later refined his approach using a pendulum instrument, which involved measuring the oscillation periods of pendulums of different masses but equal lengths. This was also the method supported by Isaac Newton in about 1680, and later, in 1832, by Friedrich Bessel, both of which greatly improved the accuracy of the measurement. Newton also realized that this theory extended to celestial bodies, calculating that the Earth and the Moon, as well as Jupiter and its satellites, fall toward the Sun at the same rate. Earth has a core of iron, while the Moon’s core is composed mostly of silicates, and their masses vary greatly. Still NASA’s about laser moon experiments Newton’s calculations are confirmed: they do indeed fall around the Sun at the same rate.

Hungarian physicist Lorand Iotvosi, late 19th century To make a torsion pendulum the pendulum approach is combined with a torsion balance and used it to test the equivalence principle even more precisely. That simple straight stick proved to be accurate enough to test the equivalence principle even more precisely. Later experiments have also employed torsion balances, such as the one used in 1964 using pieces of aluminum and gold as test masses.

Illustration of microscope satellite mission.
in great shape , Illustration of microscope satellite mission.


In his 1916 paper confirming the principle of equivalence, Einstein cited the Etvos experiment, which laid the foundation for his general theory of relativity. But general relativity, while it works quite well at the macroscale, breaks down at the subatomic scale, where the laws of quantum mechanics apply. So physicists are looking for equivalence violations at those quantum scales. This would be evidence of potential new physics that could help integrate the two into a grand theory.

One way to test equivalence at the quantum scale is to use matter-wave interferometry. It is related to the classic Michelson–Morley experiment, which attempts to trace the motion of the Earth through a medium called the luminiferous aether, which physicists of the time used to enter space. Thomas Young, late 19th century used such a tool For his famous double-slit experiment to probe a particle or wave of light – and light as we now know it, is both. same is true for,

Earlier experiments using matter-wave interferometry measured the free fall of two isotopes of the same atomic element, in vain expected to detect minute differences. In 2014, a team of physicists thought that perhaps there was not enough difference between their compositions to achieve extreme sensitivity. so they the isotope used Different elements, namely rubidium and potassium atoms, in their version of those experiments. The laser pulses ensured that the atoms fell on two different paths before recombination. The researchers observed telltale interference patterns, indicating that the equivalence is still within 1 part in 10 million.

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