Einstein’s equivalence principle is questioned

Einstein’s equivalence principle is questioned

An orbital experiment to check whether objects really fall at the same speed in a gravitational field.

In the late 1500s, the Italian scientist Galileo Galileo conceived an experiment that changed the basis of physics. He wondered what would happen if two objects with different scales were dropped from the Leaning Tower of Pisa?

At that time, the prevailing theory of gravity, developed almost 2000 years ago by the Greek philosopher and scientist Aristotle, attributed the dependence of the speed of an object falling on its specific gravity, that is, heavier objects fall faster than light ones.

Galileo believed that the mass is insignificant for the speed of the object falling. Everything falls to the ground at the same time, no matter how much it weighs. From this, he concluded that in vacuum all bodies would fall at the same speed, laying the foundation for the general theory of relativity Albert Einstein, published 100 years ago.

The concept, known as the “Equivalence Principle,” was well tested on Earth, but scientists are wondering if it will be questioned if the measurements are accurate enough.

To test this principle, the French space agency is conducting an experiment called “Microscope”. To this end, a 668-pound satellite was sent as a secondary payload on board the Soyuz rocket, which was launched last week from the European Kourou space center in French Guiana. The microscope contains two cylinders of the same mass, one of which is of titanium, and the second of platinum-rhodium alloy. Both will be in zero gravity and thus, the sensors will be able to measure the acceleration of gravity with an accuracy of one millionth of a billion gravity. The experiment on Earth was about 100 times less sensitive, mainly due to random seismic vibrations found in nature and human activity.

“We are awaiting confirmation of Einstein’s theory,” writes Pierre Tubul, a leading scientist at the Microscope mission, in a discovery email.

"If the equivalence principle is not confirmed, the door to a new physics will open in addition to the general theory of relativity, there may be a new type of interaction or a new type of particles for this interaction," he added.

“Any violation of the equivalence principle will be vital,” the French space agency CNES writes in an experiment summary posted on its website. "This would be the first sign of new physical phenomena ... which are not explained by our standard physics model."

Scientists plan to compare the relative motion of the masses of the cylinders over two years. The device was turned on this week for a two-month check. The main stage will begin in July.

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