A new space-based experiment conducted by the European "microscope" satellite proved with unprecedented accuracy that objects made of different materials fell at exactly the same speed under the action of gravity.

Category：science

2025-03-09

text | Xu Rui

As the pillar of Einstein general relativity and the main content of middle school science course demonstration, the weak equivalent principle has passed the most rigorous test so far.

A new space-based experiment conducted by the European "microscope" satellite proved with unprecedented accuracy that objects made of different materials fell at exactly the same speed under the action of gravity.

"It's great to prove Einstein's theory with such high accuracy." Eugene Lim, an theoretical physicist at King's College London, UK, who was not involved in the study, said the findings were not surprising, but these experiments could help physicists narrow the scope of gravity theory that conforms to quantum theory and better predict black hole behavior.

Simply put, the weak equivalent principle shows that gravity is universal, that is, no matter what the object is composed of, it will accelerate in the same way under the gravitational field of .

"microscope" satellite. Image source: CNES 2015

For centuries, physicists' experimental exploration of the above principles has never stopped.

Among them, the most famous demonstration (probably fictional) is a free fall experiment conducted by astronomer Galileo at the Leaning Tower of Pisa, Italy. He is said to have two spheres of different mass fall at the top of the tower and see them landing at the same time.

Today, the forefront of exploring the principle of weak equivalent is in space. The main mission of the "Microscope" satellite launched in 2016 is to verify Einstein's principle of weak equivalent.

'microscope' that orbit the Earth is placed inside a series of charged cylinders made of platinum and titanium alloys, which are electrostatically maintained in place.

satellite orbits is equivalent to a falling state. At least in terms of gravity, the inner cylinder is basically maintained in a constant free fall state.

At the same time, an extremely sensitive electronic sensor measures the voltage required to keep each cylinder relatively stationary.

If one cylinder accelerates faster than another, the voltage that keeps it in place will be higher.

Related research published in " Physical Review Express " on September 14 pointed out that the results were as expected - the acceleration of the two cylinders was always the same throughout the experiment.

Manuel Rodrigues, a research engineer at the National Institute of Aeronautics and Astronautics (ONERA) and the above-mentioned task leader, pointed out that the research results will not rewrite any textbooks, but it "imported 10 times faster" than previous experiments.

"The accuracy of the new research has added confidence to various studies in related aspects in the past. We now know that the results obtained from other experiments are reliable," Lim added.