For some time (eg. Galileo) we have known that 1 kilogram of lead falls as quickly as 1 kilogram of feather – if, however, no force other than gravity is applied to it, for example the friction of air, what is obtained in a void. However, between 2016 and 2018, a satellite, Microscope, orbiting at an altitude of 710 kilometers, tested this 400-year certainty by reiterating the body’s fall experiments.
The sentence, published on Wednesday 14 September, in twelve articles, in Physical Review Letters And Classical and quantum gravity, it is clear: Galileo was right.
The difference in acceleration between two freely falling bodies is less than 10-15.
And not just a little. His observation remains correct, as the researchers have been able to verify: the difference in acceleration between two bodies in free fall is less than 10-15. Consider an accuracy by which the weight of“Half a microgram flies on a 500,000-ton supertanker”.
The image, which hails an unprecedented record, was used by Manuel Rodrigues, project manager and member of the National Office for Aerospace Studies and Research (Onera), during a press conference on Wednesday.
Galileo had measured up to a difference of 1 thousandth (10-3). The result is even a hundred times better than that provided by other measurements made on Earth in 2007, and ten times better than Microscope’s preliminary conclusions in 2017.
Another victory for general relativity
With such precision, Albert Einstein was also right. To develop his famous theory of general relativity, in 1915 he elevated Galileo’s observation as a founding principle: a falling body is like an accelerating object. Gravity and acceleration are equivalent.
But the experiment was not destined for the history of science, but for its future. The researchers wanted to see if the microscopic forces could be overlooked by Einstein and others and if they would slow or speed up the masses. This heresy is not so reckless, as there is already evidence that general relativity does not explain everything, such as the abnormal rotation of galaxies or the acceleration of the expansion of the Universe. And, inevitably, a surrogate theory would be synonymous with new forces or particles.
The construction of the 300-kilogram satellite of the National Center for Space Studies (CNES), designed by Onera and whose data were analyzed by the Côte d’Azur Observatory with a large number of researchers from the National Center for Scientific Research (CNRS), is It was therefore decided twenty-five years ago, with the aim of finding a hitch in the principle of equivalence.
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