The observations of the European Space Laboratory did not invalidate the “principle of equivalence” according to which the bodies fall similarly into the void, whatever their mass and their composition.
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For beautiful lurette (that is to say Galileo), we know that 1 kilogram of lead falls as quickly as 1 kilogram of pen-if however no other force than gravity is applied there, for example the Air friction, which is obtained in a vacuum. However, between 2016 and 2018, a satellite, a microscope, in orbit at 710 kilometers above sea level, tested this quadrical certainty by reiterating experiences of falling bodies.
The verdict, published Wednesday September 14, in twelve articles, in Physical review Letters and classical and quantum gravity , is final: Galileo was right.
and not just a little. Its observation remains exact, as precisely as the researchers were able to verify it: the difference in acceleration between two bodies in free fall is less than 10 -15 sup>. Or a precision thanks to which we could detect the weight of “a fly of half a-microgram on a 500,000-ton supertanker”.
The image, which comes to salute 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 , Wednesday.
Galileo had measured up to a difference of 1 thousandth (10 -3 ). The result obtained is also a hundred times better than that provided by other measures made on earth in 2007, and ten times better than the preliminary microscope conclusions in 2017.
a new victory for general relativity
With such precision, it was even Albert Einstein who was right. To develop his famous theory of general relativity, in 1915, he had raised in principle founding the observation of Galileo: a body which falls is as an object that accelerates. Severity and acceleration are equivalent.
But experience was not intended for the history of science, rather for their future. The researchers wanted to see if microscopic forces would not have been forgotten by Einstein and others, and if they would brake or accelerate the masses. This heresy is not so reckless, since evidence already exists that general relativity does not explain everything, for example the abnormal rotation of galaxies or the acceleration of the expansion of the universe. And, inevitably, a replacement theory would be synonymous with new forces or particles.
The construction of the 300 -kilograms satellite from the National Center for Spatial Studies (CNES), designed by Onera and whose data was analyzed by the Observatory of the Côte d’Azur with a large number of researchers from National Center for Scientific Research (CNRS), was therefore decided twenty-five years ago, with the aim of finding a hitch in the principle of equivalence.
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