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Make lie Galileo, Newton and Einstein. This is the objective of the bold scientific experiment that will start to 711 kilometers from the Earth to the satellite Microscope CNES (CNES). After several delays due to weather, and an abnormality of the Soyuz rocket, it was put into sun-synchronous orbit, Monday, April 25, from the Guiana Space Centre in Kourou. It will test for two years, the truth of one of the major assumptions of modern physics: the “principle of equivalence”
Observed by Galileo and Newton, to the rank of “theory. heuristic “by Albert Einstein who used it as the basis for his work on general relativity, it says that all bodies fall in free fall in a vacuum at the same speed, whatever their weight or their chemical composition. An assertion that has been verified experimentally by physicists until the thirteenth decimal place. But “has long been a source of amazement to scholars’ , told a few days before the launch, the physicist Thibault Damour of the Institut des Hautes Études Scientifiques (Bures-sur-Yvette, Essonne).
High accuracy
Microscope will have to establish whether the statement is true, with a degree of accuracy on a hundred times greater than all ever made tests. It will consist says lead investigator Peter Touboul (National Board of Study and Aerospace Research [Onera]), “to drop into space two cylinders – one platinum and one in titanium – inserted one in the other. Then put these metal parts in free fall by describing their orbits around the Earth series “. If the equivalence principle is true only to a certain degree, so we should see a difference in the electrostatic forces generated by the device to maintain equal altitude and the acceleration of the two objects of different chemical compositions.
What would , for sure, a major event for physics. Some of the models developed by the specialists of “string theory” – which claims together in one framework, general relativity (which describes gravity) and quantum physics (which accounts for the other fundamental interactions or forces of nature ) – provide for the possibility that the equivalence principle is violated. A default layout that says Thibault Damour, “pave the way for the discovery of other dimensions in the universe – up to seven plus four of space and time as we know it – and that ‘to the identification of an additional fundamental interaction “. A new force of nature, long-range, superimposed on the severity, able to act differently on the nuclei of atoms, as their power is greater or less!
Eight cold gas thrusters
Conceived in 1991, selected a first time in 1999, then a second in 2004, the mission has been slow to take off. Its design entrusted to CNES has also been a challenge due to multiple disruptions suffered by a satellite in flight: drag produced in the residual atmosphere of our planet, the solar wind particles from outer space, variations of the geomagnetic field, crunches due to temperature variations between day and night …
This is why, explains Yves André, project leader at CNES Microscope, “the satellite 303 kg Myriade we have ensured the project management was equipped with eight cold gas thrusters supplied by the European Space Agency [ESA] “. They constantly keep microscope at the correct altitude and under the proper acceleration, exercising spurts delicate equivalent to those that would be needed to lift on Earth … a grain of sand.
Implying also Géoazur laboratory (OCA-CNRS), the German Space agency, DLR and the German metrology institute, PTB, and the laboratory of applied Space technology and microgravity of the University of Bremen, ZARM, mission would have been possible without the technology of “space ultrasensitive electrostatic accelerometers” developed by Onera, whose Microscope is the fifth flight aboard a satellite.
These instruments will they put in clear violation of the equivalence principle? “If that happened, it is certain that it would encourage the launch of other space missions devoted to basic science” , estimated at Kourou, just before the shooting, Jean-Yves Le Gall, Chairman CNES.
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