DECRYPTION – The French satellite Microscope has not challenged the principle of equivalence, on which the theory of general relativity is based.
It’s a famous but puzzling experience that will bring back memories of high school for some. Take a lead ball and a feather, drop them into a vacuum bell. Which will hit the ground first? The counter-intuitive answer is that they will fall at exactly the same speed. It was Galileo who first had the intuition of this universality of free fall: in a vacuum, an object always falls in the same way, regardless of its mass, shape or composition. This phenomenon does not seem obvious to us because we live in the air, where the lead ball hits the ground first; we have the false impression that it is because it is more strongly attracted by the ground, but it is in reality because the friction of the air slows down the feather much more easily…
It was in an attempt to find the limits of this rule of fundamental physics that France launched the Microscope satellite in 2016 (the result of close collaboration…
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