It's a famous but puzzling experience that will bring back high school memories for some.
Take a lead ball and a feather, drop them into a vacuum bell jar.
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...
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OUR FILE - Elizabeth II, a rock and a symbol for England
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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