Dear people,
we all know the marble-experiments of galileo or the "falling feather and falling lead"-experiment on our moon, where both objects (seem to?) touch the ground simultaneously because there ist no air drag and free fall does not depend on the mass of an object. After all the years I still don't understand how this can be compatible with newtonian laws of gravity, which claims that higher masses attract stronger?
Why couldn't it be that the feather and the lead don't touch the moon ground at the exact moment, but the lead touches the ground some micro- or nanoseconds earlier, because it has a higher mass, which is therefore attracted stronger? Why couldn't it bee that the "simultaneous fall" just seems to be simultaneous because our eyes or even our detectors are not able to distinguish the very slight difference (considering that the moons mass is so heavy in comparison with the mass-difference between the feather and the lead, so that the time-difference is negligible, but still there)?
Thanks.
There is such a difference in the masses that the time of free fall should not only differ in microseconds. The mass is the measure of inertia, and is proportional to the gravitational attraction (or weight) too. They cancel to give the same trajectory, as a simple calculus shows. Now that doesn't explain the "why." But it is taken as a postulate, called the equivalence principle, which gives the general relativity, a gravitation theory. The equivalence principle has been tested with very high accuracy, without failing. In general relativity, the trajectory of a body has mere geometrical origin, generalising the straight line motion.
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