ED1 - Teaching Einsteinian Physics to School Students |
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Speaker |
Spallicci , Alessandro D.A.M. |
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| Talk Title |
Newtonian Free Fall Learnt at Youth, Now Revisited with an Einsteinian View |
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Abstract |
Let us consider the legendary Pisa tower experiment in the Piazza del Miracoli by Galilei and ask ourselves if, neglecting air, stone size, Earth non-spherical shape and rotation, one kilogram stone falls like one of two kilograms. Young students spontaneously say no, often by a factor two or so, while teachers may say "exactly yes". Actually, they are both wrong. The right reply is "approximately yes" and depends on where we observe the fall. The difference between the two fall times is minuscule being of the order of the stone/Earth mass ratio, thus not yet measurable by state of the art technology. So why caring? We should care because it is not pedagogical to present approximations as exact and sacred laws of physics to digest as dogmas; because best students will remain puzzled by the superficiality and awkwardness of the explanations; because this ratio may take larger values and be of considerable influence in the Solar System. But especially because the heavier mass will fall faster or slower than the lighter one according to whether the observer is standing in the Piazza - that is at fixed distance from the Earth centre - or at a fixed distance from the joint (Earth and stone system) centre of mass. The physics dependency on the observer location appears in Newtonian classical mechanics, e.g. in collisions, de Coriolis force, and rises to feature of paramount significance in Einstein's general relativity. |
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