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Phenomenon/Feynman: (context here: magnetic field, coil) the changeover from north to south should not concern us, the two are also mere agreements. -the change is not a phenomenon!
((s) The two would be reversed: top/bottom and right/left at the same time, therefore no change! (As if you looked at the original image from behind: now north is at the bottom, but the vector now also points to the right instead of to the left.)
True Phenomenon/Feynman: for example, if we have an electron moving through a field that points into the book page: if we then use the formula for the force v x B, we find that the electron, in accordance with the physical law, will deviate in the displayed direction.
The phenomenon is that we have a coil with a current that runs in a certain circumferential direction, and an electron that circulates in a certain way. That is physics, regardless of how we call everything. ((s) Because the electron is not both positive and negative at the same time.)
Feynman: Now we carry out the same experiment in a mirror: now the force is reversed if we calculate it according to the same law, and this is good, for the corresponding movements are then mirror images! (>Chirality).
Reflection/Chirality/Symmetry/Feynman: the main thing is that in the study of any phenomenon there are always two or an even number of right-handed rules and that the phenomena as a result always look symmetrical.
However, it may appear as if we could indicate the north pole of a magnet!
E.g. compass needle really points north.
Vs: but of course this is again a local property that has to do with the geography of the earth.
It is as if we were talking about in which direction Chicago is (north of Pittsburgh), so it does not count!
That the compass needle has a bluish color is only a convention!
If, however, a magnet had the property that small hairs grow on its north pole, but not on the south pole, that would be the end of the law of mirror symmetry.
E.g. telephone call to a Mars resident: we could send him right-polarized light and say: "This is right-turning light".
We could indicate our size in the diameter of hydrogen atoms. And this is how absolute length can be defined.
But we could not define "left" with the fact that our heart beats on the left side. Maybe his beats on the right!
Vom Wesen physikalischer Gesetze München 1993
Vorlesungen über Physik I München 2001