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I want to understand the principal of least action intuitively, away from any mathematical proof.


marked as duplicate by Chair, Qmechanic classical-mechanics Sep 12 '18 at 14:46

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    $\begingroup$ I'm removing the quantum mechanics tag because I believe that it's best understood in the context of classical mechanics/newton's laws and only later applied to QM. $\endgroup$ – Chair Sep 12 '18 at 13:09
  • $\begingroup$ Possible duplicate of Why the Principle of Least Action? $\endgroup$ – Chair Sep 12 '18 at 13:10
  • $\begingroup$ Note that your intuition may or may not have anything to do with my intuition. You say 'least action' and I see a fuzzy green carpet in my mind. $\endgroup$ – Jon Custer Sep 12 '18 at 13:24
  • $\begingroup$ Are you familiar with Occam's razor? $\endgroup$ – Lewis Miller Sep 12 '18 at 13:35
  • $\begingroup$ Is Feynman's take on this good enough to answer your question? feynmanlectures.caltech.edu/II_19.html $\endgroup$ – Farcher Sep 12 '18 at 14:43

Well, this question is rather opinion based but I will make an effort to answer it according to my intuition. The principle of least action is the fact that physical processes happening in nature must happen in the "least complicated" way possible.

What I mean by "least complicated" can be understood by an example: Suppose that a classical particle has to move inside an isotropic space from a point $A$ to a point $B$. Then according to the least action principle, it has to propagate on the straight line connecting these points. It must not follow any other way because it doesn't have to complicate things (since the space is isotropic for example).

In a similar way, all physical processes have to follow the least action principle just like the above example of the propagating particle in an isotropic space. This explanation is just my intuition on this subject. I am sure that you will get other beautiful explanations as well.


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