Principle of Least Action, 3.2.1

How does the particle find the right path?

Does it ‘smell’ the neighboring paths to find out whether or not they have more action?

In the case of light, when we put blocks in the way so that the photons could not test all the paths, we found that they couldn’t figure out which way to go, and we had the phenomenon of diffraction.

— Chapter 19. The principle of least action

— Volume 2. Mainly electromagnetism and matter

— The Feynman Lectures on Physics

2011.06.02 Thursday ACHK