physics

(This is a writeup of Exercise 1.3 from Sussman and Wisdom’s "Structure and Interpretation of Classical Mechanics". See the solutions repository for more.) Law of Reflection Geometry Calculus Law of Refraction Calculus Geometry The problem explores some consequences for optics of the principle of least time. The exercise states: Fermat observed that the laws of reflection and refraction could be accounted for by the following facts: Light travels in a straight line in any particular medium with a velocity that depends upon the medium. The path taken by a ray from a source to a destination through any sequence of media is a path of least total time, compared to neighboring paths. Show that these facts imply the laws of reflection and refraction. ...

In my ongoing quest to lay a more solid foundation for this new, strange life as a machine learning “researcher”, I’ve been going through various foundational concepts and ideas and trying to build up rock solid intuitions that I can lean on for years. (Why the hell didn’t I do this back in school??) Entropy is my latest obsession - thermodynamic entropy, and information entropy, and the ways in which these two things are similar. ...