In special relativity, the action for a particle has a beautiful, geometric interpretation: it's the length of the worldline that the particle traces out as it moves through spacetime. Get the notes for free here: https://courses.physicswithelliot.com...

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This video is part 2 of a series about the principle of least action. The first video was about a particle in Newtonian mechanics. The third is about a particle in general relativity, and the fourth is about a string in string theory.

Part 1 Introduction to the principle of least action:    • Explaining the Principle of Least Act...  

Part 3 The action in general relativity:    • How Einstein Uncovered the Path a Par...  

Part 4 The action for string theory:    • The First Thing You'll Learn in a Str...  

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About physics mini lessons:
In these intermediate-level physics lessons, I'll try to give you a self-contained introduction to some fascinating physics topics. If you're just getting started on your physics journey, you might not understand every single detail in every video---that's totally fine! What I'm really hoping is that you'll be inspired to go off and keep learning more on your own.

About me:
I’m Dr. Elliot Schneider. I love physics, and I want to help others learn (and learn to love) physics, too. Whether you’re a beginner just starting out with your physics studies, a more advanced student, or a lifelong learner, I hope you’ll find resources here that enable you to deepen your understanding of the laws of nature. For more cool physics stuff, visit me at https://www.physicswithelliot.com.