Massé R.P., Massé K.E. Physics: Principle of Least Action

3rd ed. — Independently published, 2022. — 151 p.The subject of this book is the principle of least action in dynamics. This principle has a long history in physics and has now evolved into very powerful analysis techniques that are successfully employed in many branches of physics. Yet the basis for this principle has remained a mystery which continues to give rise to speculations of all sorts. In this book we will consider the basis of the principle of least action. We will begin with a review of the history of the principle of least action. We will define action in physics and we will discuss metaphysical causes that have been proposed to explain the principle. We will present the mathematical implementation of the principle of least action as the calculus of variations. We will then derive Newton’s equations of motion from physical field theory and show how this leads to the principle of least action.True PDF