The Philosophiæ Naturalis Principia Mathematica, or in English, Mathematical Principles of Natural Philosophy, is one of the foundational works of modern physics and mathematics.
In addition to being the first major treatise to seek to unify all mathematics since Euclid nearly 2000 years earlier, it built upon the works of Galileo, Copernicus, Kepler and Descartes (to name but a few). Famously, it introduced the laws of gravitation and motion, which formed the basis of classical mechanics for centuries thereafter.
Much of the Principia has stood the test of time fairly well – for the most part, it has been refined rather than replaced. Newton’s work remained supreme in mathematics until the 20th century, when relativity and quantum mechanics began to expose it limitations. And although Newton’s laws fail at these extremes, they are superb approximations at the scale of everyday life (in this case, defined as reaching from the smallest visible objects up to entire solar systems).
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Man on the Moon — R.E.M.
One of the most revolutionary theories of physics of all time, Albert Einstein’s General Theory of Relativity turned the celestial mechanics of Isaac Newton on its head, and set the stage for the quantum mechanical revolution in physics that characterised the Twentieth Century. Along with Heisenberg, Bohr, Schrodinger, Feynmann and others, Einstein’s work changed the way we understand our world, but even in that august company, Einstein is a titan among giants, a man whose name has become a byword for genius.
The General Theory of Relativity resists easy summation. It was created to reconcile various anomalies in Newton’s theory of Universal Gravitation, as well as between Newton and Einstein’s earlier Special Theory of Relativity, and forms an important part of our current understanding of physics, gravitation and cosmology – the Big Bang Theory draws upon it, for example.