![]() But in return for taking that brave step, relativity rewards us with a universe that is strikingly beautiful and far more fantastic than anything a science fiction writer could have invented. It forces us to jettison our preconceptions about time and velocity and mass. But a more serious version of this answer is that special relativity is the best subject I know for teaching us to think in new ways. The short answer is that relativity is just too much fun to skip over. Why should you put in the effort to learn an esoteric branch of physics you may never use? So you might wonder whether you really need to know relativity. But in everyday life its role is mostly hidden. And it’s fundamental to understanding a lot of astrophysics and nuclear physics and elementary particle physics. You’ll need it if you ever write software for satellite-based navigation systems (GPS and similar), which require super-accurate timing on satellites orbiting at thousands of miles per hour. In order to master relativity, you’ll need to take on this challenge and wrestle with the concepts until they fall into place.Īnother thing you should know about special relativity is that it doesn’t have many direct practical applications. Unlearning the Newtonian concept of time and replacing it with the far richer version in relativity theory can be quite a challenge. In particular, Newtonian mechanics rests on an oversimplified conception of time. You see, the problem with Newton’s laws isn’t merely that the equations aren’t quite right it’s that the underlying concepts turn out to be inadequate. What makes relativity difficult to learn is not the mathematics, but the concepts. The main difference you’ll notice is that a lot of the formulas now involve square roots. The mathematics of special relativity is no more difficult than that of Newtonian mechanics: basic algebra and calculus, using derivatives to define velocity and acceleration. ![]() That theory is beyond the scope of these brief lessons.) (Ten years later Einstein published what he called his general theory of relativity, which is actually a revised theory of gravity. Relativity replaces Newton’s laws, and the related principles of momentum and energy conservation, with new versions that are accurate at all speeds. It tells us that Newton’s laws of motion are only approximate, and become especially inaccurate when we apply them to objects that move extremely fast. This “theory” is a revised framework for the laws of mechanics. “Relativity” is short for what Albert Einstein called his “special theory of relativity”, published in 1905. In preparing these lessons I’ve drawn heavily on the treatments in the three special relativity texts listed at the end under Further Reading. This is nearly double the class time for relativity that a traditional introductory course would allocate, but in my mind it’s the absolute minimum. In my own introductory physics course I deliver these five lessons during five 50-minute class sessions, and we spend two more class sessions discussing the assigned homework problems. ![]() I’ve tried to emphasize depth more than breadth, addressing the most important conceptual issues and introducing the conceptual tools (including spacetime diagrams) that show how the theory fits together. It is intended as a compromise between the extremely rushed treatments of relativity that appear in standard introductory physics textbooks, and the more leisurely treatments that appear in books dedicated to teaching just relativity. This introduction to special relativity is for anyone who is already comfortable with the Newtonian concepts of velocity, acceleration, momentum, and energy. Relativity in Five Lessons Relativity in Five Lessons Daniel V.
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