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This video combines sections 1, 2, and 3 of chapters 3 of the videos in my new series of Cosmology. I'm going through Dr. Barbara Ryden's textbook "Introduction to Cosmology". If you follow along, you'll get a full upper-division undergraduate course in Cosmology. I used this textbook at William Paterson University. If you haven't watched chapters 1 and 2 yet, go back and start from there.
This course will cover the current state of the science of Cosmology. To follow along, it'll be a good idea for you to ge to know your calculus. Here are the topics of this video:
Introductory Cosmology:
Chapter 03: Newton versus Einstein
-- 01: The Way of Newton
-- 02: The Special Way of Einstein
-- 03: The General Way of Einstein
When we wish to understand how the universe works, we need to start from the very beginning from the Greeks up through Newton, who gave us his magnum opus on motion and gravity. However, while it was a triumph, there were clouds on the horizon. Here, we learn all about Newton's formulation of Gravity. I cover the History of Gravity, What Exactly are the Forces of Nature? Euclidean Space and Time, Newton's reflections on Gravity's Mystery, Testing the Equivalence Principle, Gauss' Law of Gravity, Deriving the Poisson Equation, and Gravity's Formulation and Usage.
Special Relativity arose out of crisis between three pillars of classical physics. Galileo’s Relativity, Newton’s Mechanics with Absolute Space and Time, and Maxwell’s Equations which demonstrated that all electromagnetic effects travel at the speed of light. This led to the serious search for the Luminiferous Aether, the Medium for light, which was then met with failure. To account for this, Einstein threw out Absolute space and time and raised the speed of light to a fundamental universal constant that acted merely as a conversion factor between space and time. The speed itself can then not be truly considered a speed, but rather how space and time combined to become Spacetime. With that, questions like “How far is a nanosecond?” and “What’s the span of time between two sides of a river?” are actually sensible. Now, in four-dimensional spacetime, we measure true distances with the invariant spacetime interval. In this video I describe the amazingly successful idea of Einstein’s Special Relativity.
Upon conquering Special Relativity, Albert Einstein spent almost a decade trying to integrate it into the framework of gravity. His breakthrough was to realize that "A falling man doesn't feel his own weight." This set him off to reconfigure gravity not as a force, but rather as the pure geometry of space and time. Here we cover, Extrinsic Versus Intrinsic Curvature
The Weak, Einstein, and Strong Equivalence Principles, Metric Theories of Gravity, Thought Experiments for the Einstein Equivalence Principle, Gravitational Redshift and the Pound-Rebka Experiment, Tests of the various form of the Equivalence Principle, and Curved Spacetime and Geodesics.
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