Notes on General Relativity
Even though I have a degree in physics I never learned general relativity properly. I took a differential geometry class and while it was one of my favorite classes at uni, it didn't go beyond 19th century math: curves and surfaces in Euclidean space and things like the Gauss-Bonnet theorem.
One day, YouTube recommended a video from the WE-Heraeus International Winter School on Gravity and Light channel. This channel contains a series of lectures that offer an introduction to the central concepts in general relativity and cosmology.
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