Download PDF Einstein Gravity in a Nutshell by A. Zee

Sinopsis

Since I started my quantum field theory text1 with a story, possibly apocryphal, about Feynman in a quantum mechanics class, I feel compelled to start this text also by telling a story, possibly true,2 about Feynman. The movie opens on a gorgeous southern California beach. We zoom in on a lifeguard, noticeably scrawnier than the other lifeguards. But on the other hand, we soon discover that he is considerably smarter. Egads, it is Dick Feynman, in the days before Baywatch! Perched on his high chair, he has been watching an attractively curvaceous swimmer with great interest, plotting how he could win the girl’s affection, all the while solving a field theory problem in his head. Suddenly, he notices that the girl is splashing about frantically. She is going under!Must be a cramp! An action hero is as an action hero does: Feynman jumps down from his lookout and goes into action.∗ The other lifeguards are already proceeding in a straight line (starting from point F, the lifeguard station, in figure 1, going along the dotted line) toward the girl (at point G). That would be the path of least distance. But no, Feynman has already calculated the path that would allow him to reach the girl in the least amount of time. Time counts more than space here: least time trumps least distance. Our hero (like other humans) can run much faster, even on a soft sandy beach, than he can swim. So the rescuer should spend more time running before plunging into the sea. A simple high school level calculation (exercise

1) shows Feynman the best path to take (see the solid line in figure 1). Our hero beats the other guys and gets to the eternally grateful girl first!

Content

1. Setting the Stage
2. From Newton to the Gravitational Redshift
3. From Newton to Riemann: Coordinates to Curvature
4. Action, Symmetry, and Conservation
5. Space and Time Unified
6. Electromagnetism and Gravity
7. From the Happiest Thought to the Universe
8. Equivalence Principle and Curved Spacetime
9. Einstein’s Field Equation Derived and Put to Work
10. Black Holes
11. Introduction to Our Universe
12. Gravity at Work and at Play
13. Aspects of Gravity
14. Gravity Past, Present, and Future

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