Physics 103 Spring 2019 NAME: Discussion Session 8 General Relativity Worksheet Having discussed Einstein's theory of Special Relativity, we now turn our attention (briefly) to Einstein's theory of General Relativity, which includes Special Relativity as a limiting case of no gravity. General Relativity describes gravity as the curvature of space and time (of spacetime). We have already seen how Special Relativity leads to some inter- esting effects; space and time blend together, events that are simultaneous for one observer are not simultaneous for another observer, and so on. General Relativity also includes all of these effects, as well as more. For instance, gravity can affect the flow of time as well - time slows down for observers in a strong gravitational field. General Relativity also predicts the existence of some very strange phenomena, such as black holes. This worksheet investigates some of the ideas of General Relativity. 1 Conceptual Questions 1. What is Einstein's Equivalence Principle? 2. If light is massless, then how can it be affected by gravity? 3. What is the proper time for light in flat spacetime? What about in curved spacetime? 4. In what ways does the gravitational theory of Einstein differ from that of Newton? 5. What is a geodesic, and why is it important in General Relativity? 6. What is the metric? What is special about the Minkowski metric? 7. Freely falling observers travel along geodesics in curved spacetime; from this point of view why might it be correct to say that standing on the ground would constitute an "accelerated" observer? 8. Suppose Bob lives in Denver (the Mile-High City), while his twin sister, Alice, lives in Death Valley (located below sea level). They have both attend their family reunion in Las Vegas. Which twin is older? By a little bit, or a lot? 9. What is the equivalent of a photon for quantum gravity? 10. In the early Universe, immediately after the Big Bang, the Universe underwent infla- tion, which is an exponential, faster than light, expansion of the Universe. If nothing can travel faster than light, how is this possible