Questions for Chapter S3
1. Explain what we mean by the straightest possible path on the Earth's surface.
2. What do we mean by spacetime?
3. What is the equivalence principle? Give an example
4. How do rules of geometry differ depending on whether the geometry is flat spherical, or saddle shaped?
5. Explain how the idea of spacetime geometry means that the universe has no center and no edges.
6. How can you tell whether you are following the straightest possible path through spacetime?
7. According to general relativity, what is gravity? With this view, why does the Earth orbit the Sun?
8. Describe the idea behind the "rubber sheet" analogy to spacetime and the limitations of the analogy. In the analogy, what does mean? Why does the curvature of spacetime near a star depend on both the star's mass and its size?
9. What is a black hole? What do we mean by the event horizon of a black hole?
10. What is gravitational time dilation? What determines how much time is slowed in a gravitational field?
11. Briefly describe several observational tests that support genera1 relativity.
12. What is gravitational lensing? According to general relativity, why does it occur?
13. Why do we see a gravitational redshift when we look at spectral lines from the Sun?
14. What are gravitational waves? What evidence supports their existence?
15. How can one measure the curvature of spacetime?
16. State the basic assumption of General Relativity and name four observed consequences.
Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly; not all of these have definitive answers, so your explanation is more important than your chosen answer.
17. The equivalence principle tells us that experiments performed on a spaceship accelerating through space at 1g will give the same results as experiments performed on Earth.
18. The equivalence principle tells us that there's no difference at all between a planet and a human-made spaceship.
19. A person moving by you at high speed will measure time and space differently than you, but you will both agree that there is just a single reality in spacetime.
20. With a sufficiently powerful telescope, we could search for black holes by looking for funnel-shaped objects in space.
21. Time runs slightly more slowly on the surface of the Sun than it does here on Earth.
22. Telescopes sometimes see multiple images of a single object, just as we should expect from the general theory of relativity.