List three ways in which this analogy is limited. Explain how the universe can be finite yet have no center and no edges. Briefly describe several observational tests that support general relativity. List five major ideas that come directly from the general theory of relativity. Give an example that clarifies its meaning.
Time is different for different observers.
Spacetime is the same for everyone . One world line is vertical, one is straight but slanted, and one is curved. Explain why the curvature of spacetime near a star depends on both the star's mass and its size. Explain how a wormhole might allow us to travel between two places that are 10 light-years apart in less than 10 years.