Physics 20083 - Current Questions
Covers material from the most recent lecture on
Wednesday, April 23.
Complete version of Study Guide #4 is
here.
- (186)
- Explain how and why Astronomers hoped to use Hubble's Law as an independent method for estimating the density of the Universe. How would a high vs a low density (and a zero density) Universe compare on a Hubble law graph? Explain why they differ.
- (187)
- Explain how current observations of galaxy radial velocities and distances compare to the expectations of Hubble's Law under the influence of gravity. Explain why these observations lead us to believe that the Universe is accelerating away from us in all directions.
- (188)
- Explain what the Cosmological Constant is. Why did Einstein originally introduce the idea of a Cosmological Constant? Why was it later abandoned?
- (189)
- How do the maximum ages for stars, clusters and galaxies compare with our estimate of the age of the Universe? Explain the signifigance of this observation in terms of cosmology and the finite nature of the Universe.
- (190)
- Explain why effectively no fusion occured prior to a time when the Universe was about 1 second old. Explain why nucleosynthesis ended when the Universe was about 3 minutes old.
- (191)
- Explain why the density of matter in the Universe has a bearing on how much Helium was created during nucleosynthesis in the first three minutes of the Universe's existence. If the Universe had been more dense at the time, would more Helium have been created? Less? The same amount? Explain.
- (192)
- Explain the horizon problem and how the theory of inflation resolves the problem.