Explorations: An Introduction to Astronomy (Arny), 7th Edition

Chapter 18: Cosmology

Thought Questions

1
Does it bother you that the Universe may expand forever?
2
Explain why the cosmological redshift is not caused in the same way as a Doppler shift (chapter 4 ) even though galaxies are being moved away from us as the Universe expands.
3
If the Universe had not expanded since the recombination era, what would the night sky look like? What would the daytime sky look like?
4
Discuss three different kinds of observational evidence for the Big Bang theory you could present if you were challenged by a skeptical child.
5
Why do most stars, including our own Sun, contain more helium than the 24% formed during the Big Bang?
6
If you draw three lines that connect at their corners on a globe (like in fig. 18.15A ), have you drawn one triangle, or two? Explain your answer. If you draw three lines that connect on a flat or saddle-shaped surface, have you drawn one or two triangles?
7
The recession velocities of distant galaxies suggest that the Universe is expanding faster today than in the early Universe. How is this similar to the process of inflation in the early Universe?
8
Why are there points below the green line in figure 18.25 (instead of above it), if the Universe is expanding faster today than in the past?
9
Dark energy accelerates the expansion of the Universe, but galaxies and solar systems hold themselves together while the distances between them increase. If the Universe continues to expand faster and faster, what will happen to our cosmic horizon? Will studying cosmology be easier or harder in the very distant future?
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