29.13.1: Review Questions
Review Questions
What are the basic observations about the universe that any theory of cosmology must explain?
2.
Describe some possible futures for the universe that scientists have come up with. What property of the universe determines which of these possibilities is the correct one?
3.
What does the term Hubble time mean in cosmology, and what is the current best calculation for the Hubble time?
4.
Which formed first: hydrogen nuclei or hydrogen atoms? Explain the sequence of events that led to each.
5.
Describe at least two characteristics of the universe that are explained by the standard Big Bang model.
6.
Describe two properties of the universe that are not explained by the standard Big Bang model (without inflation). How does inflation explain these two properties?
7.
Why do astronomers believe there must be dark matter that is not in the form of atoms with protons and neutrons?
8.
What is dark energy and what evidence do astronomers have that it is an important component of the universe?
9.
Thinking about the ideas of space and time in Einstein’s general theory of relativity, how do we explain the fact that all galaxies outside our Local Group show a redshift?
10.
Astronomers have found that there is more helium in the universe than stars could have made in the 13.8 billion years that the universe has been in existence. How does the Big Bang scenario solve this problem?
11.
Describe the anthropic principle. What are some properties of the universe that make it “ready” to have life forms like you in it?
12.
Describe the evidence that the expansion of the universe is accelerating.