Choose the best answer for the following question.
Which of the following does not provide strong evidence for the Big Bang theory?
(a) observations of the cosmic microwave background
(b) observations of the amount of hydrogen in the universe
(c) observations of the ratio of helium to hydrogen in the universe

What is the Cosmological Principle, and how is it important to our understanding of the universe?

What is Hubble’s law? Explain what we mean when we say that Hubble’s constant is between 21 and 23 kilometers per second per million light-years.

The most distant galaxies that astronomers have observed are much easier to see in infrared light than in visible light. Explain why that is the case.

In which type of galaxy would you be most likely to observe a massive star supernova: in a giant elliptical galaxy or in a large spiral galaxy? Explain your reasoning.

Choose the best answer to given of the following. Explain your reasoning with one or more complete sentences.
When the ultraviolet light from hot stars in very distant galaxies finally reaches us, it arrives at Earth in the form of
(a) X rays.
(b) slightly more energetic ultraviolet light.
(c) visible light.

Distinguish between the disk component and the halo component of a spiral galaxy. Which component includes cool gas and active star formation?

How do spiral and elliptical galaxies differ in terms of the presence or absence of disk and halo components? How does this difference explain the lack of hot, young stars in elliptical galaxies?

The distance of a galaxy from our solar system is 10 Mpc. (a) What is the recessional velocity of the galaxy? (b) By what fraction is the starlight from this galaxy redshifted (that is, what is its z value)?

Choose the best answer for the following question.
When a proton and an antiproton collide, they
(a) repel each other.
(b) fuse together.
(c) convert into two photons.

Choose the best answer for the following question.
The charge of an antiproton is
(a) positive.
(b) negative.
(c) neutral.

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences.
How do we determine the Milky Way’s mass outside the Sun’s orbit?
(a) from the Sun’s orbital velocity and its distance from the center of our galaxy
(b) from the orbits of halo stars near the Sun
(c) from the orbits of stars and gas clouds orbiting the galactic center at greater distances than the Sun

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences.
Why do disk stars bob up and down as they orbit the galaxy?
(a) because the gravitational pull of other disk stars always pulls them toward the disk
(b) because of friction with the interstellar medium
(c) because the halo stars keep knocking them back into the disk

How can we use orbital properties to learn about the mass of the galaxy? What have we learned?