Choose the best answer to following. Explain your reasoning with one or more complete sentences.
Which of the following does inflation help to explain?
(a) the origin of hydrogen
(b) the origin of galaxies
(c) the origin of atomic nuclei

Answer the following questions based on the information provided.
How much cooler is the universe now (at an age of $4\times10^{17}$ s) than it was at an age of 1 second?
a. Its current temperature is one hundred-millionth ($10^{-8}$) the temperature at an age of 1 second.
b. Its current temperature is one hundred-thousandth ($10^{-5}$) the temperature at an age of 1 second.
c. Its current temperature is one-hundredth ($10^{-2}$) the temperature at an age of 1 second.
d. Its current temperature is one ten-billionth ($10^{-10}$) the temperature at an age of 1 second.

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

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 for the following question.
The current temperature of the universe as a whole is
(a) absolute zero.
(b) a few K.
(c) a few thousand K

Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly.
Patterns in the cosmic microwave background tell us about conditions in the early universe that ultimately led to galaxy formation.

Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly.
The main reason the night sky is dark is that stars are so far away.

Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly.
In the distant past, the cosmic microwave background consisted primarily of infrared light.

Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly.
Inflation is a nice idea, but there are no known ways to test whether it really happened.

Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly.
According to the hypothesis of inflation, the “flat” geometry of the universe most likely arose by chance.

Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly.
According to the hypothesis of inflation, large-scale structure in the universe may have originated as tiny quantum fluctuations.

What was the approximate temperature of the universe at an age of 5 minutes?
a. about 300 K
b.about $10^{6}$ K
c.about $10^{9}$ K
d.about $10^{12}$ K

What is antimatter? How were particle-antiparticle pairs created and destroyed in the early universe?