1. Which of the following correctly lists our \cosmic address" from small to large?
(a) Earth, solar system, Milky Way Galaxy, Local Group, Local Super Cluster, universe
(b) Earth, solar system, Milky Way Galaxy, Local Super Cluster, Local Group, universe
(c) universe, Local Super Cluster, Local Group, Milky Way Galaxy, solar system, Earth
(d) universe, Local Group, Local Super Cluster, Milky Way Galaxy, solar system, Earth
(e) Earth, Local Group, Local Super Cluster, Milky Way Galaxy, solar system, universe
(a) is the right answer.
2. How long is a light-second?
(a) 3:00 ▯ 10 m
(b) 1:80 ▯ 10 m
(c) 1:08 ▯ 10 m
(d) 2:59 ▯ 10 m
(e) 9:47 ▯ 1015m
(a) is the right answer. The speed of light is c = 3:0▯10 m=s. So one light-second
is c ▯ (1sec) = 3:0 ▯ 10 m.
3. If you are looking at a star that is 4 light-years away from Earth, you are looking at:
(a) The star as it is right now
(b) The star as it was 4 years ago
(c) The star as it will be 4 years in the future
(d) The star as it was 4 ▯ 3:0 ▯ 10 years ago
(e) The star as it will be 4 ▯ 3:0 ▯ 10 years in the future
(b). The light has to travel for 4 years to get to Earth.
4. Which one of the following is the correct description or the right usage of the Astronomical
(a) 1 AU is the average distance of the most distant planet in the solar system from our
(b) When the parallax angle of an astronomical object is a small angle p, then the distance
to that object is given by 1AU=p.
(c) 1 AU equals 1.3 light-second.
(d) 1 AU equals 1:5 ▯ 10 km.
(e) None of the above
(b). It’s the distance of Earth from the sun. 500 light-seconds or 1:5 ▯ 10 km. 8
Distance measurement using parallax relies on our knowing 1 AU accurately.
1 5. What is the current estimate of the age of the universe?
(a) 1:4 ▯ 10 years
(b) 1:4 ▯ 10 years
(c) 1:4 ▯ 10 years
(d) 1:4 ▯ 10 years
(e) 1:4 ▯ 10 years
(e). 14 billion years.
6. Which one of the following is a false description of an astronomical object?
(a) A star is a hot ball of gas powered by nuclear reaction at its core.
(b) A galaxy is an island of stars in space containing 10 ▯ 10 stars held by gravity.
(c) The observable universe may not be the whole universe.
(d) The star systems can form a cluster, but galaxies do not form clusters.
(e) A star system can have more than one star in the system.
(d). For instance, the Local Super Cluster is a cluster of galaxies including our
7. Where or when is the \star stu▯" formed?
(a) Only during the ▯rst 300,000 years of the universe
(b) Only inside relatively light stars like our sun
(c) Only inside stars much heavier than our sun
(d) Only when a supernovae explosion occurs
(e) Inside any bright star
(e). \Star stu▯"means heavier elements of which we are made. It is made
inside bright stars. See the summary of Chapter 1.
NOTE ADDED: Although (a-d) are clearly wrong since star stu▯ cannot be
generated only in those times or places, I can see that one can conceivably be
confused by the quali▯er any in (e). Hence, I am going to give everyone full
mark for this one.
2 8. If the distance to galaxy A from us is the farther than the the distance to galaxy B from
us, which of the following is right?
(a) If the two galaxies are within our Local Group, they can move in any directions, but
the speed of A must be greater than the speed of B.
(b) If the two galaxies are within our Local Group, they can move in any directions, but
the speed of B must be greater than the speed of A.
(c) If the two galaxies are within our Local Group, they can only move away from us but
their speed can be essentially random.
(d) If the two galaxies are outside of our Local Group, they can move in any directions,
but the speed of B must be greater than the speed of A.
(e) If the two galaxies are outside our Local Group, they only move away from us and the
speed of A is greater than the speed of B.
(e). Universe expands. Farther galaxies receed faster. This is the raisin problem
in the homework.
9. Which one of the following falsely describes a part in scienti▯c method?
(a) Making a hypothesis
(b) Performing experiments to test the hypothesis
(c) Analyzing the experimental outcome to determine the validity of the hypothesis
(d) Deciding that the hypothesis will apply to all physical situations when it is con▯rmed
(e) Making a new hypothesis based on the experimental outcome
(d). One can never be sure that one’s hypothesis will apply to all physical
situations. One cannot decide what a law of nature should be.
10. Which of the following correctly describes Kepler’s ▯rst law?
(a) There are comets that goes around the sun only once.
(b) The moon is pulled by Earth just as Earth is pulled by the moon.
(c) The sun sits at one of the two foci in Earth’s elliptic orbit.
(d) A moving object will keep its velocity unless there is a force acting on it.
(e) All forces are attractive.
(c). Kepler’s ▯rst law states a planet’s orbit