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Quiz 1
Physics 55: Introduction to Astronomy
Professor Henry Greenside
Friday, September 9, 2005
This quiz is closed book. You can use a scientific calculator but no other electronic device. If you have any
questions during the quiz, please do not hesitate to ask me.
True or False Questions (1 point each)
Please circle “T” for true or “F” for false to indicate the truth of the following statements.
1. T / F All the moons in our solar system are smaller than the smallest planet Pluto.
2. T / F Because galaxies have so many stars, when two galaxies collide, many of their stars will bump
into each other.
3. T / F Experiments indicate that the universe is about 1.4 billion years old.
4. T / F A news article about the composition of comets was mentioned this week in the Announcements
part of the Physics 55 webpage.
5. T / F If, through a telescope, you see two glowing objects such that one object is further away than
the other, then the closer object is younger in age than the further object.
6. T / F The total mass of the nine planets, millions of asteroids, billions of Kuiper belt objects, and
trillions of Oort cloud objects exceeds the mass of the Sun.
7. T / F In the mathematical expression,
2
1
=1−
,
ψ3
3+η
if the positive quantity ψ (lower case Greek psi) becomes bigger, the positive quantity η (lower case
Greek eta) becomes smaller.
Multiple Choice Questions (4 points each)
Circle the letter that best answers each of the following questions.
1. The typical number of stars in a galaxy, the approximate number of galaxies in the observable universe,
and the approximate number of neurons in the human brain all have similar values equal to about
(a) 106 .
(b) 1010 .
(c) 1024 .
(d) 1040 .
2. The astronomer Carl Sagan, creator of an immensely popular 1980 television series called Cosmos, told
his TV audience that “we are star stuff” because the elements in our bodies
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(a) are similar in composition to the elements found in stars.
(b) were created by chemical reactions in the space between the stars.
(c) were made by nuclear fusion in our Sun.
(d) were produced by nuclear fusion in stars other than the Sun.
(e) are the same as those in famous television stars like himself.
3. Galaxies are important to the human species because
(a) without galaxies, there would not have been a Big Bang.
(b) galaxies provide the gravity that prevents us from falling off the Earth,
(c) galaxies collide frequently which allows material from different parts of the universe to be exchanged.
(d) galaxies recycle elements produced in stars into future generations of stars so that the amount of
elements besides hydrogen and helium increases over time.
4. Sound travels with a speed of about 300 m/s in air at room temperature. By analogy to a light-year,
which of the following lengths is closest to the value of a “sound-hour”?
(a) 10 km
(b) 100 km
(c) 1,000 km
(d) 10,000 km
Open Questions
( 10 points) List the following distances in
the appropriate order on the line below.
increasing size by writing their corresponding numbers in
1. The radius of the Milky Way.
2. One light-month.
3. The radius of the sun.
4. The average earth-moon distance.
5. The typical distance between stars.
6. 1 AU.
7. The radius of the star Deneb.
8. The typical distance between galaxies.
9. The size of the solar system (as defined by its outermost planet Pluto).
10. The typical distance of an object in the Oort cloud to the Sun.
Answer:
Extra credit (3 points): Name one of the women that I mentioned in class as making an outstanding
contribution to astronomy and describe in a few words what her contribution was.
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