Assignment #4

Question 1

What did classical Greek astronomers believe?

Answer 1

the motions of the heavens could be described by uniform circular motion

Question 2

What did Greek philosophers use to understand the mysteries of the universe?

Answer 2

religion and astrology

Question 3

Gravity obeys an inverse square relation. What does this statement imply about the force due to gravity between two masses?

Answer 3

it will decrease as the square of the distance between the two masses increases

Question 4

Which planet cannot transit (i.e. pass in front of) the Sun, as seen from Jupiter?

Answer 4

Saturn

Question 5

What was Tycho Brahe’s greatest contribution to astronomy?

Answer 5

his 20 years of careful observations of the planets

Question 6

Whose writings became so famous that he was known throughout the Middle East simply as “The Philosopher”?

Answer 6

Aristotle

Question 7

What is the relationship between Kepler’s laws of planetary motion and Newton’s laws of motion and universal gravitation?

Answer 7

Newton’s laws can explain Kepler’s laws

Question 8

Why did most astronomers accept a geocentric model of the universe for 2000 years?

Answer 8

astronomers were unlikely to question the authority of Aristotle

Question 9

The orbit of the Moon is an ellipse with the Earth at one focus. What is located at the other focus?

Answer 9

nothing

Question 10

If the mass of the Earth decreased by a factor of 2, with no change in the radius, what would happen to your weight?

Answer 10

it would decrease by a factor of 2

Question 11

Galileo’s telescopic discovery of mountains on the Moon was controversial because it suggested something about the Moon. What was it?

Answer 11

that the moon is not a perfect sphere

Question 12

What do we call an orbit that has the same period as the rotation period of the Earth?

Answer 12

a geosynchronous orbit

Question 13

When we say that gravitation is universal, what do we mean?

Answer 13

all objects exert gravitational force on its moon and vice versa

Question 14

What is another name for the star the Inuit call Nuuttuittuq, meaning “the one that never moves”?

Answer 14

polaris

Question 15

When viewing from Earth, which objects can be seen to undergo retrograde motion in the night sky?

Answer 15

only planets that are more distant from the sun than earth

Question 16

What belief was held in Pre-Copernican astronomy?

Answer 16

the Earth was at the centre of the universe

Question 17

How did Galileo’s observations of moons orbiting Jupiter conflict with the geocentric model of the universe of his time?

Answer 17

the moons did not appear to orbit the Earth

Question 18

What are scientific models used for?

Answer 18

to make specific predictions that can be tested through observations or experiments

Question 19

What is the term for a single conjecture that can be tested?

Answer 19

hypothesis

Question 20

Describe Kepler’s third law of planetary motion.

Answer 20

the larger the orbit, the longer its orbital period

Question 21

What is the term for a well-supported system of rules and principles that can be applied to a wide variety of circumstances but that is not universally accepted?

Answer 21

theory

Question 22

How does the force of gravity that Earth exerts on you compare to the force of gravity that you exert on Earth?

Answer 22

They are equal

Question 23

Why do astronauts feel weightless when in orbit around Earth?

Answer 23

They are falling around Earth at the same rate as the spaceship

Question 24

What did Galileo’s observations of a complete set of phases of Venus prove?

Answer 24

that Venus orbited the sun

Question 25

On average, Saturn is 10 AU from the sun. What is the approximate orbital period of Saturn?

Answer 25

32 years

Question 26

What did Kepler base his three laws of planetary motion on?

Answer 26

precise observations of the apparent motions of planets

Question 27

In Ptolemy’s view of the universe, what is at the centre of a planet’s epicycle?

Answer 27

the deferent

Question 28

Why does Mars appear to brighten during its retrograde motion?

Answer 28

mars is closest to Earth during this time

Question 29

What two numbers tell us the size and shape of an ellipse?

Answer 29

semi-major axis and eccentricity

Question 30

Given its orbital period of 76 years, what is the average distance of Comet Halley from the sun?

Answer 30

18 AU

Question 31

The Copernican and Ptolemaic systems used a key factor. What was that factor?

Answer 31

uniform circular motion

Question 32

What does the eccentricity of a planet’s orbit describe?

Answer 32

deviation in shape when compared to a circle

Question 33

What was the basis for Isaac Newton’s conclusion that a force from the Earth must be acting on the Moon?

Answer 33

a force is needed to accelerate the moon toward the earth, away from straight-line motion

Question 34

At which lunar phases are tides at their lowest?

Answer 34

first and third quarter moon

Question 35

What principle was Copernicus unable to provide evidence against?

Answer 35

uniform circular motion

Question 36

What is perigee?

Answer 36

the point in an object’s orbit around earth when the object is closest to earth

Question 37

What was Eratosthene’s mathematical contribution to the history of astronomy, even though it was incorrect?

Answer 37

he attempted to calculate earth’s radius by utilizing the position of sunlight and measuring the length of shadows