Astronomy: Chapter 3

Question 1

Explain why there is a tidal bulge on BOTH sides of the earth.

Answer 1

There are bulges on both sides of the earth because of the gravitational pull of the moon.
tidal bulge due to inertia
tidal bulge due to gravity

Question 2

How did ancient greeks know that the earth was spherical?

Answer 2

Find out.

Question 3

Contributions of Aristotle, Eratosthenes, Hipparchus, Ptolemy

Answer 3

Aristotle: find out
Eratosthenes: proved that the earth was a sphere and found out the approximate circumference of earth.
Hipparchus: magnitude scale.
Ptolemy: explained retrograde motion through epicycles in which planets move in loops forward and backwards.

Question 4

Compare Copernicus heliocentric solar system with Ptolemy’s geocentric solar system. How does each explain the retrograde motion of the planets? ‘

Answer 4

Heliocentric - “sun-centered”- explains retrograde motion by planets passing each other.

Geocentric - “earth - centered” - explains retrograde through epicycles in which planets move in loops.

Question 5

Kepler’s three laws of motion

Answer 5

1. ) The orbit of every planet is an ellipse with the sun at one of the two foci.
2. ) A line joining a planet and the sun sweep out equal areas in equal times.

3.) The square of the orbital period of a planet is directly proportional to the cube of the semi - major axis of its orbital (p^2 = a^3)

Question 6

Mention several of Galileo’s telescopic observations and explain how they support the heliocentric viewpoint of the solar system.

Answer 6

• because earth’s moon is uneven and rough, it means that the “heavens” or outer space must not be perfect.
• NOticed that jupiters moons would disappear from day to night. this showed that the planets do not orbit around the earth as the center.
• venus moon also has 8 phases: our moon is not special.

Question 7

What is the difference between mass, volume, and weight? give some examples.

Answer 7

• Mass is the matter contained within an object.
• Volume is the amount of space in an object.
• weight is the force of gravitational attraction on an object; it is the mass times the gravity.

Question 8

What does the gravitational force between two objects depend on? Give a numerical example of how the force varies with distance.

Answer 8

The gravitational force of two objects depends on mass and distance.

Question 9

Explain Newton’s three laws of motion.

Answer 9

1. ) Inertia: things that are moving stay moving. things that are at rest, stay at rest. (a body continues at rest or in uniform motion in a straight line unless acted upon by some force.)
2. ) a bodys change of motion is proportional to the force acting on it, and in the direction of the force.
3. ) when one body exerts a force on a second body, the second body exerts an equal and opposite force back on the first body.