Chapter 3

Question 1

Geocentric Model

Answer 1

Earth-centric

Question 2

Who was one of the first prominent proponents of the geocentric model?

Answer 2

Claudius Ptolemaeus 90-168 CE

Question 3

Prograde Motion

Answer 3

Eastward Motion

Question 4

Retrograde Motion

Answer 4

Planets appear to move westward for a time before resuming their normal eastward direction

Question 5

Why did early astronomers believe the geocentric model?

Answer 5

1) We couldn’t feel earth’s rotation around the sun.
2) Various religious believes reinforced mankind sense that the world was made for them or they were the highest form of life.

Question 6

Epicycle

Answer 6

A small circle superimposed on each plant to explain retrograde motion.

Question 7

What are the three major assumptions of early astronomers?

Answer 7

1. The earth is the center of the solar system.
2. The planets and sun orbited in uniform circles.
3. Objects in space are made up of a different substance than the earth.

Question 8

Heliocentric Model

Answer 8

Planets are orbiting the sun including earth.

Question 9

What assumptions did Copernicus dispel of in his model.

Answer 9

1. the earth is the center of the solar system.

2. Objects in space are made up of a different substance than the earth.

Question 10

What did Copernicus still include in his model?

Answer 10

1) Epicycles (althought they were greatly reduced

2) The planets and sun orbited in uniform circles.

Question 11

What was a major element that was missing from Copernicus’ work?

Answer 11

He had no proof that his model was correct other than it being mathematically more simplistic.

Question 12

Empirical Science

Answer 12

Based on observational data which seeks to describe patterns.

Question 13

Tycho Brahe

Answer 13

Studied law before seeing a solar ecclipse. Granted an island by the king. Hired a mathwiz Kepler as his intern to confirm if his model was true. Made detailed notes of positions of planets over several years using protractors.

Question 14

Geo-Heliocentric Frame

Answer 14

Tycho’s solution between the Heliocentric and Geocentric Model. The planets orbited the sun and the sun and planets orbited the earth.

Question 15

Johannes Kepler

Answer 15

Mathematician who was a proponent of the Copernican Model. Corrected Tycho’s model and further proved the Copernican model was correct. Derived three laws to describe planetary motion.

Question 16

Kepler’s First Law

Answer 16

Planets orbit in ellipses with the sun at one of the two foci. Eccentricity is = distrance from the center of focus/semimajor axis

Question 17

How do you calculate eccentricity

Answer 17

E= Distance from the center of focus/ semimajor axis

Question 18

Kepler’s Second Law

Answer 18

A line between the planets and sun sweeps out in equal areas in equal time. Orbit at perihelion must be faster to cover the same area as the aphelion.

Question 19

Perihelion

Answer 19

Point in orbit closest to sun

Question 20

Aphelion

Answer 20

Point in orbit furthest away from the sun.

Question 21

Kepler’s Third Law

Answer 21

Period of the planet squared=semimajor axis of orbit cubed. For all planets a3/p2=1

Question 22

Using Halley’s Comet’s Period of 76 years calculate the semimajor axis of its orbit.

Answer 22

17.94 au. 76^3=a3

Question 23

Galileo

Answer 23

First astronomer to use a telescope to observe and report significant objects

Question 24

What were Galileo two biggest discoveries?

Answer 24

1) Moons around Jupiter.

2) Phases of Venus

Question 25

What did Galileo observe when he looked at the moons of Jupiter?

Answer 25

1) Originally thought they were moons
2) Observed Jupiter remained relative in the same spot but the moons moved.
3) Observed moons would disappear and reappear
4) Deduced that they must be moons in orbit around Jupiter.

Question 26

What were the scientific consequences of Galileo’s discovery that Jupiter had moons?

Answer 26

1) Good observational evidence that other planets have moons just like earth.
2) Our planet is not unique.
3) More arguments for the Heliocentric model.

Question 27

What did Galileo observe when looking at Venus in a telescope?

Answer 27

Observed phases similar to that of the moon?

Question 28

How did the Heliocentric model fit the observational data of Galileo vs the Geocentric model for the phases of Venus?

Answer 28

In the Geocentric Model, one would predict that the full venus phases would not be visible because of its proximity to the sun. But in the Heliocentric model one would predict phases similar to that of the moon.

Question 29

What was important about Galileo’s observations about the phases of Venus?

Answer 29

1. Actual evidence that the planets orbit the sun rather than the earth.
2. Venus is closer to the sun that earth.

Question 30

What was the most likely reason Galileo was placed under house arrest?

Answer 30

Wrote “Dialogue on the Two World Systems” in 1632. In which two philosophers and a layperson discuss the two competing models. The lay person “Simplicio” made arguments which closely resemble that of the pope.

Question 31

Sir Isaac Newton

Answer 31

1) Invented Calculus at the age of 23.
2) Proposed three laws that explain planetary motion.
3) Founder of classical mechanics.

Question 32

Newton’s Laws

Answer 32

1) Law of Inertia. An object in motion or at rest will remain in motion or rest unless acted upon by another force.
2) F=MA Force causes motion
3) Equal and Oppisite. For every force there is an equal and opposite force.

Question 33

Newton

Answer 33

kgms^-2=kgm/s^2

Question 34

Force

Answer 34

A push or a pull. Causes an object to accelerate.

Question 35

Gravitational Force

Answer 35

Objects experience an acceleration due to gravity. Equal to 9.8m/s2 on earth Acceleration due to gravity points to the center of earth.

Question 36

Where is gravity weakest and strongest on earth

Answer 36

Weakest on the equator and strongest at the poles because there is less distance to the center of earth.

Question 37

What did Galileo Observe about falling objects?

Answer 37

Observed that objects of different masses fall at the same rate.

Question 38

What does gravitational force depend on?

Answer 38

1) The mass of the objects

2) The distance between the objects.

Question 39

Newton’s Law of Gravity

Answer 39

Fgrav=Gx (m1*m2)/r^2 G is the universal gravitational constant of 6.67 * 10^-11