Chapter 4

Question 1

Pythagoras

Answer 1

“nature can be described with mathematics”

Question 2

Aristotle

Answer 2

“universe is governed by physical laws”

Question 3

geocentric model

Answer 3

the sun, planets and stars revolved around the Earth

ancient Greek and Chinese scholars

Question 4

directions on the celestial sphere

Answer 4

stars: East to West

sun and moon: West to East

Question 5

planet

Answer 5

Greek word for “wanderer”

Question 6

retrograde motion

Answer 6

occational westward motion of the planets caused by Earth passing another planet

opposite of “direct motion” (Eastward)

Question 7

Ptolemy

Answer 7

developed the ptolemaic system of the solar system using epicycles

last great Greek astronomer

Question 8

deferent

Answer 8

larger circles which epicycles moved along

Question 9

Almagest

Answer 9

13 volume life work of Ptolemy

considered the bible of Astronomy for 1000 years

Question 10

Occam’s razor

Answer 10

William of Occam (14th century English philosopher): when two hypothess can explain the avalible data, the hypotheses requiring the fewst new assumptions should be favored

Question 11

Nicolaus Copernicus

Answer 11

16th century Polish lawyer, mathematician, and physician who formulated a heliocentric model of the solar system, determined that the orbits of the planets must be near the ecliptic, and determined the period of a planet is related to the size of its orbit

Question 12

Heliocentric model

Answer 12

proposed by Aristarchus in 3rd century BCE

Question 13

inferior planets

Answer 13

Mercury and Venus

Question 14

superior planets

Answer 14

Mars, Jupiter, and Saturn (Uranus and Neptune

Question 15

synodic vs sidereal period of planet

Answer 15

synodic period of a planet is the time between two identical configurations as seen from Earth; the sidereal period is the true orbital period of the planet

Question 16

orbital geometry of superior planet

Answer 16

closest to the Earth at “opposition” and farthest at “conjunction” (two points on line between Earth and the Sun)

at conjunction, it is only above the horizon during the day; at opposition, it is highest at midnight

Question 17

orbital geometry of inferior planet

Answer 17

closest at “inferior conjunction” and furthest at “superior conjunction”

visible at sunset at “greatest eastern elongation” and visible at sunrise at “greatest western elongation”

Question 18

de revolutionibus orbium coelestium

Answer 18

“On the Revolutions of the Celestial Spheres” published by Copernicus

Question 19

Tycho Brahe

Answer 19

Danish astronomer who showed the heavens change and are imperfect

Had two observatories on the island of Hven where he made detailed observations of the stars and planets

Believed in a Ptolemaic universe because he could not detect parallax

Question 20

Kepler’s Laws

Answer 20

1. the orbit of a planet about the sun is an ellipse with the sun at one focus
2. a line joining a planet and the sun sweeps out equal areas in equal intervals of time.
3. The square of the sidereal period of a planet is directly proportional to the cube of the semimajor axis of the orbit.

Question 21

Galileo Galilei

Answer 21

first astronomer to use the telescope beginning in 1610

observed topography on the moon, innumerable stars in the Milky Way, 4 moons of Jupiter, and phases of Venus

Showed proof that Earth and the planets orbited the sun.

Question 22

aphelion

Answer 22

point where a planet is farthest from the sun

Question 23

perihelion

Answer 23

point where a planet is closest to the sun

Question 24

escape speed of the Earth

Answer 24

11.2 km/sec

Vescape= (2GM/R)^1/2

Question 25

Newton's Laws and Kelper's Laws

Answer 25

Kepler's 1st law is a consequence of the law of universal gravitation (the 1/r^2 factor) Kepler's 3rd law follows naturally from the Law of Universal Gravitation

Question 26

proof of Newton's laws

Answer 26

Hallys Comet and the prediction of Neptune due to its pull on Uranus

Question 27

tidal forces

Answer 27

differences in the gravitational pull at different points in an object can cause galaxies to pull apart

Question 28

spring tides

Answer 28

large tide cause by the combined gravitational pull of the sun and the moon in line

Question 29

neap tides

Answer 29

smaller tides caused by the sun and moon pulling at a 90 degree angle

Question 30

formation of the moon

Answer 30

Earth's tidal effects on the moon deformed the moon while it was still hot and caused its long axis to always point to the Earth. This caused the moon's deformity and synchronous rotation which remains today.