The Birth of Modern Astronomy

Question 1

What was so mysterious about planetary moton in our sky to early astronomers?

Answer 1

Like the Sun and Moon, planets usually drif
eastward relatve to the stars from night to night; but sometmes, for a few weeks or few months, a planet turns
westward in its apparent retrograde moton

Question 2

Why did the ancient Greeks reject the real explanaton for planetary moton?

Answer 2

Most Greeks concluded that Earth
must be statonary, because they thought the stars could not be so far away as to make parallax undetectable

Question 3

How did Copernicus, Tycho and Kepler challenge the Earth-centered idea?

Answer 3

Copernicus created a sun-centered
model; Tycho provided the data needed to improve this model; Kepler found a model that ft Tycho’s data

Question 4

Which astronomers challenged the Earth-centered idea?

Answer 4

Copernicus, Tycho and Kepler

Question 5

How did Copernicus, Tycho and Kepler challenge the Earth-centered idea?

Answer 5

Copernicus created a sun-centered
model; Tycho provided the data needed to improve this model Kepler found a model that ft Tycho’s data

Question 6

What was Galileo’s role in solidifying the Copernican revoluton?

Answer 6

His experiments and observatons overcame the remaining objectons to the Sun-centered solar system. (Tycho’s observatons of comet and supernova already challenged this idea.)

Question 7

Using his telescope, Galileo saw:

Answer 7

• Sunspots on Sun (“imperfectons”)
• Mountains and valleys on the Moon (proving it is not a perfect sphere)

Question 8

Who invented telescopes and thermometers?

Answer 8

Galileo

Question 9

Who discovered Moon’s craters, Jupiter’s moons, phases of Venus, and stars in Milky Way?

Answer 9

Galileo

Question 10

Kepler’s 1st law of planetary motion

Answer 10

1. The orbit of each planet is an ellipse with the Sun at one focus

Question 11

Kepler’s 2nd law of planetary motion

Answer 11

2. As a planet moves around its orbit it sweeps our equal areas in equal tmes

Question 12

Kepler’s 3rd law of planetary motion

Answer 12

3. More distant planets orbit the Sun at slower average speeds: p^2 = a^3
   p = orbital period in years
   a = avg. distance from Sun in AU

Question 13

Does 3-rd Kepler’s law depends on masses of planets?

Answer 13

No

Question 14

Will a small rock and a big planet have the same period of rotaton if they happen to be at the same distance to the Sun?

Answer 14

Yes

Question 15

Which planet is the fastest in a solar system - Mercury, Venus Mars, Jupiter? Which Kepler’s law explains it?

Answer 15

Mercury (Kepler’s 3rd law)

Question 16

What did Copernicus conclude?

Answer 16

Copernicus concluded that Earth is a planet and that all the planets circle the Sun. Only the Moon orbits Earth

Question 17

What did Copernicus conclude?

Answer 17

Copernicus argued that the apparent motion of the Sun about Earth during the course of a year could be represented equally well by a motion of Earth about the Sun.

Question 18

Could Copernicus prove that Earth revolves about the Sun?

Answer 18

no

Question 19

Why, in Copernicus’s time there was little motivation to carry out observations or experiments to distinguish between competing cosmological theories

Answer 19

In Copernicus’ time, in fact, few people thought there were ways to prove whether the heliocentric or the older geocentric system was correct. A long philosophical tradition, going back to the Greeks and defended by the Catholic Church, held that pure human thought combined with divine revelation represented the path to truth.

Question 20

Who showed that rest is no more natural than motion.

Answer 20

Galileo

Question 21

accelerate

Answer 21

—change their speed or direction of motion.

Question 22

Galileo’s Astronomical Observations about jupiter

Answer 22

• Galileo found four moons revolving about Jupiter in times ranging from just under 2 days to about 17 days. This discovery was particularly important because it showed that not everything has to revolve around Earth.
• Within a few months, he had found that Venus goes through phases like the Moon, showing that it must revolve about the Sun,

Question 23

Meridian

Answer 23

a half-circle extending from your horizon due north, through your zenith, to your horizon due south

Question 24

What is a circumpolar star?

Answer 24

a star that always remains above your horizon

Question 25

You are standing on Earth’s equator. Which way is Polaris, the North star?

Answer 25

on the northern horizon

Question 26

Orion is visible on winter evenings but not summer evenings because of

Answer 26

the location of Earth in its orbit.

Question 27

He discovered that Jupiter has moons.

Answer 27

Galileo

Question 28

Kepler’s third law, p2 = a3, means that

Answer 28

all orbits with the same semi-major axis have the same period.
the period of a planet does not depend on its mass.
a planet’s period does not depend on the eccentricity of its orbit.
planets that are farther from the Sun move at slower average speeds than nearer planets.

Question 29

From Kepler’s third law, a hypothetical planet that is twice as far from the Sun as Earth should have a period of

Answer 29

more than 2 Earth years.

Question 30

Kepler’s second law, which states that as a planet moves around its orbit it sweeps out equal areas in equal times, means that

Answer 30

a planet travels faster when it is nearer to the Sun and slower when it is farther from the Sun.