Name ______________________________
Study Guide
(Answer Key)
Earth Systems Ch. 22 & 23
1. Who developed a geocentric model of the universe describing the motions of the planets?
Ptolemy
2. Which of our current planets were known to the ancient Greeks? Mercury, Venus, Earth, Mars,
Jupiter
3. How did Aristotle decide the Earth was round? It always casts a curved shadow during a lunar
eclipse
4. Define retrograde motion. The apparent westward movement of a planet against a
background of stars.
5. Define celestial sphere. A transparent, hollow sphere on which the stars traveled daily around
Earth.
6. Define equatorial plane. An imaginary plane that cuts through the Earth perpendicular to the
axis of rotation.
7. What did the geocentric model of the universe state? The Earth was the center of the
universe.
8. What did the Ptolemaic model of the universe state? Earth was the center of the universe.
9. Which scientist proposed three laws of planetary motion using Tycho Brahe’s data? Kepler
10. Who was the first astronomer to propose a sun-centered solar system? Copernicus
11. Which scientist first discovered that Venus had phases, just like the moon? Galileo
12. Define mass. The measure of how much matter is in an object.
13. Define weight. The force that gravity exerts on an object.
14. What is the shape of a planet’s orbit? elliptical
15. What did Newton determine about planet’s orbits? He determined the nature of the forces
that keep the planets in their orbits.
16. What scientist was the first to use a telescope in astronomy? Galileo
17. Who discovered the true shape of planetary orbits? Kepler
18. Which astronomer spent 20 years plotting the positions of the planets? Brahe
19. Make a list of Galileo’s astronomical discoveries. Sunspots, mountains on the moon, Jupiter’s
four largest moons
20. What does the third law of planetary motion state? The period of revolution of a planet is
related to the planet’s distance to the sun.
21. Define perihelion. The point at which Earth is closest to the sun.
22. Define aphelion. The point at which Earth is farthest from the sun.
23. Define precession. Earth’s axis slowly but continuously points in different directions.
24. What movement of Earth is responsible for day and night? rotation
25. Define rotation. The turning or spinning of a body on its axis.
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Define revolution. The motion of the Earth around the Sun.
What causes the seasons on Earth? Earth’s tilted axis.
Define perigee. The point at which the moon is closest to the Earth.
Define apogee. The point at which the moon is farthest from the Earth.
What is the moon’s period of revolution and its period of rotation? Revolution-27 1/3 days;
Rotation-27 1/3 days (They are the same).
What is the length of daylight on the moon? 2 weeks
What occurs when the moon casts its shadow on Earth? Solar eclipse
What are round depressions on the moon’s surface called? Craters
What are the oldest features on the moon called? Highlands
How old is the moon compared to Earth? About the same age as Earth
List the planets known to have rings. Jupiter, Saturn, Uranus and Neptune
List the Jovian planets. Jupiter, Saturn, Uranus and Neptune
List the terrestrial planets. Mercury, Venus, Earth and Mars
What is the most obvious difference between the Jovian and terrestrial planets? Size
Describe what occurred in nebular theory. Formation of the solar system from a huge cloud of
dust and gases
Which planets show evidence of water erosion? Earth and Mars
Which planet has a crater surface similar to Earth’s moon? Mercury
Which planet has the greatest temperature extremes? Mercury
Which planet has a dense carbon dioxide atmosphere and high surface temperatures? Venus
How many known satellites does Mars have? 2
What is the atmosphere of Venus composed mainly of? Carbon dioxide
Which planet has a greater mass than all the remaining planets and moons combined? Jupiter
Which planet could be described as a large, dirty ice ball? Pluto
Which planet has the “Great Dark Spot”? Neptune
Which planet’s axis of rotation is almost parallel with the plane of its orbit? Uranus
Which planet was recently determined to have one satellite? Pluto
Which way does a comet’s tail always point? Away from the sun
Define a coma. The glowing head of a comet
Define meteor. The small particles that produce a streak of light upon entering Earth’s
atmosphere
Define meteorite. The remains of extraterrestrial particles that are found on Earth’s surface.