Which of the Earth's motions causes day and night?

What causes the seasons?

What are solstices and equinoxes? How are they related to the seasons?

How would the seasons be different if Earth were not tilted on its axis?

What is the law of universal gravitation?

What two factors determine the force of gravity between two objects?

Suppose the moon were closer to Earth. How would the force of gravity between the Earth and the moon be different?

What two factors act together to keep Earth in orbit around the sun?

Why doesn't Earth simply fall into the sun?

How would Earth move if the sun (including its gravity) suddenly disappeared? Explain your answer.

What causes the moon to shine?

Why does the moon appear to change shape during the course of a month?

What is an eclipse?

How is a solar eclipse different from a lunar eclipse?

Why isn't there a solar eclipse and a lunar eclipse each month?

What causes the tides?

Explain why most coastal regions have two high tides and two low tides each day.

Compare the size of high and low tides in a spring tide and a neap tide. What causes the difference?

Name three major features of the moon's surface.

How did the moon's craters form?

Why is the moon's surface much more heavily cratered than the Earth?

Describe the range of temperatures on the moon.

Compare Earth and the moon in terms of size and surface gravity.

What is the relationship between the moon's surface gravity, lack of an atmosphere, and temperature range?

What was the solar system like when the moon formed?

Explain the various stages in the formation of the moon.

What is a rocket?

How do rockets create thrust?

Describe how a multistage rocket works.

What is the main advantage of a multistage rocket compared to a single-stage rocket?

What was the "space race"?

Place these events in the correct sequence:

first humans on the moon;

Sputnik I;

first American in space;

John Glenn orbits Earth;

NASA formed;

Yuri Gagarin Orbits Earth.

What is the space shuttle? What is its main advantage?

What is a space station? A space probe?

What are the roles of space shuttles, space stations, and probes in the space program?

Explain how the length of the day and year are related to Earth's movement through space.

Suppose you moved two objects farther apart. How would this affect the force of gravity between those objects?

Why is there a high tide on the side of Earth closest to the moon? Why is there a high tide on the side of Earth farthest from the moon?

How did the invention of the telescope contribute to our knowledge of the moon's surface?

Why do temperatures vary so much on the moon?

Mars's axis is tilted at about the same angle as Earth's axis. Do you think Mars has seasons? Explain your answer.

How are mass and weight different?

What are the geocentric and heliocentric systems?

How was Copernicus's model of the universe different from Ptolemy's model?

People often say the sun rises in the east, crosses the sky, and sets in the west. Is this literally true? Explain.

How did Kepler use Tycho Brahe's data?

What did Kepler discover about the orbits of the planets?

What objects make up the solar system?

What are the eight planets, in order of increasing distance from the sun?

List the three layers of the sun's interior, starting from the center.

Where is the sun's energy produced?

Compare how energy moves through the radiation zone and the convection zone.

What three layers make up the sun's atmosphere?

Which of the sun's layer's produces its visible light?

Why is it usually impossible to see the sun's corona from Earth?

Describe three features found on or just above the sun's surface.

Why do sunspots look darker than the rest of the sun's photosphere?

How are the four inner planets similar to one another?

Venus is much farther from the sun than Mercury is. Yet average temperatures on Venus's surface are much higher than those on Mercury. Explain why.

How are the gas giants similar to one another?

Why do all the gas giants have thick atmospheres?

Compare the structure of a typical terrestrial planet with that of a gas giant.

What is a comet?

What are the different parts of a comet?

How does a comet's appearance change as it approaches the sun? Why do these changes occur?

What is an asteroid?

Where are most asteroids found?

How did the asteroids form?

What is a meteoroid?

What are the main sources of meteoroids?

What are the differences between meteoroids, meteors, and meteorites?

What conditions does life on Earth need to survive?

Why do astronomers think there could be life on Europa?

Scientists think that in the past Mars may have had the conditions needed for life to exist. What are these conditions? Do they still exist?

What characteristic do Mars and Europa share with Earth that makes them candidates to support extraterrestrial life?

What is the solar wind?

Why does Mercury have very little atmosphere?

Why can astronomers see the surface of Mars clearly but not the surface of Venus?

What evidence do astronomers have that water once flowed on Mars?

Do you think astronomers have found all of the moons of the outer planets? Explain.

Why would the discovery of liquid water on another planet be important?

List the main types of electromagnetic waves, from longest wavelength to shortest.

Why are images from the Hubble Space Telescope clearer than images from telescopes on Earth?

What are the two major types of optical telescope?

How does a refracting telescope work?

How does the atmosphere affect electromagnetic radiation?

Why are many large optical telescopes located on mountaintops?

Would it make sense to place an X-ray or gamma ray telescope on a mountaintop? Explain why or why not.

Name at least three characteristics used to classify stars.

What is the difference between apparent brightness and absolute brightness?

Stars A and B have about the same apparent brightness, but Star A is about twice as far from Earth as Star B. Which star has the greater absolute brightness? Explain your answer.

What is a light-year?

What is parallax?

What two characteristics of stars are shown in an H-R diagram?

Identify two ways in which astronomers can use an H-R diagram.

What is a nebula?

How does a star form from a nebula?

How is a protostar different from a star?

What factor determines how long a star lives?

A star is twice as massive as the sun. Will its lifespan be longer, shorter, or the same as that of the sun?

What is a white dwarf? How is it different from a neutron star?

Why do some stars become white dwarfs and others become neutron stars or black holes?

What will happen to the sun when it runs out of fuel?

What is a binary star?

Are all binary stars part of star systems? Explain.

Some binary stars are called eclipsing binaries. Explain why this term is appropriate.

Name the main types of galaxies.

What type of galaxy is the Milky Way?

Suppose astronomers discover a galaxy that contains only old stars. What type of galaxy is it likely to be?

What is scientific notation?

How is scientific notation useful to astronomers?

What was the big bang?

When did the big bang occur?

How old is the solar system?

What force caused the solar system to form?

Place the following events in the proper order:

planets form;

planetesimals form;

solar nebula shrinks;

nuclear fusion begins in the sun

What is dark matter?

How do scientists know that dark matter exists?

What evidence has led scientists to predict that the universe will continue to expand forever?

Is a light year a unit of distance or a unit of time? Explain.

Why can't astronomers measure the parallax of a star that is a million light-years away?

At what point in the evolution of a star is the star actually born?

Where in our galaxy does most star formation take place?

What is Hubble's law?

How can astronomers detect dark matter if they cannot observe it directly?

How does a star's mass affect its lifetime?