Phases and Eclipses

Earth-Sun-Moon Review

By Christine Boudreau

Multiple Choice

Jackson enjoys looking up at the night sky and writing about the variety of objects he sees. On one special occasion, he wrote in his journal that he saw a streak of light going across part of the sky. Which answer best describes what Jackson saw?

• Meteorite: A cold mixture of dust and ice that develops a long tail as it nears the sun

• Meteor: A cold mixture of dust and ice that develops a long tail as it nears the sun

• Meteorite: A streak of light made when an object burns up as it enters Earth's atmosphere

• Meteor: A streak of light made when an object burns up as it enters Earth's atmosphere

The correct answer is D. A meteor is a streak of light made when an object burns up as it enters Earth’s atmosphere, so B and C are not correct. A comet, not a meteorite, is a cold mixture of dust and ice that develops a long tail as it nears the sun, so A is not correct.

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​Explanation

Fill in the Blanks

The planets in the solar system orbit in a plane around the sun in line with the traditional zodiac constellations.

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​Explanation

Multiple Choice

Adam and his family are planning a trip to Alaska in either June or December. During the summer months in the Northern Hemisphere, the weather is typically warmer and the days are longer. During the winter months in the Northern Hemisphere, the weather is typically cooler and the days are shorter. Adam’s family decides to travel in June based on this information.

Why does Earth have seasons?

• because Earth rotates on its axis as it revolves around the sun

• because Earth's axis is tilted as it revolves around the sun

• because the moon blocks the sun during the winter months

• because the moon's gravitational pull is stronger during the summer months

The correct answer is B. Earth has seasons because Earth’s axis is tilted as it revolves around the sun. Earth’s rotation on its axis causes the day-night cycle, so A is not correct. The moon blocks the sun during solar eclipses, which are short-term events that occur throughout the year, not just during the winter, so C is not correct. The moon’s gravitational pull is about the same throughout the year, so D is not correct.

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Explanation

Multiple Choice

Ancient scientists proposed many theories based not only on scientific observations, but also on religion and philosophy. These scientists, including Aristotle and Ptolemy, had developed an early model of the solar system. This model appeared to describe the motions they observed in the heavens. Which of the following objects is at the center of this model?

• sun

• star

• moon

• Earth

The correct answer is D. Ancient scientists observed the objects in the sky seeming to orbit around Earth, so they developed a model of the heavens with Earth at the center. The sun is at the center of the heliocentric model of the solar system, developed long after Aristotle and Ptolemy, so A is not correct. The ancients believed the stars to be fixed in place on a sphere beyond the orbits of all the other objects in the heavens around Earth, so B is not correct. The ancients correctly modelled that the moon orbits Earth, but did not place it at the center of their model, so D is not correct.

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​Explanation

Multiple Choice

Stephen learned that there are two forces that keep the moon in orbit around Earth. How do these forces keep the moon from flying off into space?

• Gravity keeps the moon in motion, and inertia attracts the moon toward Earth.

• Gravity attracts the moon toward Earth, and inertia keeps the moon in motion.

• Gravity attracts the moon toward Earth, and the distance keeps it from going further away.

• Mass weighs the moon down so it stays close to Earth, and inertia keeps the moon in motion.

The correct answer is B. Gravity attracts the moon toward Earth and vice versa. The moon’s inertia keeps the moon in motion. These two forces keep the moon in orbit around Earth, so A, C, and D are not correct.

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Explanation

Multiple Choice

The diagram is a model of the geocentric solar system described by Ptolemy. For this model to fit our observations of the sky, what will the motion of the stars be?

• The stars do not move.

• The stars must revolve around Earth.

• The stars revolve around the sun each day.

• The stars do not need to move because the planets revolve around Earth.

The correct answer is B. In the geocentric model, stars are fixed to surface of a sphere outside the orbits of the other objects in the heavens. As observed from the surface of Earth, the stars appear to revolve around Earth each day, so A is not correct. The same stars appear in the sky from one night to the next. In order for this to fit the geocentric model, the stars would need to revolve around Earth, not the sun, each day, so C is not correct. The question is asking about the motion of the stars, not about why the stars do not need to move, so D is not correct.

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Explanation

Multiple Choice

The diagram is a model of the sun-Earth system. What is the correct way to describe the time at Position 3 in the northern hemisphere?

• winter equinox, December

• summer equinox, June

• summer solstice, June

• fall solstice, September

The correct answer is C. At position 3 the northern hemisphere is tilted toward the sun, which occurs on the summer solstice sometime during the month of June. Equinoxes occur during the spring and fall, not winter or summer, so A and B are not correct. Solstices occur during the winter and summer, not spring or fall, so D is not correct.

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​Explanation

Multiple Choice

On the left is an illustration of the path of the sun in the sky at a location in the northern hemisphere. The paths shown are the most extreme seen at that location. On the right is an illustration of Earth’s position around the sun throughout one year. Which of these is the correct movement of Earth in the right diagram and the movement of the paths of the sun in the left diagram?

• Between 3 and 2 the path moves between B and C

• Between 1 and 3 the path moves between C and B

• Between 2 and 4 the path moves between B and A

• Between 4 and 1 the path moves between C and B

The correct answer is D. As Earth moves between positions 4 and 1 on right diagram, Earth is moving from winter to spring, so the path moves between C and B on the left diagram. Earth is moving from summer to fall between 3 and 2, so the path moves from A to B, not B to C, so A is not correct. Earth is moving from spring to summer between 1 and 3, so the path should move from B to A, not from C to B, so B is not correct. Earth is moving from fall to winter between 2 and 4, so the path moves from B to C, not B to A, so C is not correct.

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Explanation

Multiple Choice

The illustration shows the orbit of the moon around Earth. In the Earth–moon system pictured there is a balance between the gravitational pull between the two objects and the inertia of the moon’s motion. If we put rockets on the moon and increased its speed, what might happen?

• The force of gravity would be less.

• It might escape its orbit of Earth.

• It might drag Earth along with it by gravity.

• It would begin to spiral in toward Earth.

The correct answer is B. Increasing the speed of the moon would only increase its inertia. Since the balance between gravity and the moon’s inertia are what keep the moon in orbit, increasing its inertia might force it to escape Earth’s orbit. The force of gravity between Earth and the moon does not change unless the distance between them changes, so A is not correct. Earth’s gravity is much greater than the moon’s, so C is not correct. Decreasing, not increasing, the moon’s inertia would cause the moon to spiral in toward Earth, so D is not correct.

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​Explanation

Poll

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