8.7 A Day and Night

Students in a science class in Marfa, Texas, made a poster with a diagram to represent a seasonal change in the Northern Hemisphere.

Which statement best describes conditions for Earth at Position 1 in the diagram?

• There are an equal number of hours of daylight and nighttime in the Northern hemisphere, and the North Pole is tilted away from the sun.

• The Northern hemisphere has the fewest hours of daylight, and Earth's axis does not tilt at this position.

• There are an equal number of hours of daylight and nighttime in the Northern Hemisphere because Earth's axis is not tilted in this position.

• The Northern Hemisphere has the fewest hours of daylight, and the North Pole is tilted away from the sun.

Which of these changes would likely occur if the rate of Earth's rotation on its axis increased?

• The length of the seasons would be shorter.

• The length of the seasons would be longer.

• The length of a day would be shorter.

• The length of a day would be longer.

The model shoes Earth in several positions relative to the Sun.

In which position is it winter in North America?

• Position 1, because North America receives the most direct sun

• Position 2, because North America is tilted towarad the sun

• Position 3, because North America is parallel to the sun

• Position 4, because North America is tilted away from the sun

A student wants to use a spinning basketball to model the day-and-night cycle on Earth.

What should the student do in order to best model the cause of the day-and-night cycle?

• Spin the ball in different directions

• Tilt the ball while it is spinning

• Paint one half of the ball black and the other half white

• Shine a bright light on one side of the ball

In the summer many people enjoy going to the beach. The photograph shows a beach in Argentina, which is located in the Southern Hemisphere.

Which diagram shows the position of Earth when it is summer in Argentina?

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A student draws the model shown.

Which of these best compares the conditions at Location X and Location Y?

• It is day at Location X and night at Location Y.

• It is winter at Location X and summer at Location Y.

• There are more hours of daylight at Location X than at Location Y.

• The moon is brighter when viewed from Location X than when viewed from Location Y.

The diagram below shows four positions in Earth's orbit around the sun.

The Northern Hemisphere experiences the beginning of spring when Earth is in -

• Position 1

• Position 2

• Position 3

• Position 4

Which of these locations on Earth experiences the least change in the number of daylight hours throughout the year?

• Equator

• North Pole

• Tropic of Cancer

• Tropic of Capricorn

Earth would not have seasons if it -

• no longer tilted on its axis

• stopped rotating on its axis

• took an additional month to orbit the sun

• revolved around the sun in the opposite direction

The beginning of autumn in North America is in September, but the beginning of autumn in South America is in March. The diagram shows the positions of Earth, the moon, and the sun on one day in September and one day in March.

Why does autumn start in different months of the year in North America and South America?

• Earth's orbit around the sun is not a perfect circle.

• North America has a larger landmass than South America.

• The moon has a greater pull on South America than on North America.

• Earth's axis has a 23.5^o tilt.