Astronomy Practice Exam

What astronomical phenomenon explains the change of seasons on Earth?

1. Earth's rotation.

2. Moon phases.

3. Earth's orbit around the sun.

4. Changes in atmospheric conditions.

The correct answer is: Earth's orbit around the sun.

The change of seasons on Earth is primarily attributed to the tilt of Earth's axis and its orbit around the sun. As Earth revolves around the sun throughout the year, different parts of the planet receive varying amounts of sunlight, depending on this axial tilt of approximately 23.5 degrees. During one part of the year, the Northern Hemisphere tilts toward the sun, resulting in longer days and more direct sunlight, which corresponds to summer in that hemisphere. Conversely, when the Southern Hemisphere is tilted toward the sun, the Northern Hemisphere experiences winter with shorter days and less direct sunlight. This cyclical pattern continues as the Earth moves along its elliptical orbit, leading to the distinct seasonal changes experienced across different regions. Although Earth's rotation also affects day and night, it is not the reason for the seasonal changes. Moon phases relate to the position of the moon relative to Earth and the sun, without any impact on the seasons. Lastly, while changes in atmospheric conditions can influence weather, they are not responsible for the fundamental seasonal shifts. The seasons are fundamentally linked to the Earth's orbit and axial tilt.