Question

2025 astronomy fall final exam (1st semester)
42 of 60
what causes the seasonal changes in temperature on earth?
because of earth’s elliptical orbit, the earth is closer to the sun during summer and farther from the sun during winter. therefore, the hottest months are during the summer, when earth is closest to the sun.
the sun shines more brightly and emits more energy during the summer, and shines less brightly during the winter.
the tilt of earth’s axis as earth orbits the sun causes longer days and more direct sunlight during summer, and shorter days and less direct sunlight in winter.
the buildup of greenhouse gases during the summer traps more heat in earth’s atmosphere, causing higher temperatures at earth’s surface. in the winter, a thinner atmosphere leads to greater heat loss from earth’s atmosphere and lower temperatures.

Explanation:

To determine the cause of seasonal temperature changes:

• The first option is incorrect: Earth’s elliptical orbit does not make it closest to the Sun in summer (perihelion is near January, winter in the Northern Hemisphere).
• The second option is incorrect: The Sun’s energy output is relatively constant; it does not “shine more brightly” seasonally.
• The third option is correct: Earth’s axial tilt (≈23.5°) causes varying sunlight angle and day length. In summer, the hemisphere tilted toward the Sun gets more direct sunlight and longer days, increasing temperature. In winter, the tilted - away hemisphere gets less direct sunlight and shorter days.
• The fourth option is incorrect: Greenhouse gas levels do not seasonally “build up” to cause seasons; seasonal temperature changes are primarily due to solar angle/day length, not atmospheric thickness or greenhouse gas fluctuations.

Answer:

The tilt of Earth's axis as Earth orbits the Sun causes longer days and more direct sunlight during summer, and shorter days and less direct sunlight in winter.