Which of the following is the primary cause of the seasons on Earth?

• A. The rotation of Earth on its axis
• B. The varying distance between Earth and the Sun during the year
• C. The gravitational pull of the Moon
• D. The tilt of Earth's axis relative to its orbital plane

Answer: (D)

Verified step by step guidance

1. Understand the concept of Earth's axial tilt: Earth's axis is tilted at an angle of approximately 23.5 degrees relative to its orbital plane around the Sun. This tilt is the primary reason for the seasons.
2. Recognize how the tilt affects sunlight distribution: As Earth orbits the Sun, the tilt causes different parts of the planet to receive varying amounts of sunlight at different times of the year. This variation leads to changes in temperature and daylight hours, which define the seasons.
3. Eliminate incorrect options: The rotation of Earth on its axis causes day and night, not seasons. The varying distance between Earth and the Sun during the year has a minimal effect on seasons because Earth's orbit is nearly circular. The gravitational pull of the Moon influences tides, not seasons.
4. Focus on the correct explanation: The tilt of Earth's axis causes one hemisphere to be tilted toward the Sun during part of the year (summer) and away from the Sun during another part (winter). This results in seasonal changes.
5. Relate the concept to real-world observations: For example, during the summer solstice in the Northern Hemisphere, the North Pole is tilted toward the Sun, leading to longer days and warmer temperatures. Conversely, during the winter solstice, the North Pole is tilted away from the Sun, resulting in shorter days and colder temperatures.