Which statement best explains the cause of the seasons?

• A. The Moon's phases
• B. The Earth's distance from the Sun
• C. Tilt of the Earth's axis and its revolution around the Sun
• D. The Sun's changing energy output

Answer: (C)

Seasons come from the tilt of Earth’s axis as it orbits the Sun. The axis is angled about 23.5 degrees relative to the plane of Earth's orbit, so different hemispheres tilt toward or away from the Sun over the year. When a hemisphere tilts toward the Sun, sunlight hits more directly and days are longer, warming the surface (summer). When it tilts away, sunlight hits at a lower angle and days are shorter, cooling the surface (winter). The distance between Earth and the Sun changes a bit during the year, but this distance change is not enough to drive the seasonal temperature differences, and the Sun’s energy output stays fairly constant season to season. The Moon’s phases don’t influence seasons.