What explains the seasons on Earth?

• A. Tilted
• B. Shaded
• C. Aligned
• D. Horizontal

Answer: (A)

Seasons are explained by the tilt of Earth's axis relative to its orbit around the Sun. The axis is angled about 23.5 degrees, so as Earth travels around the Sun different hemispheres tilt toward or away from the Sun at different times of year. When the Northern Hemisphere tilts toward the Sun, the Sun’s path is higher in the sky, the days are longer, and sunlight is more direct, producing summer. When that hemisphere tilts away, the Sun sits lower, days are shorter, and sunlight is weaker, producing winter. Around the spring and fall (the equinoxes), day and night are roughly equal, marking the seasonal transitions. The distance to the Sun changes a bit throughout the year, but the tilt is what mainly drives the seasonal temperature differences.