Earth's seasons are caused by which factor?

Earth's seasons are caused by which factor?

• A. Axial tilt during orbit around Sun
• B. Moon phase
• C. Solar output fluctuations
• D. Global wind patterns

Answer: (A)

Seasons come from the tilt of Earth's axis as it orbits the Sun. The axis is tilted about 23.5 degrees relative to its orbital plane, so at different times of year the Northern and Southern Hemispheres lean toward or away from the Sun. When a hemisphere tilts toward the Sun, sunlight hits more directly and days are longer, warming that hemisphere. When it tilts away, sunlight is more oblique and days are shorter, cooling it. This difference in sun angle and daylight length is what creates the seasonal warmth and cold. The other factors don’t drive the seasonal cycle. Moon phase doesn’t change how sunlight falls on Earth, solar output variations are too small on yearly timescales to create the seasons, and global wind patterns influence weather more than they cause the regular seasonal shift. The shape of Earth’s orbit can slightly alter distance from the Sun, but that effect is minor compared to the tilt’s impact on sunlight angle and daylight duration.

Seasons come from the tilt of Earth's axis as it orbits the Sun. The axis is tilted about 23.5 degrees relative to its orbital plane, so at different times of year the Northern and Southern Hemispheres lean toward or away from the Sun. When a hemisphere tilts toward the Sun, sunlight hits more directly and days are longer, warming that hemisphere. When it tilts away, sunlight is more oblique and days are shorter, cooling it. This difference in sun angle and daylight length is what creates the seasonal warmth and cold.

The other factors don’t drive the seasonal cycle. Moon phase doesn’t change how sunlight falls on Earth, solar output variations are too small on yearly timescales to create the seasons, and global wind patterns influence weather more than they cause the regular seasonal shift. The shape of Earth’s orbit can slightly alter distance from the Sun, but that effect is minor compared to the tilt’s impact on sunlight angle and daylight duration.