What is the primary factor that affects the seasons on Earth?

The primary factor that affects the seasons on Earth is the tilt of Earth's axis. Earth is tilted at an angle of approximately 23.5 degrees relative to its orbit around the Sun. This axial tilt is significant because as Earth orbits the Sun throughout the year, different parts of the planet receive varying amounts of sunlight at different times.

During summer in the Northern Hemisphere, this region is tilted toward the Sun, resulting in longer days and more direct sunlight, which leads to warmer temperatures. Conversely, during winter, the Northern Hemisphere is tilted away from the Sun, leading to shorter days, less direct sunlight, and cooler temperatures. The Southern Hemisphere experiences opposite seasons; when it is summer in the Northern Hemisphere, it is winter in the Southern Hemisphere, and vice versa.

Although the distance from the Sun does have some effect on Earth's climate, it is not the primary cause of the seasonal changes. The curvature of the Earth contributes to variations in sunlight but is primarily a consequence of the axial tilt rather than a direct cause of seasons. The rotation of the Earth leads to day and night cycles but does not influence seasonal temperature variation. Thus, it is the axial tilt that fundamentally determines the characteristics of the seasons on our planet.