Here's why:
* Earth's Tilt: Earth's axis of rotation is tilted at approximately 23.5 degrees relative to its orbital plane around the Sun. This tilt means that different parts of the Earth receive varying amounts of direct sunlight throughout the year.
* Summer and Winter: When a hemisphere is tilted towards the Sun, it receives more direct sunlight and experiences summer. During this time, the days are longer and the Sun is higher in the sky. The opposite hemisphere is tilted away from the Sun, receiving less direct sunlight and experiencing winter.
* Spring and Fall: As Earth orbits the Sun, the amount of direct sunlight received by each hemisphere gradually changes. During the transition periods between summer and winter, the days and nights are roughly equal in length, and these periods are known as spring and fall (or autumn).
In summary, Earth's axial tilt is the primary reason for the changing seasons.
