Astronomy Practice Exam 2025 – Complete Preparation Guide

The seasons on Earth are primarily caused by the tilt of the Earth's axis. This axial tilt is approximately 23.5 degrees from the perpendicular to the plane of the ecliptic, which is the orbit that Earth follows around the Sun. As Earth orbits the Sun throughout the year, different regions of the planet receive varying amounts of sunlight due to this tilt.

During summer in the Northern Hemisphere, for example, the North Pole is tilted toward the Sun, resulting in longer days and more direct sunlight, which makes it warmer. Conversely, during winter, the North Pole is tilted away from the Sun, leading to shorter days and less direct sunlight, which causes colder temperatures. The Southern Hemisphere experiences opposite seasons at the same times due to this axial tilt.

Factors such as the distance from the Sun, Earth's rotation speed, and the shape of Earth contribute to other aspects of our climate but do not directly cause the seasonal changes. The variation in intensity and duration of sunlight due to the axial tilt is the fundamental reason why we experience seasons.