The changing of seasons on Earth is primarily caused by the tilt of the Earth's axis and its orbit around the sun. The Earth's axis is tilted at an angle of approximately 23.5 degrees relative to its orbital plane, leading to varying amounts of sunlight received at different latitudes throughout the year. As Earth orbits the sun, this tilt causes seasonal changes in the intensity and duration of sunlight, resulting in seasonal variations such as summer, winter, spring, and fall. These variations influence ecosystems, weather patterns, and agricultural practices.