The seasons on Earth change primarily due to the tilt of the planet's axis and its orbit around the Sun. Earth's axis is tilted at an angle of approximately 23.5 degrees, which affects how sunlight is distributed across the planet throughout the year. When the Northern Hemisphere is tilted toward the Sun, it experiences warmer temperatures and longer days, marking summer, while the Southern Hemisphere experiences winter. Conversely, when the Southern Hemisphere is tilted toward the Sun, it enjoys summer, and the Northern Hemisphere goes through winter. The changing seasons create variations in weather and ecosystems.