What is the primary cause of seasonal changes on Earth?

The primary cause of seasonal changes on Earth is due to Earth's axial tilt. The planet is tilted on its axis at an angle of approximately 23.5 degrees relative to its orbital plane around the Sun. This tilt affects how sunlight is distributed across the Earth's surface throughout the year. As Earth orbits the Sun, different hemispheres receive varying amounts of solar radiation at different times of the year.

For instance, during the Northern Hemisphere's summer, this hemisphere tilts toward the Sun, resulting in longer days and more direct sunlight, which leads to warmer temperatures. Conversely, during the Northern Hemisphere's winter, it tilts away from the Sun, resulting in shorter days and less direct sunlight, resulting in cooler temperatures. This axial tilt is what creates the distinct seasons experienced in various parts of the world.

Factors such as distance from the Sun, the speed of Earth's orbit, and solar flare activity do have influences on climate and weather patterns, but they do not primarily dictate the seasonal changes experienced each year. Distance from the Sun has less variation over the year and does not substantially affect the changing seasons, while solar flare activity reflects short-term solar phenomena rather than seasonal changes.