What is the main cause for the seasons on Earth?

The main cause of the seasons on Earth is the tilt of Earth's axis as it orbits the Sun. This axial tilt, which is approximately 23.5 degrees, affects how sunlight reaches different parts of the Earth at various times of the year. As the Earth orbits the Sun, different hemispheres receive varying amounts of sunlight depending on the tilt of the axis. For example, during summer in the Northern Hemisphere, that part of the Earth is tilted toward the Sun, resulting in more direct sunlight and longer days. Conversely, during winter, that hemisphere is tilted away from the Sun, leading to less direct sunlight and shorter days. This variation in sunlight creates the seasonal changes we experience throughout the year.

The distance of the Earth from the Sun does not have a significant effect on the seasons as the distance changes relatively little during the year. The rotation of the Earth on its axis leads to day and night but does not affect the seasonal climate. Lastly, while the gravitational pull of the Moon influences tides and has some minor effects on Earth’s orientation, it does not directly cause the seasons. Thus, the tilt of Earth's axis is the primary reason for the seasonal variations in climate.