What causes seasons on Earth?

The changing seasons on Earth are primarily caused by the tilt of Earth's rotational axis as it orbits the Sun. Earth's axis is tilted at an angle of approximately 23.5 degrees relative to its orbital plane. This tilt means that during different times of the year, different parts of the Earth receive varying amounts of sunlight.

For example, when the Northern Hemisphere is tilted toward the Sun, it experiences summer with longer days and more direct sunlight, resulting in warmer temperatures. Conversely, when the Northern Hemisphere is tilted away from the Sun, it receives less direct sunlight, leading to shorter days and colder temperatures, which is winter. The Southern Hemisphere experiences opposite seasonal changes at the same times.

The distance from the Sun does not significantly contribute to the seasons, as Earth's orbit is nearly circular, and the variation in distance is not enough to account for temperature changes throughout the year. The Earth’s rotation speed affects the length of day and night but not the climate or seasons. Lastly, while the Moon does influence Earth through gravitational forces (creating tides), it does not affect seasonal changes. Thus, the tilt of Earth's axis is the key factor in the changing seasons.