The main reasons for the changes in the 24 solar terms are

Revolution and rotation. It takes 365.24 days for the earth to go around the sun, while it takes 24 hours for the earth to rotate once. In the process of revolution, the angle between the earth's rotation axis and the revolution orbit surface will change, which will lead to the different positions of direct sunlight on the earth in different seasons, thus causing the changes of natural phenomena such as temperature and precipitation. Therefore, the main reason for the change of the 24 solar terms is the revolution and rotation of the earth.