Phenomenon description
The earth's orbit is approximately a perfectly circular ellipse, while sunlight Probably near one of the focal points. The rotation of the earth always keeps a certain angle with respect to the sun, so at different times of the earth's revolution, the distance between a point on the earth and the angle of the sun's radiation is different, resulting in the difference in the amount of heat received in time and the change in temperature and duration of day and night. Therefore, the four seasons come into being. In the same way, because the equator is always under direct sunlight, the tropical area only has summer. There are also polar days and nights at the poles of the earth for the same reason.
The earth is opaque.
In fact, during the summer solstice, the earth is at aphelion, but the sun shines directly on the Tropic of Cancer. During the winter solstice, the earth is at perihelion, but the sun shines directly on the Tropic of Cancer. This proves that the distance of the sun is secondary, and the key to obtaining solar heat is the sun's height.
