Why is apohelion and summer solstice not the same day?

Perihelion and perihelion are related to the revolution of the earth, and solar terms reflect the four seasons. The rotation of the four seasons is not only related to the revolution of the earth, but also related to the rotation axis.

The earth is a sphere with an axis of rotation. At every point in the earth's orbit, the direction of the axis of rotation is parallel. The angle between the equatorial plane and the rotation axis is 23.5, so the angle between the rotation axis and the ecliptic plane (that is, the orbital plane) is about 66.5. When the north pole of the autobiographical axis is close to the sun, the sun is between the equator and the Tropic of Cancer, and the summer solstice in our northern hemisphere is the day when the sun directly hits the Tropic of Cancer.

However, if you connect the apohelion and perihelion into a line (the long axis of the orbit-because the orbit is elliptical) and compare it with the projection line of the earth's rotation axis on the rotation axis, you can know that on the day when the earth reaches the apohelion, the two lines do not overlap and the included angle is very small. The fact that the earth's rotation axis does not point to the sun means that the sun will not directly hit the Tropic of Cancer on this day, and this day is not the summer solstice.

When the earth moves in orbit for a short time, that is, the projection line of the earth's rotation axis passes through the sun, this day is the summer solstice, June 22.

Every year, the date of the earth's distant day is not exactly the same, just like February adds one day every four years.

I hope it helps you!