Why does the earth's rotation speed change from winter solstice to vernal equinox?

The change of the earth's rotation speed from winter solstice to vernal equinox;

From the winter solstice to the vernal equinox, the earth is closer to the sun, and the revolution speed will be slightly accelerated.

Reasons for speed change:

Because the sun deviates slightly from the center of the earth's orbit, the distance between the sun and the earth changes slightly with the revolution of the earth, and the revolution speed of the earth also changes accordingly. According to Kepler's third law of the universe, the areas swept by planets in unit time are equal, so perihelion runs fast, with an angular velocity of 6 1 '/d and a linear velocity of 30.3 km/s, while apohelion runs slowly, with an angular velocity of 57 '/d and a linear velocity of 29.3 km/s, with an average angular velocity of about 1/ day and an average linear velocity.

From the vernal equinox to the autumnal equinox, it is the summer half year in the northern hemisphere. During this period, the sun shines directly in the northern hemisphere, and the days in the northern hemisphere are longer than the nights. The higher the latitude, the longer the day and the shorter the night. On the day of summer solstice, the daytime length at all latitudes in the northern hemisphere reaches the maximum in a year, while in the Arctic Circle and its northern region, the sun never sets all day, resulting in extreme sunlight. The southern hemisphere is the opposite.

From the autumnal equinox to the vernal equinox of the following year, it is the winter half year in the northern hemisphere. During this period, the sun shines directly in the southern hemisphere, and the nights in the northern hemisphere are longer than the days. The higher the latitude, the longer the night and the shorter the day. Among them, on the winter solstice, the daytime at all latitudes in the northern hemisphere reaches the minimum value in a year, while in the Arctic Circle and its northern region, the sun stays out all day, resulting in extreme night. The southern hemisphere is the opposite. At the vernal equinox and the autumnal equinox, the sun shines directly on the equator, and the length of day and night is equal all over the world, each being 12 hour.

The existence of the ecliptic angle actually means that the axis of rotation is inclined to the earth's orbital plane during the earth's revolution around the sun. Since the earth axis is perpendicular to the equatorial plane of the celestial sphere, the intersection angle between the earth axis and the earth orbital plane should be 90-23 26', that is, 66 34'. No matter where the earth rotates, this tilt remains the same.

During the revolution of the earth, the spatial orientation of the earth axis has not changed obviously for a long time. The north pole points to Alpha Ursa minor, that is, near Polaris, which is the position of the north pole of the celestial sphere. That is to say, the earth axis moves in parallel during the revolution, so no matter where the earth revolves, the angle between the earth axis and the earth orbit plane is constant, and the angle between yellow and red is also constant.