Why is the summer solstice the longest day?

Because on the summer solstice, the sun shines directly on the Tropic of Cancer, which is the highest latitude that solar energy reaches in the northern hemisphere in a year. This day is also the longest day in a year in the northern hemisphere. The higher the latitude, the longer the day in the northern hemisphere.

After the summer solstice, the direct position of the sun will move south, and the daytime in the northern hemisphere will be shortened. "Summer Solstice" is the northernmost day of the year, the longest sunshine day in the northern hemisphere, and the longest day that exceeds the night time. But the daylight hours are getting longer from south to north everywhere. This is because the days are long and the nights are short due to the tilt of the earth's rotation axis, and the closer it is to the poles, the more obvious it is.

Extended data

The summer solstice is the tenth of the twenty-four solar terms. The "Twenty-four solar terms" were originally determined by the bucket handle direction of Beidou, which means noon, that is, the summer solstice. The current "twenty-four solar terms" are divided by the method of "constant gas", that is, each solar term corresponds to a certain position reached by the earth every time it runs 15 on the ecliptic, and the summer solstice is when the sun runs to 90 degrees on the ecliptic.

Seen from the ecliptic plane, the sun is on the background of Taurus, Gemini and Cancer. The summer solstice is the northernmost day of the sun in a year, the limit of the sun's northward movement and the longest day in the northern hemisphere. The higher the latitude, the longer the days. This is because the "long day and short night effect" caused by the tilt of the earth's rotation axis is more obvious as it approaches two levels.

On the day of the summer solstice, except the south pole of the Antarctic circle and the polar night area, the sunrise direction in all parts of the earth starts from the northeast and sets in the northwest. The summer solstice is the northernmost day of the sun in a year and the limit of the sun's northward movement. On this day, the northern hemisphere gets the most solar radiation, almost twice as much as the southern hemisphere. After the summer solstice, the Tropic of Cancer and its northern region, the midday sun altitude angle also began to decrease.

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