Dahe Daily·Yu Video Reporter Liu Ruichao Kang Yafei There is a famous story in "Liezi·Tang Wen", which is "Two Children Debating the Sun" in the textbook, "Confucius traveled eastward and saw two children arguing and asked why." Two children analyze from different angles when the

Dahe News·Yu Video Reporter Liu Ruichao Kang Yafei

There is a famous story in "Liezi·Tang Wen", which is " Two children arguing about the sun " in the textbook, " Confucius traveled east, saw two children arguing, and asked them Therefore". Two children analyze from different angles when the sun is closest to the earth.

Although it is not clear at the moment when the sun is closest to the earth during the day. But there is a time of year when we are closest. According to analysis and speculation, at 15:11 on July 4, the earth reaches the aphelion of its orbit, and everyone will see the "minimum sun of the year" at that time.

It’s the same sun, why is it still called “minimum”? As we all know, the earth's orbit around the sun is not a perfect circle, but an ellipse with an eccentricity of 0.0167. Since the distance between the sun and the earth is not fixed, aphelion is about 5 million kilometers farther than perihelion.

According to analysis, in early January every year, the earth passes through perihelion, and in early July, the sun passes through aphelion. The two time points correspond to the moments of the year when the apparent diameter of the sun is largest and smallest.

Specifically for this year, the time when the earth reaches aphelion is 15:11 on July 4. At that time, the apparent diameter of the sun will be 31 minutes and 28 seconds, which is approximately 3.4% smaller than the apparent diameter of the sun visible when the earth passes perihelion on January 4 this year.

You may be confused, why is the sun far away from the earth, but the hottest period of the year is about to arrive in most parts of the northern hemisphere? According to analysis, the four seasons changes are mainly affected by the yellow-red angle. The existence of the yellow-red angle causes the direct point of the sun on the earth to move between 23 degrees 26 minutes north and south latitude. In summer, the northern hemisphere has a high sunlight exposure angle, long illumination time, and receives a lot of radiation energy, so it is also the hottest.

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Source: Dahe Daily·Yu Video Editor: Wang Fenghua