debate

The story took place in Lu State more than 2,000 years ago. One day, Confucius met two children on the road and was vying for red. Confucius went up and asked them, "Why are you arguing over?"

The two children rushed to tell Confucius that they were arguing about which of the morning and noon sun were close to us.

One child said: "I think the morning sun is close to people when it comes out. It is far from people at noon. Because the morning sun looks like a bonnet, the noon sun looks so small as a dish. This does not mean the morning. The sun is only close to us, and the sun at noon is too small to be small?"

Confucius heard it feels reasonable. But before he even nodded, the other child immediately retorted:

"When the morning sun came out, it was cold and suffocating everywhere. It was as hot as standing at the boiling water at noon. It was not because the morning sun was far away from us, but it felt cold. Is it hot when the sun is near us?"

Confucius also felt that it made sense. But in this way he could not conclude that the two children who made it really make sense.

The two children saw Confucius's plausible appearance, and they were anxious to squat. One hand pulled Confucius and said, "You can give us a comment on the big man, and see who is right at the end!" Two children Confucius had a problem with the full-fledged economy. The university asked the family to shake his head helplessly and honestly admitted that he could not figure out who was right or wrong.

The two children were very disappointed. They looked at the back of Confucius and teased and said: "I also said that he was very knowledgeable! It turned out to be just that!"

Children more than 2,000 years ago, from their life experience, they can realize that the object is close to the distance and the distance is small; the same heat source is near the heat and the cold is the reason, and to judge the sun's distance, it is commendable. However, it is not surprising that it is impossible to accurately understand many astronomical phenomena outside the Earth, subject to the level of scientific understanding at that time. Kong Shengren is also not a prophet. His knowledge is also limited by the historical conditions at that time. We can't demand him as well.

Now we know that the change of the distance between the sun and the earth in a day is negligible. The morning sun is a little farther away from us, and it is a little closer at noon. The difference between the two is about equal to the radius of the earth, which is only equivalent to 1/2300 of the distance between the sun and the earth. This does not affect the size of the sun and the heat radiated by the sun to the earth. .

The sun in the morning looks bigger, and the sun at noon is smaller, which is actually a visual error. Because, when the morning sun just rises from the horizon, the sun is bigger when there are ground objects such as mountains and trees, and the sun at noon is high in the open sky, which is smaller. In fact, using the instrument to measure the apparent diameter of the sun, if you do not consider the effect of atmospheric refraction on the horizon, it will be the same in the morning and evening. As for the temperature of the ground, it depends mainly on the solar elevation angle. In the morning, the sun is oblique, the area irradiated by the same sunlight is large, and the solar radiation per unit area is small. At the same time, because the thickness of the oblique sunlight passes through the atmosphere, the atmosphere is weakened by the solar radiation, and the ground radiation is radiated at night. The heat loss to the ground before and after the outing is extremely high, so the morning temperature is low and it looks cool. At noon, on the one hand, the sun is the highest, the sun is direct or close to direct, and the heat is concentrated. On the other hand, the thickness of the sun through the atmosphere is small, the solar radiation is weakened less, and the ground heat surplus, the temperature has risen, therefore, It is much hotter at noon. In fact, for the speed of light of 300,000 kilometers per second, the slight difference in the distance between the morning and the noon will not affect the amount of solar radiation reaching the ground.

The two children had a problem with Confucius who was full of economics. The university asked the family to shake their heads helplessly and honestly admitted that they could not figure out who was right or wrong.

Third grade: Jiang Jialin