Marginal weather

When the weather is clear, the farthest distance s (unit: km) that a person can see the sea can be estimated by the square of the formula S = 16.88h, where h is the height of eyes from the sea level (unit: m). If a person stands on the shore and observes, he can see when the height of his eyes from the sea level is1.5m..

Answer: 25.32 kilometers.

If you board an observation deck, how far can you see when your eyes are 35 meters above sea level? Answer: 590.80KM.

People's eyesight is different. Normal people's vision is 25cm, and the scenery beyond 4km is not easy to see. When it exceeds 500 meters, there will be blurred scenery images. When the distance is shortened to 250~270m, you can clearly see the outline of the scenery, and if you want to identify the types of flowers and trees, it will be shortened to tens of meters.

People's field of vision is limited. The average distance to see fighters in the air is about 8 kilometers, which is the average when the weather is clear. When it is foggy, rainy and dusk, the visibility is poor, and the distance you can see is greatly reduced. Moreover, everyone's eyes are very different. Some pilots can see the plane 20 kilometers away, and some can't see it as close as 8 kilometers. In addition, it also has a lot to do with the size of the plane, so the bomber can see farther. Another feature of the naked eye is that if you have seen a plane, if you keep staring at it, let it fly away gradually until 10 km later, you can't see it. On the contrary, looking for a plane in the sky, sometimes it has flown 5 kilometers and can't be found. At present, 8km is a universally recognized (unspecified) value.

Of course:

A pair of normal eyes, its sight distance can reach infinity. You can see the moon 380,000 kilometers away from the earth at night, and even the stars hundreds of millions of light years away, which is proof. But the resolution of the naked eye is limited, and the difference is great. According to tests, the resolution of people with normal vision is about one thousandth to one thousandth. For example, you stand in Tiananmen Square, next to Chairman Mao Memorial Hall, 400 meters away from the national flag. If you can see the top of a flagpole with a diameter of 20 cm, your eye resolution will be one thousandth. In this way, when you fly at an altitude of 10 km overlooking the ground, you can clearly see railways, highways and the Great Wall which is more than 5 meters wide.