Experts predicted the time of the annular eclipse. How to predict the time of annular eclipse?

It is reported that bamboo slips from the Three Kingdoms period have been found. Zhuge Liang's birthday is July. What illusion was the sky that day? Eclipse? . What was your initial reaction?

Are people happy or suspicious when they find that Zhuge Liang's birthday is recorded in the original documents? The birth of the eclipse, the thief? People are unlucky. Calm down and talk to each other right away. Don't think about it. Do you know that the news must be false?

I often ask my students and me this question. ? Now all I can think about is something. In ancient times, what could I do to support myself or change the world? ?

For thousands of years, we have stood on the shoulders of human civilization. What do we have more than the ancients and what common sense do we know?

The distance between the hand and the wall is obvious, which affects the shadow and shadow area: the farther the object is from the projection screen, the smaller the shadow area ratio on the screen.

For example, the chronology of Spring and Autumn Annals records the diet on the second day from 700 BC to 400 BC. The ancients did not understand solar and lunar eclipses, and predicted terrible good or bad luck with astronomical phenomena. If we can travel far from ancient times and correctly predict eclipses and calendars, we will not only support ourselves, but also serve the gods.

Want to correctly calculate and predict the occurrence time and observable range of solar and lunar eclipses. The premise is to clarify the basic principle of the formation of eclipse.

As we all know, light travels in a straight line in a uniform medium. When the light emitted by a point light source is blocked by an object, a clear black shadow will be formed according to the outline of the object. In reality, many light sources (from the sun to the desk lamp) are not a point, but have a certain size, which is equivalent to the combination of infinite multi-point light sources. If the shadows of all these point light sources overlap, so-called umbra and penumbra are formed.

From the outermost point of the light source, draw the area where the light travels in a straight line and the shadow behind the object. The overlapping positions of shadows are umbra, and light cannot reach here. The area where the shadow is illuminated by some light sources is the penumbra, in other words, it looks like the light source of the penumbra, and the penumbra area is not too dark.