In cold knowledge series, Panda Chewing Books introduced you to category of history, category of life, etc. Today we will talk about category of science, hoping to give you many years of experience.01. Why do stars twinkle?
"Twinkle, twinkle, sky is full of little stars" are words that are familiar to everyone, but have you ever thought that stars we see twinkle?
We see twinkling of stars not due to a change in brightness of stars themselves, but due to occlusion of atmosphere.
The atmosphere is between us and stars. As starlight passes through atmosphere, it is affected by density and thickness of atmosphere.
Atmosphere is not completely transparent, its transparency will vary with density. Therefore, when we look through it at earth at stars, we see that stars seem to twinkle.
I don't know why, but I've already seen a night scene full of stars in big cities. Think about it, when I was a child, such a beautiful scene will never be seen again.02. The thicker glass, less likely it is to explode when heated?
I don't know in real life if you get impression that in very cold conditions, when hot water is suddenly poured into a glass, glass bursts easily. one is easier to blow up?
I suppose your first reaction would be to say "thin cup", but that's not case. In fact, everything is just opposite. Does it undermine your thinking again? Why is it so?
If a glass is cold and hot water is suddenly poured on it, its inner wall will expand rapidly due to effects of thermal expansion and contraction. And because glass is a poor conductor of heat, if cup wall is very thick, heat cannot be quickly transferred to outer wall, which will cause inner wall to expand and leave outer wall unchanged, so it will cause glass to burst. Then, on contrary, thin glass is not easy to break.
How about that, isn't that a lot of knowledge? Learned to teach a small child ~ a magical physical phenomenon ~03. Why is sea water mostly blue and green?
There is a joke on internet because fish saliva bubbles are "blue~blue~blue~" so sea water is blue hahaha~
We all know from experience that, at first glance, unaffected sea water is blue or green, but if you touch it with your hands, you will find that sea water has no color at all, just like our everyday life. There is no difference in contact with water, why is that?
Actually, color we see is a phenomenon caused by ability of sea water to absorb light.
Only green light can be absorbed by sea water and reflected back. When sea water is deeper, green light is also absorbed and sea water appears blue.04. What color is sun?
This question was briefly mentioned last time. The color of sun itself is white, not orange, red, or dazzling golden yellow that we see. Why is there such a big difference in what people see with naked eye? ?
The reason is that when light emitted by sun passes through atmosphere, among visible light, light with a shorter wavelength is either absorbed by atmosphere or scattered, leaving only yellow light and some red light, so in our eyes Sun can be only yellow or red, like setting sun.
If you take a spaceship to leave Earth's atmosphere and look at sun in space, you will find that true color of sun is white.
When your child asks you a question like this, you should know how to answer it~05. Why do leaves change color?
High school biology parents should know that leaves are green in spring and turn yellow in autumn, and discoloration is due to chemical 'chlorophyll' they contain.
In autumn, leaves turn yellow because days are shorter and temperature in autumn is lower than in summer, so leaves stop producing chlorophyll and remaining nutrients are transported to trunk and roots for storage.
Leaves lack green chlorophyll, while other chemical pigments appear, so we see more yellow and brown leaves.
Curious children collect fallen leaves on ground, will they ask you this question?06. Why do fallen leaves on ground look up?
Haha, I don't think most parents are aware of this issue. If one day your child asks you this question, don't say that he is talking nonsense~ It's true.
The frontal cells of leaves are arranged neatly and densely and contain many chloroplasts, which are called palisade tissues. On back side, there are few chloroplasts in cells, which are loosely arranged and pass into a spongy tissue, lighter than front side. The front is heavier than back, so when leaves fall, back is often at top.Share interesting knowledge, all in pandas book
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