Why do the stars twinkle?

We see the stars shining, not because the luminosity of the stars themselves changes, but because of the occlusion of the atmosphere.

The atmosphere is between us and the stars. When starlight passes through the atmosphere, it will be affected by the density and thickness of the atmosphere.

The atmosphere is not absolutely transparent, and its transparency will change according to the density.

So when we look at the stars through it on the ground, we will see that the stars seem to be flashing.

2. Why do people yawn?

when we feel tired, a lot of carbon dioxide has been produced in our bodies.

when there is too much carbon dioxide, oxygen must be added to balance the body's needs.

Because these residual carbon dioxide will affect our body's functional activities, then our body will send out a protective reaction, so we will yawn.

yawning is a deep breathing action, which will make us breathe in more oxygen and expel carbon dioxide than usual, and it can also eliminate fatigue.

3. Why can snakes walk without feet?

snakes have many scales, which is the outermost layer of armor. Scales are not only used to protect the body, but also to be their "feet".

when a snake crawls forward, its body will be S-shaped. And every scale outside the S-shape will tilt up to help the snake catch the uneven road when it moves forward. These scales cooperate with the snake's muscles and can push the body forward, so the snake can walk without feet!

4. Why do sunflowers always bloom toward the sun

There is a substance called "auxin" in the stem under the sunflower disk. This substance has the function of accelerating reproduction, but it is anti-optical, and whenever it encounters light, it will run to the backlight side. So when the sun rises, the stem of the sunflower immediately hides to the backlight side, and it seems that the whole plant bends in the direction of the sun.

5. Why does hair turn white when people get old?

There is a substance called melanin in our hair. The more melanin, the darker our hair will be. If there is less melanin, the hair will turn yellow or white. When human beings reach old age, the various functions of the body will gradually decline, and the formation of pigments will be less and less, so the hair will gradually turn white!

6. Why do fireflies glow?

Fireflies glow because there is a light emitter at the end of their abdomen, which is filled with many phosphorus-containing luminescent substances and luminescent enzymes, so that fireflies can emit flashing light. The purpose of fireflies is not only to illuminate, but also to courtship, vigilance, trapping and other purposes.

This is also a communication tool for them. Different kinds of fireflies emit light in different ways, frequencies and colors, so they can convey different messages.

7. why do you growl when you are hungry?

when you are hungry, you will purr. This is because the food you have eaten before is almost digested, and although your stomach is empty, the gastric juice in your stomach will continue to secrete.

At this time, the contraction of the stomach will gradually expand, and the liquid and gas inside will be stirred up, causing a purring sound. Don't feel embarrassed about your stomach growling next time! Because this is a normal physiological action.

8. Why can't ostrich fly?

a kind of huge ostrich, but they can't fly to the sky! This is not because their wings are useless, but because their feathers are too soft and their wings are too small to fly at all. In addition, the ostrich's muscles are underdeveloped and its sternum is flat, which is not helpful for flying. Ostrich live in Africa, and because they have lived in desert areas for a long time, their bodies have gradually evolved into what they are now in order to adapt to the environment.

9. why can't food in cans go bad easily?

Lunch meat, black bean and tomato sauce beans are all delicious canned foods, which can be stored for a long time without spoiling easily. This is because the can is sealed, so bacteria can't enter.

when people make canned food, they pump all the air out of the canned food and then seal it. In the absence of air, even if the food inside is stained with a little bacteria, they can't survive or reproduce!

1. Why do babies cry all the time when they are born?

babies will cry when they are born, not because they are unhappy, but because they are taking their first breath of air!

When babies are born out of their mother's body, the first breath of air they breathe will rush to their throats, which will violently impact the vocal cords, make them vibrate, and then make a sound similar to crying.

11. Why does the lizard's tail keep bouncing when it is broken?

In order to protect themselves, many lizards also use protective colors to hide their eyes and ears.

When some lizards are attacked, their tails will be broken due to the severe muscle contraction. Because some nerves are still alive in the broken tail, it will keep bouncing, thus distracting the enemy and escaping. Don't think that their lives will end like this. In fact, it only takes a few months, and their tails will grow back and move on.