Short scientific knowledge 10 words

Introduction to scientific and technological knowledge 1. Common sense of science and technology

1. Why do the stars twinkle? We see the stars shining, not because the luminosity of the stars has changed, 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 its 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 supplemented to balance the needs of the body. Because these residual carbon dioxide will affect our body's functional activities, then the body will send out a protective reaction, so we yawn.

Yawning is a deep breathing action, which will let us breathe in more oxygen and expel more carbon dioxide than usual, and it can also eliminate fatigue. 3. Why can snakes walk without feet? Snakes have many scales, which are the outermost armor on their bodies.

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.

Every scale outside the S-shape will tilt upward 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 towards the sun? There is a substance called "auxin" in the stem under the sunflower disk.

This substance has the function of accelerating replication, but it is anti-optical, and it will run to the backlight side whenever it encounters light. So when the sun rises, the stem of the sunflower immediately hides to the side of the backlight, as if the whole plant is bent in the direction of the sun.

5. Why does hair turn white when people are old? There is a substance called melanin in our hair. The more melanin, the darker our hair will be. Without melanin, hair will turn yellow or white.

When human beings reach old age, 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 emit light because there is a luminous body at the end of their abdomen, which is filled with a lot of phosphorus-containing luminescent substances and luminescent enzymes, so that fireflies can emit flashing light. The purpose of fireflies is not only lighting, but also courtship, vigilance and trapping.

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 information. 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 has almost been digested. Although the stomach is empty, the gastric juice in the 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 and purr. Don't be embarrassed by your stomach growling next time! Because this is a normal physiological action.

8. Why can't ostriches fly? A giant ostrich, but they can't fly into 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 conducive to flying.

Ostriches live in Africa. Because they have lived in desert areas for a long time, their bodies gradually evolved into what they are now in order to adapt to the environment. 9. Why can't it go bad easily? Lunch meat, black bean shad, tomato sauce beans.

They are all delicious canned food, which can be preserved for a long time without deterioration.

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 contaminated with a little bacteria, they can't survive or reproduce! 10. Why does the baby cry all the time when it is born? Babies cry when they are born, not because they are unhappy, but because they are taking the first breath of air! When babies leave their mother's body and are born, the first breath of air will rush to their throats, violently impact the vocal cords, make them vibrate, and then make a sound similar to crying. 1 1. Why do lizards keep bouncing up after their tails are broken? In order to protect themselves, many lizards also protect their eyes and ears; When some lizards are attacked, their tails will be broken due to the severe contraction of their muscles.

Because there are still some nerves alive in the broken tail, it will keep bouncing, thus distracting the enemy and running away. 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 continue to live.

12. Why is the squirrel's tail so big? Don't look at the relaxed mouse tail! When the squirrel jumps around the tree, its tail plays a great role. It can keep balance when the squirrel jumps to the tree to avoid falling and being injured.

In addition, this big tail can play a more protective role in winter, tightly surrounding the squirrel's body, which is convenient and practical. 13. Why can't a person have one or three thumbs? The average person has five fingers, each with a different length.

However, does anyone realize that besides the thumb, other fingers also have three sections, while the thumb alone has only two sections? It turns out that the number of joints is just the same as the other four fingers. If it is three knots, the thumb will appear weak, so that it can't lift heavy objects; If there is only one section, it can't grasp things freely with the other four fingers! 14. Why don't you scratch yourself? When others scratch ourselves, we will feel itchy and laugh constantly; However, when we scratch ourselves, we not only don't laugh, but also don't itch.

Based on our psychological preparation, the brain will send out a message that there is no danger, and the nerves will relax, so that they will not laugh and itch! 15. Why are most seawater blue and green? Looking at the sea, it is often found that the sea water is blue-green. However, when you pick up the sea water, you can only see it as transparent and colorless as old water.

It turns out that the sea itself is around us.

2.50 scientific tips

1. Why do sunflowers always face the sun? Sunflower stems contain a wonderful auxin.

This auxin is very afraid of light. When it is illuminated, it will go to the backlight side, and the cells on the backlight side will multiply rapidly. Therefore, the backlit side will grow faster than the bright side, which will bend the sunflower to light.

2. Why do the stars twinkle? We see the stars shining, not because the luminosity of the stars has changed, 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 its density. So when we look at the stars through it on the ground, we will see that the stars seem to be flashing.

3. 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 supplemented to balance the needs of the body.

Because these residual carbon dioxide will affect our body's functional activities, then the body will send out a protective reaction, so we yawn. Yawning is a deep breathing action, which will let us breathe in more oxygen and expel more carbon dioxide than usual, and it can also eliminate fatigue.

How high is the blue sky? "Blue sky" is actually the earth's atmosphere. The atmosphere surrounds the earth's air and is divided into five layers according to the air density, with a total thickness of 2000-3000 kilometers.

But most of the air is concentrated below 15 km from the ground, and the higher the air, the thinner it is. How thick the atmosphere is, how high the blue sky should be.

5. Why are there no stars in the daytime? Because part of the sunlight is scattered by the gas and dust in the atmosphere during the day, the sky is very bright and the light radiated by the sun is so strong that we can't see the stars. 6. What celestial bodies are there in the solar system? There are nine planets in the solar system.

They are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. In addition, there are many asteroids, comets and meteors in the solar system, and there are 2958 officially numbered asteroids.

The most famous comet is Halley's comet. 7. Why does it thunder? This is a natural phenomenon that negative electricity meets positive electricity.

When it rains, some clouds in the sky are positively charged and some are negatively charged. When two clouds meet, they will discharge, emit bright and bright lightning, and at the same time release a lot of heat, which will make the surrounding air heated, expand and make a loud noise. This is thunder. 8. Why can an airplane fly into the sky? This plane has two wings, like those of a bird. It has a propeller.

The wing can generate lift and lift the plane into the air; Propeller can produce the ability to push the plane forward. Therefore, the plane can fly into the sky like a bird.

33. For a quartz clock hanging on the wall, when the battery runs out and stops, its second hand often stops at the position of "9" on the dial. This is because the second hand is most hindered by the large torque at the "9" position.

9. Before water boils, bubbles in water rise and vibrate up and down due to convection. Most bubbles burst under the pressure of water, and their bursting sound and vibration sound are very loud with the container. After water boils, it is isothermal up and down, and the bubble volume increases. Under the action of buoyancy, it will explode when it reaches the water surface, so the noise is relatively small.

10. Fire-water incompatible substances must reach the ignition point when burning. Because of the large specific heat of water, water can absorb a lot of heat when it comes into contact with fire, thus reducing the temperature of ignition materials; At the same time, the vaporized water vapor surrounds the burning object, making it impossible for the object to contact with air. Without air, combustion cannot be carried out. 1 1. Sit on the ground and walk for 80,000 days. Because the radius of the earth is 6370 kilometers, every time the earth makes a circle, the distance that objects on its surface "walk" is about 40003.6 kilometers, about 80000 miles.

This is a poem sung by * *, which also scientifically reveals the relationship between motion and stillness-motion is absolute, and stillness is always relative to the reference object. 12. According to the principle of lever balance, if the power arm is a fraction of the resistance arm, then the power is several times the resistance.

If the weight of the arm is very large, it is entirely possible to "dial one or two kilograms." 13. When the distance between molecules is large (more than several hundred angstroms), the attraction between molecules is very small, almost zero, so it is difficult to reassemble a broken mirror.

14. If the directions of the components are the same, the resultant force is equal to the sum of the components. 15. Tofu can't be hung with hemp rope. When the pressure is constant, if the stress area is small, the pressure will be great.

16. True gold is not afraid of fire, and truth is not afraid of argument. Judging from the melting point of gold, although it is not the highest, it is 1068℃, while the temperature of general flame is about 800℃. Because the temperature of the flame is lower than the melting point of gold, gold cannot be melted. 17. With a long whistle, people in the valley should give a long whistle. After many reflections, the sound can form a loud echo, which lasts for a long time. As if the mountains were shouting and the valleys were echoing.

18. Looking at the sky from the well, you can see very little. Because light travels along a straight line, from the knowledge of geometric drawing, the frog's field of vision will be very small. 19. It can be seen from the pressure formula that when the pressure is constant, the smaller the stress area, the greater the pressure.

People will feel very uncomfortable sitting on such a blanket. 20. Good years are bright. Because snow is a bad conductor of heat, when it covers crops, it can well prevent heat conduction and air convection, so it can play a role in heat preservation.

2 1. It is cold before frost and cold after snow. In the late autumn night, the temperature near the ground suddenly turns cold (the temperature is below 0℃), and the water vapor in the air condenses into small ice crystals and adheres to the ground to form frost, so it feels "cold before frost". When snow melts, it needs to absorb heat to reduce the temperature of the air, so we have the feeling of "cold after snow".

22. Eggs touch stones-overreached eggs touch stones. Although the force is the same, the pressure that each object can bear is certain. If this limit is exceeded, the object may be damaged. Eggs can withstand less pressure, so they will break.

23. Before the jade is polished, the surface is uneven and the light is diffuse. After the jade is polished, the surface is smooth and the light is mirrored. 24. The fan is cool and suitable for summer.

3. Little knowledge of environmental protection (about 50 words short)

The recyclable resources in life mainly include: (1) waste paper: newspapers, book paper, wrapping paper, office paper, advertising paper, cartons, etc. Note that paper towels and toilet paper cannot be recycled because of their strong water solubility. (2) Plastics: all kinds of plastic bags, plastic foams, plastic packaging, disposable plastic lunch boxes and tableware, hard plastics, plastic toothbrushes, plastic cups, mineral water bottles, etc. (3) Glass: glass bottles and broken glass pieces, mirrors, light bulbs, thermos bottles, etc. (4) Metals: cans, tin cans, toothpaste skins, etc. (5) Cloth: mainly including waste clothes, tablecloths, towels, cloth bags, etc. If every 1 ton of waste paper is recycled, 850 kilograms of paper can be made, 300 kilograms of wood can be saved, and pollution can be reduced by 74% compared with the same output; Every 1 ton plastic beverage bottle can recover 0.7 tons of secondary raw materials; Every recovered 1 ton of scrap steel can produce 0.9 tons of good steel, which saves 47% cost and reduces 75% air pollution compared with ore smelting. Reduce water pollution and solid waste by 97%. So far, the environmental problems that have threatened human survival and been recognized by human beings mainly include: global warming, ozone layer destruction, acid rain, fresh water crisis, energy shortage, sharp decline of forest resources, land desertification, accelerated extinction of species, garbage disaster, toxic chemical pollution and many other aspects. (1) Global warming refers to the increase of global temperature. The global average temperature of nearly 65438+ has experienced two fluctuations of cold-warm-cold-warm, which can always be regarded as an upward trend. Since 1980s, the global average temperature has obviously increased. The global average temperature of 198 1~ 1990 was 0.48℃ higher than that of 100 years ago. The main reason for global warming is that human beings have greatly increased in the past century.

4. Lack of popular science knowledge

The speed of light in the Milky Way is so great that it takes 100000 years for the light to travel completely.

The speed of light is about 186000 km \ sec. The farthest star we can see with the naked eye is actually looking at the past 4 billion years ago.

It takes a long time for the light from that star to enter your eyes. Average life time to go to the toilet: half a year's life, eating time: three years' life, speaking time: ten years' life, sleeping time: 22 years' life, hair length: 1000 kilometers' life, tears capacity: 65 liters' life, peeling weight: 47.5 kilograms' life, cell count: 750 trillion, walking distance: 22,500 kilometers? I still have a lot of short science knowledge.

Then ask, because I don't have time to input so much popular science knowledge now. My real name is Zuo, thank you.

5. Popular science knowledge should be as simple as 100 words.

1 Weather refers to meteorological phenomena that occur in a short time (from several minutes to several days), such as thunderstorm, hail, typhoon, cold wave and strong wind.

2. What is climate climate refers to the long-term average of various meteorological elements in a long period (month, season, year, year, even hundreds of years, etc.). It is a comprehensive reflection of the basic characteristics of cold, warm, dry and wet weather conditions in a region.

3. Climate resources Climate resources refer to natural substances and energy widely existing in the atmosphere, such as light energy, heat energy, precipitation and wind energy. , can be directly or indirectly used by people, forming wealth, with use value. It is a very precious renewable natural resource and the basic condition for the survival and development of human society, and has been widely used in all aspects of the national economy and people's livelihood.

4. Microclimate Microclimate is a unique climate in some areas under the same climate background, which is formed due to the inconsistency of topographic orientation, soil conditions and vegetation. The characteristics of microclimate are mainly manifested in the drastic changes of individual meteorological elements and the differences of individual weather phenomena.

Urban climate is a local climate or microclimate formed under the macro-climate or regional climate background due to the influence of urbanization. The urban climate is characterized by five islands, namely, heat island, wet island, dry island, rainy island and mud island.

6. Heat island effect Heat island is a comprehensive phenomenon of microclimate change caused by people changing the urban surface, and it is one of the most obvious characteristics of urban climate. Due to the acceleration of urbanization, dense urban buildings, asphalt roads and cement pavements have greater heat capacity and heat absorption rate than the soil and vegetation in the suburbs, which makes the urban area store more heat and radiate it to the surrounding areas and the atmosphere, resulting in the temperature in the urban area being generally higher than that in the surrounding suburbs at the same time. The high-temperature urban area is surrounded by low-temperature suburbs, just like an island in the sea of Wang Yang. This phenomenon is called urban heat island effect.

7. Why the air pressure in winter is higher than that in summer refers to the pressure produced by the air column per unit area on the earth. The air pressure in a place often changes. When the air pressure drops, it is rainy, the weather rises and the weather turns fine. There are many reasons for the change of air pressure. The change of temperature is a very important reason for the change of pressure. When the air is cooled, the air contracts, the density increases, the weight of air column per unit area increases, and the air pressure also increases. Therefore, the arrival of cold air is always accompanied by the increase of air pressure; When warm air comes, the air pressure tends to drop. Winter is a world of cold air and summer is a world of warm air, so obviously, the air pressure is high in winter and low in summer.

6. Small scientific knowledge should be simple

▲. What is the universe? A: The universe is the floorboard of everything in the world. It has no boundary, no end, no beginning and no end.

▲. How big is the Milky Way? A: Many stars combine to form a huge galaxy. The galaxy where the solar system is located is called the Milky Way. The Milky Way is like a discus, with a width of about 80,000 light years, a center thickness of about 1 0.2 million light years, and a total number of stars exceeding10,000.

▲. Why can't I see the stars during the day? A: Because part of the sunlight is scattered by gas and dust in the atmosphere during the day, the sky is very bright and the light radiated by the sun is so strong that we can't see the stars. ▲. What celestial bodies are there in the solar system? A: There are nine planets in the solar system.

They are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. In addition, there are many asteroids, comets and meteors in the solar system, and there are 2958 officially numbered asteroids.

The most famous comet is Halley's comet. ▲. Why do stars have different colors? A: The color of a star depends on its temperature.

Different colors represent different surface temperatures: the surface temperature of blue stars is high and that of red stars is low. ▲. What is the brightest star? A: The brightest star in the sky is Sirius Canis with a magnitude of 1.46.

8.7 light years from the earth. ▲. How to find Polaris? A: It's easy to find Polaris in the sky: first find Ursa major, and then find the Big Dipper.

A straight line leads from the two Polaris at the edge of the spoon head, extends past and passes through the Polaris. The distance from Polaris to the spoon head is exactly five times the distance between two Polaris.

You can also find Polaris through Cassiopeia. ▲. How high is the blue sky? A: The "blue sky" is actually the earth's atmosphere.

The atmosphere is the air around the earth, which is divided into five layers according to the air density, with a total thickness of 2000-3000 kilometers. But most of the air is concentrated below 15 km from the ground, and the higher the air, the thinner it is.

How thick the atmosphere is, how high the blue sky should be. ▲. Why is the sky blue? A: When sunlight hits the earth's atmosphere, blue light is most easily separated from other colors, diffused into the air, and then reflected.

The light of other colors has strong penetrating power, and shines on the earth through the atmosphere, so we can only see the blue light in the sun when we look at the sky. ▲. Why is the sky red at sunset? A: Because sunlight travels a long distance in the atmosphere at sunset.

Except for red light, all other colors of light can't travel that far, and they all disappear before they reach our eyes. Only red light runs farthest and can reach our eyes, so we see that the color of the sky turns red at sunset.

▲. Will the moon shine? The moon is not a star. It can't shine, but it can reflect sunlight. Although only 7% of the light it reflects can reach the earth, it is enough to light up the night on our earth.

▲. How many stars can we see? A: We can see 7,000 stars from the earth with the naked eye, but because the earth is round, no matter where we stand on the earth, we can only see half of the sky, and the stars near the horizon are not clear, so our naked eye can only see about 3,000 stars. ▲. How high is the temperature of the sun? A: The central temperature of the sun is as high as192,000,000℃ and the surface temperature is 6000℃.

But because the sun is far away from us, with1.500 million kilometers, we don't feel so hot. ▲. Why does the earth turn? A: Because the earth has gravity, it is precisely because of this gravity that the earth turns.

The rotation speed of the earth is per hour 1700 km, that is, 470 meters per second; The revolution speed is about 29.8 kilometers per second. ▲. Why is the sun white at noon? Answer: Because at noon, the sun can shine directly on the ground, unlike things on the ground (such as mountains, trees, buildings and turbid air) in the morning and evening, it is still the original white light, which makes people afraid to open their eyes.

▲. Why is it difficult to walk on the moon? A: Because the gravity on the moon is very small, it is easy to slip when walking, and only 20 steps can be taken in one minute. If you walk in a hurry, it's easy to fly. Once it flies, it is unstable for a long time. Therefore, it is very difficult to walk on the moon.

▲. Why doesn't the earth shine? A: Because the temperature of the earth is relatively low, the hottest place (the core) is two or three thousand degrees, unlike the temperature of the sun, which will cause thermonuclear reaction, so the earth will not shine. ▲. Why can't people feel that the earth is turning? A: Because the earth is very big and rotates smoothly, we are also following it. We take ourselves as a reference, so we can't feel the earth spinning.

▲. What is thunder? A: This is a natural phenomenon that negative electricity meets positive electricity. When it rains, some clouds in the sky are positively charged and some are negatively charged. When two clouds meet, they will discharge, emit bright and bright lightning, and at the same time release a lot of heat, which will make the surrounding air heated, expand and make a loud noise. This is thunder.

▲. What is a meteor shower? A: There are many small celestial bodies in the universe flying at their own orbits and speeds. Some blew themselves up and some collided with other celestial bodies.

But they kept flying. When their orbits meet the earth's orbit, they fall to the ground like raindrops. This phenomenon is called meteor shower.

▲. Where is the cloud going? A: Clouds are water vapor floating in the air. Air is also constantly flowing in the air.

The flow of air is the wind, which blows away the clouds. The faster the air moves, the faster the cloud moves.

▲. Why can an airplane fly into the sky? A: An airplane has two wings. Just like the wings of a bird, it also has a propeller. The wing can generate lift and lift the plane into the air; Propeller can produce the ability to push the plane forward.

Therefore, the plane can fly into the sky like a bird.

7. Less scientific and technological knowledge is shorter.

Our motherland is becoming more and more powerful, more and more developed and more advanced in science and technology! Looking at history, we have come step by step from ancient times to the present.

At that time.

At the ceremony, I have seen the scientific and technological development of our motherland, novel tanks, cars,

There are some rare weapons and equipment. I am surprised that the technology of our motherland is too developed now.

Technology is indispensable to us human beings, and we will use our technology anywhere.

Now our school is also holding this science and technology festival, so that students can write their own scientific papers or tabloids and invent them themselves.

Or draw a picture of science and technology, which not only improves students' love and understanding of science and technology, but also improves their practical ability. I also took part in this activity and found it very meaningful. I found some online.

And information, and parents with the brain, their own inventions.

How interesting and meaningful it is to draw your own imaginary scientific and technological paintings!

8. Daily popular science knowledge (simple)

1. Volatile organic pollutants such as benzene, toluene and xylene in furniture can lead to fetal congenital defects.

2. The most environmentally friendly detergent is soap. 3. 194 1 year, Chinese physicist Wang proposed an experimental scheme to verify the existence of neutrinos. Half a year later, American scientists conducted experiments according to this scheme and confirmed the existence of neutrinos.

4, put the sanitary ball in the closet, it will produce a certain sublimation, and it will become smaller after a while. When using air conditioner in summer, the temperature should be set at 26-28 degrees.

6, restaurant kitchen lampblack will produce pollution and harm to health, so you should install lampblack purification device. 7. Eating iodized salt can meet the human body's iodine intake. The salt people usually use is iodized salt.

Because of the volatility of iodine, we should seal the iodized salt. 8. Geothermal energy, wind energy, solar energy and other energy sources that can avoid air pollution after use are called clean energy.

9. Fragrant plastic book covers, pencils and other fragrant stationery are deeply loved by primary and secondary school students. But according to professionals, these pungent stationery will threaten human health because it contains a lot of formaldehyde.

10, nuclear power plants must always adhere to the principle of quality first and safety first. 1 1. Two thousand years ago, people thought that the earth was the center of the whole universe, until17th century, Galileo used his telescope to observe that the earth revolved around the sun.

12, the height from the ground, the less atmospheric molecules, the less light scattered by air molecules, so the sky becomes dark. 13, wild animals contain a large number of parasites, and people can easily induce some parasitic diseases such as cerebral cysticercosis, paragonimiasis and intestinal parasitic diseases.

14. The first flying man in the history of manned space flight in China was Yang Liwei. 15. It is best to soak the bought vegetables in clear water for 10-20 minutes, which can remove most of the residual pesticides.

/KOOC-0/6,/KOOC-0/96/KOOC-0/April/KOOC-0/2, the former Soviet Union astronauts traveled into space for the first time in the "Dongfang-1" spacecraft. 17, solar energy is solar radiation energy, and the surface temperature of the sun is about 6000℃.

18, 1964 China's first atomic bomb exploded successfully. 19, the only scientist who won the Nobel Prize twice in history was Madame Curie.

20, medical alcohol 75 degrees. 2 1, the folk ghost fire is actually the result of phosphorus spontaneous combustion in the air.

22. The cross section of an ordinary thermometer is circular, while the cross section of a thermometer is similar to a triangle. The thermometer of this shape is mainly used to enlarge the liquid column and facilitate reading.

23. When insects fly, their wings vibrate. Butterflies flap their wings 5-6 times per second, and bees flap their wings 300-400 times per second. When they are all flying behind you, you can feel the bees flying behind you by hearing. 24. In the human body, the most acidic liquid is gastric juice.

The former Soviet Union launched the first artificial satellite. 26. When driving, the speed of 80km/h is 25% less than that of110 km/h. ..

27. The child made a mistake when doing his homework. It's best to persuade him not to use correction fluid. 28, automobile exhaust contains nitrogen dioxide, carbon monoxide, hydrocarbons and other harmful substances.

29. Frost is when the temperature of an object or crop drops to 0? Below c, the water vapor in the air condenses directly on the objects or crops on the ground and becomes white ice crystals. 30, 1954, the former Soviet Union built the world's first nuclear power plant.

3 1, and the core temperature is above 5000℃. It was the Wright brothers who invented the plane.

33. Nineteen ancient poems: Altair, Hehan female. Vega is located in Lyra.

34. The most representative constellation in the winter night sky is Orion. 35. Ding Zhaozhong, a famous Chinese-American physicist, won the 1976 Nobel Prize in Physics for his discovery of the long-lived heavy-mass meson.

36. The rated frequency standard of power system in China and most countries in the world is 50Hz, and that in a few countries is 60HZ. Comets are called "broom stars" and have a long tail like a broom.

38. The color of the sun is white. 39. Trees can absorb carbon dioxide and release oxygen through photosynthesis.

40. All the colors on the color TV screen are composed of three primary colors, which are green, red and blue. 4 1, China's hybrid rice is world-renowned, and Yuan Longping is known as the "father of hybrid rice" internationally.

42. According to the star area, there are 88 constellations throughout the day.

9. Simple encyclopedia of scientific knowledge

Human body is 65% water, eggs 76% water, fish 85% water and vegetables 90% water.

Common ways to know objects are: seeing with eyes, smelling with nose, touching with hands and tasting with tongue. Never smell, let alone taste, an object you don't understand.

Water is a colorless, transparent and shapeless liquid. Water has capillary phenomenon and surface tension.

Water can dissolve many substances. Water pollution includes agricultural pollution, industrial pollution and domestic pollution.

Among our common materials, some come directly from nature and are called natural materials: wool, wood, stone and so on. Some of them are not directly from nature, but are processed and called artificial materials: paper, iron, glass, plastic and so on.

Papermaking is one of the four great inventions in ancient China and so on.