Why do sunflowers always face the sun? The stem of sunflower contains a wonderful auxin.
This auxin is very afraid of light. When it is exposed to light, it will go to the backlight side, and at the same time, the cells on the backlight side will multiply rapidly. Therefore, the backlight side will grow faster than the light side, which will make the sunflower bend phototropically.
2. 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.
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 added to balance the body's needs.
Because these residual carbon dioxide will affect the functional activities of our body, then the body will send out a protective reaction, so it yawns. Yawning is a deep breathing action, which will let us breathe in more oxygen and expel carbon dioxide than usual, and also eliminate fatigue.
How high is the blue sky? "Blue sky" is actually the earth's atmosphere. The atmosphere surrounds the earth's air, 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 becomes. 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 very strong, so 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 and positive electricity meet together.
When it rains, some clouds in the sky have positive electricity and some have negative electricity. When the two clouds meet, they will discharge, emit bright and bright lightning, and at the same time release a lot of heat, so that the surrounding air will be heated, expanded and make a loud noise. This is thunder. 8. Why can an airplane fly into the sky? The plane has two wings, like the wings of a bird, and it has a propeller.
The wing can generate lift and lift the plane in the air; Propeller can produce the ability to push the plane forward. Therefore, the plane can fly into the sky like a bird.
33, hanging on the wall of the quartz clock, when the battery power is exhausted and stop walking, its second hand often stops at the position of "9" on the dial. This is because the second hand is most hindered by the heavy torque at the "9" position.
9. Before water boils, bubbles in the water rise and vibrate up and down due to convection, and most bubbles burst under the pressure in the water, and their cracking sound and vibration sound produce * * * sound with the container, so the sound is very loud. After the water boils, it is isothermal up and down, and the bubble volume increases. Under the buoyancy, it will burst as soon as 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 contacts with fire, so that the temperature of the ignition material will be reduced; At the same time, the vaporized water vapor surrounds the burning object, making it impossible for the object to contact with air, and without air, combustion cannot be carried out. 1 1. Sit on the ground and walk 80,000 miles a day. Because the radius of the earth is 6,370 kilometers, every time the earth turns around, the distance that objects on its surface "walk" is about 40,003.6 kilometers, about 80,000 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, the power is several times the resistance.
If the arm of the weight is very large, it is entirely possible to "dial one or two kilos". 13. A broken mirror cannot be reunited. 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 reunite a broken mirror.
14. People are United, and if the directions of the components of Taishan Movement are the same, the resultant force is equal to the sum of the components. 15. Tofu can't be lifted with hemp rope. When the pressure is constant, if the stress area is small, the pressure will be large.
16. True gold is not afraid to be refined by fire, and truth is not afraid to argue. From the melting point of gold, although it is not the highest, it also has 1068℃, while the temperature of general flame is about 800℃. Because the temperature of flame is less than the melting point of gold, gold cannot be melted. 17. With a long whistle, people in Shanming Valley should give a long whistle in the mountains. After many reflections, the sound can form a loud echo, which lasts for a long time. It seems that the mountains are screaming and the valley is echoing.
18. Looking at the sky from a well, you can see very little. Because light travels along a straight line, from the knowledge of geometric mapping, the frog's field of vision will be very small. 19. According to the pressure formula, when the pressure is constant, the smaller the stress area, the greater the pressure.
People will feel extremely uncomfortable sitting on such a felt. 20. Snow shines in good years. Because snow is a poor conductor of heat, when it covers crops, it can prevent heat conduction and air convection well, so it can play a role in heat preservation.
2 1. It is cold before frost and cold after snow. On the night of late autumn, the air temperature near the ground suddenly becomes 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 lower the temperature of the air, so we have the feeling of "cold after snow".
22. Eggs hit rocks-overreached eggs hit rocks. Although the force is the same, the pressure that each object can bear is certain. If it exceeds this limit, the object may be damaged. Eggs can withstand less pressure, so they will break.
23. Before the jade is not polished, its surface is scraggy, and the light is diffused. After the jade is polished, its surface is smooth, and the light is specularly reflected. 24. Fans have a cool breeze, which is suitable for summer but not winter.
2. About 20 words of common sense of science and technology
3. Why can snakes walk without feet? Can a snake walk without feet? Snakes have many scales on their bodies, which is the outermost layer of armor. Scales are not only used to protect their bodies, but also can be their "feet". When snakes crawl forward, their bodies will be S-shaped. And every scale outside the S-shape will be tilted to help snakes grasp the uneven road when they move forward. These scales cooperate with snake muscles and can push their bodies to crawl forward, so snakes 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 reproduction, but it is anti-optical, and it will run to the backlight side whenever it meets light. So when the sun rises, the sunflower stem will immediately hide to the backlight side, and it seems that the whole plant is bent towards the sun. 5. Why do people get old? When people get old, their hair will turn white. There is a substance called "melanin" in our hair. The more melanin there is, the darker the hair will be. If there is less melanin, the hair will turn yellow or white. When human beings reach old age, various functions of the body will gradually decline, and the formation of pigment will be less and less, so the hair will gradually turn white! 6. Why do fireflies glow? Do fireflies glow? Fireflies emit light 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. Fireflies emit light for purposes of courtship, vigilance, trapping and so on, in addition to lighting. 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 are they hungry? 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. 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 stir up, causing a purring sound. Don't be embarrassed by the growling of the stomach next time! Because this is a normal physiological action. 8. Why can't ostriches fly? Can't an 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, ostrich's muscles are underdeveloped and its sternum is flat, which is not helpful for flying. Because ostrich lives in Africa for a long time, its body has gradually evolved into what it is now in order to adapt to the environment. 9. Why is the food in cans not easy to go bad? Does the food in canned food not go bad easily? Lunch meat, black bean, tomato sauce beans.
They are all delicious canned foods, and they can be stored for a long time without going bad. This is because the canned food is sealed, so bacteria can't enter. When people make canned food, they take out all the air in it and seal it. Without air, even if the food inside is stained with a little bacteria, they can't survive or reproduce! 10. Why do babies cry all the time when they are born? Do babies always cry 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 leave their mother's body and are born, 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.
3. 50 little scientific knowledge around you
Science is everywhere. Here are 50 scientific tips 1.
Why do you see lightning first and then hear thunder? Light waves travel faster in air than sound speed by 2. Who was the first Olympic champion in China? Xu Haifeng III.
Who invented glasses? Roger? Bacon 4. Why does the bike move? Bicycle tires rub against the ground.
Who are the following titles? Poet Immortal-Li Bai, Poet Saint-Du Fu, Shi Gui-Li He, Poet Bone-Chen Ziang, Poet Crazy-He Zhizhang 6. What does the moon revolve around? How long does it take to make a revolution? Earth, 27.32 days 7.
What are the three plains in China? Northeast Plain, North China Plain, Middle and Lower Yangtze Plain 8. How many earthquakes are there on the earth every year? About 5 million times.
What is the smallest and coldest star in the solar system? Pluto 10. What is the thickness of the earth? The atmosphere 1 1.
Why is there a black box on the plane? It is used to record all kinds of situations on the plane during the crash and help people understand the cause of the accident 12. What are the customs during the Spring Festival? Sweep the house, set off firecrackers, post Spring Festival couplets, eat New Year's Eve dinner, etc. 13.
What animal can predict earthquakes? Cattle, horses, rabbits, chickens, ducks, dogs, snakes, rats, fish, etc. 14. What plant blooms first and leaves later? Chimonanthus praecox, kapok, forsythia suspensa, peach tree, winter jasmine, pear tree, silver willow, bauhinia chinensis, Jiexiang, Lycoris radiata and plum blossom 15.
How do bees make hives? Every worker bee has a wax gland at the waist, which can secrete wax. This kind of wax becomes soft and tough after chewing through the mouth, and it can be used to build a beehive 16. Why is the medicine bottle light? Because light colors can reflect light, and dark colors absorb more light when exposed to sunlight, drugs are easy to deteriorate 17.
Who invented the steam engine? Watt 18. Which dinosaur is the hardest? Stegosaurus 19.
What is the blood of the earth? Magma 20. What is the skeleton of the earth? Rock 2 1.
Why don't you watch welding sparks? It contains an ultraviolet ray harmful to the eyes. Why can't you turn off the lights and watch TV? The screen and image of the TV set are relatively small. In the dark, the vision should be highly concentrated and expanded, and it is particularly sensitive to the strong reflection of the light on the TV screen, which will make the eyes suffer from * * * and the vision will drop by 23%.
Who are the top ten marshals of the Chinese people? Zhu De, Peng Dehuai, He Long, Chen Yi, Liu Bocheng, Luo Ronghuan, Xu Xiangqian, Nie Rongzhen, Lin Biao, *** 24. Write down in order what dynasties existed in ancient China. Xia, Shang, Zhou, Qin, Han, Sui, Tang, Song, Yuan, Ming and Qing 25.
Why don't rabbits need to drink water? Because the rabbit's staple food, vegetables, contains a lot of water, which is enough for the body's needs. If there is more water in the intestine, it will suffer from gastroenteritis. But rabbits can also drink water when they are short of water.
What is a meteor? It means that meteoroids (usually including cosmic dust particles and solid blocks) running in interstellar space are attracted by the earth due to the perturbation of the earth's gravity when they approach the earth, and then enter the earth's atmosphere and burn with the atmosphere. Name some outstanding astronomers in the history of China.
Zhang Heng, his party, Guo Shoujing and Li Shanlan 28. Who is the inventor of the battery? Volt 29.
Where is Mount Vesuvius? Italy 30. Who are the first two astronauts to reach the moon 1? Armstrong and Aldrin 3 1.
Which province and city is Mount Tai in? Taishan City, Shandong Province 32. Which countries does the Amazon River flow through? Brazil, Peru and Colombia 33.
Which countries does the Irrawaddy River flow through? China, Myanmar 34. What are the five most precious gems in the world? Diamonds, sapphires, rubies, emeralds and opals.
What was the name of the ancestor of fish? Amphioxus 37 Which fish can shine? Ankang fish, Sparus glabra, dragon head fish, light-eyed fish, etc.
How many muscles does a person have? A * * * has more than 600 muscles. Will all the wood float on the water? No, there is a kind of "steel tree" that won't float on water.
What is the biggest flower? Dawanghua 4 1. Who invented anesthesia? Hua tuo 42.
What is the capital of France? Paris 43. What is the capital of England? London 44.
What is the capital of Japan? Tokyo 45. What is the capital of Italy? Rome 46.
What is the capital of the United States? Washington 47. What bird was one of the ancestors of birds? Archaeopteryx 48.
What are the four major seafood products in China? Pseudosciaena crocea, Pseudosciaena crocea, hairtail and squid. What is the largest mammal? Blue whale 50.
What is the largest amphibian? Giant salamander
4. A complete collection of scientific and technological knowledge
What are the three parts of sunlight? Of the eight planets, the most massive is Jupiter, the largest freshwater lake in China, the head of the five mountains in Poyang Lake, and the rotation of Mount Tai is around the earth axis passing through the north and south poles, with the direction from west to east. The farther away from the poles, the faster the rotation speed. The largest mammal in the world is the blue whale. Which city is called London 2 1 What is the main energy source of the century? What kind of pollution is called the windmill power generation kingdom in Denmark? What kind of pollution is called the world's top killer? The planet closest to the sun is Mercury Green Mud Observatory. In which country is Britain's dry ice carbon dioxide? China's Bi Sheng invented letterpress printing in the Northern Song Dynasty. Why is it that China is a land power and a maritime power? With a land area of 9.6 million square kilometers, it is the largest country in Asia and one of the largest countries in the world, ranking third in the world after Russia and Canada.
China's mainland coastline starts from the mouth of Yalu River in the north and ends at the mouth of Beilun River in the south, with a length of more than18,000 kilometers, and the island coastline is more than 32,000 kilometers. There are more than 6,500 islands; According to the relevant provisions of the United Nations Convention on the Law of the Sea and China's proposition, the sea area under China's jurisdiction is about 3 million square kilometers. China has a vast sea area and abundant resources, so China is also a maritime power.
Why do space junk do great harm? They become potential killers of satellites and orbiting space stations, which seriously threaten the safety of astronauts. You know, space junk runs at the speed of the universe.
An oncoming metal particle with a diameter of 0.5 mm is enough to puncture the sealed flight suit; Dust that people can't distinguish with the naked eye (such as paint crumbs and coating powder) can also kill astronauts; A piece of debris the size of an aspirin tablet can "cripple" a satellite and send a spacecraft costing hundreds of millions of dollars to a dead end. The tiny space junk can seriously change the surface performance of spacecraft because of its large quantity; Slightly large space debris will damage the surface materials of spacecraft, cause impact pits and damage surface devices; High-speed impact of space debris will vaporize itself and the surface materials of the impacted spacecraft into plasma clouds, which will eventually lead to spacecraft failure.
Interesting science and technology once, Newton was so absorbed in his experiment in the laboratory that he even forgot the time to eat. His assistant took some eggs and sent them to the laboratory. He said to Newton, "Here are some eggs. Cook them yourself."
Newton said, "OK, thank you. Please put the eggs there." After that, he immersed himself in the experiment again.
After a long time, Newton was hungry and remembered that he hadn't eaten lunch. So, he took a small pot, put the eggs in the pot, put them on the stove, and began to do experiments again.
After half an hour, Newton finished the experiment. At this time, he remembered the eggs in the pot.
He opened the lid and saw that there were no eggs in it, only a pocket watch. Newton was surprised and looked up. The eggs were still on the table, but the pocket watch on the table was gone.
It turned out that Newton was so absorbed in the experiment that he cooked the pocket watch as an egg. 1, who knows how the sea freezes? Everyone thinks that seawater is salty and won't freeze.
In fact, after the temperature is lowered, the solubility of water will also decrease, that is, salt will be precipitated. In this way, the water freezes.
2. Who knows if Altair exists now? What we are seeing now is the "light" it gave off a long time ago. As for whether it exists now, only people in the Altair galaxy know that the light we observe from the earth is still the light emitted by a stable star.
Moreover, the average star's life span is more than 6 billion years. Therefore, the solar cell phone battery that Altair should still exist now comes out. This battery is the product of combining ordinary lithium batteries and other solar cells. The technicians attach a thin layer of crystalline silicon photoelectric conversion sheet to the back of the lithium battery, and the single crystal silicon receives the current generated by illumination and charges the lithium battery through a protection circuit. In fact, as long as there is light except sunlight, the solar cell phone battery can be automatically charged, and it will not be overcharged no matter how long the exposure time is due to the holding circuit.
Although introduced, this kind of battery can generate electricity 1 minute when exposed to sunlight for 5 minutes, and it can be used for two or three days when exposed to a desk lamp for one night. In addition, this kind of battery still has the function of ordinary mobile phone battery. If the light is weak, you can use the mobile phone charger to charge it.
Sandstorm Sandstorm is a disastrous weather phenomenon in which wind and sand interact with each other. Its formation is closely related to the global greenhouse effect, El Nino phenomenon, sharp decline of forests, destruction of vegetation, species extinction, abnormal climate and other factors. Among them, the overexploitation of natural resources, excessive deforestation and excessive land reclamation caused by population expansion are the main reasons for sandstorms.
As a kind of high-temperature disaster, sandstorms can not occur in all windy places. Only in those areas with dry climate and sparse vegetation can sandstorms occur. The topsoil of * * * land is easily rolled up by big storms to form sandstorms or even strong sandstorms. Sandstorms are no less harmful to people and buildings than typhoons and tornadoes.
Recently, sandstorms have appeared in the northwest and even the northeast of China, especially in the northwest, and have been hit by sandstorms for more than 20 times. Why is the air on the seashore so fresh? The waves constantly beat the coast every day, and the tides rise and fall, bringing beautiful scenery and pleasant waves to the coast, as well as humid coastal air.
The air in the seashore contains a lot of negative oxygen ions, which are called "air vitamins". They can enter the human body through breathing, improve the ventilation function of the lungs, and increase the oxygen inhalation and carbon dioxide exhalation. In the general public places in the city, the negative oxygen ions per cubic centimeter are 10-20, indoor ones are 40-50, green lawns are 100-200, and the seashore can reach more than 1 10,000, which is several hundred times that of indoor ones! Negative oxygen ions are negatively charged ions, which have bactericidal effect and can inhibit the reproduction of bacteria in the air.
A large number of negative oxygen ions improve the function of human sympathetic nerve, make people refreshed and energetic, and also increase the content of hemoglobin in blood. Therefore, there are many sanatoriums on the seashore, because the seashore air has a therapeutic effect on people suffering from emphysema, hypertension, neurasthenia, asthma, anemia and other diseases, which is beneficial to human health and makes people refreshed.
5. About 20 words of scientific knowledge. Thank you.
Small scientific knowledge
Why does sorbet get angry?
The reason why sorbet bubbles is that there is a lot of water vapor invisible to the eyes in the outside air. When it comes to cold sorbet, it will liquefy into droplets and surround it when it is cold. It seems that sorbet is "bubbling".
Why do sunflowers always face the sun?
The stem of sunflower contains a wonderful auxin. This auxin is very afraid of light. When it is exposed to light, it will go to the backlight side, and at the same time, the cells on the backlight side will multiply rapidly. Therefore, the backlight side will grow faster than the light side, which will make the sunflower bend phototropically.
Why does cicada shed its skin?
The shell (exoskeleton) of cicada is hard and can't expand with the growth of cicada. When the cicada grows to a certain stage, the exoskeleton of cicada restricts the growth of cicada, and the cicada takes off the original exoskeleton, which is cicada slough.
6. encyclopedia of scientific knowledge (30 words)
Scientific common sense in life:
1, why is the sorbet steaming?
The reason why sorbet bubbles is that there is a lot of water vapor invisible to the eyes in the outside air. When it comes to cold sorbet, it will liquefy into droplets and surround it when it is cold. It seems that sorbet is "bubbling".
2. Why do sunflowers always face the sun?
The stem of sunflower contains a wonderful auxin. This auxin is very afraid of light. When it is exposed to light, it will go to the backlight side, and at the same time, the cells on the backlight side will multiply rapidly. Therefore, the backlight side will grow faster than the light side, which will make the sunflower bend phototropically.
3. Why do cicadas molt?
The shell (exoskeleton) of cicada is hard and can't expand with the growth of cicada. When the cicada grows to a certain stage, the exoskeleton of cicada restricts the growth of cicada, and the cicada takes off the original exoskeleton, which is cicada slough.
4. How do bees make honey?
Bees spit the collected sweet juice of flowers into an empty hive. At night, they suck the sweet juice into their honey stomachs for modulation, then spit it out and swallow it. It takes 100~240 times to make sweet honey.
5, hanging on the wall of the quartz clock, when the battery is exhausted and stops walking, its second hand often stops at the position of "9" on the dial. This is because the second hand is most hindered by the heavy torque at the "9" position. Common sense of science
6. Sometimes, when the tap water is discharged from the adjacent faucet, there are occasional bursts of noise. This is because the water pipe vibrates when the water rushes out of the faucet.
7. When taking pictures on TV, turn off the camera flash and indoor lighting, so that the pictures taken are clearer. Because the reflected light of flash lamp and illumination lamp on TV screen will interfere with the transmitted light of TV picture.
8. Frozen meat thaws faster in water than in air at the same temperature. Hot nails cool faster in water than in air at the same temperature. A cup filled with boiling water cools faster when immersed in water than in air at the same temperature. All these phenomena show that water has better heat transfer than air,
9. When there is cold water in the pot, the water droplets attached to the outer surface of the pot bottom can only be burned dry after a long time on the flame, and they will not boil until they are burned dry. This is because the water droplets, the pot and the water in the pot keep heat conduction and the temperature is almost the same. As long as the water in the pot is not boiled, the water droplets will not boil, and the water droplets will be evaporated on the flame and gradually burned dry.
10, out-of-shape mirror, the farther away from the mirror, the more out-of-shape. Because the image in the mirror is formed by the reflection of the silver-plated surface behind the mirror, uneven silver-plated surface or uneven glass thickness will produce out-of-shape The farther away a person is from an out-of-shape mirror, the more the reflected light on the silver-plated surface deviates from the normal position according to the principle of light amplification, and the more out-of-shape the mirror is.