Encyclopedia of popular science knowledge 100, 50 scientific knowledge

50 little scientific knowledge1. Rabbits communicate by patting ground with their feet. Most ground-slapping rabbits are male rabbits, which is a way of expressing their emotions to female rabbits.

2. The largest monkey in world is baboon, and smallest is tamarin.

3. The real name of "Four different elephants" is elk, a rare animal in our country.

4. Why does sorbet smoke?

Sorbet smokes because there is a lot of invisible water vapor in outside air. When it encounters a very cold sherbet, it turns into mist and surrounds sherbet when it is cold. It seems that sorbet "gassing" "The same.

5. Why do sunflowers always face sun?

Sunflower stems contain wonderful auxin. This auxin is very sensitive to light. When it meets light, it moves to backlight side, and at same time stimulates cells on backlight side to multiply rapidly, so backlight side grows faster than light side, which causes sunflower to produce phototropic bending.

6. Why do cicadas shed their skin?The shell (exoskeleton) of cicadas is hard and cannot expand as cicadas grow. When cicadas grow to a certain stage, cicada's exoskeleton limits cicada's growth. The cicada removes original exoskeleton, which is a cicada swamp.

7. How do bees make honey? Bees first spit sweet juice from plucked flowers into an empty hive. At night, they suck sweet juice into their honey stomach to cook it, then spit it out and swallow it again. 100 to 240 times finally into sweet honey.

8. Why do stars twinkle? We see twinkling stars not because of change in luminosity of stars themselves, but because of occlusion of atmosphere. The atmosphere is between us and stars. As starlight travels through atmosphere, it is affected by density and thickness of atmosphere. The atmosphere is not absolutely transparent, its transparency depends on density. Therefore, when we look through it at earth at stars, we see that stars seem to twinkle. 9. Why do people yawn? When we feel tired, body produces a lot of carbon dioxide. When there is too much carbon dioxide, oxygen must be added to balance body's needs. Since this residual carbon dioxide will affect functional activities of our body, at this time body sends a defensive reaction, so we yawn. Yawning is a deep breathing action that allows us to take in more oxygen and exhale carbon dioxide than usual, and also eliminates fatigue. 10. Why can snakes walk without legs? Snakes have a lot of scales, which is outer layer of armor on their bodies. The scales are used not only to protect body, but also their "legs". As snake crawls forward, its body takes on an S-shape. Each scale outside of S-shape will be raised to help withlest grab onto rough road as she moves forward. These scales interact with snake's muscles and can push body forward to crawl, so snake can walk without legs! 11. Why do people get gray hair when they age? In our hair there is a substance called melanin. The more melanin it contains, darker hair will be. And if there is little melanin, hair will turn yellow or white. When people reach old age, various functions of body gradually decrease, and production of pigment becomes less and less, so hair gradually becomes white!

12. Why do fireflies glow? Fireflies will glow because there is a light emitter at end of their abdomen, filled with many phosphor luminescent substances and luminescent enzymes, so that fireflies can emit flickering lights. The purpose of light of fireflies is not only for illumination, but also for courtship, warning, trapping and other purposes. It is also a tool for their communication. Different types of fireflies have different methods of emitting light, frequencies and colors of emitting light, and they use this to convey different messages. 13. Why does my stomach growl when I'm hungry? When you are hungry, you will grumble. This is because food you ate before is almost overcooked. Although stomach is empty, gastric juice in stomach will continue to be secreted. At this time, contractions of stomach will gradually expand, and liquid and gas inside will agitate, causing a gurgling sound. Don't be embarrassed that your stomach will growl next time! Because it is a normal physiological action. 14. Why don't ostriches fly? A species of ostrich with a huge body, but they can't fly into sky! It's not that their wings don't work, it's that their feathers are too soft and their wings are too small to fly. In addition, ostrich has underdeveloped muscles and a flat sternum, which is not conducive to flight. Ostriches live in Africa. Since they lived in desert areas for a long time, their bodies gradually evolved into what they are today to adapt to environment. 15. Why doesn't jar food spoil? Meat for dinner, dace in black bean sauce, beans in tomato sauce... all these are delicious canned foods that last a long time and do not spoil. This is because jars are sealed so bacteria cannot get inside. When people make canned food, all air is pumped out of can, and then it is sealed. In absence of air, even if food inside is colored by a small amount of bacteria, they cannot survive or reproduce! 16. Why do babies cry when they are born? Babies wheeze when they are born, not because they are unhappy, but because they take their first breath! When babies are born outside their mother's body, their first breath of air rushes down their throats, hitting their vocal cords hard, causing them to vibrate and make a cry-like sound. 17. Why does a lizard keep jumping after being brokentail? To protect themselves, many lizards also use a protective covering to hide eyes and ears of humans, and when some lizards are attacked, their tails come off due to violent muscle contraction. Due to fact that some nerves are still alive in broken tail, it will continuously bounce, thereby distracting enemy so that he can escape. Do not think that their life will end this way, in fact, it only takes a few months for tail to grow back and continue to live.

18. Why does a squirrel have such a big tail? Don't look at squirrel's tail! While squirrel is jumping up and down tree, its tail is doing a lot of work. He can balance a squirrel while jumping up a tree to avoid falling and getting hurt. In addition, this large tail can play a more protective role in winter by tightly surrounding body of squirrel, which is convenient and practical.

19. Why can't a person's thumb have one or three knots? The average person has five fingers, and length of fingers varies. However, has anyone noticed that, in addition to thumb, other fingers also have three joints, and thumb has only two joints? .. It turns out that its number of joints exactly matches other four fingers. If there are only three joints, thumb will appear weak and will not be able to lift heavy objects; if there is only one joint, it won't be able to interact with other four fingers to grasp objects freely! 20. Why don't I feel itchy when I scratch? When others scratch, we feel itchy and constantly laugh, however, when we scratch ourselves, we not only don't laugh, but we don't feel itchy either. Based on our mental preparation, brain will send message "no danger" and nerves will relax accordingly, so we won't laugh out loud and feel itchy! 21. Why is sea water mostly blue and green? Looking at sea, I often find that sea water is blue-green. However, when you scoop up sea water, all you see is that it is as clear and colorless as water was in past. It turns out that sea water itself is not much different from water that we come into contact with every day, and it is also transparent. The green color we see is actually a phenomenon caused by ability of seawater to absorb light. Only green light can be absorbed by seawater and reflected; when sea water is deeper, green light is also absorbed and sea water looks blue. 22. Why do you have goosebumps? There are fine hairs on surface of our skin, and under each pore there is a muscle that straightens hairs. When irritated by nerves (for example, anger, fear, cold, etc.), body temperature drops. , and hair straightening muscle will contract and cause hair to stand up, forming goosebumps. In addition to its role as isolation, this physiological system can also make an animal appear larger than it really is, thus scaring off enemy.

23. Sea Horseborn from womb of father? Almost all animals also breed as females, but seahorse is born male. The male seahorse has an egg-hatching sac on its abdomen that resembles a kangaroo's "brood pouch", and female seahorse releases eggs into male seahorse's hatching sac. The male seahorse then takes over responsibility of breeding, and after about three weeks, a baby seahorse hatches from father's body.

24. Why do leaves change color? The reason leaves change color is due to chemical they contain, chlorophyll. When autumn comes, daylight hours are shorter than summer and temperatures are cooler, so leaves stop producing chlorophyll and remaining nutrients are transported to trunk and roots for storage. The green chlorophyll is missing from leaves, at same time other chemical pigments appear, so we see more yellow and brown leaves.

25. Why are there fallen leaves? When autumn comes, more water evaporates from leaves than in summer, but roots absorb less water than in summer. To reduce tree's water loss, cells of stem begin to form a layer of shedding that insulates leaves from trunk after nutrients have completely left leaves, allowing leaves to fall. 26. Why do whales splash water? The whale is a mammal, but its nose does not have a shell, and its nostrils grow on top of its head. Living in water, it breathes with lungs that can store a lot of air at a time, so it doesn't need to go to surface of water often to breathe. But when he comes to surface of water to breathe, he breathes through his nose, and loud sound waves that are emitted from body when breathing are caused by pressure.

27. How big is Milky Way? Many permanent centers together form a huge galaxy, and galaxy in which solar system is located is called Milky Way. The Milky Way is like a large disk, about 80,000 light-years wide and about 12,000 light-years thick at center, with a total of over 1,000 stars.

28. Why can't I see stars during day? Because some of sunlight is scattered by gas and dust in atmosphere during day, sky is very brightly lit, and light emitted by sun is very strong, so we cannot see stars.

29. What celestial bodies are in solar system? There are nine planets in solar system. This is in order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto. In addition, there are many asteroids, comets and meteors in solar system, and there are 2958 officially numbered asteroids. The most famous comet is Halley's Comet.

30. What is height of blue sky? The "blue sky" is actually Earth's atmosphere. The atmosphere surrounds earth's air, which is divided into 5 layers according to air density, and has a total thickness of 2000-3000 kilometers. But most of air is concentrated from ground below 15 kilometers, and higher you goyou are alone, thinner air becomes. What a dense atmosphere, how high must be blue sky. 31. What happened to thunder? Answer: It is a natural phenomenon when negative and positive electricity meet together. When it rains, some clouds in sky are positively charged and some are negatively charged. When two kinds of clouds meet together, they discharge and emit very bright lightning. At same time, they radiate a lot of heat. , due to which surrounding air quickly heats up, expands and makes a loud noise - thunder.

32. Why can planes fly into sky? Answer: An airplane has two wings, like a bird, and it also has propellers. Wings can generate lift to keep aircraft in air, and propellers can generate power to push aircraft forward. Therefore, plane can take off into sky like a bird.

33. When a quartz clock hanging on wall runs out and stops moving, its second hand often stops at "9" position on dial. This is due to fact that second hand slows down gravitational moment most at position "9". 34. The "burning" of an electric furnace is conversion of electrical energy into internal energy and does not require oxygen. Oxygen can only oxidize electric furnace wire and shorten its service life.

35. When a pot is filled with cold water, water droplets adhering to outer surface of bottom of pot may burn dry for a long time on fire, and they will not boil until they are dry. Or maintain thermal conductivity, temperature is about same until water in pot boils, water drops will not boil, and water drops will gradually burn dry due to evaporation on flame

36. There are several small holes on side of gas nozzle of gas furnace that communicate with outside world, but natural gas will not be emitted through small holes on side, but only from nozzle. , This is because gas flow rate in nozzle is large, according to principle of fluid mechanics, flow rate is high, pressure is low, and surface pressure of air flow is lower than atmospheric pressure outside side hole, so that natural gas is not thrown out through small hole on side of nozzle .

37. The mirror is out of shape, farther a person is from mirror, more out of shape. Since image in a mirror is formed by reflection from silver plated surface behind mirror, uneven silver plated surface or uneven glass thickness causes aliasing. For a non-standard mirror, farther a person is from mirror, greater deviation from normal position of reflected light on silver-plated surface, due to principle of light amplification, and greater deviation from normal position. -The shape of mirror will be. 38. The praying mantis is known as "magical insect-catching swordsman"

39. In Uganda, in Africa, there is a species of mice that can eat cats. This type of mouse is similar toordinary house mice, except that mouth has an extra layer of hard shell that is very hard. This type of mouse can emit bursts of strong odor, after cat smells it, it becomes paralyzed, trembling and unable to move. At this time, mouse jumped over, bit off cat's throat with its sharp teeth, sucked out blood, and then dragged cat to a secluded place to eat it slowly.

40. A species of munia in Amazon, when its companion sadly dies, other birds of same species bring multicolored petals and green leaves to their companion's corpse as a "flower burial", each hanging its head to offer condolences to deceased. 41. Why is sky red in morning and evening? In morning and evening, before and after sunrise and sunset, colorful clouds often appear in sky. The formation of morning glow and sunset glow is due to scattering effect of air on light. When sunlight enters atmosphere, it collides with atmospheric molecules and particles suspended in atmosphere and is scattered. These atmospheric molecules and particles do not themselves emit light, but because they scatter sunlight, each atmospheric molecule forms a source of scattered light. According to Rayleigh's law of scattering, violet, blue and blue light with shorter wavelengths in solar spectrum are most easily scattered, while red, orange and yellow with longer wavelengths have a high transmittance. Therefore, we see that clear sky is always blue, and light above horizon is only yellow, orange and red light with a longer wavelength. After these rays are scattered by impurities, such as air molecules and water vapor, sky there takes on bright colors.

42. Why is it hard to break a water bottle? There are two identical glass bottles, one is empty and other is filled with water, and they fall to ground from same height at same time, which bottle is easy to break? Generally speaking, heavy bottles are easy to break. However, when bottle is filled with water, water in bottle has a different function, which can reduce deformation of bottle and make bottle less likely to break. Glass bottles break, mainly due to deformation. When an empty bottle hits ground, ground puts pressure on bottle and bottle deforms from outside to inside and finally shatters. The bottle is filled with water, and since water is incompressible, deformation is reduced, making it less likely that bottle will break. Fill bottle with water and screw cap on tightly so that it does not break.

43. Hara-flavored food is poisonous In everyday life, people often encounter food spoilage. Food spoilage is a process of decomposition and alteration of proteins, carbohydrates and fats in foods, and its degree depends on type of food, type and number of microorganisms and conditions.ii environment. Usually fat spoilage is mainly due to rancidity, which is a kind of mutagenic food contamination. Enzymes, ultraviolet rays and oxygen produced by microorganisms can decompose neutral fat in food into glycerol and fatty acids, and fatty acids are further decomposed to form peroxides and oxides, and then to form rancid products such as ketones and aldehydes with a special pungent odor. , namely so-called challah taste. Eating foods with an unpleasant odor due to poor marketing and long storage leads to poisoning. Clinical manifestations are mainly gastrointestinal symptoms.

44. Laughter can make people healthy, because laughter can make a person's lungs expand their breathing capacity and improve blood circulation: accelerate endocrine activity, happy emotions increase appetite and increase digestive juices.

45. The reason maple leaves turn red is because one of them is action of anthocyanin, and other is that chlorophyll is constantly decomposed due to cold and replaced by anthocyanin.

46. Inspired by dolphins, scientists have created an underwater acoustic detection device - an echo sounder

47. Nomenclature and type specimens of organisms: Scientists give a Latin scientific name to every organism they have studied but not registered, including two Latin genus names and a species name, called double name method. , 1758. First created by Swedish scientist Linnaeus. The specimens on which name is based are called type specimens, one of which is designated as holotype and rest as paratype.

48. Vitamin C is declining and should not be eaten with seafood.

49. New furniture usually contains formaldehyde, and concentrated ammonia water50 can be used to absorb formaldehyde. Sausages, cured meats, and pickles contain sodium nitrite, which, under certain conditions, can produce aminonitrite in human body. conditions and cause cancer. Substance