Dust is a Chinese word, Pinyin: ch é n â i.One refers to flying dust;The two fingers are just like dust;The third refers to the bottom of the society;The fourth metaphor is dirty or dirty things, and the five fingers are not decorated with dust on the ground.
In physics, dust refers to rock particles and metal particles floating in the universe.In the vast and empty universe, except for all kinds of stars, planets, comets, asteroids and other celestial bodies, there is not a complete vacuum.In fact, there are a lot ofCosmic dustThese dust may seem insignificant, but it can have a noticeable impact on people's lives.
New research finds that more than 5000 tons of alien dust fall on the earth every year.The research results were published in the academic journal Earth and Planetary Science Letters on April 15, 2021.[3]
The Book of Rites - Part I of Qu Li: "If there is water in front, it will contain green banners; if there is dust in front, it will containCrowing kite。”
Chuang Tzu's Happy Journey: "Wild horses, dust, and creatures blow each other with their breath."
The Relics of Xuanhe in the Great Song Dynasty: On the first day of June, when it was hot and in the sand stains, every wind blew, the dust was like fog, the face was faint, and there was no water spring.[4]
Roushi"No one has heard her lamentation": "The wind blows away the dust on her body and the pain in her chest."
Historical Records: Biographies of Qu Yuan and Jia Sheng:“ZhuonaoIn the sludge, cicadas exult in the turbid filth to float outside the dust. "
"Four Journeys: A Crusade Encounters a Teacher Alone": "Why love the dust when shaking clothes and climbing mountains?"
Lu Xun"Graves - Cultural Paradoxes": "It is not to surpass the dust, extricate oneself from human affairs, or to be ignorant and ignorant, but to follow others, they can be silent."
3. Refers to the bottom of the society.
Ming Feng Menglong's "A warning to the world: Zhao Chun'er revives the Cao Family Village": "There is aMrs. Liang, can identify in the dustHan Shizhong。”
Ming Ling Mengchu's "Surprise at the Beginning of Making a Tablet. Volume 8": I am not a person who sucks. I feel that my brother has a meal. Because our money is light and our loyalty is heavy, if my brother is not in the dust, he knows how Xiao Ke, a stranger, would gladly pay.[5]
Qing Niuxiu's "Record of General Wu Liuqi's Military Affairs": "The outstanding heroes in the sea must be found in the dust
The poem "Wanjiang River and Wendengyan" written by Liang Gong in the Qing Dynasty: "The article is dry weather, and the surname is not dusty."[6]
6. Ming and Qing vernacular words
It refers to the ground containing dust that has not been decorated.
Ming Wu Chengen《Journey to the West》The 14th time: The tiger squatted on the dust and dared not move.But he hit him on the head, and his brain was flushed with pink, and his teeth were sprayed with a few beads of jade to frighten ChenXuanzangRoll the saddle and fall the horse.
realistic meaning
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Dust refers to particles floating in the air, such as dust.The main components of the atmosphere arenitrogen, accounting for about 78%, followed byoxygen, accounting for about 21%,carbon dioxide0.25%, the rest are other gases and impurities.Other gases include helium, neon, argon, xenon, krypton and other trace gasessteam。Other impurities refer to dust, bacteria, gas solvents, etc. floating in the air.
Under normal circumstances, the air is colorless and transparent, and it is difficult for us to see the impurities in the air inadvertently with the naked eye.
If a ray of sunlight shines into the house, you can see the originally transparent air. Under the sunlight, the dust passes throughRay refraction, reflection and other functions, obviously floating in the air, large and small, dense.According to scientific statistics, in the indoor environment, every cubic meter of air contains more than 0.5 μ m of dustNumber of particlesAbout 40 million to 50 million.There are countless bacteria attached to the dust particles.
stayAir compressorUnder the influence ofheat exchangeAccording to the calculation of relevant formula, the original atmospheric pressurestateAfter being compressed to 0.8Mpa (gauge pressure), the volume of 4.8m3 of air will be finally compressed to 1m3.From this process alone, it can be seen that there will be 192 million to 240 million dust particles greater than 0.5 μ per cubic meter of compressed gas with 0.8Mpa pressure.
In addition, in the process of being compressed, the atmosphere brings lubricating oil and mechanical wear debris into the air compressor.According to the principle of air thermodynamics, the compressed air will have a large amount of supersaturatedsteamIt is restored to water drops and discharged.
Physical analysis
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Analyze the material,Cosmic dustIn fact, it is no different from the composition of the earth.However, for various reasons, these dust particles have not been able to converge into a star, butparticulateSuspended inCosmic spaceinUnder the action of proper gravity, these dusts are likely to gather together in a dense cloud like mannerAstronomical telescopeThe camera often looks gorgeous and colorful, so people call it "nebula" vividly.
The origin of cosmic dust has always been a mystery.One theory is that cosmic dust comes from ordinary stars with relatively low temperature and slow burning process.The dust is released through the solar wind and then dispersed into space.However, according to the research on the density of matter contained in the solar wind, some scientists believe that the solar wind cannot provide enough density of cosmic dust.Therefore, another guess is that these tiny dust particles are likely to come fromSupernovaThe explosion of.According to British scientistsGalaxyThe youngest supernova in“Cassiopeia-The observation conducted by α "found that there was a large amount of cold dust in the area where the residue after the explosion was located, and its weight may be four times that of the sun.These scientists believe that if all supernovae erupt outward on this scaleCosmic dustIf so, it can basically reach the amount of cosmic dust in the universe.Therefore, compared with ordinary stars, supernovae may be the source of cosmic dust.
Significant impact
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Hubble confirms that planets originate from dust and gas
These beautiful dust have a very direct impact on people's lives.For example, according to statistics,Cosmic dustIt is the fourth largest source of dust on the earthEarth's environmentAnd climate.Every hour, about one ton of cosmic dust will enter the earth, while only one piece of dust will rotate around the sun at the speed of 100000 kilometers per hourDust cloudIt will bring 30 million kilograms of dust to the earth every year.This number is huge.In addition, American researchers have also compiled a computer program that can simulate the impact of cosmic dust on the Earth over 1.2 million years to study the impact of cosmic dust on the Earth in the long term.The simulation results show that the impact of cosmic dust on the earth can reach a peak every 100000 years.And these dust did not disappear gradually, but gathered on the earth, which may be the source of past natural disasters.New evidence found by paleontologists shows that individual species of plants and animals are not extinct at once, but gradually and slowly, which may be related toCosmic dustThe slow effect of the.
Light echo
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Astronomers recently capturedLarge Magellanic Cloudfour hundredLight yearOne ofSupernovaThe dazzling "light echo" produced is caused by dust.This means that observers on Earth may actually have seen the explosion that should have happened 400 years ago.Because the star emits light before dying, scientists can understand its past by studying the "light echo".
The Large Magellanic Cloud where the supernova remnant 0509-67.5 is located
Harvard UniversityAstronomer Armin Rest said: "We have the opportunity to observe the past and present of supernovae. We can see the light reflected by dust after the explosion andsupernova remnant 。The whole process is like having a time machine.
”Leicester and other astronomers used NASA'sChandra X-ray ObservatoryXMM in Europe-NewtonObservatory andGeminiThe observatory staged their discovery, and the relevant details were published in two papers published recently in the Astrophysical Journal, of which Leicester was the co-author.Leicester said that the team of astronomers monitored the reflected light waves of SNR 0509-67.5 for about five years, with the aim of producing a delayed video.He said, "As the light from the explosion spreads outward,Interstellar gasAnd dust will send them to all corners of the universe, just like fog reflects light.In this case, they will arrive at the earth longer thanDirect light。” Liszt Explain that although it is older, the reflected light andSupernovaThe research value of direct light is consistent."Everything related to light has been preserved, so we can analyze the spectrum of this supernova and determine its type, including what elements it produced." He pointed out that carbon, oxygen and heavier protons necessary for life can be found in the spectrum or "signature".The "light echo" of SNR 0509-67.5 is not the first time to be observed, but Liszt said that their importance in this field is increasing.He said: "Our ability to observe 'light echoes' is improving every year, such as the progress made in detectors and other telescope technologies. We may compare these' echoes' with their supernova debris, in order to more accurately estimate the distance between them and the Earth. In astronomy, distance is one of the most difficult data to determine."
Related news
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Dust fountain
Halo formed by dust
1. On February 13, Beijing time, according to the report of NASA's space network, American astronomers found aDust fountain, which will open up the mystery of the source of a large amount of dust in the universe for scientists.In fact, because of aSolar magnetic fieldOur solar system experiences cosmic dust storms at least three times as frequently as a few years ago.Sometime in the next 10000 years, we will pass through areas with more dense dust.Where does all this dust come from.This problem has been puzzling astronomers.U.S.AUniversity of ChicagoAstronomy andAstrophysicsProfessor Donald York said: "We don't know what this material is, what it is made of, or how it enters space."
York and his colleagues found a dust fountain, which seems to be what they have been looking for.This dust manufacturing plant is aDouble star system, located in the middle of the striking beautiful red rectangular nebula, this strange geometric nebula composed of gas and dust is 2300 away from usLight year。Astronomers believe that one of the twin stars in the red rectangular nebula is generating dust.The hydrogen element in its core has basically burned out, so it no longer supports thethermonuclearPrimary stage of fusion
Form.York and his colleagues explained that, as they called them, these "postAsymptotic giant branchThe star disintegrated, generating enough heat to ignite a new fuel: helium.During the transition of tens of thousands of years, such a star will gradually lose its outer atmosphere.Dust is believed to be formed byStellar radiationThe pressure is thrown out of this cooling outer layer.
In a double star system, two stars often share material, or one side takes material from the other side.Therefore, a disk structure composed of matter will be formed around the smaller and slower stars.York explained: "After the formation of the disk like structure, they often form jet streams and eject some substances out of the original system, distributing these substances in space." This is what researchers think they are observing in the red rectangular nebula.
The discovery will be published in the Astrophysical Journal next month.The researchers said that the study is of far-reaching significance because the dustStar formationThe way of scientific theory is very important.York said: "If the nebula composed of gas and dust collapses due to its own gravity, it will become very hot immediately and start to evaporate." Some things that may be dust must cool the nebula quickly to prevent it from being heated again.
The big star in the red rectangular nebula is one of those stars that cannot be condensed in their atmosphere due to too hot dust, but there is still a huge dust around itGas ring。
Weitz's research team was in the United States for seven yearsNew MexicoThe Cape Abbott Observatory used a 3.5-meter telescope to observe the stars for about 15 hours.Weitz said, "Our observation found that the most likely is between the gravity or the large stars in the red rectangular nebula and the sun like companion starsTidal gravityCause matter to leave the outer layer of a large star. "
Some of this material eventually forms a disk of dust around smaller stars.After about 500 years, the matter gradually turns intoSmall star。Just before this happened, this smaller star passed in the opposite direction called“bipolar jets ”Two gases ofJetSome substances are ejected.Other materials are pulled by the surface layer of the big star to form a disk like structure around the two stars, and then cooled.
Weitz explained, "such as iron, nickel, silicon, calcium and carbonHeavy elementCoagulation into solid particles, which is what we see after leaving this systemInterstellar dust。”It's hard for the telescope to catchCosmic dustBecause it only lasts about 10000 years, it is a short time in the life of stars.The opportunity that can be caught is extremely accidental.
Astronomers in the vicinity of the EarthGalaxyOther objects similar to the red rectangular nebula were observed in.This shows that during the billions of years of the Milky Way, the Weitz research team saw this process quite common."This process is very similar to the process we observed in the red rectangular nebula. It may have occurred hundreds of millions of times since the formation of the Milky Way Galaxy," Weitz said
Startling conclusion
black hole
Where did human beings originate? Astronomers believe that the whole earth was made of dust surrounding the early sun, and nothing like solid matter in the solar system.But where does the dust itself come from? This has always been an unsolved mystery.lately,university of manchester According to the researchers, they have solved the mystery of the origin of the dust, and the answer is black hole.The discovery will be published in the new issue of Astrophysical Journal Letters.Modern space dust is ejected from stars formed 10 billion years ago, but these stars were too young when the solar system formed 4.5 billion years ago, so it is impossible to produce so much dust.The early dust in the universe must have come from somewhere else.Assumption of researchersa quasarIs the possible source of early dust, and“Spitzer”Space telescope, made a more detailed observation of a quasar called PG2112+059, which is 8 billion light years away from the Earth.
The researchers carried outspectral analysisIt is found that the dust around the PG2112+059 quasar contains a large number of rock forming minerals, including silica (basically small sand grains) andcorundumAluminum oxide (known asRubyAnd sapphire) and is calledPericlaseMagnesium oxide (present in marble).
Researchers say that these substances may be indispensable for the formation of stars, planets and lifeCosmic dustAn important source of.These minerals must bea quasarIt is generated becausethe outer spaceTheir crystalline structure is difficult to exist for a long time under the harsh conditions of,cosmic raysIt will destroy them into amorphous glass shape, which indicates that they are newly formed.Moreover, corundum and periclase have never been detected in space dust before.This association between dust and quasars provides strong evidence for the idea that quasars create dust.
Halo formed by dust
3. The view of most astronomers that planets are composed of cosmic dust has been further proved.NASA（NASA）Two ofAstronomical telescopeThe early and late stages of planet formation are clearly observed.
according toReutersOn December 10, it was reported that two telescopes of NASA——hubble space telescope And Spitzer Telescope, which captured six young stars, astronomers foundCosmic dustThe ring formed around these six stars is the same size as the sun.Hubble observed a very young star as big as the sun. It is only about 50 million to 250 million years old. It is surrounded by a huge ring of dust, which may form planets in the future.
According to the report, most astronomers believe that planets form in the dust and gas around young stars, and the younger the planet, the larger its dust ring.such asJupiterAt first, it was a mass of gas. Later, it became a land planet composed of many rocks. During its rotation, these rocks collided with each other and finally became one.
Astronomers said in a telephone briefing,hubble space telescope The observed dust ring of this young star is large enough to form aGaseous planetBut it may not be enough to form a terrestrial planet like Earth.Astronomers think so because they have detected in previous observations of the dust ring of stars that, although no planets can be seen around the dust ring, there is a unique gravitational force of planets in the dust ring swaying.[2]
