Written by | Wu Jianyong
Editor-in-charge | Wang Yudan
The first part of the series is about the fire of diamonds and how jewelry businesses can pursue perfect fires to sell for a good price. This article talks about how scientists have used fire to increase human vision by hundreds of millions of times and extend it to the edge of the universe. In addition, I would like to promote the craftsmanship spirit of optical instruments, that is, full of passion for light and fire, obsessively pursuing perfection, which is what we call "not crazy, not alive". Without the extreme pursuit of fire, there would be no earth-shattering scientific discoveries today.
The light is colorful
As mentioned in the previous article, the "fire" of diamonds is essentially the phenomenon that white light is refracted into a variety of colors of light. We often see rainbows, walk through the sand in the sun, and often see the little flashes of light reflected by the sand grains (stars and fires of sand grains). But when the scientist Newton bought a "triangular prism that can divide light into rainbows," he had a different view from ordinary people. The essence of these phenomena, Newton said, is that white light is actually a mixture of seven different colors of light. It is easy to talk about it, but to persuade all the people in ancient and modern China and abroad, you need to have a more clever means, that is, to prove it with experiments. His most skillful experiment was that not only could white light be separated into seven colors of light, but also that the seven kinds of light could be combined and then re-transformed into white light (Figure 1). According to this experiment, he said that different colors of light are caused by "particles" of different colors (i.e., photons).
Newton's statement that light is a photon poked the ant honeycomb and opened a century of scientific debate. Half of the scientists approve and defend the photon theory, while the other half strongly oppose it, believing that light is a light wave. Whether light is a particle or a wave has been debated for hundreds of years, each with experimental evidence of iron. It wasn't until quantum mechanics emerged that the debate came to a conclusion. This conclusion is that and the mud - light is both particles and waves (the so-called wave-particle duality), you say that light is a wave or a particle is right, but it is also wrong, because you think that waves or particles can only choose one or the other. But as long as you can see things from the perspective of quantum mechanics, everything is naturally reasonable. Sure enough, after that, everyone stopped arguing (of course, there were also folk science and a few philosophers who did not give up).
In addition, Newton said that white light has "seven" colors because he was paying homage to ancient Greek philosophy and worshipping the fan-like number seven. In fact, the color of the light is continuous, and the "seven colors" have neither reason nor evidence.
Figure 1 Newton's spectroscopic experiment White light can not only be divided into multiple colors, but also the various colors can be combined to become white light.
Spread out the rainbow
So, what is the situation when the phenomenon of "seven colors of light" has reached the hands of craftsmen? The German glass craftsman Josef von Fraunhofer (1787-1826) first came up with the ultimate gameplay: spreading the rainbow wide and wide. At this point, for the convenience of narration, we will give "fire" a more formal name, called "light spectrum". Chinese the meaning of "score", taken from "family tree" "musical score". The meaning is to separate the white light and spread it widely on the table, so that it is easy to study.
For the spectrum of sunlight that has been spread a hundredfold, Furum and Fei certainly did not find a dividing line that clearly separated the seven colors, so Newton's light division was wrong.
However, Furum and Fei found that there are many vertical dark lines in the spectrum (Figure 2)! Although he did not know what these dark lines were at the time, his obsessive-compulsive obsession prompted him to constantly improve the instrument, spreading the spectrum wider and wider, seeing more and more dark lines, and finally he found 574 dark lines in the spectrum of sunlight. These thin black lines were named "Furang and Fei Lines". With today's technology, millions of furlanges and fissures can already be seen in the spectrum of the Sun.
Figure 2 The spectrum of sunlight should be read like this: from right to left is red, orange, yellow, green, blue, and purple, and both sides are black because out of the visible range, the eye can not see. The black area on the right is called "infrared" to see the outside of the light red. Although invisible to the infrared eye, special cameras ("night vision" cameras) can see. Close to the heating, the skin can also feel the infrared light it emits, that is, thermal energy. The black zone on the left is called "ultraviolet", that is, beyond purple. It is also invisible to the eye but can tan the skin, destroy DNA and cause skin cancer. The visible spectrum and the adjacent infrared and ultraviolet regions can be roughly divided into 9 groups of Flange and Fei lines, A to H, and each group can be subdivided into more groups and thin lines.
What exactly is this thin dark line in the spectrum? In fact, when light passes through the electron cloud around the atom, the electron cloud "eats" the light. An electron cloud of shape eats only a particular color of light, and if this color is eaten, it leaves a black line in the spectrum where the color originally came from. Nature is so magical that sunlight encounters many atoms on its way through space to Earth and deals with the electron clouds outside these atoms. For example, when encountering 100 million hydrogen atoms, their electron clouds all dance the same dance, dancing one trick and eating one color, and dancing another trick eats another color of light. After that, a set of four black lines (the Bal end line system) produced by the dancing of the cloud of hydrogen atoms and electrons appears in the spectrum of sunlight. Hydrogen is so, helium is so, sodium oxide calcium iron magnesium mercury is also like this, like fingerprints have their own characteristics. Thus , the Furlang and Fissin lines are collections of many atomic features absorbed on the spectrum.
It is said that the black lines in the solar spectrum were discovered by the British chemist W.H. Wollaston 12 years before they were discovered by Flange and Fei. But Wallaston was a serious scientific man (academician, the discoverer of precious metals palladium and rhodium), and the scientific man was not as crazy as a technical man, so the black line was not named after Wallaston, but was only mentioned by later historians. In contrast, Furum and Fei were really caught up in the act of separating the spectra wider, and he even invented an instrument called a "spectrometer" (Figure 3).
Fig. 3 Spectrometer Fulang and Fei (the one standing in the middle of the foreground) show scientists his newly invented spectrometer.
The scientific significance of the Furang and Fei lines
The beautiful phenomenon of Furum and Fei Line has made immortal contributions in many fields of science. Here are two simple examples:
One is to understand the chemical composition of distant stars. The universe is large, the stars are too far away and the temperature is so high that it is impossible for humans to go up and sample and analyze. Based on this, it was concluded at that time (the 18th century) that humans would never know the chemical composition of certain stars.
But as soon as these scientists talk, they punch their mouths. 45 years after the discovery of the Furang and Fei line, Kirchhoff and Bunsen discovered that burning metal produces bright colored light (brain patch fireworks), and these colored lights are bright lines in the spectrum, which exactly coincide with the position of the Fulang and Fei lines (black lines). So Kirchhoff says that burning atoms emit bright lines, and cold atoms absorb light to produce black lines. Furang and the Fei line are actually caused by the absorption of light by atoms. If the Furang and Fei lines in the starlight spectrum are exactly consistent with the absorption lines of hydrogen, helium, and sodium ions on Earth, it means that there is hydrogen, helium, and sodium in those places, so we can know what chemical elements are on distant stars without sampling in the field.
The second example is proof of the expansion of the universe. The expansion of the universe means that the stars are flying towards the outside of the universe, far away from us. However, the stars we see are immobile, so how do we know they are all moving away from us at high speed? Since 1848, many astronomers have found that the position of the Furon and Fei lines of distant galaxies is different from that of nearby planets (Figure 4). And not one line is different, all lines move in the direction of red, a phenomenon called "redshift".
Why does redshift prove that the universe is expanding? We've all had the experience of sirens screaming when you're standing on the side of the street and an ambulance speeding up in the distance; and the sirens become muffled again as the ambulance passes past you and drifts away. That is to say, the same siren, when it is rapidly approaching you, the tone will rise, and when it quickly leaves you, the tone will decrease, this phenomenon is called the Doppler effect. Light and sound are both waves, so the Doppler effect will also occur. The change in tone of a sound wave can correspond to a change in the color of the light wave. Therefore, the lower pitch of the siren when it is far away from you can correspond to the red shift of the Furang and Fei line, indicating that the distant stars are moving away from you. The astronomer Edwin Hubble (1889-1953) studied thousands of stars in 1919 with the most powerful 2.5-meter telescope of the time and made a surprising discovery: the farther away we are, the more the redshift of galaxies becomes. Using redshift as a metric, we can know that most of the stars seen belong to the Milky Way, which is our home, and there are thousands of "extragalactic galaxies" similar to the Milky Way beyond the Milky Way, and their redshifts are many and therefore very far away. This law, called Hubble's law, hints at the expansion of the universe.
Figure 4 Redshift The spectrum of nearby (left) and distant (right) stars has the same proportion of Flange and Fevy lines, but the furlang and Fevy lines of distant starlight appear in redder regions of the spectrum, which is a phenomenon of redshift.
Since the star spectrum has a redshift, is there a blueshift? If the redshift is the expansion of the universe, does the blueshift mean that the universe is shrinking? That's a good question. In fact, most galaxies in the sky are redshifting, but there are also a few galaxies that are blueshifting, which only means that some galaxies are approaching us, and does not affect the conclusion that the entire universe is expanding (just as the return of the shore does not affect the flow of a river of spring water to the east).
Andromeda ( M31 ) is one of the few blue-shifted extragalactic galaxies. Calculated, this fairy is rushing towards us at a crazy speed of 116 kilometers per second, and in four billion years, it will collide with and merge with our milky way, by which time the night sky will be illuminated by multiple bright stars like brilliant fireworks (Figure 5).
Figure 5 Andromeda's earth-shattering collision with the Milky Way This picture is a celestial phenomenon 4 billion years later. Based on Hubble research and computer simulations, created by artists. The source of the image is https://grist.org/living/galaxy-right-ahead-the-milky-ways-on-course-for-a-head-on-collision/.
The secret book of the telescope craftsman
The purpose of the craftsman's study of the spectrum is still very different from the romance of scientific discovery, and the purpose of The study of Fulang and Fei is to make a fortune, and really to make a fortune because of it.
Fulang and Fei became orphans at the age of 11 and went to work as apprentices in a glass workshop. He was uneducated and a self-taught Glass maker. He miraculously survived a fatal accident in which a factory collapsed and was recognized by The Bavarian Prince Maximilian I, Josef, who was on the spot to direct the disaster. The prince was very fond of talent, paid for Fulang and Fei to buy books, and ordered the workshop owner to allow him to light the lamp at night to study (the boss was distressed that lamp oil was very expensive). After FuLang and Fei became adults, they heard that grinding lenses could make money, so they did it for a lifetime. Due to his ingenuity, the astronomical telescopes he built were ordered by major observatories.
If you want to do good things, you must first use them, and if you want to have a good astronomical discovery, you need a good telescope. Astronomers at that time knew that Fulang and Fei's telescope was much clearer than that built by others.
The secret of Fulang and Fei grinding a perfect lens is to use Fulang and Fei line to calibrate the lens. He found that in the orange-yellow region of the spectrum, there are several dark lines that can be used to examine the quality of the lens. Only a perfectly polished lens can distinguish these tiny black lines in the solar spectrum.
In the warm Bavarian sunshine, Fulang and Fei calmly played with his technical secrets in his workshop, and the order of the big observatory chased after the ass, and the money was received softly. In the hands of a craftsman, small secrets can also create great economic value.
The telescopes of Fulang and Fei also have a very valuable secret, which is more complicated and needs to be said slowly. Many friends have read the "Biography of Yue Quan", which has such a passage: "Emperor Taizong rode the Wutai Mountain into the incense, was lured by Pan Renmei to watch the spirit card, and saw the dressing floor of Empress Xiao's mother-in-law of the Tianqing Liang King in Northern Youzhou, but saw that the upper floor emitted five colors of light..." According to my civil science level research, the so-called "translucency card" is the telescope in the original form, and the "multicolored millimeter light" is the small rainbow around the object. This small rainbow around the object can destroy the resolution of the image, and the jargon is called "chromatic aberration", which is something that all optical instruments try to avoid (Figure 6 left). Chromatic aberration, like the principle of diamond fire, is caused by different refractive indexes of light at different wavelengths in the medium. Therefore, the fire that is to be greatly promoted in the diamond industry is the enemy of the optical instrument industry.
From hundreds of years ago to the present, the main technique for reducing chromatic aberration has been to make composite lenses made of two different materials of glass ("flint" glass [leaded glass] and "crown glass" glass [crown glass] [boron glass]). This composite lens is also known as an "achromat" lens (Figure 6 on the right). The achromatic lens was invented in 1729 by the English amateur scientist Hall (who was a lawyer in his own practice).
The achromatic lens reached Fulang and Fei and was played another level. He found that the crown glass at that time had microscopic defects, and the thicker the defects, the more serious the accumulation. Therefore, this glass cannot actually be used as a large non-chromatic objective lens for astronomical telescopes. To this end, Fulang and Fei developed a new large glass furnace and built their own brand of glass, crushing other companies.
Figure 6 Chromatic aberration and achromatic lens On the left, a cheap telescope sees a distant object, surrounded by a small rainbow.
In addition to adding boron to the crown glass, there are also people who add a small amount of zinc, phosphorus, fluorine, and even rare earth metal lanthanum. Many of the formulations to this day are the secrets of some premium optical instrument brands. The high-end camera lenses we buy at great prices are mainly to buy these industry secrets.
Speaking of the secret recipe of the crown glass, insert a hearsay wild history. Although the quality of Canon lenses is exaggerated by everyone, NASA's project in the sky is not used. Why? It turned out that the crown glass in the Canon DSLR advanced lens used the secret recipe of fluoride, which was relatively fragile. During a spacewalk, one of the lenses in the lens was cold and shattered, missing all the photos that should have been taken here. NASA lost tens of billions (not yet yen) in an instant, so it was painful, and from then on, the heavens only used Kodak and Nikon, and never dared to use Canon again.
With good glass, there must be good processing. Fulang and Fei were also crazy about lens processing, and the processing accuracy of advanced optical lenses had to reach the level of nanometers, which was a technical difficulty in processing astronomical telescope lenses at that time. Furon and Fei built a new grinder specifically for this purpose to solve this problem.
After a few years, the Bavarian Optical Institute led by Fulang and Fei became the first in the world. Even Britain, an established scientific power, could not make such good optical instruments.
KefuLang and Fei have always been a "civil subject" and have no academic qualifications. In his own words, "I don't have time to play tricks, my research is for the practical purpose of improving telescopes." Until 1822, the University of Erlangen-Nuremberg (FAU, Univ. Erlangen-Nuremberg) only to give him an honorary doctorate degree.
Fulang and Fei really don't have much time. Like many glassmakers at the time, he died at the age of 39 (1826) from lung diseases associated with heavy metal poisoning due to lack of knowledge of occupational protection.
Why telescopes need large apertures
Furon and Fei Fa Cai are because of large-bore lenses. So why do astronomical telescopes use large-bore lenses? This is because the larger the lens, the more light is entered, and the darker celestial bodies can be seen.
In addition, the resolution of the optical instrument is also determined by the size of the lens. What is "resolution"? It is the ability to see two points clearly. The optical resolution of the human eye is the viewing angle "one point", which means that the angle of view is ninety degrees from the horizon to the zenith, and dividing one degree of it into sixty parts is the perspective of one point (Figure 7).
At the same time, the caliber of the human eye pupil is only about two millimeters, which determines the light collection capacity and resolution of the human eye. Therefore, although the stars in the sky can be seen, except for the sun and moon, the perspective of most celestial bodies is smaller than the resolution of the human eye, so even if it is a huge galaxy, it is only a point of light in the human eye. There are only 110 galaxies larger than one point that the human eye can see in the sky, called Messier objects.
If you think about it, our naked eye can barely see 110 of the hundred billion galaxies in the universe, and we know the "incompetence" of human beings and the importance of telescopes.
Figure 7 Human eye resolution The resolution of the human eye refers to the ability to distinguish between two points, not whether it can be seen. The upper two points in the right image can be distinguished, and the lower two points are fused indistinguishable. But in both cases the point of light can be seen. Most of the stars seen in the night sky are a point, and their shape cannot be distinguished.
Take an example from the time of Galileo to illustrate the resolution of the human eye. Galileo's telescope has a diameter of 3.8 centimeters, which can increase the resolution of the human eye by about twenty times. At that time, all the noble ladies in the city shouted around his telescope, looking for their jaws at the celestial wonders. One day Galileo was really surrounded by the nobles (according to the history of the wild), and said to his grandmother, "Today I will open your eyes to an astronomical miracle." So he set up his telescope and pointed it at Venus (Venus) in the western sky. The long gung star is no longer a dazzling bright spot in the telescope, but a crooked crescent. Unexpectedly, his grandmother took a look at it and said dismissively, "What a miracle, I have seen it for a long time." It turned out that his grandmother belonged to one in ten thousand good eyes in humans, and the resolution was high enough to directly see the profit and loss of Venus.
The age of the Giant Refracting Telescope
Furon and Fei's telescopes far surpassed those of the Galileo era, and his masterpiece was the 9-inch (24 cm) refracting telescope (Figure 8), which was hundreds of times stronger than the resolution of the human eye. Furon and Fei ushered in the "age of the great refractor ear" (the great refractor ear). Observatories competed to customize Fulang and Fei's telescopes, just as today's major hospitals snapped up the strongest medical imaging machines. However, the age of the giant refracting telescope lasted only 70 years, and the aperture increased from 24 centimeters in 1826 to 125 centimeters in 1900, and then withdrew from the stage of history like dinosaurs.
This is because the lens is heavier with aperture, and since the refracting telescope's lens is illuminated in the middle, the lens can only rely on its edges to support its own weight. We learned in middle school that glass is liquid rather than solid, and that glass deformation caused by self-weight is enough to destroy the imaging accuracy of large lenses.
The rise of reflecting telescopes
So, did the development of large telescope technology stop in the era of Fulang and Fei? Of course not. There are two types of telescopes, refractive and reflective (Figure 8). The refractive type is like a camera lens, where light passes through the middle of the lens and then focuses on the eye. The reflective type is to use a mirror to reflect light to collect light and focus it on the eye. Galileo and Flange and Fei's telescopes were refractive, while modern telescopes are mostly reflective.
Figure 8 Two basic types of telescopes
Reflective telescopes no longer need to let light pass through the glass lens, but plate the glass surface with metal, reflecting the light like a mirror to collect the light. Although the lens is still glass, it can be supported by many points from the base below, so that even if the telescope is large, there will be no problem of the lens deformation due to self-weight.
The world's largest optical telescope is the 39-meter-aperture Extremely Large telescope (ELT). The ELT is composed of 798 lenses with a diameter of 140 cm precisely synthesizing a diameter of up to 39.3 meters, with a lighting capacity of 100 million times that of the human eye, and a resolution of 0.005 arc seconds (Figure 9). What is the concept of this resolution? Using it to look at the surface of the moon, you can see the lunar module left on it by the American moon landing that year. Unfortunately, the ELT has been planned for many years and has not yet been built.
Figure 9 Imaginary view of the Very Large Telescope at the European Southern Hemisphere Observatory. Why do you need to have several lasers next to you when you work? Because the atmospheric flow causes its density to change constantly, it is equivalent to adding an imperfect lens in front of the telescope. With the laser, the current atmosphere can be detected unevenly, and the main mirror of the telescope can be immediately topped in different places below, so that the main mirror is slightly deformed, so that the resolution reduction caused by the uneven atmosphere can be compensated.
Space telescopes
However, telescopes are large, and the theoretical resolution is very high, but the telescope on the ground must pass through the Earth's atmosphere, and atmospheric disturbances will destroy the resolution and make the telescope unable to make it possible (see Figure 9 for explanations). To avoid this flaw, people want to launch large reflecting telescopes into space, without the interference resolution of the atmosphere to the next level. As early as 1923, people began to advertise telescopes in space, but the funding and technology were not settled until 1970, and NASA and the European Space Agency jointly supported the Hubble Space Telescope program. Hubble is named in honor of the astronomer Hubble, who discovered that aliens are farther away and have a greater redshift. Hubble's main mirror diameter reaches 2400 cm (Figure 10).
Figure 10 Hubble telescope outside the atmosphere at sunset
In 1990, the space shuttle took off with the Hubble telescope. However, the start did not go well, and the image transmitted back by the telescope was vague (Figure 11). It turned out that the engineer who polished the main mirror was confused and used the wrong parameters. This is also too ridiculous, the telescope has passed countless tests, acceptance, even if there is a craftsman like Furang and Fei among the contractors, he will not wait until the telescope is on the day to find out.
Figure 11 Hubble's 2.4 m main lens. Mistakes are only a few tenths of a hair's hair
The project leader pressed the 10,000 grass and mud horses galloping in his heart to study the remedy plan, knowing that the Hubble plan itself is not easy, and the space shuttle carrying the repair project alone has had two major accidents of aircraft destruction and death. If it is not repaired well in the sky, the huge amount of money wasted is still a small matter, and I am afraid that I will give the people a bad impression and make the space telescope plan unable to turn over for decades.
Finally, in 1993, the shuttle brought a corrective lens module with it, which allowed Hubble to reach the resolution of the design. After that, Hubble lived up to expectations and worked diligently for 30 years, sending back a large number of stunning photos (Figure 12), which greatly advanced human understanding of the universe.
Figure 12 The masterpiece of the Hubble image shows the dots of stars in the Milky Way; the next is the birth process of stars in an extragalactic galaxy (a large number of blue new stars in red smoke), and the blue smoke ring in the lower left is a large amount of gas thrown out when a star dies.
Hubble deep space field
Think about how crowded the space telescope that astronomers have been waiting for for 70 years to finally be online, waiting in line to use it. Hubble can only look at a small area in the sky at a time (like a small area of tennis tennis from a hundred meters away), and there are so many interesting phenomena in the sky that many scientists can't queue up for a lifetime. In this case, if there is a plan to use Hubble to stare slowly at an empty sky for ten days, many people will think that the planner is crazy. Yet this happens to be one of Hubble's most popular programs, called the Deep Space Field Program.
The Deep Space Program began with the Christmas and New Year holidays of 1995. Several scientists picked one of the most empty areas of the sky (in the middle of the Big Dipper, as far away from the Milky Way as possible), and stared at it for ten days, more than 100 hours.
The result is jaw-dropping, such a small empty area actually saw 3,000 galaxies similar to the Milky Way! (Figure 13), and this area is very small, only one part of the entire sky 24 millionths.
The unexpected discoveries of the Deep Space Field program are yet another reminder of human insignificance, as our Earth sits on the scale of the solar system and is too small to see. Placing the solar system on the scale of the Milky Way is absolutely insignificant as one hundred billion stars, and the Hubble deep space field tells us that the Milky Way is only one in a hundred billion on the scale of the universe. And is the space between two galaxies in the deep space field also filled with farther and more galaxies? This question can no longer be answered by Hubble, who has been in service for a long time, because these galaxies are too far away, and their light has long since moved red to the infrared light region that Hubble cannot see, and infrared light is absorbed by the Earth's atmosphere, so these more distant galaxies can only be answered by Hubble's successor, the Webb Space Telescope.
The "pigeon" Webb telescope, which has been in place for many years, was finally launched on Christmas Day 2021. Webb's position in space was more than a million kilometers from Earth, much farther than the moon, and he couldn't send someone to fix it like Hubble did. Therefore, it is more necessary to make the ingenuity of the maker almost crazy, which is the main reason why it has been delayed launch. Let's wish Webb the best of luck bringing humanity a broader view closer to the edge of the universe (according to the latest news, Webb has weathered the most worrisome technological hurdles and has successfully unfolded a complex umbrella that is heading for its destination).
Figure 13 Hubble Deep Space Field, thousands of galaxies similar to the Milky Way have been found in the otherwise empty space region, and their light comes from the early days of the birth of the universe and only reaches Earth today.
Chinese Sky Eye
At present, the world's largest telescope is China's 500-meter Aperture spherical radio telescope (FAST), commonly known as the "Chinese Sky Eye" (Figure 14). FAST doesn't look at starlight, it just looks at radio waves. Starlight and radio waves are both radio waves, but the wavelength of visible light is short, and the wavelength of radio waves is long.
Figure 14 500-meter Aperture Radio Astronomical Telescope (FAST) in Guizhou
FAST is a heavy weapon of the world's astronomical science, and once it was put into operation, it was willing to participate in a number of hot research, such as the search for aliens. The universe is so big, human beings are so small, and without aliens it would certainly be a huge waste of space. As the world's largest radio telescope, FAST naturally undertakes the task of listening to extraterrestrial civilizations texting us. The special equipment on China's Celestial Eye can automatically filter out the natural signals generated by celestial bodies and the artificially generated radio signals on the earth from the vast sea of radio waves, and then screen out a small number of possible signals for human study. FAST has the largest caliber and high sensitivity, and it is appropriate to undertake such a task.
Of course, fast's main task is still classical scientific problems, such as the study of "fast electric explosions" (commonly known as "flash in the universe"). This fan-like astronomical phenomenon can emit enormous amounts of energy in a fraction of a thousandth of a second. Because the appearance time of electric explosions is very short and cannot be recorded by ordinary telescopes for long exposures, large telescopes have unique lighting advantages: after FAST runs, multiple rapid explosions are recorded in a short period of time.
Another study was a large-scale measurement of the 21 cm line of hydrogen atoms. The so-called "21 cm line" is a bright line at 21 cm in the hydrogen atom spectrum, similar to a bright line emitted by the burning metal mentioned earlier, but this line is invisible to the eye in the microwave band. Since it is a bright line, it also produces redshift with the movement of the object, so measuring the redshift of different celestial regions can draw the three-dimensional structure of the universe at that point.
Some believe that both rapid electric explosions and the 21-centimeter line of hydrogen atoms are related to extraterrestrial civilizations. For example, an alien civilization might use this 21 cm line
Double the frequency to text.
It is an irrational number that does not exist in nature, one knows
Civilizations can claim their existence at this frequency, and the receiver can also grasp it, using the high abstraction of mathematics as a civilization to confirm the existence of other civilizations.
The spirit of Nam Ren Dong
Nan Rendong is a key figure in China's Heavenly Eye and a craftsman I admire (Figure 15). He was born in 1945 to a poor family in Jilin Province. His genius was an oil painting artist, but after being admitted to Tsinghua University in 1963, he was transferred to the Radio Department, and when he graduated in 1968, he was assigned to the Radio Factory in Tonghua City, Jilin Province. In the great trend of history, individuals are always wrapped up in the ends of the earth. The main characteristic of a craftsman is to constantly create a micro-environment conducive to his own development in the face of adversity, and to show brilliance in it.
After graduating from Tsinghua University, Nan Rendong started as an apprentice in the metalworking workshop, and was proficient in riveting and welding samples, plus electroplating and forging, and even opened the mountain to set off cannons. The "Xiangyang brand" semiconductor radio he participated in developing and the desktop computer of Jilin University both showed his artistic genius. After the reform and opening up, he was admitted to the Beijing Astronomical Observatory, and after receiving his doctorate in 1985, he was a visiting scholar at the Dwingelo Radio Observatory in the Netherlands, and as the initiator of the Chinese side, he promoted the cooperation between the VLBI, a large astronomical instrument between China and the Netherlands.
Since 1994, he has led the team to be responsible for the key aspects of FAST site selection, pre-study project establishment, feasibility study and preliminary design. In order to select the site, he traveled through the mountains of southwest China with hundreds of satellite remote sensing maps, comparing more than 1,000 depressions for 12 years. In 2006, the FAST project was approved by an international review. In July 2007, the FAST Project was officially approved by the state as a major scientific device in the "Eleventh Five-Year Plan". The project officially started in 2011 and was inaugurated in 2016. Nan Rendong's craftsmanship spirit played a key role in the establishment and construction of China's Tianyan project.
Figure 15 Nan Rendong at the FAST construction site Some friends who can look at the picture say that they are masters of craftsman spirit. I don't look at the picture, but from his two pairs of glasses, you can see the meticulous spirit and the simplicity of practicality.
Big Telescope Leaderboard
After mentioning so many telescopes, let's sum up and have a big aperture competition (Figure 16). Figure (1) shows the world's largest caliber Chinese sky eye, and only one edge is shown in the figure. (2) The second largest 305-meter Puerto Rican Arecibo radio telescope, which has been in service for 53 years since its completion in 1963, fell into disrepair due to insufficient funding, and collapsed and scrapped in 2020. (3) For the largest optical telescope project, the 100-meter aperture optical telescope planned by Europe, but due to financial problems, the project was cut down and reduced to the ELT (4) currently under construction. (5) The Hawaiian 30-meter telescope under construction. (7) and (8) the Hubble and Webb Space Telescopes, respectively. (6) It is the Guo Shoujing Telescope of Hebei Xinglong Observatory (Large Celestial Area Multi-objective Optical Fiber Spectroscopic Telescope, LAMOST), which is used to study the structure of the universe. The idea is good, the equipment is advanced, but the hard wound is too close to the densely populated area, the light pollution is serious, and the sunny weather is less.
Modern telescope belongs to the big science, a project always has to go through a lot of argumentation, many good projects are often cut because of funding problems, so good projects must have good science, to get the support of the general public is more likely to set up projects, get financial support.
For the issue of funding, the strategies of Nam Indong and Fulanghefei are different. Fu Lang and Fei are silent, and the kung fu reaches the user naturally pays money. And Nan Rendong, in addition to doing enough kung fu, also painstakingly persuades peers to recognize and invest in the country. A foreign colleague said, "Nan Rendong often speaks English is difficult to understand, but the reasoning spoken is extremely clear. ”
Figure 16 Comparison of the apertures of the world's large telescopes
epilogue
The eyes are the windows of the mind, and the information brought by the eyes is 90% of the total amount of information received by the brain from the outside world. The eye is good at observing the world's colors: the human eye can only distinguish about 100 gray levels for black and white images, but can easily see millions of different colors for color images. As a result, the resolution of optical instruments for colored light has reached an extremely strict level. The telescope introduced in this article brings the edge of the universe closer, and the next article is ready to introduce microscopy technology, how to expand human eyes to the microscopic world of "one sand and one world, one flower and one heaven". (Winter break 2021 in The Town of Gaiseburg)
Plate editing | -Xiao Guiyue-