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CHILDREN'S SCIENTIFIC LABORATORY
How to hear the sun. Children's Science Lab
Directory / Children's Science Lab Sunny voice... An unusual combination of words, isn't it? We are all accustomed to the concepts of "sunlight", "sun rays", in a word, to the fact that our star can be seen. But what else can you hear... The hypothesis of the existence of a solar voice was put forward by the Gorky astronomer, whose works are well known in our country and abroad, Professor Vladimir Vyacheslavovich Radzievsky. Moreover, he even predicts how the sunny voice will sound: in it you can hear the roar of hurricanes, and the howling of storms, and the measured roar of the sea surf, and a bizarre combination of other sounds hitherto unknown to us. And being deciphered, this voice, perhaps, will reveal many secrets of our star. How was the unusual idea of listening to the Sun born? Vladimir Vyacheslavovich, answering this question, says that a phenomenon that is not so rare in science has happened when they are looking for one thing, but find something completely different. But the history of his idea is not only an example of unusual, unexpected turns in an exciting scientific search, it is also an example of stubbornly following the logic of search, the ability to bring what has been started to its logical end. Radzievsky studied how light pressure affects the movement of celestial bodies. To do this, he needed to find the most accurate way to measure the pressure of light. The accuracy achieved in the classical experiment of P. N. Lebedev was not enough. Nevertheless, it is best to start the story by remembering what light pressure is and how Lebedev's experiment was carried out, during which the existence of this pressure was first proved and its magnitude was measured. In a glass vessel in a vacuum on a thin thread, the famous physicist suspended a gimbal with two light "fly wings" (see Fig.). So the scientist called the thinnest metal leaves with a diameter of about 5 mm. One of these wings was silvered, the other was blackened. Through a system of lenses, the light of a powerful electric arc was directed at them. And then the following happened: the blackened surface absorbed the light, while photons were reflected from the silvered surface, bounced off, thereby giving this winglet an additional impulse. As a result, the suspension with wings twisted. The experience of P. N. Lebedev, as is known, proved that light pressure exists. And according to the angle of twisting of the suspension, it was possible to approximately establish its value. Accurate measurement and calculation of light pressure is very important for astronomers who need to calculate the course of stars. This pressure, for example, largely determines the appearance and shape of cometary tails. However, the experience of P. N. Lebedev, given in the last year of the last century, for today's problems, as we have already said, does not provide the required accuracy. Radzievsky was looking for a clearer way to measure. Somehow he came across a book called "Hearing and Speech." The author of the book argued that the human ear is much more sensitive than the eye. It would seem that comparing these two senses with each other is as pointless as, say, comparing the quality of musical works and confectionery. After all, the eye reacts to an electromagnetic field, and the ear to an acoustic one. Nevertheless, there is a rational grain in such a comparison. The relative superiority of the ear over the eye is obvious from this example. The eye is not able to catch the sequence of frames on the movie screen, which occurs at a frequency of only 24 frames per second. And the tympanic membrane of the ear is a method of pressure with a frequency of up to 20 thousand hertz. The scientist also remembered that for a long time there has been a very simple and convenient device for testing hearing - a thermophone. With its help, tested, for example, recruits in the army. The thermophone is a sealed box with a blackened wire, from which there is one exit - into the ear. A current of 1 ampere is applied to the wire, which is modulated by an alternating current of sound frequency - 600 hertz. The variables here are vanishingly small: the amplitude of the alternating current, for example, is one ten-millionth of a volt. For 1/600 of a second, the wire has time to expand a little, in the next microinterval it shrinks a little ... But even these insignificant vibrations the ear hears, however, each person has different ways, which is used to test hearing. These facts led Radzievsky to the idea: if hearing is so sensitive, perhaps with its help it will be possible to measure light pressure more accurately? To check, he conducted a simple experiment (see Fig.). The scientist made a disk in which five round holes of equal diameter were cut out at the same distance from each other. The disk starts to rotate at a speed of 100 rpm and a powerful beam of light is directed at it. Behind the disc, opposite one of the holes, there is a sealed box with a silver-plated membrane. A thin tube comes out of the box and is inserted into the ear. Within a minute, the light is blocked 500 times and reopened, the membrane is either under the influence of light, or not. Therefore, it should sound, experiencing periodic exposure to light pressure. The experience was a success. The sound was strong enough. It only remained to calibrate its strength, and it was possible to calculate the value of light pressure ... Eureka? Success, some too easy, could not but alert the real researcher. For verification, the scientist (as he himself admits - purely intuitively) blackened the membrane with soot. The sound should have disappeared, or at least become significantly weaker. After all, light pressure is proportional to the coefficient of light reflection, and for a blackened surface it is negligible. However, something quite different happened. The membrane literally roared!
It became clear that it was not light pressure that manifested itself mainly in the experiment. What then is the reason for the observed phenomenon? Obviously, the researcher suggested that the soot simply heats up under the influence of the light flux and cools when the light is blocked (remember the wire in the thermophone). Consequently, the air layer adjacent to the membrane periodically expands and contracts. Elastic air vibrations are transmitted to the eardrum. Once again, this clue was confirmed by a new experiment, where instead of a powerful electric arc, an ordinary light bulb served as a light source. The effect was manifested, but the sound, of course, became quieter. Strictly speaking, the test experiment is not difficult to reproduce. To do this, you need a simple device - an ordinary medical phonendoscope, with which the doctor listens to the patient. Picking it up, you will see that a nut is screwed onto the sound-collecting chamber, firmly pressing a rigid membrane to the chamber (see Fig.). Unscrew it, cover the inside of the chamber with a thick layer of soot, and then put the nut and membrane back in place, carefully checking their tightness. Rubber tubes and ear tips should also be airtight. After all, the sound energy arising in the chamber is negligible, and the slightest leakage of it will lead to failure. If you now bring the phonendoscope to the light bulb (the distance between them will depend on your hearing acuity and can vary from 10 cm to 1 m), you will hear a smooth low buzz corresponding to the sound of a tuning fork with a frequency of 50 hertz. Someone may have doubts - is the sound caused by an alternating electromagnetic field? Try blocking the light with any opaque screen. The sound will immediately disappear and appear at the same moment when the screen is removed. On the contrary, a transparent screen, for example, made of plexiglass, does not remove the sound of a light bulb.
The origin of sound here is exactly the same as in the experiment described above. Radzievsky called this phenomenon the photophone effect, and the device for its detection (the "stethoscope modernized" with the help of soot) - the photophone. A person with a technical mindset will immediately come up with how to practically use a photophone. Well, at least to check the quality of light bulbs. The nature of the sound of the light bulb, apparently, should be associated with the technical condition of the filament.
But, of course, the light bulbs are not the main thing. In the end, they know how to determine their quality even without a photophone. Pondering over the discovered effect, Radzievsky suddenly caught himself in a simple and at the same time extraordinarily daring thought. If the photophone hears an ordinary XNUMX-watt light bulb, it means that it can also respond to an immeasurably more powerful emitter - the Sun ... Here we have traced in general terms the path of the origin of the idea of listening to the Sun. A thoughtful reader, even from these few events and facts, will probably be able to guess that Vladimir Vyacheslavovich belongs to that infrequent type of researchers who are called "idea generators" in the scientific world. Indeed, it is difficult to even count, let alone list, all the hypotheses put forward by him over the course of many years of scientific activity. At the same time, the scientist willingly shares his ideas with colleagues, primarily with his students working in many cities of the country. Although some of his hypotheses were not confirmed - this is inevitable in science, but other ideas are fruitfully developed. And it is also easy to see that Radzievsky can do without expensive equipment or some special devices. He is always rescued by non-standard thinking, fiction and creative imagination. To make sure of this, we will still have new opportunities. Let's return to the hypothesis. Sunlight, like the light of a light bulb, is actually not at all as smooth as it appears to the naked eye. When viewed through a telescope, the surface of our luminary resembles boiling rice porridge. Each grain of "porridge" - a granule - is the result of a convective breakthrough through the photosphere of the Sun of a more incandescent mass of gas from its depths. The size of each granule is from 150 to 1000 km, its average lifetime is 3-5 minutes, and the temperature is 300-500 degrees higher than the surrounding background. Every hundredth of a second, about 50 granules are born and die, and at the same time about a million of them are observed on the Sun. Hence the impression of boiling porridge. All these processes of constant birth and death of granules inevitably give the sunlight a "trembling", the frequency of which fluctuates in a wide sound spectrum, including, of course, audible. And then fantasy suggested to the scientist that in such a colorful sound picture hurricanes should thunder, storms howl ... And behind them are real physical processes, which, perhaps, can tell a lot about themselves. True, one must also learn to decipher the language of solar storms and whispers. So, the opportunity to hear the Sun, you see, seems very tempting. But the Sun, although it has a colossal power of radiation, is, as we remember, at a distance of 150 million kilometers. You can't bring it to a photophone like a light bulb. Will the sound of the device be caused by rays coming from such a distance? Radzievsky made the necessary calculations. It turned out that to test the hypothesis, a powerful telescope with a mirror diameter of at least 6-7 m is needed. What does the telescope have to do with it? Its purpose is not only (and not so much) to bring the studied celestial bodies closer to the observer, but to amplify the signals coming from them. The gain increases with the square of the mirror diameter. Only with a powerful amplifier - a telescope, the possibility of hearing the voice of the sun became real (see Fig.).
A few years ago such telescopes did not exist. And with Radzievsky everything was limited to an article in a special scientific journal. Colleagues' opinions about Radzievsky's idea were divided. One of the most serious arguments of skeptics sounds like this: the noises in the atmosphere are so strong that through them the voice of the sun will not reach the Earth. In response to such doubts, Vladimir Vyacheslavovich gives a well-known example with ... bats. Everyone knows that bats are nocturnal. They see poorly, but move with the help of ultrasonic signals, emitting a wave that is reflected from surrounding objects and, returning to them, makes it possible to correctly orientate. At one time, scientists decided to check: is their lifestyle simply related to the habit of sleeping at certain hours or does it have other, deeper reasons? To do this, bats were put on a plane and transported across several time zones, shifting their day by 8 hours. And what - the mice calmly sat on the poles until sunset, and with the onset of darkness they began their usual flights. Radzievsky explains this fact as follows. The Earth reacts to solar radiation like a giant absorbing membrane. This reaction is expressed in noise that is not audible to humans, but is well captured by more sensitive bats. For them, noise is a powerful background against which their own weak signals are lost. Therefore, during the day they are deprived of the possibility of orientation. After sunset, the noise disappears, and the mice are able to move around. Atmospheric noises, which also exist at night, do not interfere with bats. This means that they are not so strong as to interfere with listening to the Sun. In a word, it's up to the future experiment on one of the powerful telescopes built in recent years. Only experience can confirm or disprove an idea. And today it is even difficult to predict what will follow the outcome of the test experiment, if it is successful. Perhaps the solar voice will provide new information about the processes taking place on our star, which are still far from fully understood. Maybe a simple photophone will become the basis of ultra-sensitive instruments that will be able to capture the noise of the Earth, born of sunlight. And this noise could tell a lot about the Earth and the Sun... Author: V. Meyerov
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