epigraph
The teacher asks: Children, what is the fastest thing in the world?
Tanechka says: The word is the fastest. You just said you won't come back.
Vanechka says: No, light is the fastest.
I just pressed the switch, and the room immediately became light.
And Vovochka objects: Diarrhea is the fastest thing in the world.
Once I was so impatient that not a word
I didn’t have time to say, I didn’t turn on the light.
Have you ever wondered why the speed of light is maximum, finite and constant in our universe? This is a very interesting question, and immediately, as a spoiler, I will give out a terrible secret of the answer to it - no one knows exactly why. The speed of light is taken, i.e. mentally accepted for a constant, and on this postulate, as well as on the idea that all inertial frames of reference are equal, Albert Einstein built his special theory relativity, which for a hundred years now has been driving scientists crazy, allowing Einstein to show his tongue to the world with impunity and grin in his coffin at the size of the pig that he planted for all of humanity.
But why, in fact, is it so constant, such a maximum, and such a final answer, there is no answer, this is only an axiom, i.e. a statement taken for granted, supported by observation and common sense, but not logically or mathematically derived from anywhere. And it is likely that it is not so true, but no one has yet been able to refute it with any experience.
I have my own thoughts on this matter, about them later, but for now, in a simple way, on fingers™ I will try to answer at least one part - what does the speed of light mean "constant".
No, I will not load you with mental experiments, what will happen if the headlights are turned on in a rocket flying at the speed of light, etc., now it’s a little about that.
If you look in a reference book or wikipedia, the speed of light in a vacuum is defined as a fundamental physical constant, which is exactly is equal to 299 792 458 m/s. Well, that is, speaking approximately, it will be about 300,000 km / s, but if right exactly- 299,792,458 meters per second.
It would seem, where does such accuracy come from? Any mathematical or physical constant, whatever you take, even Pi, even the base of a natural logarithm e, even though the gravitational constant G, or Planck's constant h, always contain some numbers after the decimal point. At Pi these decimal places are currently known about 5 trillion (although only the first 39 digits have any physical meaning), the gravitational constant today is defined as G ~ 6.67384(80)x10 -11 , and the constant plank h~ 6.62606957(29)x10 -34 .
The speed of light in vacuum is smooth 299,792,458 m/s, not a centimeter more, not a nanosecond less. Do you want to know where such accuracy comes from?
It all started as usual with the ancient Greeks. Science, as such, in the modern sense of the word, they did not exist. Philosophers ancient greece that's why they were called philosophers, because at first they invented some kind of crap in their head, and then with the help of logical conclusions (and sometimes real physical experiments) they tried to prove it or disprove it. However, the use of real-life physical measurements and phenomena was considered by them as "second-class" evidence, which cannot be compared with first-class logical conclusions obtained straight from the head.
The first to think about the existence of light's own speed is the philosopher Empidocles, who stated that light is movement, and movement must have speed. He was objected to by Aristotle, who argued that light is simply the presence of something in nature, and that's it. And nothing is moving. But that's more! Euclid and Ptolemy so they generally believed that light is emitted from our eyes, and then falls on objects, and therefore we see them. In short, the ancient Greeks were dumb as they could, until they were conquered by the same ancient Romans.
In the Middle Ages, most scientists continued to believe that the speed of light was infinite, such as, say, Descartes, Kepler and Fermat.
But some, such as Galileo, believed that light had a speed, which meant that it could be measured. The experience of Galileo is widely known, who lit a lamp and shone on an assistant who was several kilometers away from Galileo. Seeing the light, the assistant lit his lamp, and Galileo tried to measure the delay between these moments. Naturally, he did not succeed, and in the end he was forced to write in his writings that if light has a speed, then it is extremely large and cannot be measured by human efforts, and therefore it can be considered infinite.
The first documented measurement of the speed of light is attributed to the Danish astronomer Olaf Roemer in 1676. By this year, astronomers, armed with telescopes of that very Galileo, were observing the satellites of Jupiter with might and main and even calculated their periods of rotation. Scientists have determined that Io, the closest moon to Jupiter, has a rotation period of approximately 42 hours. However, Roemer noticed that sometimes Io appears from behind Jupiter 11 minutes early, and sometimes 11 minutes late. As it turned out, Io appears earlier in those periods when the Earth, revolving around the Sun, approaches Jupiter at a minimum distance, and lags behind by 11 minutes when the Earth is in the opposite place of the orbit, which means it is farther from Jupiter.
Stupidly dividing the diameter of the earth's orbit (and at that time it was already more or less known) by 22 minutes, Remer received the speed of light 220,000 km / s, about a third missing the true value.
In 1729, the English astronomer James Bradley, observing parallax(slight location deviation) stars Etamin (Dragon Gamma) opened the effect aberrations of light, i.e. change in the position of the stars closest to us in the sky due to the movement of the Earth around the Sun.
From the effect of light aberration, discovered by Bradley, it can also be deduced that light has a finite propagation speed, which Bradley seized on, calculating it to be approximately 301,000 km / s, which is already within 1% accuracy of the value known today.
Then all the clarifying measurements by other scientists followed, but since it was believed that light is a wave, and the wave cannot propagate on its own, something needs to be "worried", the idea of the existence of a "luminiferous ether" arose, the discovery of which failed miserably in the American physicist Albert Michelson. He did not discover any luminiferous ether, but in 1879 he specified the speed of light to 299 910 ± 50 km/s.
Around the same time, Maxwell published his theory of electromagnetism, which means that it became possible not only to directly measure the speed of light, but also to derive it from the values of electrical and magnetic permeability, which was done by refining the value of the speed of light to 299,788 km/s in 1907.
Finally, Einstein declared that the speed of light in a vacuum is a constant and does not depend on anything at all. On the contrary, everything else - adding velocities and finding the correct frames of reference, the effects of time dilation and changes in distances when moving at high speeds, and many other relativistic effects depend on the speed of light (because it is included in all formulas as a constant). In short, everything in the world is relative, and the speed of light is the value relative to which all other things in our world are relative. Here, perhaps, Lorentz should be given the palm, but let's not be mercantile, Einstein is Einstein.
The exact determination of the value of this constant continued throughout the 20th century, with every decade scientists have found more and more digits after the decimal point at the speed of light, until vague suspicions began to form in their heads.
Determining more and more accurately how many meters in vacuum light travels per second, scientists began to wonder, what are we all measuring in meters? After all, a meter is just the length of some platinum-iridium stick that someone forgot in some museum near Paris!
And at first the idea of introducing a standard meter seemed great. In order not to suffer with yards, feet and other oblique fathoms, the French in 1791 decided to take as a standard measure of length one ten millionth of the distance from the North Pole to the equator along the meridian passing through Paris. They measured this distance with the accuracy available at that time, cast a stick from a platinum-iridium (more precisely, first brass, then platinum, and only then platinum-iridium) alloy and put it in this same Parisian chamber of weights and measures, as a sample. The further you go, the more it becomes clear that earth's surface is changing, the continents are deformed, the meridians are shifting and they scored one ten millionth part, and they began to consider the length of the stick that lies in the crystal coffin of the Parisian "mausoleum" as a meter.
Such idolatry does not suit a real scientist, this is not Red Square for you (!), and in 1960 it was decided to simplify the concept of a meter to a completely obvious definition - a meter is exactly equal to 1,650,763.73 wavelengths emitted by the transition of electrons between energy levels 2p10 and 5d5 of an unexcited isotope of the element Krypton-86 in a vacuum. Well, how much clearer?
This went on for 23 years, while the speed of light in a vacuum was measured with increasing accuracy, until in 1983 it finally dawned on even the most stubborn retrogrades that the speed of light is the most accurate and ideal constant, and not some kind of an isotope of krypton. And it was decided to turn everything upside down (more precisely, if you think about it, it was decided to turn everything right back upside down), now the speed of light with is a true constant, and a meter is the distance that light travels in a vacuum in (1/299,792,458) seconds.
The real value of the speed of light continues to be refined even today, but what is interesting is that with each new experience, scientists do not specify the speed of light, but the true length of a meter. And the more accurately the speed of light is found in the coming decades, the more accurate the meter we will eventually get.
And not vice versa.
Well, now back to our sheep. Why is the speed of light in the vacuum of our Universe maximum, finite and constant? I understand it this way.
Everyone knows that the speed of sound in metal, and indeed in almost any solid body, is much higher than the speed of sound in air. It is very easy to check this, just put your ear to the rail, and you can hear the sounds of an approaching train much earlier than through the air. Why is that? Obviously, the sound is essentially the same, and the speed of its propagation depends on the medium, on the configuration of the molecules of which this medium consists, on its density, on the parameters of its crystal lattice - in short, on the current state of the medium through which the sound is transmitted.
And although the idea of a luminiferous ether has long been abandoned, the vacuum through which electromagnetic waves propagate is not exactly absolute nothing, no matter how empty it may seem to us.
I realize the analogy is a bit far-fetched, isn't it? on fingers™ same! Precisely as an accessible analogy, and in no way as a direct transition from one set physical laws to others, I just ask you to imagine that the speed of propagation of electromagnetic (and in general any, including gluon and gravitational) oscillations is sewn into the four-dimensional metric of space-time, which we, out of the kindness of our hearts, call vacuum, as the speed of sound in steel is sewn into a rail . From here we dance.
UPD: By the way, I suggest to "readers with an asterisk" to fantasize whether the speed of light remains constant in a "difficult vacuum". For example, it is believed that at energies of the order of temperature of 10 30 K, the vacuum stops simply boiling with virtual particles, but begins to "boil away", i.e. the fabric of space is falling apart, the Planck values are blurred and lose their physical meaning, and so on. Would the speed of light in such a vacuum still be c, or will it mark the beginning of a new theory of "relativistic vacuum" with corrections like Lorentz coefficients at extreme speeds? I don't know, I don't know, time will tell...
Long before scientists measured the speed of light, they had to work hard to define the very concept of "light". One of the first to think about this was Aristotle, who considered light to be a kind of mobile substance that spreads in space. His ancient Roman colleague and follower Lucretius Car insisted on the atomic structure of light.
To XVII century two main theories of the nature of light were formed - corpuscular and wave. Newton belonged to the adherents of the first. In his opinion, all light sources emit the smallest particles. In the process of "flight" they form luminous lines - rays. His opponent, the Dutch scientist Christian Huygens, insisted that light is a form of wave motion.
As a result of centuries-old disputes, scientists have come to a consensus: both theories have the right to life, and light is the spectrum of electromagnetic waves visible to the eye.
A bit of history. How was the speed of light measured?
Majority scientists of antiquity were convinced that the speed of light is infinite. However, the results of the studies of Galileo and Hooke admitted its limit, which was clearly confirmed in the 17th century by the outstanding Danish astronomer and mathematician Olaf Roemer.
He made his first measurements by observing the eclipses of Io, a satellite of Jupiter, at a time when Jupiter and the Earth were located on opposite sides of the Sun. Roemer recorded that as the Earth moved away from Jupiter at a distance equal to the diameter of the Earth's orbit, the delay time changed. The maximum value was 22 minutes. As a result of calculations, he received a speed of 220,000 km / s.
Fifty years later, in 1728, thanks to the discovery of aberration, the English astronomer J. Bradley "refined" this figure to 308,000 km / s. Later, the speed of light was measured by the French astrophysicists Francois Argo and Leon Foucault, having received 298,000 km / s at the “output”. An even more accurate measurement technique was proposed by the creator of the interferometer, the famous American physicist Albert Michelson.
Michelson's experiment to determine the speed of light
The experiments lasted from 1924 to 1927 and consisted of 5 series of observations. The essence of the experiment was as follows. A light source, a mirror and a rotating octagonal prism were installed on Mount Wilson near Los Angeles, and a reflecting mirror 35 km later on Mount San Antonio. First, light through a lens and a slit fell on a prism rotating with the help of a high-speed rotor (at a speed of 528 rpm).
The participants in the experiments could adjust the rotational speed so that the image of the light source was clearly visible in the eyepiece. Since the distance between the peaks and the frequency of rotation were known, Michelson determined the speed of light - 299796 km / s.
Scientists finally decided on the speed of light in the second half of the 20th century, when masers and lasers were created, which are distinguished by the highest radiation frequency stability. By the beginning of the 1970s, the measurement error had dropped to 1 km/sec. As a result, on the recommendation of the XV General Conference on Weights and Measures, held in 1975, it was decided to consider that the speed of light in vacuum is henceforth equal to 299,792.458 km/sec.
Can we reach the speed of light?
It is obvious that the development of the far corners of the universe is unthinkable without spaceships flying at great speed. Preferably at the speed of light. But is it possible?
The barrier of the speed of light is one of the consequences of the theory of relativity. As you know, an increase in speed requires an increase in energy. The speed of light would require virtually infinite energy.
Alas, the laws of physics are categorically against this. At speed spaceship at 300,000 km / s, particles flying towards it, for example, hydrogen atoms, turn into a deadly source of powerful radiation equal to 10,000 Sieverts / s. It's about the same as being inside the Large Hadron Collider.
According to scientists at Johns Hopkins University, while in nature there is no adequate protection against such a monstrous cosmic radiation. Erosion from the impact of interstellar dust will complete the destruction of the ship.
Another problem with light speed is time dilation. At the same time, aging will become much longer. The visual field will also be distorted, as a result of which the ship's trajectory will pass as if inside a tunnel, at the end of which the crew will see a shining flash. Behind the ship will remain absolute pitch darkness.
So in the near future, humanity will have to limit its high-speed "appetites" to 10% of the speed of light. This means that it will take about 40 years to fly to the nearest star to the Earth - Proxima Centauri (4.22 light years).
(including light); one of the funds. physical permanent; represents the limiting speed of propagation of any physical. influences (cf. Relativity theory) and is invariant upon transition from one frame of reference to another.
S. s. in the environment with" depends on the refractive index of the medium n, which is different for different frequencies v ( Light dispersion):. This dependence leads to a difference group velocity from phase velocity light in the environment, if we are not talking about monochromatic. light (for S. of page in vacuum these two sizes coincide). Experimentally determining with", always measure group S. with. or so-called. signal speed, or the rate of energy transfer, only in some special. cases not equal to the group.
For the first time S. with. determined in 1676 by O. K. Roemer (O. Ch. Roemer) by changing the time intervals between eclipses of Jupiter's satellites. In 1728, it was established by J. Bradley, based on his observations of the aberration of starlight. In 1849, A. I. L. Fizeau (A. N. L. Fizeau) was the first to measure S. s. by the time it takes the light to pass a precisely known distance (base); since the refractive index of air differs very little from 1, ground-based measurements give a value very close to s. In Fizeau's experiment, a beam of light from a source S(Fig. 1), reflected by a translucent mirror N, periodically interrupted by a rotating toothed disk W, passed the base MN(approx. 8 km) n, reflected from the mirror M, returned to disk. Getting on the tooth, the light did not reach the observer, and the light that fell into the gap between the teeth could be observed through the eyepiece E. From the known speeds of rotation of the disk, the time for light to travel through the base was determined. Fizeau obtained the value c = 313,300 km/s. c) a mirror. Reflecting from the mirror, the beam of light was directed to the base and, upon returning, fell again on the same mirror, which had time to turn through a certain small angle (Fig. 2). With a base of only 20 m, Foucault found that S. s. is equal to 298000 500 km/s. Schemes and basic. the ideas of the experiments of Fizeau and Foucault were repeatedly used in subsequent works to determine S. s. Obtained by A. Michelson (see. michelson experience) in 1926, the value of km / s was then the most accurate and was included in the international. physical tables. quantities. 
Rice. 1. Determination of the speed of light by the Fizeau method.
Rice. 2. Determination of the speed of light by the rotating mirror method (Foucault method): S - light source; R - rapidly rotating mirror; C is a fixed concave mirror, the center of which coincides with the axis of rotation R (therefore, the light reflected from C always falls back on R); M - translucent mirror; L - lens; E - eyepiece; RC - accurately measured distance (base). The dotted line shows the position R, which has changed during the time the light travels the path RC and back, and the reverse path of the beam of rays through the lens L, which collects the reflected beam at point S "and not again at point S, as it would be with a fixed mirror L. Velocity lights are set by measuring the offset SS".
S.'s measurements with. in the 19th century played a big role in, further confirming the wave theory of light. Foucault's 1850 comparison of S. s. the same frequency v in air and water showed that the speed in water, in accordance with the prediction wave theory. A connection was also established between optics and the theory of electromagnetism: the measured S. s. coincided with the speed of e-magn. waves calculated from the ratio of e-mag. and e-static. units of electric charge [experiments by W. Weber and F. Kohlrausch in 1856 and subsequent more accurate measurements by J. C. Maxwell]. This coincidence was one of the starting points for the creation by Maxwell in 1864-73 of el-magn. theories of light.
In modern S.'s measurements with. modernized is used. Fizeau's method (modulation. method) with the replacement of a gear wheel with an el-optical, ., interference or to-l. another light modulator that completely interrupts or attenuates the light beam (see. Light modulation). The radiation receiver is a photocell or photomultiplier.Application laser as a light source, ultrasonic modulator with stabilizers. frequency and increased accuracy of measuring the length of the base made it possible to reduce measurement errors and obtain the value of km/s. In addition to direct measurements of S. s. according to the time of passage of a known base, indirect methods are widely used, which give greater accuracy. So, with the help of a microwave vacuum cleaner. [TO. Frum (K. Froome), 1958] at a wavelength of radiation = 4 cm, the value of km/s was obtained. With an even smaller error, S. s is determined. as a quotient of the division of independently found and v atomic or molecular spectral lines. K. Evenson (K. Evenson) and his staff in 1972 on the cesium frequency standard (see. Quantum frequency standards) found, with an accuracy of up to 11 decimal places, the frequency of the CH 4 laser radiation, and according to the krypton frequency standard, its wavelength (about 3.39 μm) and obtained ± 0.8 m / s. By the decision of the General Assembly of the International Committee on Numerical Data for Science and Technology - CODATA (1973), which analyzed all available data, their reliability and error, S. s. in vacuum it is considered to be equal to 299792458 ±1.2 m/s.
The most accurate measurement of c is extremely important not only in general theoretical. plan and to determine the value of other physical. quantities, but also for practical goals. These include, in particular, the determination of distances by the time of passage of radio or light signals in radar, optical location, light ranging, in satellite tracking systems, etc.
Lit.: Vafiadi V. G., Popov Yu. V., speed of light and its importance in science and technology, Minsk, 1970; Taylor W., Parker W., Langenberg D., Fundamental constants and quantum theory, trans. from English, M., 1972. A. M. Bonch-Bruevich.
The topic of how to measure, as well as what the speed of light is, has been of interest to scientists since antiquity. This is a very fascinating topic, which from time immemorial has been the object of scientific disputes. It is believed that such a speed is finite, unattainable and constant. It is unattainable and constant, like infinity. However, it is finite. It turns out an interesting physical and mathematical puzzle. There is one solution to this problem. After all, the speed of light still managed to be measured.
In ancient times, thinkers believed that speed of light is an infinite quantity. The first estimate of this indicator was given in 1676. Olaf Remer. According to his calculations, the speed of light was approximately 220,000 km/s. It was not quite the exact value, but close to the true.
The finiteness and estimate of the speed of light were confirmed after half a century.
In the future, the scientist fizo It was possible to determine the speed of light from the time it takes the beam to travel the exact distance.
He set up an experiment (see figure), during which a beam of light departed from the source S, reflected by mirror 3, interrupted by toothed disk 2, and passed through the base (8 km). Then it was reflected by mirror 1 and returned to the disk. The light fell into the gap between the teeth and could be observed through eyepiece 4. The time it took for the beam to pass through the base was determined depending on the speed of rotation of the disk. The value obtained by Fizeau was: c = 313,300 km/s.
The speed of propagation of a beam in any particular medium is less than this speed in a vacuum. In addition, for different substances, this indicator takes on different values. After few years Foucault replaced the disk with a rapidly rotating mirror. The followers of these scientists repeatedly used their methods and research schemes.
Lenses are the basis of optical devices. Do you know how it is calculated? You can find out by reading one of our articles.
And you can find information about how to set up an optical sight consisting of such lenses. Read our material and you will not have questions on the topic.
What is the speed of light in vacuum?
The most accurate measurement of the speed of light is 1,079,252,848.8 kilometers per hour, or 299 792 458 m/s. This figure is valid only for conditions created in a vacuum.
But to solve problems, the indicator is usually used 300,000,000 m/s. In a vacuum, the speed of light in Planck units is 1. Thus, the energy of light travels 1 Planck unit of length in 1 unit of Planck time. If a vacuum is created in natural conditions, then X-rays, light waves of the visible spectrum and gravitational waves can move at such a speed.
There is an unequivocal opinion of scientists that particles that have mass can take a speed that is as close as possible to the speed of light. But they are not able to reach and exceed the indicator. The highest speed, close to the speed of light, was recorded in the study of cosmic rays and during the acceleration of certain particles in accelerators.
The value of the speed of light in any medium depends on the refractive index of this medium.
This indicator may be different for different frequencies. Precise measurement of the quantity is important for the calculation of other physical parameters. For example, to determine the distance during the passage of light or radio signals in optical location, radar, light ranging and other areas.
Modern scientists use different methods to determine the speed of light. Some experts use astronomical methods, as well as measurement methods using experimental techniques. An improved Fizeau method is often used. In this case, the gear wheel is replaced by a light modulator, which weakens or interrupts the light beam. The receiver here is a photoelectric multiplier or photocell. The light source can be a laser, which helps to reduce the measurement error. Determination of the speed of light the time base can be passed by direct or indirect methods, which also allow you to get accurate results.
What formulas are used to calculate the speed of light
- The speed of light in a vacuum is an absolute value. Physicists designate it with the letter "c". This is a fundamental and constant value, which does not depend on the choice of the reporting system and characterizes time and space as a whole. Scientists suggest that this speed is the limiting speed of particles.
Formula for the speed of light in vacuum:
c = 3 * 10^8 = 299792458 m/s
here c is the speed of light in vacuum.
- Scientists have proven that speed of light in air almost equals the speed of light in vacuum. It can be calculated using the formula:
Really, how? How to measure the highest speed in universe in our modest, Earthly conditions? We no longer need to puzzle over this - after all, for several centuries so many people have worked on this issue, developing methods for measuring the speed of light. Let's start the story in order.
speed of light is the propagation velocity of electromagnetic waves in vacuum. It is denoted by the Latin letter c. The speed of light is approximately 300,000,000 m/s.
At first, no one thought at all about the question of measuring the speed of light. There is light - that's great. Then, in the era of antiquity, the opinion that the speed of light was infinite, that is, instantaneous, dominated among scientific philosophers. Then it was Middle Ages with the Inquisition, when the main question of thinking and progressive people was the question "How not to get into the fire?" And only in the era Renaissance and Enlightenment the opinions of scientists have bred and, of course, divided.
So, Descartes, Kepler and Farm were of the same opinion as the scientists of antiquity. But he believed that the speed of light is finite, although very high. Actually, he made the first measurement of the speed of light. More precisely, he made the first attempt to measure it.
Galileo's experience
Experience Galileo Galilei was brilliant in its simplicity. The scientist conducted an experiment to measure the speed of light, armed with simple improvised means. At a great and well-known distance from each other, on different hills, Galileo and his assistant stood with lit lanterns. One of them opened the shutter on the lantern, and the second had to do the same when he saw the light of the first lantern. Knowing the distance and time (the delay before the assistant opens the lantern), Galileo expected to calculate the speed of light. Unfortunately, in order for this experiment to succeed, Galileo and his assistant had to select hills that are several million kilometers apart. I would like to remind you that you can by filling out an application on the site.
Roemer and Bradley experiments
The first successful and surprisingly accurate experiment in determining the speed of light was the experience of the Danish astronomer Olaf Römer. Roemer applied the astronomical method of measuring the speed of light. In 1676, he observed Jupiter's moon Io through a telescope and found that the time of the satellite's eclipse changes as the Earth moves away from Jupiter. The maximum delay time was 22 minutes. Assuming that the Earth is moving away from Jupiter at a distance of the diameter of the Earth's orbit, Roemer divided the approximate value of the diameter by the delay time, and received a value of 214,000 kilometers per second. Of course, such a calculation was very rough, the distances between the planets were known only approximately, but the result turned out to be relatively close to the truth.
The Bradley Experience. In 1728 James Bradley estimated the speed of light by observing the aberration of stars. aberration is a change in the apparent position of a star caused by the movement of the earth in its orbit. Knowing the speed of the Earth and measuring the angle of aberration, Bradley got a value of 301,000 kilometers per second.
Fizeau's experience
To the result of the experiment of Römer and Bradley, the then academia reacted with disbelief. However, Bradley's result was the most accurate for more than a hundred years, right up to 1849. That year the French scientist Armand Fizeau measured the speed of light using the rotating shutter method, without observing celestial bodies but here on Earth. In fact, this was the first laboratory method after Galileo to measure the speed of light. Below is a diagram of its laboratory setup.
The light, reflected from the mirror, passed through the teeth of the wheel and was reflected from another mirror, 8.6 kilometers away. The speed of the wheel was increased until the light was visible in the next gap. Fizeau's calculations gave a result of 313,000 kilometers per second. A year later, a similar experiment with a rotating mirror was carried out by Léon Foucault, who obtained the result of 298,000 kilometers per second.
With the advent of masers and lasers, people have new opportunities and ways to measure the speed of light, and the development of the theory also made it possible to calculate the speed of light indirectly, without making direct measurements.
The most accurate value for the speed of light
Mankind has accumulated vast experience in measuring the speed of light. To date, the most accurate value of the speed of light is considered to be the value 299 792 458 meters per second received in 1983. It is interesting that further, more accurate measurement of the speed of light turned out to be impossible due to errors in the measurement meters. Now the value of the meter is tied to the speed of light and equals the distance that light travels in 1/299,792,458 seconds.
Finally, as always, we suggest watching an informative video. Friends, even if you are faced with such a task as independently measuring the speed of light with improvised means, you can safely turn to our authors for help. you can fill out an application on the website of the Correspondence. We wish you a pleasant and easy study!