From a physics point of view, this is an incorrect question. You are accustomed to thinking that in our world there is globally one time that flows the same for everyone, that by this time we measure the speed of movement of bodies. That is, if you take many good clocks and synchronize them all, then they will continue to go synchronously forever. From your school curriculum you know that motion is relative. And if you are flying, for example, in an airplane with the windows rolled up, it is impossible to determine whether you are flying or not, because all reference systems moving relative to one, where free bodies do not accelerate, are equal (they are called inertial). This picture of the world (Galilean mechanics) dominated physics until the beginning of the 20th century. A lot happened then and in the end I had to abandon this picture. But what is really happening and what was wrong?
But in fact there is light, and it behaves in a completely counterintuitive way. Its speed is always equal to the speed of light. For example, you are sitting on the bank of a river, the current speed is 1 m/s. A boat is floating along the river with the current, the speedometer shows 10 m/s. At what speed is the boat moving relative to you? Apparently 11 m/s. But light doesn't behave that way. If you shine a flashlight, you will measure the speed of light to be about 300,000 km/s. And on the boat, passengers will measure the same speed. And even if an airplane flies above you, on the airplane the speed of the same ray of light will be 300,000 km/s. And on a satellite that flies at a speed of, say, 8 km/s relative to the Earth, the speed of the same ray will not be 299,992 km/s, but the same 300,000 km/s. Just like that. This is called the constancy of the speed of light.
How can this even be? A difficult question, answered by the theory of relativity. The fact is that Galileo's mechanics are not correct. There is no absolute time scale, and it is not always possible to synchronize clocks. For example, if someone is moving at high speed relative to you, you will see that time passes slower for him, as if the film was run at a speed of not 24 frames per second, but 20 or less. He won’t feel it and won’t be able to understand it to himself. This is a purely relative effect. The same for him, you, oddly enough, will also look inhibited. The situation is symmetrical, you are also moving relative to him. And this is observed experimentally, for example, a neutron, with a half-life of 16 minutes, lives much longer if it is accelerated to high speeds. Precisely because for observers his time flows more slowly. And this is not the only effect. For example, events that are simultaneous for you will not be simultaneous for a moving observer and vice versa. A moving observer will appear compressed in the direction of movement. And so on, so on, so on. All these strange things happen because both distance scales and time scales are relative and different for different observers at different speeds. But nevertheless, all inertial frames of reference are equal. Everything depends only on relative speeds and movements.
In more detail, if you are interested, you should deliberately delve into the special theory of relativity. Her mathematics is not much beyond the scope of the school curriculum. You can understand it quantitatively solely with the help of school algebra, even derivatives are not needed. It is worth reading, for example, the corresponding Feynman lectures from the second volume or from various collections. Or any more or less passable university textbook on mechanics (mechanics is taught in the first semester, first year, there is nothing super complicated in it). Maybe there are some other good books, but I won’t name them right away.
So the answer to your original question is that when bodies move relative to you at high speed, the mechanics for them are completely different, unlike ordinary ones, completely unintuitive and non-obvious. And for all observers the speed of light is constant. Therefore, there cannot be an observer who moves at the speed of light; for him, light would be at rest and a contradiction would result. And for light it is generally impossible to introduce the concept of time, you can only externally describe it like this. For him, time seems to be infinitely slow, standing still. The criterion is mass, everything massive lives like us, at a constant speed of light relative to itself. For us, everything that does not have a rest mass always moves at the speed of light, but the concept of time does not exist for such objects. So you can speed up and speed up and speed up. And always measure the same speed of light. And from the point of view of, for example, the Earth, your speed will approach the speed of light, but will never reach it. And your time will slow down. And in the direction of movement you will shrink. And many more interesting things.
The speed of light is the most unusual measurement quantity known to date. The first person who tried to explain the phenomenon of light propagation was Albert Einstein. It was he who came up with the well-known formula E = mc² , Where E is the total energy of the body, m- mass, and c— speed of light in vacuum.
The formula was first published in the journal Annalen der Physik in 1905. Around the same time, Einstein put forward a theory about what would happen to a body moving at absolute speed. Based on the fact that the speed of light is a constant quantity, he came to the conclusion that space and time must change.
Thus, at the speed of light, an object will shrink endlessly, its mass will increase endlessly, and time will practically stop.
In 1977, it was possible to calculate the speed of light; a figure was given as 299,792,458 ± 1.2 meters per second. For rougher calculations, a value of 300,000 km/s is always assumed. It is from this value that all other cosmic dimensions are based. This is how the concept of “light year” and “parsec” (3.26 light years) appeared.
It is impossible to move at the speed of light, much less overcome it. At least at this stage of human development. On the other hand, science fiction writers have been trying to solve this problem on the pages of their novels for about 100 years. Perhaps one day science fiction will become a reality, because back in the 19th century, Jules Verne predicted the appearance of a helicopter, an airplane and the electric chair, and then it was pure science fiction!
Light is one of the key concepts of optical physics. Light is electromagnetic radiation that is accessible to the human eye.
For many decades, the best minds struggled with the problem of determining at what speed light moves and what it is equal to, as well as all the calculations that accompany it. In 1676, a revolution occurred among physicists. A Danish astronomer named Ole Roemer refuted the claim that light travels through the universe at unlimited speed.
In 1676, Ole Roemer determined that the speed of light in a vacuum is 299792458 m/s.
For convenience, this figure began to be rounded. The nominal value of 300,000 m/s is still used today.
Under normal conditions for us, this rule applies to all objects without exception, including X-rays, light and gravitational waves of the spectrum that is tangible to our eyes.
Modern physicists studying optics have proven that the speed of light has several characteristics:
- constancy;
- unattainability;
- limb.
Speed of light in different media
It should be remembered that the physical constant directly depends on its environment, especially on the refractive index. In this regard, the exact value can change, because it is determined by frequencies.
The formula for calculating the speed of light is written as s = 3 * 10^8 m/s.
You might be interested in
The speed of light in water differs from the same speed in vacuum. To find out its value, you need to divide the number 299,792,458 by 1.33. The result will be a number 225407 km/s- this is the speed of light propagation in water.
The speed of light in air in km is 1,079,252,848.8 (or 299,700 km/sec). To find it, you need to divide the speed of light in a vacuum by the refractive index of air. The answer can be displayed in either kilometers per hour or meters per second.
Is the speed of light the maximum possible speed?
Many schoolchildren and students wonder: what speed is greater than the speed of light? Is there such a thing at all? The answer is clear: no!
The speed of light propagation in a vacuum is considered an unattainable value. Scientists have not come to a consensus on what can happen to atoms that reach this limit.
Among other things, the researchers found that a particle with mass can approach the speed of a light beam. But she cannot catch up with it, much less exceed it. The maximum speed of light remains unchanged for now.
The closest numerical indicator was achieved in the study of cosmic rays. They were accelerated in specially equipped particle accelerators, taking into account the wavelength.
Why is this number so important? The fact is that vacuum envelops all outer space. Knowing how light behaves in a vacuum, we can imagine what the maximum speed of travel in our Universe is.
Why is it impossible to travel faster than light?
So why is the CPC constant unable to be overcome under normal conditions? Based on the theory, we can safely say that in a situation of excess, the fundamental law of the construction of the world will be violated, to be specific - the law of causality. According to this law, the effect cannot get ahead of its cause.
Let's consider this paradox using a specific example: it cannot happen that a deer first falls dead, and only then the hunter shoots, killing him. So, when the SRS increases, the unfolding actions should begin in the reverse order. As a result, time must go backwards, and this contradicts all established laws of physics.
Einstein and vacuum: final calculation results
Currently, most people on the planet know that the maximum permissible value for the movement of material objects and various signals is the speed of light in a vacuum. Who was the first to think of this?
The idea that it is impossible to exceed the speed of light was expressed by the great physicist Albert Einstein. He formalized his observations and called them the theory of relativity.
Einstein's greatest theory is still unshakable. It will remain so until real evidence is presented that it is possible to transmit a signal at a speed exceeding the SPC in a vacuum. This moment may never come.
However, several studies have already been conducted that foreshadow a disagreement with some points of Einstein's most famous theory. Measuring superluminal speeds is already possible under given conditions. It is noteworthy that the theory of relativity is not completely violated.
The first successful measurement of the speed of light in a vacuum was made by Olaf Roemer in 1676. He calculated the speed of light from the motion of Jupiter's satellites. Modern value c = 299792458 m/s.
How the speed of light was measured
How is the speed of light measured?
Philip Gibbs
The speed of light c in vacuum has not been measured. It has an exact fixed value in standard units. By international agreement in 1983, a meter is defined as the distance traveled by light in a vacuum in a time of 1/299,792,458 seconds. The speed of light is exactly 299792458 m/s. An inch is defined as 2.54 centimeters. Therefore, in non-metric units, the speed of light also has an exact value. This definition makes sense only because the speed of light in a vacuum is constant, and this fact must be confirmed experimentally (see Is the speed of light constant?). It is also necessary to experimentally determine the speed of light in media such as water...
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Although in everyday life it is rare for anyone to directly calculate what the speed of light is, interest in this issue manifests itself in childhood. Surprisingly, we all encounter the sign of the speed constant of propagation of electromagnetic waves every day. The speed of light is a fundamental quantity due to which the entire Universe exists exactly as we know it.
Surely, everyone, watching in childhood a flash of lightning and the subsequent clap of thunder, tried to understand what caused the delay between the first and second phenomenon. Simple mental reasoning quickly led to a logical conclusion: the speed of light and sound are different. This is the first introduction to two important physical quantities. Subsequently, someone received the necessary knowledge and could easily explain what was happening. What causes the strange behavior of thunder? The answer is that the speed of light, which is about 300 thousand km/s, is almost a million times faster than...
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epigraph
The teacher asks: Children, what is the fastest thing in the world?
Tanechka says: The fastest word. I just said, you won’t come back.
Vanechka says: No, light is the fastest.
As soon as I pressed the switch, the room immediately became light.
And Vovochka objects: The fastest thing in the world is diarrhea.
I was once so impatient that I didn’t say a word
I didn’t have time to say anything or 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 right away, as a spoiler, I’ll give away the terrible secret of the answer to it - no one knows exactly why. The speed of light is taken, i.e. is mentally accepted as 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 of relativity, which has been pissing scientists off for a hundred years, allowing Einstein to stick his tongue out at the world and grin in his grave with impunity above...
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Quick answer: 300,000 km per second.
The speed of light in a vacuum is the absolute value of the speed of propagation of electromagnetic waves in a vacuum. It refers to the fundamental physical constants that characterize not just individual bodies or fields, but the properties of the geometry of space-time as a whole. According to modern concepts, the speed of light in a vacuum is the maximum speed of particle movement and the propagation of interactions.
The most accurate measurement of the speed of light based on a reference meter was carried out back in 1975. Then it became known that the speed of light is 299,792,458 m/s. Or 1,079,252,848.8 km/h. In conversation, we are usually not so scrupulous, and therefore we speak more simply: the speed of light is 300,000 kilometers per second (rounded value).
It is interesting that they knew about the speed of light back in ancient times. The first estimate of the speed of light was given by astronomer Olaf Christensen Römer when he noticed that eclipses of Jupiter’s satellite Io were delayed...
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Having received many thanks from the science-starved population of this country, we decided to continue the educational program for those who in childhood dreamed of becoming a scientist, but somehow it didn’t work out. To spite all specialists and candidates, violating every single methodology and rule of good scientific text, we write in an accessible language about the discoveries of modern (and not so modern) science and attach random pictures from the Internet.
Today we will talk about the speed of light, why it is constant, why everyone “runs” at this speed and is surprised by it, and what the hell is going on.
As a matter of fact, attempts to measure the speed of light began a very long time ago. All sorts of Keplers and others believed that the speed of light is infinite, and Galileo, for example, believed that it was possible to determine the speed, but it was difficult, since it was very large.
Galileo and others like him turned out to be right. In the 17th century, a certain Roemer inaccurately calculated the speed of light when observing the eclipses of the moons of Jupiter. Well, in the future...
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Artist's representation of a spaceship making the jump to the "speed of light." Credit: NASA/Glenn Research Center.
Since ancient times, philosophers and scientists have sought to understand light. In addition to trying to determine its basic properties (i.e. whether it is a particle or a wave, etc.), they also sought to make finite measurements of how fast it moves. Since the late 17th century, scientists have been doing just that, and with increasing precision.
In doing so, they gained a better understanding of the mechanics of light, and how it plays an important role in physics, astronomy and cosmology. Simply put, light travels at incredible speeds and is the fastest moving object in the universe. Its speed is a constant and impenetrable barrier and is used as a measure of distance. But how fast is it moving?
Speed of light (s):
Light moves at a constant speed of 1,079,252,848.8 km/h (1.07 billion). Which turns out to be 299,792,458 m/s....
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It is limited by the magnetic and dielectric constant of vacuum. с = (e0*mu0*)^-2
oh, I meant to say with = (e0*mu0*)^-0.5
By the way, it’s interesting: the Universe (i.e. space) is infinite, but why can’t the speed be infinite?
Maybe it (the universe/speed) is infinite, but limited?
Because light and the universe are weakly connected to each other. But the speed of the universe is, yes, infinite))
what is the speed of the universe?
The speed at which the universe moves))
Never mind, for an infinite body the concept of speed makes no sense...
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We often say that the speed of light is maximum in our Universe, and that there is nothing that could move faster than the speed of light in a vacuum. And even more so - us. Approaching near-light speed, an object acquires mass and energy, which either destroys it or contradicts Einstein's general theory of relativity. Let's say we believe in this and look for workarounds (like creating a warp engine or understanding the paradoxes of quantum mechanics) in order to fly to the nearest star not for 75,000 years, but for a couple of weeks. But since few of us have a higher physics education, it is not clear: why do people on the streets say that the speed of light is maximum, constant and equal to 300,000 km/s?
There are many simple and intuitive explanations for why things are this way, but you can start to hate them. An internet search will lead you to the concept of “relativistic mass” and how it requires more force to accelerate an object that is already moving at a high speed. This...
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1 kilometer per hour [km/h] = 0.277777777777778 meters per second [m/s]
Initial value
Converted value
meter per second meter per hour meter per minute kilometer per hour kilometer per minute kilometer per second centimeter per hour centimeter per minute centimeter per second millimeter per hour millimeter per minute millimeter per second foot per hour foot per minute foot per second yard per hour yard per minute yard per second mile per hour mile per minute miles per second knot knot (UK) speed of light in vacuum first cosmic speed second cosmic speed third cosmic speed speed of rotation of the Earth speed of sound in fresh water speed of sound in sea water (20°C, depth 10 meters) Mach number (20°C, 1 atm) Mach number (SI standard)
More about speed
General information
Speed is a measure of the distance traveled in a certain time. Speed can be a scalar quantity or a vector quantity - the direction of movement is taken into account. The speed of movement in a straight line is called linear, and in a circle - angular.
Speed measurement
Average speed v found by dividing the total distance traveled ∆ x for total time ∆ t: v = ∆x/∆t.
In the SI system, speed is measured in meters per second. Kilometers per hour in the metric system and miles per hour in the US and UK are also widely used. When, in addition to the magnitude, the direction is also indicated, for example, 10 meters per second to the north, then we are talking about vector velocity.
The speed of bodies moving with acceleration can be found using the formulas:
- a, with initial speed u during the period ∆ t, has a finite speed v = u + a×∆ t.
- A body moving with constant acceleration a, with initial speed u and final speed v, has an average speed ∆ v = (u + v)/2.
Average speeds
Speed of light and sound
According to the theory of relativity, the speed of light in a vacuum is the highest speed at which energy and information can travel. It is denoted by the constant c and is equal to c= 299,792,458 meters per second. Matter cannot move at the speed of light because it would require an infinite amount of energy, which is impossible.
The speed of sound is usually measured in an elastic medium, and is equal to 343.2 meters per second in dry air at a temperature of 20 °C. The speed of sound is lowest in gases and highest in solids. It depends on the density, elasticity, and shear modulus of the substance (which shows the degree of deformation of the substance under shear load). Mach number M is the ratio of the speed of a body in a liquid or gas medium to the speed of sound in this medium. It can be calculated using the formula:
M = v/a,
Where a is the speed of sound in the medium, and v- body speed. Mach number is commonly used in determining speeds close to the speed of sound, such as airplane speeds. This value is not constant; it depends on the state of the medium, which, in turn, depends on pressure and temperature. Supersonic speed is a speed exceeding Mach 1.
Vehicle speed
Below are some vehicle speeds.
- Passenger aircraft with turbofan engines: The cruising speed of passenger aircraft is from 244 to 257 meters per second, which corresponds to 878–926 kilometers per hour or M = 0.83–0.87.
- High-speed trains (like the Shinkansen in Japan): such trains reach maximum speeds of 36 to 122 meters per second, that is, from 130 to 440 kilometers per hour.
Animal speed
The maximum speeds of some animals are approximately equal to:
Human speed
- People walk at speeds of about 1.4 meters per second, or 5 kilometers per hour, and run at speeds of up to about 8.3 meters per second, or 30 kilometers per hour.
Examples of different speeds
Four-dimensional speed
In classical mechanics, vector velocity is measured in three-dimensional space. According to the special theory of relativity, space is four-dimensional, and the measurement of speed also takes into account the fourth dimension - space-time. This speed is called four-dimensional speed. Its direction may change, but its magnitude is constant and equal to c, that is, the speed of light. Four-dimensional speed is defined as
U = ∂x/∂τ,
Where x represents a world line - a curve in space-time along which a body moves, and τ is the "proper time" equal to the interval along the world line.
Group speed
Group velocity is the speed of wave propagation, describing the speed of propagation of a group of waves and determining the speed of wave energy transfer. It can be calculated as ∂ ω /∂k, Where k is the wave number, and ω - angular frequency. K measured in radians/meter, and the scalar frequency of wave oscillation ω - in radians per second.
Hypersonic speed
Hypersonic speed is a speed exceeding 3000 meters per second, that is, many times faster than the speed of sound. Solid bodies moving at such speeds acquire the properties of liquids, since, thanks to inertia, the loads in this state are stronger than the forces that hold the molecules of a substance together during collisions with other bodies. At ultrahigh hypersonic speeds, two colliding solids turn into gas. In space, bodies move at exactly this speed, and engineers designing spacecraft, orbital stations and spacesuits must consider the possibility of a station or astronaut colliding with space debris and other objects when working in outer space. In such a collision, the skin of the spacecraft and the spacesuit suffer. Hardware developers conduct hypersonic collision experiments in special laboratories to determine how intense impacts the suits can withstand, as well as the skin and other parts of the spacecraft, such as fuel tanks and solar panels, testing their strength. To do this, spacesuits and skin are exposed to impacts from various objects from a special installation at supersonic speeds exceeding 7500 meters per second.
