What is the mass of a photon?

People have long been accustomed to the fact that one of the characteristics of any matter is mass. It is inherent not only to such large objects as planets and stars, but also their analogs from the invisible microcosm - protons and electrons. Sir Isaac Newton in his time brilliantly proved the relationship between the gravitational forces and the mass that the body possesses. In the framework of his theory, calculations of celestial mechanics are still successfully performed. A time after the creation of Newton's theory, it became necessary to make substantial modifications to it, since some phenomena remained inexplicable. This problem was solved by A. Einstein, having formulated his "special theory". At the same time, the famous formula E = m * (c * c) appeared, indicating the interrelation of energy, mass and speed of light. Applying the formula to the particles, it quickly became clear that the mass of the photon (particle of light) is zero. At first glance, this contradicts common sense, but everything is just like that. The mass of the photon at zero velocity of its motion is zero. But when a particle overcomes 300 thousand km / s - it acquires the usual mass. However, recently it is believed that the mass of the photon, however, is zero. And then the value that follows from the formula H * v = m * (c * c), is a relativistic mass. So what exactly is the photon mass? The formula, indeed, is. Only it is more complex and the calculation is performed through the momentum value of a given particle.

Since the energy E for a photon is H * v, the mass can be determined from the formula:

M = (H * v) / (c * c)

But since a photon, in fact, being light, can not exist in principle at velocities less than "s" (300 thousand km / s), then the mass found above is correct only for the state of motion.

The impulse can be found through

P = (m * v) / sqrt (1- (v * v) / (c * c))

The presence of a pulse indicates energy. Indeed, if on a summer day you put your hand under the sun's rays, then the heat is clearly felt. It is possible to explain this phenomenon through the transfer of energy by some particle possessing a certain mass moving at a high speed. This is what is observed in relation to light. Therefore, the mass and momentum of the photon are so important, although in this case it is not always possible to operate with the usual concepts.

At numerous forums on the Internet, debates are underway about the nature of light and how to perform calculations. Obviously, the question of what the photon mass is equal to, can not yet be considered closed. New models make it possible to explain the observed processes in a completely different way. In science, this always happens: for example, first the Newton theory was considered complete and logical, but it soon became clear that a number of amendments were needed. Despite this, nothing prevents us now to use the known properties of the light flux: a person has learned to see with devices through the dark; Supermarket doors automatically open before the visitor; Optical networks have achieved previously unprecedented data transfer rates; And special devices have made it possible to convert the energy of sunlight into electricity.

Why does a photon at rest have no mass (and does not exist at all)? There are several explanations for this. First, this conclusion follows from the formulas. Second - since light has a dual nature (it is both a wave and a stream of particles), then, obviously, the concept of mass is completely inapplicable to radiation. Third - a logical: imagine a fast rotating wheel. If you look through it, then instead of spokes you can see a kind of fog, a haze. But you should start to reduce the speed of rotation, as the haze gradually disappears, and after a complete stop, only the spokes remain. In this example, a haze is a particle called a "photon". It can be observed only in motion, and with a strictly defined speed. If the speed falls below 300 thousand km / s, then the photon disappears.