Classical physics is of the opinion that any observer, regardless of location, will receive the same results in their measurements of time and extent. The principle of relativity states that observers can get different results, and such distortions are called "relativistic effects". When approaching the speed of light, Newtonian physics moves aside.
Speed of light
Scientist A. Michelson, who measured the speed of light in 1881, realized that these results would not depend on the speed at which the radiation source was moving. Together with E.V. Morley Michelson in 1887 conducted another experiment, after which it became clear to the whole world: no matter in which direction the measurement is taken, the speed of light is everywhere and always the same. The results of these studies were contrary to the ideas of physics of that time, because if light moves in a certain medium (ether), and the planet moves in the same medium, measurements in different directions cannot be the same.
Later, the French mathematician, physicist and astronomer Jules Henri Poincaré became one of the founders of the theory of relativity. He developed the Lorentz theory, according to which the existingthe ether is motionless, so the speed of light relative to it does not depend on the speed of the source. In moving frames of reference, Lorentz transformations are performed, and not Galilean ones (the Galilean transformations accepted until then in Newtonian mechanics). From now on, Galilean transformations have become a special case of Lorentz transformations, when moving to another inertial frame of reference at a low (compared to the speed of light) speed.
The relativistic effect of length contraction, also called the Lorentz contraction, is that for the observer, objects moving relative to him will have a shorter length.
Albert Einstein made a significant contribution to the theory of relativity. He completely abolished such a term as "ether", which until that time was present in the reasoning and calculations of all physicists, and he transferred all concepts of the properties of space and time to kinematics.
After the publication of Einstein's work, Poincaré not only stopped writing scientific papers on this topic, but also did not mention the name of his colleague in any of his works, except for the only case of reference to the theory of the photoelectric effect. Poincare continued to discuss the properties of the ether, categorically denying any publications of Einstein, although at the same time he treated the greatest scientist with respect and even gave him a brilliant testimonial when the administration of the Higher Polytechnical School in Zurich wanted to invite Einstein to become a professor at the educational institution.
Even many of those who are completely at odds with physics and mathematics, at least in general terms, what the theory of relativity is, because it is perhaps the most famous of scientific theories. Its postulates destroy ordinary ideas about time and space, and although all schoolchildren study the theory of relativity, it is not enough just to know the formulas to understand it in its entirety.
The effect of time dilation was tested in an experiment with a supersonic aircraft. The exact atomic clocks on board, after returning, began to lag behind by a fraction of a second. If there are two observers, one of which is standing still, and the second is moving at some speed relative to the first, the time for the observer who is stationary will go faster, and for the moving object, the minute will last a little longer. However, if the moving observer decides to go back and check the time, it will turn out that his watch shows a little less than the first. That is, having traveled a much greater distance on the scale of space, he "lived" less time while moving.
Relativistic effects in life
Many believe that relativistic effects can only be observed when the speed of light is reached or approaching it, and this is true, but you can observe them not only by accelerating your spaceship. On the pages of the scientific journal Physical Review Letters, you can read about the theoretical work of the Swedishscientists. They wrote that relativistic effects are present even in a simple car battery. The process is possible due to the rapid movement of electrons of lead atoms (by the way, they are the cause of most of the voltage in the terminals). This also explains why, despite the similarities between lead and tin, tin-based batteries do not work.
The speed of rotation of electrons in atoms is rather low, so the theory of relativity simply does not work, but there are some exceptions. If you move further and further along the periodic table, it becomes clear that there are quite a few elements heavier than lead in it. A large mass of nuclei is balanced by increasing the speed of electrons, and it can even approach the speed of light.
If we consider this aspect from the side of the theory of relativity, it becomes clear that the electrons in this case must have a huge mass. This is the only way to preserve the angular momentum, but the orbital will shrink along the radius, and this is indeed observed in heavy metal atoms, but the orbitals of "slow" electrons do not change. This relativistic effect is observed in the atoms of some metals in s-orbitals, which have a regular, spherically symmetric shape. It is believed that it is as a result of the theory of relativity that mercury has a liquid state of aggregation at room temperature.
Objects in space are from each otherover vast distances, and even when moving at the speed of light, it will take a very long time to overcome them. For example, to reach Alpha Centauri, the nearest star to us, a spacecraft at the speed of light will take four years, and to reach our neighboring galaxy, the Large Magellanic Cloud, it will take 160,000 years.
It is still possible to fly to Alpha Centauri and back, because it will take only eight years, and for the inhabitants of the ship, who feel the effect of time dilation, this period will be much less, but upon returning from a trip to a neighboring galaxy, astronauts will find that in their native the planet has already passed three hundred and twenty thousand years, and human civilization, perhaps, has long ceased to exist. Thus, relativistic effects allow people to travel through time. This is considered one of the main problems of space exploration, because what is the point of conquering outer space if there is no way to return?
In addition to the famous time dilation, there is also the relativistic Doppler effect, according to which, if the source of waves starts moving, then the waves propagating towards this movement will be perceived by the observer as "compressed", and towards the removal of the wavelength will be increased.
This phenomenon is typical for any waves, so it can be observed in the example of sound in everyday life. The reduction of a sound wave is perceived by the human ear as an increase in tone. So,when the signal of a train or car is heard from afar, it is lower, and if the train passes by the observer, while making a sound, then its height will be higher at the moment of approach, but as soon as the objects equalize and the train begins to move away, the tone will sharply become lower and further will continue on lower notes.
These relativistic effects are due to the classical analogue of the change in frequency when the receiver and source move, as well as relativistic time dilation.
Among other things, modern physicists are increasingly discussing the magnetic field as a relativistic effect. According to this interpretation, the magnetic field is not an independent physical material entity, it is not even one of the manifestations of the electromagnetic field. The magnetic field from the point of view of the theory of relativity is just a process that occurs in space around point charges due to the transfer of an electric field.
Proponents of this theory believe that if C (the speed of light in vacuum) were infinite, then the propagation of interactions in speed would also be unlimited, and as a result, no manifestations of magnetism could arise.