What is the Special Theory of Relativity?

The Principle of Relativity was introduced by Galileo Galilei 300 years before Albert Einstein first published his paper On the Electrodynamics of Moving Bodies in 1905.

There is no absolute reference system in Galileo's Principle of Relativity. Consider A and B observers to understand this better. According to observer A, observer B is going to the right with v speed. In the same way, according to observer B, observer A is going to the left with v speed. Both observers are right to say that the other observer is moving, since there is no absolute reference system, so it is possible to switch between fixed reference systems. Here, the term “fixed reference system referans refers to reference systems that do not accelerate, ie do not change the speed, since the accelerating motion in the Galileo Transformations cannot be regarded as a reference system.

Imagine yourself in a train to understand why, the train's windows are closed with a black curtain (you are not in the dark because there is light inside the train). Assume that the train does not have accelerated movements such as swaying, turning, accelerating or decelerating. On a train like this, how do you know if the train is going at a constant speed or is it stopping?

The answer is quite simple: You can't understand. You can do all kinds of experiments inside the train, but you can't tell if the train is moving unless you look outside. Likewise, when you look out the window, you can say that the train (and therefore you) is not moving, and that the whole world is going to the other side because, as we said before, there is a switch between fixed reference systems.

But you cannot say the same in an accelerated train. To understand this, assume that your train is accelerating. If you have already taken the subway, you will feel a backward force as you know. But in an experiment where the train (and you) stop but the whole world accelerates to the other side, you don't feel such a force. So when you're inside the train, you can tell whether the train is accelerating without saying dışarı I don't feel force in any direction, so the train doesn't accelerate. ”Or orum I feel force in one direction, then the train is accelerating. Adan

In another thought experiment, suppose that you turn your arms around and turn around. You feel a "centrifugal force" because you are accelerating as you rotate, so you feel a force out of your arms (and your head is spinning; but that's not the point). But you will not feel such a force if the whole world revolves around you while you are standing.

The three laws (now known as Newton's Laws) published by Isaac Newton in the Principia are consistent with the Galileo transformations. However, the four equations (now known as Maxwell's Equations) that combine electricity and magnetism introduced by James Clerk Maxwell in his 1865 book A Dynamical Theory of the Electromagnetic Field did not match Galileo's transformations.

For example, imagine a charged object, because the object is charged, it emits an electric field. Let's say that a skateboarder with a certain speed for you threw forward. When charged objects travel at a constant speed, they form a magnetic field. You can find the magnetic field that the object emits based on its speed, but when you calculate this magnetic field from the skateboarder's reference system, the result is different.

Another problem of Maxwell's Equations with Galileo Transformations is related to the speed of electromagnetic waves. According to Maxwell's Equations, electromagnetic waves are propagated at the speed of light (and even therefore visible light is a kind of electromagnetic wave); however, which reference system this speed is based on remains a question mark. For this reason, scientists thought that space is an object called an ether, that light is scattered in this matter, and that it spreads at the speed of light according to the reference system.

That's why Michelson and Morley designed an experiment (now known as the Michelson-Morley Experiment) in 1887 to show the existence of the prisoner. In this experiment, they sent a ray of light to the side of Earth and a ray of light to the other side. It was expected that the speed of light sent to the side of the Earth would be faster than the speed of light sent to the other side. But Michelson and Morley came up with a different result. The speed of light sent to both sides remained the speed of light.

The result of the experiment was that the speed of light was independent of the speed of the light source. Some scientists thought that the work also moved with the Earth, and therefore the speed of light remained constant. Hendric Lorentz tried to solve this problem by revealing that objects close to the speed of light shorten in space. But all these solutions alone were not enough. The young Albert Einstein, then a civil servant at the Swiss Patent Institute, published his article On the Electrodynamics of Moving Bodies in 1905, described as annus mirabilis. In his article he put forward his equations through only two postulates:

• The laws of physics are the same in every fixed reference system (Galileo Principle).
• The speed of light is the same for each fixed reference system (Michelson-Morley Experiment).

Einstein, who formulated his equations according to these two postulates, showed that time and space are not invariant as thought since Newton and may be different for each reference system.

Result of Special Theory of Relativity

Let's look at the results of the Special Theory of Relativity, which radically changes our ideas about space and time and opens up our horizons:

• Space and time cannot be handled separately. Space - time is a whole and every object moves at the speed of light in space - time. Therefore, an object moving in space moves more slowly in time.
• If observer B is traveling at a constant speed relative to observer A, time is slower for observer B than observer A. However, according to observer B, time is slower for observer A, not for him.
• Simultaneity may vary between observers. An event that occurs simultaneously for one observer may not occur simultaneously for another observer
• According to a certain observer, the length of the body travels at a constant speed in the direction of travel.
• They never reach the speed of light because it requires infinite momentum and energy to bring mass objects to the speed of light. Massless objects have to go at the speed of light.
• If we energize an object while it is stationary (without a velocity), its mass increases as much as the speed of light divided by the square. (E=mc²)

This theory, however, was unable to explain the reference frames that act in a momentum. In 1915, Einstein developed the General Theory of Relativity and showed that space-time is bent and twisted by mass objects, and what we call “gravitational force aslında is only the way that space-time objects move in space.