# Where can I learn something about the theory of relativity

## general theory of relativity

### Introduction and repetition

Albert Einstein special theory of relativity represents an extension of classical physics. Its phenomena, namely the Length contraction, Time dilation and relativistic mass increase, are direct consequences of the special relativity principle and the Constancy of the speed of light. Special relativity is a theory about Inertial systems. These are reference systems that are at rest or move in a straight line and uniformly. Einstein felt that his theory did not cover accelerated systems as a flaw in his theory and tried to formulate it more generally. Ten years after the publication of the special theory of relativity, he finally published the in 1915 general theory of relativity.

### The general theory of relativity

The general theory of relativity (GTR) is a highly complex and abstract theory that requires sound physical and mathematical knowledge. This makes it difficult to go into the details. Instead, you become some Phenomena and Consequences get to know the theory.

### The equivalence principle

The GTR is a theory about that Gravity. The Equivalence principle states that it local no difference between the accelerating effect of a force and the one Gravitational field gives. Local here means small enough that tidal forces or the spherical shape of a gravitational field are negligible. The requirement that the heavy mass equal to the inert mass is.

### A thought experiment

Imagine that you are in a closed cabin with no windows and you drop a ball on the floor. Then it is impossible to distinguish whether the ball is attracted by the force of gravity (gravitation) of the earth or whether the cabin floor is moving towards the ball because it is being accelerated upwards.

Likewise, it is impossible to distinguish within the cabin whether you are in the free fall on the earth or in the weightlessness of space.

### Curvature of space-time and its consequences

The ART is also a theory about that Spacetime geometry. According to her, mass or matter causes one Space-time curvature. This is often illustrated by a stretched elastic cloth. As long as it is unencumbered, it is straight and even. But if you put a ball on it, which symbolizes the mass, it bends through and bends yourself. The same thing happens with spacetime near heavy masses like the sun.

Light always spreads along the shortest route between two points. Because of the curvature of the room it can happen that the shortest route no straight line is more. The light is bent.

Another consequence is that gravitational time dilation and Length contraction. In the vicinity of heavier masses, distances become shorter and clocks slower. The astronauts in the international space station ISS are actually aging a bit more quickly than the people on earth.

### Experimental evidence of ART

Einstein's theory revolutionized the common notion of gravity that had existed since Isaac Newton. But first of all it had to be proven experimentally, which was not possible in Einstein's time due to the limited technical possibilities. But there are now a few experimental findingsthat prove the ART with outstanding accuracy.

For one thing, the Light deflection in the gravitational field be proven during a solar eclipse. In the physicists' telescopes, a star was visible that actually lies behind the sun in its shadow. But its light is deflected around you due to the gravity of the sun and is visible to us.

It was also possible to prove that clocks go slower by using the Duration of a radar signal measured from earth to Venus and back again. Since the signal passed the sun, it was slightly slower than it should be.

Finally, it was only through the ART die Perihelion of Mercury to describe correctly.