Einstein's Relativity

Introduction

Imagine you are looking at a clock. The time you are looking at is not the true time; it is rather the time that you saw a very short while ago. The light reflecting off the clock takes time to reach your eyes. Now imagine traveling away from the clock at a certain velocity. The light would take longer to reach your eyes, as both you and the light are moving in the same direction. Because of this, the time you see on this clock is what it was some time ago. However, if you are moving at the speed of light away from the clock, the light from the clock will never reach you. From this phenomenon, you never “see” the time. At this point, time for you, relative to the time where the clock is, has stood still.

Scientists use Einstein’s theory of relativity in order to explain the creation of a black hole as well as the time functions in and outside of a black hole. The theory of relativity combines the theory of Special Relativity and the Equivalence Principle.

Special Relativity

The Special Relativity Theory relatively unifies space and time. Space contracts near mass, as it takes up space; and dilates away from mass, as there is now more space. On the other hand, time dilates near mass and contracts away from it. When mass is stationary, it does not have energy. Energy, after all, is mass with velocity. Masses at high velocities will exert energy lots of energy. When mass is stationary, light has to travel a shorter distance, and when mass is accelerated, time is slowed down as it takes longer to “see the time” (see introduction to this section). Time contracts away from it, as the further away mass and the further light has to travel before it “gives” the time. Time and space are thus inversely related.

Equivalence Principle

The Equivalence theory relatively unifies energy and mass, or in other words acceleration and gravity. Firstly, matter with a certain amount of acceleration becomes energy as it moves so fast that it is capable of exerting power, a property of energy. Einstein’s theory, E = mc^2 or Energy = mass x the acceleration of light (~3.00 x 10^8 m/s) squared. The acceleration of light, in other words, is the speed of light, as light is an absolute value with one speed, and is fast enough to transform mass in to energy. Energy accelerates and matter exerts gravity (gravity is essentially a “downward” acceleration) and thus, if energy and matter are similar, there also is no difference between acceleration and gravity. Imagine an elevator resting on the Earth’s surface with gravity acting on it and an elevator accelerating upwards in space. To an observer inside the elevator with no windows, there is no physical experiment that he or she can perform to distinguish between the two elevators. A person inside the elevator accelerating upwards in space, believes that he or she is at rest as both the elevator and the person are moving up at the same acceleration and relative to the elevator, that person is rest. This is no different to the elevator at rest at Earth. Thus, there is no physical difference between an acceleration of an object and an object with gravity action on it. Even if gravity was pulling the elevator down in the first scenario, both the person and the elevator are moving down at the same pace and, relative to the elevator, the person is not moving.

Theory of General Relativity

The General Theory of Relativity, formed in 1915, combines Special Theory of Relativity of 1905 and the Energy-Mass Equivalence Theory of 1905. It does this by relatively unifying space, time, energy and matter. Matter exerts gravity in general relativity and it is this motion, or acceleration, along with the matter in motion, that distorts the fabric of spaces. Matter in motion is known as energy, so in other words energy helps to create an indent in space-time. As the indent grows, a black hole occurs. Of course, condensed matter with zero volume and infinite density can only create black holes by creating an indent with infinite depth. Time comes in to play as a dimension of a black hole. To a person falling in to the black hole, time will slow down until it freezes (from the perspective of an outside observer), just above the event horizon. For the person at the event horizon, time passes as normal, since it is relative. This is as a person is going in to the black hole at a very fast pace and as one drops down, the speed increases due to gravity to a point where it is traveling at the speed of light (where time stops), above the horizon.