Relativity theory explained. Interesting explanation of time, length, mass and space.

In olden Newtonian mechanics mass, time, length, and space were treated as absolute. In the wave theory of light was assumed that a medium was present in space. From the thin theory of light assumed ether exists in space and that ether medium pervaded all space in the universe. 

But that was not correct. There is no medium pervaded in space. After the Michelson and Morley experiment the medium ether was not found, because when light travels in ether medium there is no difference in speed. 

In general sound waves propagate through only a medium but light waves have no need to propagate medium it’s also propagate vacuum. Due to these reasons, the concept of ether and absolute space becomes meaningless.

In Einstein’s view, time, mass, length, and space are interdependent and are not absolute. Einstein’s special theory of relativity deals with objects and systems. The objects and systems are either moving at a constant speed concerning one another or at rest.  

What is time?

We know that time depends upon the rotation of the earth. Time is differing from one planet to another planet. According to classical mechanics, two events occur simultaneously for all observers, irrespective of their position or motion. This means simultaneity is absolute for all observers.

If two observers observe time, the first person is observing in the rest position with an S₁ frame of reference and the other person observes in motion with an S₂ frame of reference. The second observer with a moving clock appears to be slowed down to a stationary observer. 

This is known as time dilation. The clock in the moving spaceship will appear to go slower than clocks on the Earth. This illusion leads many scientists to think about time machines and many creators create time machine movies.

What is mass?

The mass of the body is independent of the motion of the body but the mass of the body is absolute and constant. Newtonian mechanics believes the mass of a body does not change with velocity. 

However, according to Einstein, the mass of the body changes with velocity which means when the object is in motion the mass of the object appears less than in the rest position.

What is space?

We can measure the position or motion of any object in space with the help of a frame of reference. The geometrical form of an object is irrespective of the position motion of the object and observer also. All physics laws are the same in all inertial frames of reference. The velocity of light in free space is a constant in frames of reference.