# The history of Einstein’s special relativity

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What forced Einstein to give special relativity, transition of science from absolute time to relative time. Twin paradox and time dilation.

When Newton discovered the laws of motion and the gravitational law, he precisely explained the elliptical motion of planets mathematically. He also considered time as an absolute quantity in universe.

Maxwell derived the equations of electromagnetism and these equations wonderfully became consistent with the essence of light and breakthrough of considering light as electromagnetic wave happened. But there were some problems for two centuries. How light travels through space? When the sound and other waves cease to pass space why the light can pass through it? In the 20th century, physicists came up with the hypothesis of Ether, which means that space is not some kind of emptiness, but there is something invisible there and that is Ether.

Einstein remained skeptical to the hypothesis of Ether. He started with a fundamental question: is there anything which is absolute in the nature? Let’s assume that there is nothing in universe and that one hypothetical ball is traveling with high speed. But how we would measure its speed? We couldn’t because for doing it we must have some other object relative to the ball. From there, he concluded that motion is a relative quantity and it only exists in relation with other objects. Likewise, if there is one ball in motion and nothing else exists you can’t also measure time because it is also relative. For example, there must be a difference between time of Jupiter and Earth, because of their motion around the Sun.

Newton had done remarkable work for measuring the motion of particles at normal speeds but Einstein questioned what will happen if somebody started to move with high velocity nearly like speed of light. For answering to that question he came up with what we know today as the “Special theory of relativity.” It is based on two postulates:

1. The laws of physics are the same in all inertial frames of reference.

2. The speed of light in free space has the same value c in all inertial frames of reference.

Time was no more absolute which could be delayed by the increasing velocity of an object ,which is also known as time dilation. There is twin paradox for explaining the time dilation which is like that:

“There are two identical twins, one of whom makes a journey into space in a high-speed rocket and returns home to find that the twin who remained on Earth has aged more.” Rehan Naqvi