Motion is the most fascinating and frequent phenomenon of the universe. It was studied by several scientists and philosopher in history. But the understanding of motion got revolutionised when sir Isaac Newton proposed three laws of motion. In which, he proposed that any object continues at rest or motion unless we apply any external force on that object. Any external force may accelerate or decelerate the object. Second law motion explain about the force applied on the object. It explain that a force applied on a object is proportional to the rate of change in its momentum and third law brought the concept of conservation of momentum.
At the same time it was observed that motion is not distinct but relative in characteristics. For e.g. a object in a train is in motion with respect to a observer on platform but same object is at rest for a observer travelling in same train. Well motion's this characteristic brought new questions that are all other physical laws distinct or relative in nature similar to motion?
Well, it was concluded that all physical laws hold true for particular frame of reference. For e.g if a person is experimenting with physical law in a train moving with 50 Kmph and another person experimenting same physical law at platform, then result of that experiment will be same for both frame of references. But when person at platform observes the same experiment experimented in moving train, result won't be same for both person due to different frame of references.
At late 19th century, a scientist James Clark Maxwell found a velocity which was very constant in any frame of reference. During study of motion of charged particle he found that when a charged particle moves around it releases electric and magnetic pulses. He called these pulses electromagnetic waves. On very mathematical calculations of speed of these waves, it was found that their value is equal to value of speed of light. And since then light had been treated as electromagnetic wave.
Well still problem of medium was unsolved and a invisible medium named aether was assumed. But with observations and experiment, scientists belied aether theory and eventually it was proved that light moves with constant speed in vaccum and doesn't need any medium.
Well In beginning of 20th century, the scientist Albert Einstein came with unprecedented ideas. He proposed that if speed of light is constant then it should be same in value for any frame of references and as speed is ratio of distance and time, distance and time must adjust themselves. And this revolutionary idea brought the concept of relativity of time and time dilation.
He proposed that in motion, space would contract but clock would seem ticked more slowly than observer's clock. For e.g. if a rod kept in a moving train would be smaller for observer outside at platform and a clock in train would tick slowly for the same observer.
According to the Einstein, these changes can be observed when speed of medium lies near the speed of light.
Well later , he brought a new idea which changed the course of physics in new era.
With his famous equation E= mc^2, he proposed that even mass is not distinct and relative in nature. He proposed that with increasing speed of any object, its mass too increases. The equation states that any object with mass consist intrinsic energy even when it is in rest. And any loss in energy due to any chemical or nuclear reaction, object will loose corresponding amount of mass. Later, this equation was the fundamental concept for atom bomb.
Introduced with a new term-Aether
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