# TIME DILATION

“Time is not the same for everyone”

Time dilation was predicted by Einstein in his special theory of relativity in 1905.

What is time dilation? It actually states that there is no absolute time. Time is relative to the frame of reference from which the observer is measuring time with the clock or generally speaking, time is relative to the observer.

The moving clock runs slower than the clocks at rest by the factor called as Lorenz factor (the moving clock’s time is Lorenz factor times the rest clock’s time). For time dilation to be observable the speed of the clocks must be nearer to the speed of the light. Clocks on earth are having very low speeds compared to the speed of light therefore, time dilation effect is negligible.

If we consider two observers named A and B. observer A is moving with velocity nearer to the speed of light and observer B is at rest and clocks are synchronized with respect to the observers. Observer B sees that A’s clock is running slower than his clock. But in A’s frame of reference, he does not experience any time dilation (his clock works normally)

The main postulate in special relativity is that speed of light is constant for every observer in the universe. Due to this postulate time dilation arises.

Time is relative like motion. Any object’s motion is relative to the frame of reference. In one frame an object may be at rest and, in another frame of reference, the same object can be in motion. Similar to motion the person who is traveling with a speed nearer to the speed of light does not get affected by time dilation with his clock. But the person who is observing sees time dilation.

Time dilation has been confirmed by observing muon the particle which is moving at the speed of light. muon is like an electron but more massive than the electron nearly 200 times more massive than the electron and some experiments have been done with the atomic clock on the earth and atomic clock in the supersonic plane they observed time dilation. The clock on a supersonic jet plane runs slower than the clock on the earth.

Paradoxes like the twin paradox and the pole-barn paradox are related to time dilation. In which twin paradox is most famous (I first read twin paradox in HC Verma book in class 12th. I tried to understand but could not understand at that time). The outline of the twin paradox is that two twins are having same age. one of the twins goes for space travel and the other twin is residing on earth. The twin who goes for space travel and comes back to earth will be aged less than the twin on the earth.

Space travelled twin is younger than the twin on the earth. This age difference is caused by time dilation.

Is time travel possible? In one sense it is possible the twin who did space travel and when came back to earth, actually came into the future on earth (his clocks are running slower). But unfortunately, we cannot travel back into the past.

Einstein incorporated time dilation in his general theory of relativity also and it is called gravitational time dilation (effect of gravity on time).

If you are excited to know more about Einstein’s special theory of relativity. You can check out the course understanding Einstein: the special theory of relativity on the Coursera platform. The link for the course is provided below. The course is amazing and very interesting. I am sure it helps to gain a lot of knowledge. This is a non-credit course and we can get a certificate as well after the completion of the course. And the level of difficulty is very easy who doesn’t have a science background can also complete the course. I urge you to give it a look.