We all know about Albert Einstein and how genius he was. Relativity is one of his greatest and most significant contribution.

Relativity; yeah I know many people scared by only hearing the world relativity. But trust me, there is nothing ‘complex’ in it. It is as easy as drinking a cup of tea!!!

So, without any further ado, here is my crisped and simplified version of relativity.

Difference between General and Special Relativity:-

When we are taking about ‘Theory of Relativity’, we actually mean the general theory of relativity as special theory of relativity is actually a ‘special case’ of general relativity.

So, what’s the difference between them???

Special relativity is based on two postulates:-

1) The rule of physics and nature of universe is same for all equally fast  

2) In vacuum of space, speed of light is constant irrespective of any observers.

But when gravity and acceleration comes into the play, then we have obey general relativity. According to this theory, massive objects in space will cause warping or distortion of space-time which we all "feel" as gravity.

Einstein's work creates a fundamental link between time and space. We intuitively envisage the universe as three-dimensional (up and down, left and right, forwards and backward) but also with a time component or dimension. The combination of these makes the 4-D environment we experience.

Albert Einstein
Young Albert Einstein

Why the term ‘relativity’ is used??

In a simple sentence, it can be explained as follows: Since, there is no “absolute” frame of reference and everything is relative that’s why the term was coined as ’Relativity’.

Still confused???....Okay let me explain it with an example….
Let suppose you are living in the year 4019, where you are travelling in a bus which is running at the half of the speed of light. You decided to fire a torch beam towards a mirror attached to the ceiling of the bus. It reflected back to a detector. According to the relativity, you can’t feel any effect due to the motion of your bus just like we don’t feel rotation of earth.

But say, your friend saw that you fired that torch beam from outside the bus. He will see something different from what you have seen. He will see the torch beam travels "up" at an angle, strikes the mirror and then travels downwards again at another angle to hit the detector. He will also notice that the light path will be longer and at a more pronounced angle than you will observe in your ship and also the time taken for the laser to reach the detector will be different. Now you may be confused as I have earlier told that in relativity we believe that the speed of light in vacuum is constant. But here, even after being the speed constant, the time is different for the two observers.

Don't get panicked!!!

This phenomenon is called the time dilation. I will dedicate an entire article on it and will explain it with mathematical detail.

In my next article, I will discuss the relation of Mass and Energy with Relativity (remember E=mc2??) so, don’t forget to subscribe to our website and follow me on social media for updates…..

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Thanks for reading.....

See you next time!!!

                                                                    -Ratnadeep Das Choudhury
                                                      Founder and Writer of The Dynamic Frequency