The Theory of Relativity: The greatest discovery of all times - Part 2

Introduction

The Theory of Relativity, being one of the greatest advancements in physics, could not be explained in a single post so to avoid confusion, I shifted this part into a second post.

The new definition of gravity

When Isaac Newton saw an apple following, he thought, ‘Would the moon fall too?’. That’s where the concept of Gravity came to be. But Newton defined it as a ‘mysterious force that the things that have mass possess which pulls things towards them’. But with the Special Theory of Relativity, Gravity was no more ‘mysterious’ or a force. Things were attracted to a heavy object just because it warps space-time to let the item fall into it. The normal visualization of this which you see on a sheet is not as accurate as the 3D interpretation.

Image source - Google | Image by - Business Insider | The warping of space-time as shown often

Image source - Google | Image by - Forbes | The actual warping of space-time in 3D

Absolute space and time

As per Newton, space and time were absolute. But Einstein said that space and time are relative. Absolute space includes absolute motion and absolute motion. To take an example of non-absolute rest and motion, imagine you are on a bus. You are sitting at rest. But the bus is moving means that you are moving. Now suppose the bus stops. Now you are at rest relative to the people inside as well as outside the bus. But the earth is still moving. And the solar system is also moving. And the Milky Way galaxy is also moving. So one can never be in absolute rest. Does this mean you are in absolute motion? No! You are in motion relative to the person who sees the earth but relative to the person sitting beside you, you are at rest! Some parts of the relativity posts may confuse you. And don’t worry! After all, they were made by the most brilliant scientist of the 20th century. Feel free to read the post as many times as you like. Relative time can be explained in another topic known as time dilation.

Time Dilation

Time slows down as one accelerates in velocity. So imagine this, there is a clock which works weirdly. This clock measures one second when a light beam moving back and forth in it goes from one point to the other. The speed of light is constant for all. So now, suppose you are on one of the clocks and your partner (say, Tim) is on another such clock which is moving. Due to this, the light on Tim’s clock has to travel a greater distance. But if time is absolute, then the speed of light will have to increase on Tim’s clock to keep time the same for both. But the speed of light is constant so time will compromise and will slow down for Tim.  You would feel his clock slow. But for him your clock is fast and his clock is correct. But then who is wrong? Actually, both of you are right!

Criticism received for his theories

Einstein also received a lot of criticism for his special theory of relativity which talked about non-absolute space and time. People said things like ‘He is not even a working physicist!’ as he was a clerk in a patent office and ‘Newton has been correct for thousands of years. How dare he oppose him!’. Some pointed out his culture. They said that all that Einstein said was ‘Jewish science’. Even Einstein was not satisfied with his first theory as it applied only when people moved in a straight line and gravity was not there. So he created the General Theory of Relativity.

The theory of General Relativity is one of humanity's greatest truths. Though it is not compatible with quantum mechanics, it has been proven to be the best theory that identifies Gravity in its real form.