Space-Time: The Fourth Dimension Theory | Einstein's Theory Of Special Relativity | Episode: 01

THE SCIENTISTS WHO BEGAN IT ALL

Albert Einstein, also known as the Genius, gave the world his theory of relativity and opened the gate to a new world in Physics. He showed us that the universe was not just bound to the three dimensions we have i.e. length, breadth and height, but there is a special fourth dimension present around us: Time. And Today we are going to see what exactly is the space time fabric according to the General Relativity theory given by him.

Now, Aristotle said that "The natural state of an object is to remain at rest". Which means that whenever an object is in motion, it tries to come at rest on its own. The natural state is at rest. This seemed obvious to everyone as: if you throw a ball, it will come at rest, if you stop pedaling, your cycle will come to rest.

But at the time of Aristotle, the concept of friction was undiscovered. That is why this idea seemed so convincing. So much, that before Galileo, no one even thought to test the assumption made by Aristotle. Galileo Galilei was the first person to deny and say that the natural state of any object is NOT at rest. He said that things are made to come at rest. For support of his answer, he even proclaimed that if Aristotle was right, then why didn't the planets that revolve around the sun come to rest. That was the time when a revolution in science took place. People got to know more about motion and friction.

Galileo also made a lot of real contributions in science. He made the Galilean Relativity. Albert Einstein himself had to take help of the Galilean relativity to prove his own Theory of Relativity. The Galilean Relativity, also known as the Principle of Relativity, theorized that every observer of a motion is correct in their point of view. This was more popularly known as the Frame of Reference. Frame of reference is such a complicated but very important topic that the whole Physics is dependent on it.

Now, here comes Isaac Newton, another great genius who has got a lot of stuff named after him. Anyways, Newton introduced two mathematical ideas to study motion clearly. Absolute Space And Absolute Time. Now, absolute space and absolute time is a concept in physics and a philosophy about the properties of the universe. According to Newton, absolute time exists independently of any perceiver and progresses at a consistent pace throughout the universe. And absolute space is a space that is not affected by what occupies it or occurs within it. But before you start getting confused about absolute space and time, you should know that the Theory of Relativity had already disproved the ideas of absolute space and time. What the SPECIAL relativity theory said was that space and time are not two different entities. We'll look deeper in them in a while.

According to Newton, light is an entity that moves with infinite speed which behaved as a particle. But, in 1676, Ole Christensen Romer first time in the history of the world, measured the speed of light. Later light was proved to be a wave in 1865 by James Clerk Maxwell in which he used his theory of electrodynamics in which he said that light is a wave which was created by the electric fields and magnetic fields' vibrations. Maxwell stated that light moves in absolute motion. Whereas Newton stated that motion is always relative. This created confusion amongst people. So to prove what he was saying, Maxwell claimed of a medium that was invisible but was present everywhere in the universe. He called this medium: Aether. According to him, the way sound waves get produced by the vibrations in air, the same way light waves get produced by the vibrations in Aether. But again, the problem became that there was no prove for the existence of aether. Some years later, the Michaelson-Morley experiment disproved the existence of aether. It showed that there was nothing called aether.

But then came Einstein with his Special Theory of Relativity. He said that space and time are not two different but the same and dependent entities. There are three things that are mainly focused in the Special relativity theory. Event, spacetime and light cone.

Space time is said to be a coordinate surface which is made up of many points. We need 4 different numbers to represent the points in the space time. And that is why we say that the universe has 4 dimensions. Each point in the space time is known as the spacetime event.

Contrary to Newton's thoughts and beliefs, Einstein said that spacetime gave rise to two new things: Light cone and proper time. Proper time is the observer's self personal time and light cone is the relativistic version of the absolute space concept.

The above image illustrates briefly about the Light Cone.

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SPACETIME EXPLAINED IN BRIEF

To tell someone your position or rather the geographical position mathematically, you'd say your x, y and z coordinates which is basically the length, breadth and height. The 3 dimensions. However, what if, a fourth dimension, time, is added to the mix! This is the idea on which the concept of Space-Time is based. First what is time? Time is something that proceeds independent of anything. It is the thing that goes on even when nothing is going on. Just think about it deeply.

So, in 1905, Einstein proposed a widely popular theory that the speed of light is independent of the motion of all observers. He also told that space and time are interconnected in a single continuum. This is known as the Special Theory Of Relativity. Einstein said that space and time are interwoven together into a 3D fabric thingy called "space-time". According to this theory, time, which has traditionally been considered as an independent entity according to the principles of classical physics, is affected when a body moves through space. This is because, according to this theory, time and space are connected and come from one single entity called spacetime.

One of the very popular examples of this is, if you were able to move with the speed of light (300000 km/s), hypothetically, then, time would slow down for you. This is the basis of "Time Travel"! Einstein also hypothesized that observers in relative motion with each other will disagree on the timing of the simultaneous events. Simply put, if one observer says that they observed two given events occur at the same time, another observer, who is in relative motion with the first one, will disagree, saying that those events happened at different times.

Einstein then did a miraculous thing! He started researching more about massive and heavy objects in the universe. He related them with the space time fabric and introduced gravity into the mix. This was his General Theory Of Relativity which was given by him in 1915, a decade after he published the theory of Special Relativity (in 1905).

According to Isaac Newton, gravity was a force that exists between any two bodies in the universe. However, according to the General Relativity Theory, all objects in the universe are a distortion in the spacetime. And this distortion creates gravity - a pulling force. The heavier the objects are, the more deeper they go into the fabric, and as they go more down, warping the spacetime fabric, thus, gravity also increases.

There are a lot of cool stuff related to Spacetime! When light bends around an enormous object, say, a black hole, the object acts as a lens. This is known as Gravitational Lensing. This helps us see objects that lie millions of kilometers behind the object operating as a lens.

Even Earth, through its rotational motion on its axes, causes a distortion in spacetime that affects space objects around it in its vicinity (the area around a planet). Everything causes distortions in Space time.

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The Theory Of Relativity, or more precisely, The General Relativity and The Special Relativity are a lot to explore in, seriously! We at Enlightened Wisdom: Smart SCIENCE, will explore The Theory Of Relativity completely in our upcoming posts! Having knowledge of all these things will enhance the way you live, in this universe.

Special relativity is an explanation of how speed affects mass, time and space. The theory includes a way for the speed of light to define the relationship between energy and matter — small amounts of mass (m) can be interchangeable with enormous amounts of energy (E), as defined by the classic equation E = mc^2.

Stay Tuned For More. Thanks for reading.

Created By: @Naman Dwivedi

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