Einstein’s theory of relativity is one of the pillars of modern physics. It is a set of natural laws that Einstein derived with the help of Lorentz transformations and Maxwell’s theory of electrodynamics. The theory of relativity has been probed and has successfully passed many experimental verification tests. Also, some of the predictions of this theory are quite remarkable, including black holes, energy-mass equivalence etc.
So, how did relativity originate? The great scientist and mathematician, arguably one of the best ones there was, Newton, had a certain affinity for time. He said that while space is relative, time is absolute. According to him, time is the same for everyone and everything in the universe. He also said that the effects of gravity will be felt instantaneously. However, with the formation of the theory of electrodynamics, it became apparent that the speed of light was a constant, no matter what the state of the body it was emitted from is.
Einstein grabbed this intuition to develop a set of rules that removed absolute time and sought a relative time. This is called the special theory of relativity. Another postulate of this theory is that the speed of light in a vacuum is constant, and that nothing can travel faster than the speed of light.
However, travelling near the speed of light is enough to result in certain logically weird scenarios. Einstein showed that if an object is moving at speeds comparable to the speed of light, the length of that object reduces, a property which is called length dilation. Similarly, time also seems to slow down when travelling near the speed of light, meaning, if you are to travel on a spaceship at near light speeds and return back to Earth after 50 years, you would have aged very less compared to the man on earth (since even our bodies are governed by biological clocks!). This property is called time dilation.
Another strange property is the accumulation of mass when something travels near light speed. The special theory of relativity predicts that something gets heavier as it travels more faster, a property called mass dilation. While relativity is needed to describe physical events that occur at near light-speeds, classical mechanics provides a good approximation at the speeds we live our lives in.
One of the most famous results of the theory of special relativity is the mass-energy equivalence. This is one of the most famous equations in modern day physics and is simply: E=mc^2. This opened up a new horizon as energy and mass, two previously separate things were shown to be intricately related to each other. In fact, nuclear bombs and nuclear energy is based on this principle!
This is the theory of special relativity. Till now, gravitational effects have not been taken into consideration. However, since the classical viewpoint of gravity was not able to describe the orbit of the planet Mercury, a new theory of gravity was sought. Einstein delivered. He modified his theory of relativity, taking into account gravitational effects, which he christened “General Relativity”.
According to this theory, gravity is not a force; it is a property by virtue in which massive objects warp space and time, creating curves. Objects that are in this region of space try to move in straight lines, but they can’t because of the curved surface. Also, I forgot to mention that Einstein unified space and time in his special theory of relativity, something which he called “spacetime”. The idea is that space and time are woven in intricate fashion and that relativistic effects apply to both.
An awesome consequence of general relativity is black holes: objects whose mass is so much that they do not even allow light to escape. General relativity also predicts gravitational lensing i.e the bending of light by a massive object. In his original theory. Going near a massive object is enough to slow time. This has been shown with the help of two atom clocks, bolted at the top and bottom of a skyscraper. The times show slight differences in the clocks after a certain interval. Einstein also included a cosmological constant “Lambda”, which he said was a property of empty space. He said that empty space behaved as if it has repulsive gravity, balancing the effects of the attractive gravity of massive objects. This theory came at a time when the universe was believed to be static. So, when the expansion of the universe was discovered in 1929 by the great astronomer Edwin Hubble, Einstein removed this and called it the biggest blunder of his life.
However, this constant might just prove to be correct. Recent observations have shown that the universe is made up of 70% dark energy, which fuels the expansion of the universe. Maybe, this constant is just what we need to figure out what dark matter really is: the repulsive nature of empty space.
The theory of relativity has many other paradoxes, interesting insights and details, all of which are greatly amplified if the mathematics is studied as well. The theory of relativity continues to inspire new generations of scientists.
So, how did relativity originate? The great scientist and mathematician, arguably one of the best ones there was, Newton, had a certain affinity for time. He said that while space is relative, time is absolute. According to him, time is the same for everyone and everything in the universe. He also said that the effects of gravity will be felt instantaneously. However, with the formation of the theory of electrodynamics, it became apparent that the speed of light was a constant, no matter what the state of the body it was emitted from is.
Einstein grabbed this intuition to develop a set of rules that removed absolute time and sought a relative time. This is called the special theory of relativity. Another postulate of this theory is that the speed of light in a vacuum is constant, and that nothing can travel faster than the speed of light.
However, travelling near the speed of light is enough to result in certain logically weird scenarios. Einstein showed that if an object is moving at speeds comparable to the speed of light, the length of that object reduces, a property which is called length dilation. Similarly, time also seems to slow down when travelling near the speed of light, meaning, if you are to travel on a spaceship at near light speeds and return back to Earth after 50 years, you would have aged very less compared to the man on earth (since even our bodies are governed by biological clocks!). This property is called time dilation.
Another strange property is the accumulation of mass when something travels near light speed. The special theory of relativity predicts that something gets heavier as it travels more faster, a property called mass dilation. While relativity is needed to describe physical events that occur at near light-speeds, classical mechanics provides a good approximation at the speeds we live our lives in.
One of the most famous results of the theory of special relativity is the mass-energy equivalence. This is one of the most famous equations in modern day physics and is simply: E=mc^2. This opened up a new horizon as energy and mass, two previously separate things were shown to be intricately related to each other. In fact, nuclear bombs and nuclear energy is based on this principle!
This is the theory of special relativity. Till now, gravitational effects have not been taken into consideration. However, since the classical viewpoint of gravity was not able to describe the orbit of the planet Mercury, a new theory of gravity was sought. Einstein delivered. He modified his theory of relativity, taking into account gravitational effects, which he christened “General Relativity”.
According to this theory, gravity is not a force; it is a property by virtue in which massive objects warp space and time, creating curves. Objects that are in this region of space try to move in straight lines, but they can’t because of the curved surface. Also, I forgot to mention that Einstein unified space and time in his special theory of relativity, something which he called “spacetime”. The idea is that space and time are woven in intricate fashion and that relativistic effects apply to both.
An awesome consequence of general relativity is black holes: objects whose mass is so much that they do not even allow light to escape. General relativity also predicts gravitational lensing i.e the bending of light by a massive object. In his original theory. Going near a massive object is enough to slow time. This has been shown with the help of two atom clocks, bolted at the top and bottom of a skyscraper. The times show slight differences in the clocks after a certain interval. Einstein also included a cosmological constant “Lambda”, which he said was a property of empty space. He said that empty space behaved as if it has repulsive gravity, balancing the effects of the attractive gravity of massive objects. This theory came at a time when the universe was believed to be static. So, when the expansion of the universe was discovered in 1929 by the great astronomer Edwin Hubble, Einstein removed this and called it the biggest blunder of his life.
However, this constant might just prove to be correct. Recent observations have shown that the universe is made up of 70% dark energy, which fuels the expansion of the universe. Maybe, this constant is just what we need to figure out what dark matter really is: the repulsive nature of empty space.
The theory of relativity has many other paradoxes, interesting insights and details, all of which are greatly amplified if the mathematics is studied as well. The theory of relativity continues to inspire new generations of scientists.
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