Relativity
The concept of Relativity is well familiar and quite old. We all are familiar with relativistic events, and we do know that different events occur in different frame of reference. If suppose I was sitting in a moving bus and look outside I would notice the trees passing by rapidly; Similarly if I was standing beside the trees, I would notice the bus passing by rapidly. Everyone is free of accusing the other person in relativity; and obviously the judge would support the person who has his similar frame of reference. We use concept of relativity in our everyday life: "What is the speed of the car? How long will I reach my destination?" The speed of the car to what? Obviously when we talk about its speed we wouldn't say relative to the sun, moon or any other planet. Its a common relative conception that we are referring to the speed of the car relative to the ground. If we were to use more complex relative comparisons then our languages would all be a mess and no one would ever be able to make up anything at right time. The idea of this notion has been discovered long before Newton and its just as simple as arithmetic addiction.
Now, If suppose your friends car is moving at the speed of light i.e (c= 3*10^8 m/s) in the negative x-axis direction and you are moving at 20 m/s in positive x-axis direction. What would be the Relative speed with respect to you?
According to the concept of Relativity, you would apply the rule and notice that 20-(-c) = 20+c m/s
where c is the speed of light.
Now the problem here is that when it was experimentally determined the answer was just c.
The concept of Relativity is well familiar and quite old. We all are familiar with relativistic events, and we do know that different events occur in different frame of reference. If suppose I was sitting in a moving bus and look outside I would notice the trees passing by rapidly; Similarly if I was standing beside the trees, I would notice the bus passing by rapidly. Everyone is free of accusing the other person in relativity; and obviously the judge would support the person who has his similar frame of reference. We use concept of relativity in our everyday life: "What is the speed of the car? How long will I reach my destination?" The speed of the car to what? Obviously when we talk about its speed we wouldn't say relative to the sun, moon or any other planet. Its a common relative conception that we are referring to the speed of the car relative to the ground. If we were to use more complex relative comparisons then our languages would all be a mess and no one would ever be able to make up anything at right time. The idea of this notion has been discovered long before Newton and its just as simple as arithmetic addiction.
- If your car was moving at 20 m/s at positive x-axis and your friend's car was moving at 10 m/s at positive x-axis then the relative velocity with respect to your car would be 20-10=10 m/s.
- If your car was moving at 20 m/s at positive x-axis and your friend's car was moving at 10 m/s at negative x-axis then the relative velocity with respect to your car would be 20-(-10)=20+10=30 m/s. The reason why I considered 10 to be -10 is because it was in the negative x direction.
Now, If suppose your friends car is moving at the speed of light i.e (c= 3*10^8 m/s) in the negative x-axis direction and you are moving at 20 m/s in positive x-axis direction. What would be the Relative speed with respect to you?
According to the concept of Relativity, you would apply the rule and notice that 20-(-c) = 20+c m/s
where c is the speed of light.
Now the problem here is that when it was experimentally determined the answer was just c.
How could that be possible? Isn't it violating Newton's understanding of relativity? So does it mean that Newton is wrong?
No. He isn't wrong but he certainly made a mistake in believing in absolute time i.e Time is the same for everyone; It is relative like motion.
Before Einstein's period, physicists used believe in a medium known as the Ether. The medium through which light travels. So in order to find out the truth about the ether, they thought of an experiment that would allow them to calculate the precise relative speed of light, i.e if they noticed the speed of light decreasing, then there must be a medium that was acting relative to this and this medium should be the ether. As soon as this was suggested Michelson and Morley, the two scientists went out to explore for the truth and the result was just the speed of light. Since the speed of light wasn't changed they decided to abandon the idea of Ether.
Special Relativity
This idea of speed of light always being constant even when added or subtracted with other relative velocity annoyed all most all physicists. In fact, the main reason why they were really annoyed was because they didn't follow the symmetry between electromagnetic waves and Newton's relativity. (I'll talk about the symmetry of electromagnetism and Einstein's Relativity in the upcoming article).
Lorentz, an eminent physicists played a very vital role in the history of special relativity. He derived the appropriate formula for this situation. Even though the problem was quite solved it still had open wounds. To fully recover the idea of relativity, Einstein, a well known theoretical physicists came in and introduced an idea that was mind boggling. He called his new theory, the Special Relativity; the special thing about it is that it changed the way we understand the universe. In his new theory
Einstein basically used Lorentz equations known as the Lorentz Factor and used it make out his own understanding of light and it turned out that all the Newton's equations is just an approximation and the original equation was quite different. In order to theorize the new corrected Einstein formula; Einstein just plugged in the Lorentz Factor into Newton's equations and found that it satisfied everything and brought back the symmetry of Electromagnetism. (Just FYI: Plugging equations wasn't all he did. He had to theorize his ideas with the help of complicated mathematics). All of physics was saved by a 26 year old German clerk working in a patent office. This elegant equations gave rise to different ideas and throws out our current common sense.
For instance: What if told you that you would age a lot slower when you reach the speed of light!
Einstein's equations tell us that if you were to travel close to the speed of light time will relatively start ticking slowly for you than the others who at rest. Its quite hard to wrap your head around this.
For instances, lets take a ride through Einstein's thought experiment:
Suppose you are now travelling at the speed of light according to Einstein's Relativity equations your time will relatively slow down and you would age very slowly. But your friend on earth will be ageing normally. Since your ageing process has been slowed down when you come to a stop you will notice that your friend would have aged more and you less. Now what does that tell you? You have successfully traveled to the future. Time travel in the future has been proved by Einstein theoretically. But Time travel in the past isn't possible.
Why time travel to the past isn't possible? This is because there are too many paradoxes. The most famous paradox is known as the Grand Father Paradox; Its a thought experiment in which if suppose you were to travel back in time to your grand father's period and kill him; you wouldn't have been born and if you weren't born how could you have traveled back in time and killed your grand father?
Time travel in the future has been confirmed by numerous experiments but time travel to the past has too many paradoxes.
If you want to know more about Special relativity and how it works download the PDF here Introduction to theory of Relativity This books covers both Special Relativity and General Relativity.
And for Lectures on Special Relativity check the video tab of my blog.
No. He isn't wrong but he certainly made a mistake in believing in absolute time i.e Time is the same for everyone; It is relative like motion.
Before Einstein's period, physicists used believe in a medium known as the Ether. The medium through which light travels. So in order to find out the truth about the ether, they thought of an experiment that would allow them to calculate the precise relative speed of light, i.e if they noticed the speed of light decreasing, then there must be a medium that was acting relative to this and this medium should be the ether. As soon as this was suggested Michelson and Morley, the two scientists went out to explore for the truth and the result was just the speed of light. Since the speed of light wasn't changed they decided to abandon the idea of Ether.
Special Relativity
This idea of speed of light always being constant even when added or subtracted with other relative velocity annoyed all most all physicists. In fact, the main reason why they were really annoyed was because they didn't follow the symmetry between electromagnetic waves and Newton's relativity. (I'll talk about the symmetry of electromagnetism and Einstein's Relativity in the upcoming article).
Lorentz, an eminent physicists played a very vital role in the history of special relativity. He derived the appropriate formula for this situation. Even though the problem was quite solved it still had open wounds. To fully recover the idea of relativity, Einstein, a well known theoretical physicists came in and introduced an idea that was mind boggling. He called his new theory, the Special Relativity; the special thing about it is that it changed the way we understand the universe. In his new theory
- Time isn't Absolute; Its different for different person at different frame of reference.
Einstein basically used Lorentz equations known as the Lorentz Factor and used it make out his own understanding of light and it turned out that all the Newton's equations is just an approximation and the original equation was quite different. In order to theorize the new corrected Einstein formula; Einstein just plugged in the Lorentz Factor into Newton's equations and found that it satisfied everything and brought back the symmetry of Electromagnetism. (Just FYI: Plugging equations wasn't all he did. He had to theorize his ideas with the help of complicated mathematics). All of physics was saved by a 26 year old German clerk working in a patent office. This elegant equations gave rise to different ideas and throws out our current common sense.
For instance: What if told you that you would age a lot slower when you reach the speed of light!
Einstein's equations tell us that if you were to travel close to the speed of light time will relatively start ticking slowly for you than the others who at rest. Its quite hard to wrap your head around this.
For instances, lets take a ride through Einstein's thought experiment:
Why time travel to the past isn't possible? This is because there are too many paradoxes. The most famous paradox is known as the Grand Father Paradox; Its a thought experiment in which if suppose you were to travel back in time to your grand father's period and kill him; you wouldn't have been born and if you weren't born how could you have traveled back in time and killed your grand father? Time travel in the future has been confirmed by numerous experiments but time travel to the past has too many paradoxes.
If you want to know more about Special relativity and how it works download the PDF here Introduction to theory of Relativity This books covers both Special Relativity and General Relativity.
And for Lectures on Special Relativity check the video tab of my blog.