What is time dilation? A little background.

In the year 1686, Isaac Newton gave three laws of motion to our world which were well accepted for the next 200 years without any doubt. But there was a big problem with these laws. Actually, these laws were working perfectly in our day-to-day life, but in the case of high speed, most of the time, these laws were not accurate, which was noticed by a few people. In the year 1906, Albert Einstein published his theory of relativity, which changed the entire physics. It showed a whole new world to scientists of which they were never aware. Einstein tried to see objects in the universe while they were traveling at the speed of light.


Time Dilation


For objects traveling at a very high speed, there are three main consequences of his special theory of relativity.

First:

For people sitting inside any object which is traveling at a very high speed, time will be slower in comparison to those people who are watching that object from outside. For example, imagine you are on Earth and you see a spaceship traveling at close to the speed of light. From your perspective, time for the people inside the spaceship will appear to be moving slower than it is for you. 

This is called time dilation. 
 

Second:

If any object is traveling at a speed nearly equal to the speed of light, an observer, who is standing outside, will see that object as smaller than its original size. Imagine a meter stick traveling at close to the speed of light. To an observer on Earth, the meter stick would appear shorter than its actual length.

This is called length contraction.   

Third:

As the speed of any object increases, its mass also increases. Imagine two rockets, A and B. Both are exactly the same and have the same mass. Now, if you launch rocket A but rocket B is still at rest, you will find that the mass of rocket A is much more than the mass of rocket B. This is because as the speed of an object increases, so does its mass.

In simple language, as the speed of any object increases, its mass also increases.  

Time Dilation:

Before diving into the topic, it's important to understand that there is no such thing as absolute rest or absolute motion. All motion is relative to some other body. Einstein's theory of special relativity is based on two assumptions: that the laws of physics are the same throughout the universe, and that the speed of light is constant for all observers in a fixed medium.

Einstein used two assumptions in his special theory of relativity: Laws of physics act as same throughout the universe and in a fixed medium, the speed of light for all observers is constant. 

Imagine you have a simple light clock that consists of two mirrors, one on the top and one on the bottom. The distance between the two mirrors is "h", and the time it takes for light to travel from the top to the bottom mirror is "T". According to the laws of physics, the speed of light is "c", so we can say that h = c*T.




Now, imagine that we put this light clock inside a spaceship that is traveling at the speed of light. For the people inside the spaceship, everything would seem normal. However, an observer outside the spaceship would see something quite different. Because the spaceship is in motion, the light clock inside it is also in motion. This means that for light to travel from the top mirror to the bottom mirror, it must take a diagonal path instead of a straight path.

As a result, the distance that the light must travel is longer than the distance between the two mirrors. And, since the speed of light is constant, this means that the time it takes for the light to travel this longer distance must be greater. This increase in time is what is known as time dilation. 



It's worth noting that time dilation has been experimentally verified using atomic clocks. The theory of special relativity and time dilation have been supported by countless experiments and observations, making it a proven reality.

As an example, imagine you have a twin brother and you both are at the same age. Now, your twin brother decides to go on a trip on a spaceship which is traveling at a high speed. You stay on earth. When your twin brother comes back, he will be younger than you. Because of time dilation, time moves slower for him as compared to you.

In conclusion, time dilation is a fascinating phenomenon that arises from Einstein's theory of special relativity. It has been experimentally verified and has real-world implications for high-speed travel and the nature of time itself.


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