Why Time Slows Down Near a Black Hole.

Friends, in the last episode, we understood space-time. In that episode, we also told you that time is relative rather than absolute. That is, it does not remain the same everywhere and under every circumstance in the universe. This means that if 2 hours have passed for you then it is not necessary that 2 hours must have passed for everyone in this universe. Slow time passes for those sitting in a fast-moving spacecraft. In the same way, for those present in the field with more gravity, the speed of time also slows down. For example, if you are close to a black hole, time will pass slow for you compared to others.

In the last episode, we also asked you why the speed of time slows down as we move closer to the block hole. Some of you gave the right answer, but no one could explain it in a good way. In this episode, we will understand this through a simple example. In that episode, some of you had also asked, through the comment, how it turns out that time is relative, not absolute. In this episode, we will also answer this question. So let's start this episode of today.

Let us first discuss why we believe that time is relative rather than absolute. According to Newton, time is absolute. That is, it remains the same everywhere and under every circumstance in this universe. For example, if an event happens in front of me at 5:00 pm, then it should happen for everyone in the universe at 5:00 pm. But what really happens, let's examine it. Suppose a bomb blast occurs. Two different people exist 10 light seconds and 20 light seconds away from that bomb blast.

It would take 10 seconds for the light emanating from that exploitation to reach the first man. While it will take 20 seconds to reach the same light to the other man. If you ask the first man when the bomb blast happened, he will say 10 seconds ago. If you do the same question with another person now, he will speak 20 seconds ago. So which of the two is correct? Actually both are right. But if time is absolute, it could not be possible. Had the time been absolute, the explosion would have happened simultaneously for both of them and both would have seen that explosion at the same time. But because it has not happened, we can say that time is relative rather than absolute and it depends on frame of reference. As I have already said, if you are traveling in a spacecraft whose speed is around the speed of light, then the time for you will be slower than others, similarly if you are in a field where gravity is very high. Even then, time will be slower for you than others. This is called time delaytion. In the next episode we will understand how and why this happens. At the moment you know that this is not the only blank fantasy but a truth which has also been verified many times. Let's know about some of these experiments. After synchronizing the time of the two atomic clock,

one was placed on the earth while the other was put into the satellite orbiting the Earth.

A few days later, when the time of both the clocks was merged, it was found that the clock time on the satellite was a few nano seconds longer than the clock on Earth. This clearly shows that due to the gravitational field of the Earth, the time for the clock on its surface passed a few nano seconds. If we talk about time delaytion and length contraction due to high speed, then we have verified this during the experiment in Large Hadron Collider.

Actually, in this the speed of the particle is 99.9% of the speed of the light. By now we have come to know that time is relative, due to which the universe itself can pass through different speeds in different places and under different circumstances. Let us now know why the time passing near the block hole slows down. To understand this, you must first understand gravity, so let's understand it first. Einstein told us that both space and time are interconnected. This is called 4 dimensional spacetime. Every object in space time curves according to its size. If an object is large, it will curve space-time more and if it is small, it will curve less.

To understand this, you can take the example of a blanket. Suppose the blanket is space-time. Now if you place it on a big ball then the blanket will be slightly slid inwards. If the small ball is able to penetrate the blanket a little, then its effect will be much less than the big ball. Because the big ball has pushed the blanket more inward, the smaller ball will also be pulled towards it. We call it gravity, the force of gravity. In this example, consider the big ball which is the Sun and you will understand the small ball which is earth, why the Earth revolves around the Sun. Many of you may be thinking that if the big ball pulls the small ball towards itself, then the earth should be hit by the sun and not in its rotation. Actually, the earth keeps rotating because it has also distorted the space-time due to which its balance remains. You can understand this thing with this video.

This means that celestial bodies with larger mass or density will warp space-time more, due to which its gravity will be higher. In other words, if the gravity of an astronomical body is high, then space-time will warp more. If we talk about black hole, then its gravity is so much that even light cannot get out of it.

In other words, black holes warp spacetime significantly. But to understand why time falls this way, let's take the speed equation.

You must have read it at some time in school. We know that speed is equal to distance by time. In this equation, first let's talk about speed, then it will be the speed of light. We know that lights run at a limited speed throughout the universe, which is 3000000 kilometers per second. But to make this example easier, we assume that the limited speed is 2 kilometers per second. Because this speed is fixed it will never change. Now come to the distance. Suppose the distance between A and B in normal space-time is 16 km.

Because we already know the speed which is 2 kilometers per second, then we can easily find the time. In this case, the time will be 8 seconds. Now if the space near the black hole talking about the warp, the distance between A and B will increase even earlier. Suppose this distance increases to 20 km, which is always a fixed speed, then it will still be 2 km per second.

In this case if we take the time, it will be 10 seconds. As you can see in the first case it took only 8 seconds to go from A to B, whereas now it is taking 10 seconds to go from A to B in the case of black hole. That is, time has slowed down. This was just a simple example. If we talk about real time delaytion and length contraction equation then it is something like this.

Some of you also commented that Einstein's space-time concept is wrong. If you think so, then you are wrong. Einstein had predicated on the basis of his space-time model that large celestial bodies distort the space-time due to which light also bends when that field passes. Due to which its path also changes.

Today, gravitational lensing phenomenon has also proved this.

That is, Einstein's space-time concept is not wrong. I hope by now you have understood why time slows down near a black hole. We will understand time delaytion and length contraction in detail in the other episode friends. That's all in today's episode.

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