#Space_interior part 1 ... Vinit Vartak ©
The James Webb telescope was launched into space on December 25, 2021 by the Ariane 5 rocket. Now, after about 4 months, she has reached her destination. After many intricate technical steps, she is now ready to explore the past. Let's look at some of the questions raised on that occasion.
What is Lagrange Point? Why was James Webb L2 launched on this point?
Let us first understand what Lagrange Point is? What are the benefits of sending a telescope or a vehicle there? Suppose you are playing with ropes. People pulling ropes on both sides are pulling it towards there side. But what if the force exerted by the people on both sides is the same? The rope will stay where it is. This means that if two forces are working in opposite directions, the result is zero.
Now we go into space. Both the earth and the moon have their own gravity. We are not thrown into space because of the gravity of the earth. We have learned in the book that the gravitational pull of the moon causes the tides on the earth. If we consider the gravity of the Moon and the Earth in a straight line, we will find that there is a point between the two when the gravitational force of the Moon and the Earth is exactly the same but in opposite directions.
The moon will pull you towards the moon and the earth towards itself. We will experience the same situation as I wrote in the middle of the rope. What happens in such a place is that the effect of gravity on both will be zero. You will not go anywhere. This place is called Lagrange Point. Which is called L1.
The great thing is that the earth, the moon and you are not stationary in space.The earth revolves around itself and the sun, while the moon revolves around the earth and the sun. This rotation causes a third force to form which is called 'centrifugal force'. Now suppose a spacecraft orbits the Moon and the Earth, then the combined gravity of the Moon and the Earth will affect it and at the same time the centrifugal force created by the rotation will act on it. Now if we consider these three forces together, we will see that there will be places where the combined gravity of the Moon and the Earth will be equal and the force of the centrifugal force acting in opposite directions will be the same. Where such places come from, one is Moon then Earth and beyond (L2) and the other is Earth then Moon and beyond (L3). In 1772, Joseph Lagrange discovered a theorem called the "General Three Body Problem". He proved that in such a three body system there are five spaces at a time where the effect of any force is zero. This is called Lagrange Point.
Why is zero force space useful for any spacecraft or telescope? The answer is simple, if no force is working on the vehicle, then there is no need to spend fuel to keep the vehicle or telescope in the same place. But that doesn't actually happen. Suppose we are both standing in the middle of a sea saw. No matter where you lean, you have to keep your hands out to balance yourself. Even the same vehicle or Telescope have to be done. In order to stay in the same position, they have to run the engine from time to time and bring it back to its destination. Of course, this process has to be done very rarely and for a long interval. Therefore, the fuel required is very nominal. The proposed life of the James Webb telescope is only 10 years. That is why it has been fueled for such a long time.
While L1 to L5 are five points, the reason for choosing L2 the same point as the way James Webb works. L2 is a point 1.5 million (1.5 million) kilometers away from the Earth. There are many advantages to this L2 point and distance. Either way the shadow of the earth constantly falls on this point. This means that no rays of the sun fall directly on it. Also, because it is so far from Earth, the telescope itself is protected from both earth radiation and sun rays. James Webb needs a temperature of 44 K, minus -233 degrees Celsius, to work. The temperature around L2 point or orbit is almost what we need & that's where James Webb is orbiting.
Why does James Webb need such a cold temperature? What is the plan to reduce and keep it?
At the time of writing, the James Webb telescope has been described as the coolest man-made object in the universe. At present the temperature of her mirrors has dropped to 50 K. It will be even lower in the coming days. So the 44K temperature she needs is almost visible. Why does James Webb need this?
In 1915, the world-renowned scientist Albert Einstein proved an extraordinary thing in his theory of general relativity. That is the expansion of the universe. Albert Einstein proved that the universe has been expanding since its inception. To understand exactly what the expansion of the universe is, let us take the example of rubber. Suppose there are two objects on each end of the rubber. Suppose you stretch the rubber, what will happen? Even if the two objects do not move away from each other, the distance between them will increase automatically due to the rubber stretch. This is exactly what is happening in the universe. The object is the galaxy of the universe and the rubber is the space in it. Now if this space were to expand, the galaxies at both ends would automatically move away from each other. At the same time the light traveling in it will also be stretched. What does it mean that the light will be stretched? So its wavelength will increase. As the wavelength increases, the light in an ultraviolet area will be visible and the visible light will travel to infrared. By now, if the universe were to expand, the light coming from a distance of 13.5 billion light-years would have been greatly stretched. This is called 'Redshift'. If you want to see more distant light and the things from which it comes, then you have to shift your telescope to infrared.
The light we see today is millions, billions of years old. The situation we see today will be millions, billions of years old. This literally means we are peeking into the past. From where the light came out to where it reached us, dust and gas must have got in its way. So that light is absorbed or blocked in it. So the light in the visible spectrum does not reach us. If the light does not reach you, you will see darkness. But the exception is infrared. Light from infrared waves cannot block the realm of gas and dust in space. He chops them up and walks away. This simply means that the universe as seen from the infrared wavelength is going to be much deeper and clearer. The James Webb telescope was built to see infrared light for two important reasons.
It is not so easy to see the light in the infrared wavelength. That's why so much care has been taken in making the James Webb telescope. The equipment is highly dependent on temperature. Even a slight difference in temperature can make such telescope blind. If the temperature of this telescope increases, then due to the heat reflected from it, the telescope cannot see the far infrared light. Now you may have noticed why temperature is so important to James Webb. That is why it is so important to keep her freezing.
For this, NASA has used many new technologies while making james webb. Also, in the next part of this series, we will find out what the door of the universe will open for James Webb and how we will be able to know about many aspects of the universe.
To be continued...
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