"Liftoff from tropical rainforest, to the edge of time itself,
James Webb begins a voyage back to the birth of the universe."
NASA launched the world's biggest and the most powerful space telescope and its name is James Webb Telescope. Using this. We can achieve somewhat time travel, it isn't possible to go back in time, but with this, we can get a glimpse of history. Millions and billions of years' history can be looked at using this telescope. More precisely, we can look 13 Billion Years back in history.
The universe began with the Big Bang 13.8 billion years ago. And this telescope can look till 13 billion years ago. About 0.7 billion years after the universe began.
The most special thing about this telescope is that it has been designed mainly to detect infrared light. When you look at the sky, with a normal telescope, you see the wavelengths of visible lights. The light that you can see with your eye.
We have studied about Electromagnetic spectrum back in school. The Electromagnetic waves in a broad spectrum. It includes X-rays, Ultraviolet rays, radio waves, microwaves, and in there, there is a small range of visible light. The light that we can see with our normal human eyes.
The normal telescopes that you can buy at any shop, help you look only at the wavelength of the visible light. The range of visible light is between blue color to red color, and red has the biggest wavelength. And as we have studied in school, with electromagnetic waves, the bigger the wavelength, the easier it is for the electromagnetic waves to pass through any object or obstacle.
For instance, the radio waves. The radio that you listen to. The wavelengths of radio waves may span more than kilometers. For this reason, you can listen to the radio waves that pass through buildings.
The wavelengths of infrared are bigger than that of red. But we can't see infrared with our eyes. The word Infrared means below red. This word comes from Latin, Infra means below.
So Infrared means Below Red because its frequency lies below that of red. And let's recall frequency is inversely proportional to wavelength.
Anything that radiates heat, emits infrared waves. Humans, animals, the Sun, fire each of these emit infrared waves. You would've seen soldiers use night goggles often, those goggles detect infrared.
Since the telescope will look at stars and galaxies of stars, and planets, all of which radiate heat, it'll be possible to capture and look at the infrared waves.
The other advantage of infrared is that when a telescope looks at stars at such a distance, stars that are billions of kilometers far from us, when the light from those stars reaches the telescope, the light has traveled such a distance, that by the time it reaches here, and as we know the universe is slowly expanding, the wavelength of the light gets stretched. The wavelength gets elongated. This phenomenon is known as the Red Shift.
With telescopes, the bigger the mirror they are equipped with, the more light they'd be able to capture. And the resolution of the image that we get will be that much higher. That's why, with the creation of more and more advanced telescopes, they are being equipped with bigger mirrors.
The James Webb has 18 hexagonal-shaped mirror segments that are 1.32 meters in diameter, flat to flat, and the secondary mirror is 0.74 meters in diameter. In short, James Webb has the biggest mirror so far.
There's a problem here. I said that everything that radiates heat emits infrared waves. When the telescope will start working, the telescope will radiate some heat too.
Some infrared waves will be emitted from within the telescope. It'll interfere with the waves coming from the galaxies, and we wouldn't be able to get good high-quality pictures. To avoid this, this James Webb Telescope will work only at the cold temperatures of -223 °C. The temperature needs to be this low for it to work.
On Earth, the temperature hasn't fallen below -89 °C. But it is possible to do it in space. It is possible because it is very cold in space unless there's sunlight. The temperature would rise rapidly if that place is exposed to sunlight. As is the case on the moon there isn't any atmosphere on the moon, The temperature may fall to -170 °C there. But as soon as the sunlight falls on the Moon, the temperature rises to 120 °C.
It is very problematic for this telescope. If the sunlight falls on this telescope, it would be problematic as everything would heat up rapidly.
To avoid this problem, a Sun Shield has been installed on this James Webb Telescope. This Sun shield is in the shape of a kite and is as big as a tennis court. So the telescope could remain protected from the Sun. For this, a very special material has been used, known as Kapton.
Several materials were tested to see which material could be used to block the Sun most effectively and to keep the telescope cool. It was later discovered that Kapton was artificially created. This Sun Shield comes with 5 layers of Kapton, and each layer is thinner than a strand of human hair.
There's a vacuum gap between each layer. So that its effectiveness could be increased. Apart from this, each layer has an aluminum coating on it. And the two layers closest to the Sun have a coating of doped silicon.
This space telescope isn't being deployed near the Earth, as the Hubble Space Telescope was. Hubble is close to the Earth and orbits around it. But this will be deployed 1.5 million kilometers away from the Earth. At the point known as the L2 point.
L stands for Lagrange Point. This point will be on the other side of the Sun, because, it is important to block the heat and light of the Sun as much as possible for the better functioning of this telescope. And the L2 Point is special because it keeps revolving with the Earth. So the Sun will be hidden throughout the revolution.
NASA has said that the entire procedure of creating and launching it is so complicated that they have identified more than 300 potential problems that may arise. More than 300 single points of failures, if any of them come true, then the entire project would be as good as over. $10 Billion has been spent on this project.
This amount is so huge that NASA had to defund several research projects and direct the money to this project to make it possible. Along with NASA, the European Space Agency and the Canadian Space Agency are also participating in this.
The scientists have pinned their hopes that using this, they would be able to study how did stars and galaxies form after the Big Bang. With this telescope, we can look 13 billion years into the past. The Hubble Space Telescope could look to only 1 billion years after the Big Bang took place. So, about 12.8 billion years ago. But the James Webb Telescope can look to 0.3 billion years after the Big Bang.
A common question is how is it possible to look into the past.
The answer to it is very simple. The light takes some time to travel the distance. And by the time the light reaches from one place to the other, a lot of time would have passed. Especially when it involves distances this large.
The light from the Sun reaches the Earth by traveling approximately 8 minutes. It means that if the Sun vanished suddenly, for example, it will take 8 minutes for people to find out on Earth, to see that the Sun has disappeared. In a way, you can say that we are looking 8 minutes into the past when we see the Sun.
Similarly, apply this logic on a large scale. The stars and galaxies that are millions of light-years away from us, when we look at them through the telescope, or we gaze at the stars from the Earth, we are seeing them as they were millions of light-years ago.
The universe is so huge that there are stars that are 13 billion light-years away from us, by the time their light reaches Earth, 13 billion years would have elapsed, and what we get to see today, are the events of 13 billion years ago. This way we can get a glimpse of history.
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