EXTENT OF THE UNIVERSE

 

Man thinks that he has invented so many things and there is no one better than us. Astronomy should studied by such a person and he realizes how insignificant and senseless man is in the universe.

Man defines God in his image. Since he has love, God must have love, and since he has hate, God must have hate. God must be angry because he is angry. Man projects all his attributes on to God. Eventually he makes God to even think like him.

Most of us know nothing about astronomy. Because when we study, in some books even if astronomy is mentioned briefly, they never touch on cosmology.

I hope that the write-up given below will interest you in astronomy. In the Mahabharata, Krishna showed his Viswaroopa to Arjuna. The Bhagavad Gita gives a wonderful description of the universe. It is said to be brighter than 1000 suns. Gods, demons, mankind and the entire universe appear in that Viswaroopa. It is said to have no beginning, middle or end and contains everything we know or do not know. It is called the unknowable, incomparable and incomprehensible.

It is difficult to predict the time when Bhagavad Gita was composed. Probably in the 3rd century BC. At that time there was no other literature in the world that showed the universe to be of such a large size.

To measure the enormous distance between stars, scientists introduced a unit called the light year. Light travels at a speed of 300,000 KM per second (2,99,792 Km/Sec to be exact). The distance light travels in one year at this speed is called a light year. This is equivalent to about 9.46 lakh crore km.

Even the description in the Bhagavad Gita is not enough to describe the universe as we know it today. If you look up at the dark night sky, how many stars can you see? Many say countless. But it is not so. There are only about 3000 stars that we can see with the naked eye.

But when using telescopes for viewing, the visible stars increase manifold. 50,000 stars can be seen with an ordinary binocular and about 3,00,000 stars with a 2 inch telescope. A 330-inch telescope can see stars 1200 million light-years away. This telescope is so powerful that it can detect the light of a candle lit on the moon.

Currently the largest telescope in the world is the “Gran Telescopio Canarias” in Spain. Its diameter is 409 inches. The range of telescopes can be very high, but these telescopes can only see 5% of the known universe. The rest of the universe can only be seen through radio telescopes.

NASA has sent telescopes into space so that we can get a better understanding about the Universe. It launched the Hubble Space Telescope in 1990. Based on the data from this telescope about 18000 scientific papers were published. Most recently in Dec 2021 a more advanced James Webb Space Telescope had been sent into space by NASA. This telescope is some 100 times more powerful than the Hubble and can see track infrared emissions. This is giving us invaluable data to us now and perhaps some 100,000 scientific papers would be published based on the data.  

In fact the entire Universe seen by us through all our instruments is only 5% and the rest 95% consist of Dark Matter and Dark Energy which we cannot detect with any of our instruments, but their gravitational effect can be seen on many stars. This is how we know that Dark Energy exists.    

Stars emit electromagnetic rays of light with different wavelengths. Some emit radiation with very short wavelengths, while others emit radiation with very long wavelengths. Radiation with very short wavelengths is absorbed by molecules in our atmosphere. Radiation with very long wavelengths is reflected back by the ionosphere.

The radiation that reaches us has a wavelength ranging from 0.0004 mm (violet radiation) to 0.0008 mm (red radiation). Only these are visible to our eyes. Another type of radiation that reaches us from stars is radio waves. This radiation has longer wavelengths than the VIBGYOR spectrum, but is not long enough to be reflected by the Earth's ionosphere.

These waves show much more of the universe than the reflecting telescopes. These waves created the field of radio astronomy. The world's largest radio telescope is located in Arecibo, Puerto Rico. Its diameter is about 1000 feet.

Our Sun is of course the closest star to us. As you know all the planets revolve around the Sun. The Sun is 14 crore 80 lakh kilometres away from us. But that is only a minuscule distance in space.

The distance of the nearest star Proxima Centauri from the Sun is 4.2 light years away or about 40 lakh crore kilometers. Our Sun is in a galaxy called the Milky Way (galaxy means a large group of stars and it also includes clouds of dust). There are one hundred thousand billion (10 raised to the power of 12) stars in our galaxy, the Milky Way. Its diameter is one hundred thousand light years.

The Andromeda Galaxy is the closest galactic neighbour to the Milky Way. Its distance from us is 29 million light years. There are about 100 billion such galaxies spread across the known universe. The diameter of the universe as we know it is 13800 million light years.

Now, even the distance of 1 light year at 9.46 lac crore Km passes right above our head. So our minds even fail to register the distance of 13800 million light years.

As I mentioned earlier the Universe has 100 billion or 10,000 crore Galaxies. Each of these Galaxies on the average contain about 100,000 crore stars. Thus the total number of stars in the known Universe aggregates to 10 raised to the power of 23. Our Galaxy itself comprises of 100,000 crore stars. In this massive ocean of stars our sun is just an average star without any significance whatsoever.

And again our instruments and even estimations take us only up to the end of the known Universe. What is beyond this we do not know and have absolutely no means of even making a guess. Perhaps after the Universe maybe billions of light years of open space and then after that another Universe? We can only speculate on that.  

When we read Astronomy we can understand our insignificance in the Universe and it inculcates humbleness into us.