December 28, 2015



We take the world as we see it around us as the given, as if it was always there. But science tells us strange, wondrous and fascinating things about the world. The world as we know it, not just the earth and the solar system – but the whole universe was at a point 1400 crore years back.

Think! What an imagination it needs to visualize that! The whole gigantic universe with its billions (100 curves) of galaxies, each containing billions of stars wasn’t even there as it is now but was concentrated at a point, called by the scientists, the singularity.

Now this is a strange fact, probably the strangest of all facts. So we obviously need to ask: why. Why was the whole universe at a point?

The answer is incredible and it lies in just understanding deeply the reality of an almost omnipotent force that governs the universe. That force is the force of gravity and it is universal. Let us proceed how to get a deep, real understanding of gravity. Since childhood we have observed things falling from a height if left free. We have observed it so many times that we take it for granted. We do not system, it, wonder about it, even feel it.

Yet, think!

Why should things fall? After all, we are not pushing it down and there is no contact between the earth, and the falling body. Isn’t it strange – this action at a distance. You leave a body and it moves towards the earth. The earth is a sphere and all objects get attracted to the centre of the earth and participates in the motion of the earth. Our atmosphere, the air we have, our oceans, everything is held onto the earth along the whole of it’s surface and circumference.

The ancients wondered about this gravity on earth. But later from 13th century onwards people began looking at the heavens too and began wondering and also, additionally, began tracing the motions of the planets the sun and the moon. They collected lot of data and bit by bit they came to understand that it was not the sun that moved around a stationary earth (as the ancients had assumed) but it was the earth (and other planets) that moved around the sun.

This whole inquiry culminated in the Kepler’s laws of motion of planets which describes the regular, uniform behavior of planets round the sun (it was not random or accidental).

Then Newton began a serious, deep inquiry in to this matter. Remember it was very early. Nothing was really clear. The heavenly motions of planets had been traced out. People observed the things falling on earth but no connection was made. It was almost as if, then the heavens were different from the earth. Newton’s incredible daring and genius lay in linking it. As legend has it, he observed an apple falling and suddenly he got this great thought. Are the motions of the apple falling and the moon falling the same? The moon ‘fall’ in the sense that if it did not fall towards the earth it would go off the straight line. It was already understood that the moon’s motion and even the planets motions were a result of two motions – one horizontally and other perpendicular and vertical towards the sun.

These two motions combined to give the almost circular motion of the moon and planets. (All circular motion is a combination of two such motions.)

Well, Newton thought about this and he suddenly got it!

He understood, in a flash of genius, that actually every mass attracts every other mass!

He got the mathematics of it also the power of attraction is directly proportional to both masses and inversely proportional to the square of the distance between them. This simply means the more any, or both of the masses, more the attractive force. Greater the distance, lesser is the attractive force. Also the reduction is as the square of the distance i.e. if distance is doubled the force is reduced 4 times, if the distance is tripled (made 3 times), the force is reduced by (3x3) 9 times!

This equation fitted with Kepler’s equation and Newton made the heavens and the earth one!

Just think! What a law Newton’s universal law of gravitation really is!

Every mass attracts every other mass in the universe and earth is merely one such mass and this law holds true for all the masses of the universe. Even 2 objects on earth actually get attracted. The reason we do not see a visible movement is because the attractive force of gravity is very weak. Unless the masses are of big size, there is not much attraction. This is the reason why things fall slowly on the moon – the mass of moon is 1/6th of the earth and hence the gravitational force (as it is called) is also 1/6the! That is why we see that wondrous (slow motion like) falling of things on the moon.

In space, things do not fall at all! They just ‘hang’ where they are! This is because the object is too far from any big size object to feel any attraction. So it just remains where it is! Isn’t this a wonder!!

Newton had literally swept the space clean and unlocked one of the deepest mysteries of the universe. Now, still a major, in fact, obvious question remained. If every mass attracts every other mass, how can the world as we see it – earth, planets, stars be at all? Should they not actually be together, this whole universe, at one place?

This was seriously asked, in the 1900s and no answer existed. The question, however, remained. Then in the 1900s another strange fact came into light.

Scientists discovered that the universe, as a whole was expanding. Every object was going away from every object. They came to know this by a phenomenon called Doppler effect. Doppler effect is very common with respect to sound. Sound consists of waves and if a body making sound is approaching you, the waves crowd together and the number of waves per second, that is the frequency increases. The opposite happens when the body making the sound is going away from you. Here, the waves are more stretched out and the number of waves per second is less. That is the frequency is decreased. Now the interesting thing is that light too is a wave and the same thing has been tested to happened to light too. A body emitting light, if its going away from you would change its frequency towards the red. This is called the red shift. If the body emitting

light is coming towards you, the n the frequency is increased and the light shifts towards the blue. This is called the blue shift. Now it was observe through countless experiments, that whenever you observe an object in the heavens, a star or a galaxy that is emitting light, it is shifting towards the red! This means that everything is going from away you. This actually means that the whole universe is expanding and everything is going away from each other.

It is then that they understood why the universe is not coming together due to gravity. Actually expansion of the universe was countering gravity. If the universe is expanding, then the whole universe must have been at a point and there must have been a big bang. This is how the scientist came to the conclusion that the whole universe was at a point and then the big bang happened.

After the big bang within moments, hydrogen atoms were created and began filling the whole space from these hydrogen atoms were born the stars, the galaxies and the solar system. How this happened will be understood in the following sections.


We have learnt that the whole matter of the universe was at one point 14 billion years back and that there was a big bang.

After the big bang what happened?

The simplest atoms of hydrogen gas were formed and they filled the blank space after millions of years. Because of the big bang, the expansion continued in all directions. But in many areas the cloud of hydrogen gas were a little closer and due to gravity formed huge regions of concentrated hydrogen gas. These are the galaxies!

Even in these regions, in some areas hydrogen gas got even further closer and formed stars. When the stars died they burst and again spread out. All the stars in each galaxy also attracted each other and formed systems of stars. The galaxies themselves attracted other galaxies, again due to gravity. Sometimes they push into each other giving various shapes of galaxies and also complicated motions. These motions continue to this day.

So you see its not just all galaxies expanding away from each other. They move themselves too and the motions never stop!

We live in a galaxy called the milky way galaxy. Sometimes in a clear night, we see a white spread in the sky, that is the milky way galaxy. Our milky way galaxy contains our Sun as just one of the billions of stars. So you can imagine how huge just the milky way galaxy is! Now there are billions of such galaxies! So the size of universe is literally unimaginable! We can only feel it.


We have learnt already that after the big bang, hydrogen gas filled the emptiness of space. We also learnt that in some huge regions galaxies are formed which are nothing but masses of hydrogen gas collecting together. In these galaxies are formed stars.

In some regions a little bit of hydrogen gas comes together in the form of clumps and this begins a process that goes on. The clump starts attractive, due to gravity the surrounding hydrogen gas. It becomes bigger and bigger. The more big it becomes the more powerfully it attracts all the hydrogen gas arrounded towards its centre!

This process goes on and on. The clump becomes bigger and bigger and bigger and attracts more and more powerfully the hydroges gas around it. Now this whole attraction towards it centre creates a very huge pressure. Now pressure is related to temperature, to the producing of heat. If you rub your hands hard, it becomes very hot. Wherever there is pressure there is heat. Heat is nothing more then the internal jiggling and wiggling of atoms/molecules inside matter. More the pressure more the temperature. If the pressure becomes huge the temperature too rises to a very high level. This is what happens inside the clump which becomes very huge. There is a high temperature of lakhs of degrees created inside the star. This removes electrons from the atoms of hydrogen. An atom contains proton and neutrons in its central nucleus and electrons orbit around it. Hydrogen atom contains one proton, one neutron and one electron. When the electrons are removed due to the high heat, a process called nuclear fusion reaction take place.

Fusion means joining together. In normal circumstances a hydrogen nucleus cannot join with another hydrogen nucleus. This is because protons are positively charged and if two nucleus of hydrogen come close together the proton in one hydrogen atom would repel the proton in the other hydrogen atom (two positives charge repel each other).

But when the temperature is extremely high the repulsion is overcome and the two nuclei actually join together, fuse together and becomes another nucleus! This nucleus contains two protons and is the element helium.

So in the star, hydrogen starts becoming helium. In this process a strange thing happens. Mass is lost and converted into huge amounts of energy (by the formula of E=mc2). This creates an outward force from the centre of the star. But there is another force too. Because the star is so huge there is an internal gravitational attraction towards the centre also.

These two forces the constant creation of nuclear energy outwards and the inner sucking force of gravitation balance each other and the star is born!

How long does this last? Obviously till the hydrogen is used up in the Star. What happens when the hydrogen is used up? The star begins the process of death. What is this process?

What are all the things that happen when hydrogen is used up?

We will see that in the next section.


When the hydrogen gas is completely used up to make helium, two things can happen depending on the size of the star.

The process of death of a small sized star (like our Sun):

When the hydrogen is used up in a small sized star, the outward force of nuclear energy created stops. Then what happens is the centre of the star shrinks but the outward covering of the star sort of floats up like a huge flare. So the star suddenly becomes big and redder. This is a red giant. Inside helium now starts a process of nuclear fusion reaction again and becomes lithium. But this does not last long as the helium is used up very quickly. After this again the outward force of nuclear energy stops and the inside of the star shrinks and the outside flares up as a second red giant. For a small size star, this is all. The red giant cools. The star becomes very small, the size of the earth but more dense. This is the white dwarf and a kind of ending of the star. The Sun being a medium sized star will go through all these processes. After 4 to 5 billion years i.e. the Sun would die.

The process of death of a big sized star:

For a large sized star too the hydrogen gets used up and there is an outward flare, this is a huge blast and it is called a Supernova. But here is the difference, inside the star the helium becomes lithium, the lithium becomes the next element and so on and there is a series of red giants. The second difference is what happens when the series ends.

Remember, if the star is huge the inner sucking gravitational force would be very huge. This huge force breaks up matter also and the star instead of becoming a white dwarf becomes a neutron star. The star contains only neutrons.

If the star is even more huge we don’t even get a neutron star it ends up as a black hole where all the matter vanishes due to the huge gravitational force directed towards the centre. Gravity here completely makes the matter vanish and light get sucked into the black hole. So this is the way stars are born and star die continuously in the universe.

In this whole universe we on earth are only a speak and in a way insignificant!


There are two main theories that explain the formation of the solar system (the sun, planets and asteroids). But the theory most widely accepted by all scientists today is the nebula theory. Long back, there was a huge mass of gas, dust and ice in the region which is now the solar system. At that time, probably due to a supernova (exploding star), this mass was disturbed. A disturbance in the universe is dangerous because if masses gets close together gravity starts acting and collapses the mass.

This is what happen the mass got closer together due to the explosion and the mass also started spinning. As they got more and more close while spinning the spinning became faster. Slowly over a period of time the whole shapeless spinning gas started becoming orderly, uniform and flat. Now this whole thing exactly like a frisbee or cake spinning very fast round and round. Slowly in certain areas this gas got closer together again due to gravity and slowly formed larger bodies called planetesimals. Even more matter flying around stuck to these planetesimals and slowly over a long period of time the solar system as we know today was formed that is the sun at the centre and the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

The question now remains as to how the sun was formed at the centre. At the centre the pressure was very high and temperature rose to lakhs of degrees and the process of formation of star started i.e. hydrogen becoming helium and releasing nuclear energy outward. This nuclear energy balanced the inner gravitation force and our Sun became stable.

There is a big gap between Mars and Jupiter and this gap is filled with numerous smaller particles which is called the asteroid belt. Why was the planet not formed in this gap? This is because Jupiter is a huge mass close to the Sun’s mass. So if any planet tried to form itself was burst into pieces by Jupiter! Thus we have this beautiful solar system with the Sun at its centre and planets around it!

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