Imagine a hot day and you are waiting for the sun to set eagerly. As soon as the sun sets, temperatures start dropping. It becomes pleasant to move out of the house. Slowly the stars emerge. First there is one, then another, then another. Soon, there are so many that counting them seems futile. As you look up at the stars, I am sure many of you would have wondered about how it all started and how we came to be. Well it all started with something that sounds very fancy (or not as it really is just plain text description) – the Big Bang.
The Big Bang is nothing but a big bang. Really. There was nothing and then there was everything, erupting in a fierce blast from just a point. And that point is smaller than the one marking the end of this sentence. This point erupted and poured out everything that is there in the universe. There are pens in the market today that boast of a dot size of 0.5 mm. But nothing compares to the point from which it all started.
Imagine squeezing yourself to the size of a dot. What would happen to your density? You won’t be able to swim after that for starters. Unless your mass somehow decreases as well. This point where everything started – the Big Bang – is an example of a singularity – a place where all known science fails.
The big bang
The Big Bang is a singularity with temperatures higher than any imaginable number. The universe started out very hot. Everything was at unease. But the universal night did come. And it came in a form called the Dark Energy.
It is easy to get irritated when it is hot, right? When you are angry, you don’t want to talk to anyone. It’s the same with electrons and protons. After the Big Bang, temperatures (and tempers) were running very high and electrons and protons did not even acknowledge each other despite living in the same home (the primordial soup – things that were ejected by the Big Bang).
It was then that dark energy came to the rescue. It made the universe to expand. And as the universe expanded, it started getting cooler and cooler. As it got cooler, every now and then, some of the elctrons and protons would stop their motions and steal glances at each other.
Slowly they realized that they were attracted to each other and finally when the temperatures had cooled enough, they combined to form the very first atoms – the hydrogen atoms. After a while the neutrons joined the party. This was mainly because they learned it the hard way. See, without joining with protons in a nucleus, neutrons can’t exist. They decay into other things. So joining the nucleus to make heavier atoms like deuterium and tritium was the natural thing to do. But all these atoms were very far apart. This was not very helpful. Considering that atoms could fuse into one another to make bigger atoms. why stop at just hydrogen and its isotopes? But everywhere, there was just gas (called dust in the scientific circles) with atoms far apart to do anything. Since the electrons and protons had joined together, things had become neutral.
There was nothing to attract one atom towards another except the force of gravity. But it was too weak. If you calculate the force with which a proton attracts an electron or repels another proton, you will find that it is much much bigger like more than 100000….0000 ( 40 zeros) times bigger. There was nothing that the force of gravity could do to bring the atoms closer. If only there was something else present. Something that could provide that extra attraction. Turns out there is something. It is called the Dark Matter.
Dark Matter forms a sphere around galaxies
How did dark matter bring the atoms closer together? Simple. Gravity. But i just said that gravity is super weak. Like weak enough that we can jump around and make merry on the earth which is so big. But at the same time, the earth’s gravity is strong enough to bring us back. Those of you who have fallen recently will appreciate this fact. Those of us (including me) who climbed trees whose branches tended to give away know that gravity is very strong. It doesn’t give a chance. It always brings things to crash. And it is persistent. It never stops in its efforts. That is why keeping your arms raised over your head for more than 5-10 minutes is such a pain.
Dark matter had gravity as its arsenal. And it was strong. There was so much mass in dark matter that not only did it bring two atoms close enough to form other bigger atoms, it brought the entire gas in some region of the universe together. This gas when confined in a space small enough became the precursor of the modern galaxies. As the atoms and molecules in this gas came closer together, they collided. This generated friction which in turn generated heat. With enough hydrogen atoms colliding together and fusing into one another, a chain fusion reaction started and the first stars were formed.
A cloud of hydrogen gas collapsing to form a star
As matter started coming together, more and more stars formed. The stars nearer to each other started forming groups that we now call galaxies. Galaxies formed clusters. And clusters formed super clusters. There are millions of super clusters in our universe. And it is just the part of the universe that we can see. There are many more in parts that we cannot see.
The milky way is but a tiny part of the Virgo Supercluster
All this while dark energy has kept expanding the universe causing galaxies far away from each other to get farther. All this while dark matter has used gravity to bring things close together and thus hold a galaxy together so that the stars in one galaxy do not stray away from each other. There is a fine balance between these two entities. While dark energy moves large groups of galaxies away from each other, dark matter makes sure that individual galaxies and clusters do not get torn apart. In their own way, they are our parents. They are responsible for making the conditions ripe enough for us and our way of life to flourish.
There is much that is known and even more that is unknown. Dark matter and dark energy are two very mysterious characters in the story of our universe. Much more needs to be learned about them. Are you up for the challenge?