14 billion years ago, a hot, dense amount of matter infinite in mass, compressed in a tiny point of space with an infinite curvature around itself exploded. New substances came into being, new types of matter; new objects like stars, galaxies, planets, solar systems and even life came into being. This is how our universe came into being with all its glory and magnificent beauty originating from a tiny speck of infinitely dense amount of matter. This is just one of the possibilities of how it all happened, we can never be sure which of our theories is right! Much like about the universe’s birth there are also theories predicting the end of the universe. Now there arises a question. Will our universe ever end? Isn’t it infinite in size and age? Did in the first place ever come into being or was it always there? The answers at first glance seem simple ( it can only be yes or no), but it is much more than just giving a definite yes or no for an answer.
For centuries, our universe was thought to be static. The regular orbits of celestial objects obviously continued but there couldn’t have been any expansion in the universe’s size.
Note: These ancient theories that we talk about were what the western thinkers thought of. On the other hand, oriental knowledge had been far more advanced than western knowledge in many aspects. But still no theories were for sure 100% accurate.
In the late 1920’s, astronomer Edwin Hubble observed the night sky with his telescope. He observed the nearby Andromeda nebula (at that time, Andromeda and the other today known galaxies were not thought to be of the same magnitude as Milky Way and weren’t regarded as galaxies) and found that the light travelling from it was blue-shifted that is it was travelling towards us. He then observed that other galaxies were also emitting some kind of particular light spectrum. Mostly the light was red-shifted which meant that the galaxies were receding from us( to understand how this red-shift and blue-shift works in determining distances between galaxies, read ‘The Origin of Everything’ article on this page itself). Certain conclusions were drawn from these observations. The greater the red-shift the faster the galaxies were receding from us and vice versa. From this we had the now generally accepted idea that the universe is expanding and is doing so at an accelerated rate. From this idea, scientists have painted some possible scenarios in which our universe could meet its end.
In the present case scenario, there is a cosmic tug of war going on between two forces: gravity and dark energy. The outcome of this battle will determine the plausible fate of our universe. The force of gravity is the force of attraction between the galaxies and dark energy is an unknown force pulling the universe apart; a sort of repulsive force. Presently, dark energy seems to be winning the race with the expansion of the universe reaching above the critical rate. So here are the three possible scenarios painted by cosmologists predicting the universe’s fate:
Suppose the expansion of our universe continues and the attraction force between galaxies keeps declining. At a particular point the galaxies will be so far apart that no force of gravity will act on any of them and they will keep floating through the universe. Here even though the rate of expansion doesn’t accelerate, the expansion continues. Stars will move away from each other, no life will be able to exist without a sustainable star to power it. Even if stars go supernova, their materials won’t be enough to create a new generation of stars. The last stars will collapse into black holes or white dwarfs. Black holes will suck all the remaining matter in their surroundings and white dwarfs too will overtime become black dwarfs losing all energy and the universe will become cold and dark like some zombie universe. This scenario is called the Big Freeze or the Heat Death of the universe.
Now suppose after the force of attraction by gravity declines and the rate of expansion keeps accelerating what would happen? This will make the repulsive force to not only overcome gravity ripping galaxies apart but also it will overcome the other fundamental forces: strong nuclear force, weak nuclear force and electromagnetic force. This will not only rip apart macroscopic objects but also atoms and subatomic particles! This scenario is called the Big Rip.
In this third scenario, scientists predict the force of gravity to overcome the repulsion of dark energy. Although this event is highly unlikely given the universe’s present rate of expansion it is a very elegant theory. At some point, the force of gravity will stop the universe’s expansion bringing it to a halt and then it will start to recollapse, which means reverse the process. As the universe consists of space-time, time too may run backwards! So in this case, we will die before we are born! As the galaxies move towards each other, the density of the universe increases. All the matter in the universe shrinks to a tiny, compact and dense point which is like the stage of the universe right before the big bang. This is called the Big Crunch. Maybe this pin-point of matter will explode in another big-bang and it can also be a never-ending process where the universe keeps expanding and contracting which means we will keep living our lives over and over again. This scenario is called the Big Bounce.
But there is yet another theory according to which the universe is infinite in time and space. On answering a question about God, Carl Sagan gave a valid argument about the universe’s infiniteness. If God created the universe then where did God come from? People may say that God always existed. Then why not save a step and conclude that the universe always existed! If we look deeply into the origins of theories describing the universe’s birth there is some subtle religious interference. The big bang model became a rapidly accepted general model of the universe because it described a moment of creation, thus the need for a creator. But Stephen Hawking in one of his papers said that the universe has no possible end. When we think of our universe we may think of it to encompass everything in a gigantic sphere or a curved sheet but Hawking thought something else. What if the universe was shaped like a shuttlecock? Even if it begins at some point, its mouth is open and we cannot conclude a specific end.
Now, many people may ask this question: Amidst all this chaos is there any hope for us? Well it is highly unlikely but many current theories are highly unlikely but still they are accepted. Let us say somehow humanity is able to relocate to a new location before the Sun becomes a red giant or before we destroy our fragile planet and we survive to see the end of the universe. Well there is a possibility that if our technology is advanced enough we can build a wormhole as a portal to another universe or to the past. Now according to string theory there are many curled up dimensions in our universe which means it is not just the usual four dimensions we think of. If these curled up dimensions are some kind of strings connecting to different zones of the universe through a small path taking less time than light’s speed, we can time travel! That means we can save ourselves by going into our own past. But with conflict, war, poverty, lack of want of knowledge and greed for some impractical development by manufacturing war tools using science will not lead our species to this stage where we unite in helping each other survive. This is another reminder, as Carl Sagan has said, of how the hate we have for each other, the wars fought, racism amongst people, sexism towards women only because we will be able to gain some kind of meaningless supremacy in a tiny sliver of our little planet is very pointless.
The universe will not destroy itself tomorrow but what about us? How much time do we have? Will we live long enough to decode its secrets or will we blow ourselves up? And what is its fate? We may never know unless we stop inviting our end closer and closer to us. We cannot possibly live long enough to witness the universe’s end but we must ensure to live long enough to understand it and to comprehend its mysteries. Then can we say that we lived a fruitful tenure on our little planet trying to understand our far and wide abode. Let us envision for this possible future and a hope for our universe to end its wonderful life in a spectacular fashion.