It was only during the 1920s and 1930s that we were able to discover that the universe is expanding. With Edwin Hubble’s crucial discovery that galaxies are moving away from each other at a fast rate, we arrived at a much complex question that what would be the fate of the universe? Many theories suggest that one day the universe will die. But wait, how? And why? It’s these type of cosmological questions that have given birth to many hypotheses that predicts the fate of the universe.
So today, let’s just dive deep into the space as we try to unravel the true fate of our Earth and ultimately the universe. We know that the universe is expanding for sure, and the reason behind the expansion is what we known as dark energy. For those who doesn’t know about Dark energy, it is a strange phenomena that scientists believe permeate the entire universe.
But as we said earlier, the universe is not only expanding, but expanding at an accelerated pace. So where is this acceleration coming from? That’s right, it’s the dark energy. Albert Einstein was the first person to conceptualize the theory by realizing that the empty space is not nothing. Now, astrophysicists consider it as the only possible explanation for the expansion of the universe.
But there is one big problem, that it’s all theoretical. There is no proof whatsoever and currently there is no possible way to test the existence of the dark matter. But luckily, we have different hypothesis that predicts how the universe will get destroyed, including everything in it.
1. The One Big Rip
In the current form, the universe in expanding. For various reasons, unknown to humans, new spaces are created everywhere uniformly. Galaxies are moving away from each other due to this continuous expansion. Similarly, the space inside a galaxy also expands, but here, gravity is strong enough to keep them together.
According to the hypothesis, we will reach the big rip at the point, when the expansion of the universe accelerates up to a maximum where space expands due to the increase in density of dark energy over time. The expansion would be so fast that gravity can’t compensate any more.
In the end the space would expand faster than the speed of light. Atoms would now be affected and they would just disband. Once the space is expanding faster than the speed of light, no particle in the universe can interact with any other particle anymore.
2. The ‘Big Freeze’ or Heat Death
This idea of ‘Big Freeze’ comes from the second law of thermodynamics, which states, that in some isolated systems (the universe), entropy will continue to increase until it reaches a “maximum value”. Entropy refers to the idea that everything in the Universe eventually moves from order to disorder. So it is the measurement of that shift.
Theoretically, once entropy reaches to its maximum value, heat in the entire universe will be distributed evenly. That means there would be no more usable energy or simply, mechanical motion within the Universe to cease and the Universe would die from ‘heat death’.
The big freeze is a reversal of the heat death in which entropy decreases over time due to the absence of dark energy. In this scenario, stars will eventually get exhausted. As existing stars run out of fuel, the universe will slowly grow darker. Eventually, black holes will appear throughout the universe, which themselves will disappear over time due to the Hawking radiation. At the end it will be all dark and cold.
3. Big Crunch
Now, what if the persisting dark energy decreases over time? In that case, in a period of few trillion years, the rate of expansion of the universe will not only slow down but will reverses. Then the gravity will become the dominating force. This would ultimately cause the Universe to shrink as distant galaxies will race at each other, merging as the universe becomes smaller and smaller. As all the components in the universe starts to compress, temperature will rise everywhere at once. Planets and the entire galaxies collide into each other and collapse in on itself. In either way our Earth and the universe are destined to die.
4. Grey Goo
It’s an odd name, isn’t it. Until now we have discussed universe ending scenarios on a cosmic level, which is starting from everywhere and mostly ending in a singularity. Well, this time it’s slightly different. Grey Goo is a term given to a hypothetical end-of-the world, which involves self replicating molecular nanotechnology. The idea behind the grey goo is a horde of out of control nano-bots that consume all biomass on our planet while replicating more of themselves.
Let’s assume that these little beasts replicate themselves in 60 seconds. Then, if we do start with just two bots, those two bots will become four, then eight, sixteen, thirty two and so on and on in no time. After an hour, we will get something like 1.15×10^18 (1152921504606846976) little bots. At this rate, it will take them to reach 3×10^433 in just one day and will soon turn our earth and everything in it their meal.
5. The Big Slurp
We are assuming that at this point you are aware of the higgs boson. For a quick reference, a big extravaganza was made by the media about the higgs boson particle that it is a kind of a big deal, which is actually a major understatement. Researchers are certain that the discovery of this particle can unlock all the riddles present in the universe. However, it’s most important to discover the true mass of the particle as it plays an important role in the ultimate fate of the universe.
According to the scientists, if the ‘god particle’ truly exists in the appropriate mass, the universe, which we are a part of may be in a serious trouble. In theory, the extra mass of Higgs Boson, added with masses of top quarks may have already resulted in a very unstable vacuum of our universe from the very start.
Many physicists are arguing the possibility of our universe hanging on the edge of stability for only god knows many years now. According to a paper in Nature in 1982, by physicists Michael Turner and Frank Wilczek, out of a sudden, a bubble of ‘true vacuum’ could generate somewhere in the universe and move outwards at the speed of light and before we realize anything we would be gone.
So, what do you think how it’s going to be?