Certain End of The Universe: 4 Forces of Nature to Watch Out For

Start of Universe and End of The Universe

Our Universe started its journey almost 14 Billion years ago. Since then inflation has expanded the Universe to the point that we can’t even see most of it. Even the observable Universe is 92 Billion Light years – meaning it would take light, the fastest object in the universe, 92 Billion years to reach from one end to the other end of the observable Universe. Sun, the biggest object in our immediate neighborhood, has a diameter of 1.4 Million km – meaning it has a diameter of 4.7 Light seconds. This means it would take light only 4.7 seconds to reach from one end to the other end of the Universe.

So, the actual Universe is much much bigger than the observable Universe. As the Universe has been expanding faster than the speed of light, the Universe may have gotten to a place where it has become an infinite Universe. From our perspective, the time scale of the Universe is enormous and humongous which our mind can not comprehend. Scientists in the past, including Albert Einstein, used to think that the Universe was eternal. Then scientists used to think that the eternal Universe had no beginning and hence there was no possibility of the end of the Universe.

However, everything changed once Edwin Hubble discovered that the Universe may not be eternal and it had a beginning. Edwin Hubble, through his telescope, discovered that the Milky Way is not the only galaxy in the Universe and that there are other galaxies. He also discovered that those galaxies are rapidly moving away from our galaxy. The further away a galaxy is, the faster it is moving away. So it is possible that all the Universe once were very close to each other.

After a lot of research and calculation, scientists figured out that the Universe indeed had a beginning 13.7 Billion years ago. We call it the ‘Big Bang’. To date, the Big Bang theory is the most persuasive theory of the start of the Universe. A Universe that is not eternal and if there is a start of the Universe then there could be an end of the Universe as well. Of course, we don’t have to worry about the end of the Universe just yet.

Compared to the human time scale, the Universal time scale is unimaginably long and for us, it may seem like an eternity and infinity. Also, it is possible that we humans will not be there to witness it. No intelligent life may exist when the end of the Universe finally comes around. But still, the end will certainly come this Universe will cease to exist.

In this article, we will talk about 4 entities or forces of nature that might bring about the end of the Universe.

1. Entropy

With our current understanding of the Universe, we could say that ‘Entropy’ which is an innate property of the Universe, will eventually cause the end the of Universe. it may happen on a very long time scale and we humans may not exist then, but the ‘Entropy’ is sure to bring about the end of the Universe. In simple terms, Entropy is the measure of order or disorder in a closed system. If a system is less chaotic and highly organized then its entropy is low and if a system is highly chaotic and highly disorganized then its entropy is high.

The concept of entropy came about when scientists were trying to figure out the properties of thermodynamics. The second law of thermodynamics states that the heat always runs downhill in the temperature gradient. Scientists observed that heat in any closed system will always disperse and any object will lose its heat until it comes to the absolute zero temperature which is -273.15 degrees Celsius. In this situation, the atoms will freeze and nothing will happen in the Universe. The law of thermodynamics implies that heat or energy in any closed system will eventually disperse. This law, coupled with the fact that the Universe is expanding at a rate faster than light, indicates the eventual end of the Universe.

In our Universe, the entropy always runs from low to high – meaning the Universe as a closed system is heading towards becoming more and more disorganized and chaotic. Just after the Big Bang, the Universe was in a low entropy state. The Universe at this time was in a perfect state. It was made of pure energy and all the forces of nature were one. Then the fundamental forces have separated from each other. The pure energy is transferred into matter. The matter clumps together and forms various structures such as galaxies, stars, planets, moons, life, etc.

At the same time, the Universe is expanding at a rate faster than the light. So, the energy that was there at the beginning, is getting more and more dispersed and the Universe is getting colder and colder. The evidence of this can be observed in the stretched wavelength and redshift of light. Any light coming from very far away galaxies gets stretched and the redshift turns to red. At current times, stars are the sources of heat and energy that give life to the Universe. However, stars are expending their fuel, hydrogen and helium, and are getting destroyed.

Once the last star of the Universe dies out, it will start the process of the end of the Universe. With the last stars gone, intelligent life will soon die out. The expansion of the Universe keeps on dispersing the matter and the energy and there will be no hydrogen that can create stars. After Trillions of years, the last black hole will die out and the Universe will become completely dark. Only black spheres of decaying and degenerative matter will remain which will die out of existence in a time scale that is beyond our comprehension.

The Universe will still keep on expanding and only photon particles and some radiation will remain. Then in some ridiculously large timescale that is beyond our comprehension, these photon particles and the radiation will stretch out and become invisible in the ever-expanding and cold Universe. Then, the time or causal relation will cease to exist in the Universe. The temperature of the Universe will reach near to absolute zero and nothing will happen in this Universe. The entropy will be at its highest and bring about the inevitable end of the Universe which scientists term ‘Heat Death’.

2. Gravity

The ‘Heat Death’ is a grim and cold end of the Universe that sounds ‘chilling’ and, to a certain extent, is ‘boring’. But there is an end of the Universe prospect that is much more eventful and might not be so bad for the fate of the intelligent life in the Universe and the Universe as a whole, as it gives a chance to the Universe to reemerge. However, before there could be a new start of the Universe, there has to be an end of the Universe. This end of the Universe will be brought about by one of the mysterious and enigmatic fundamental forces – gravity.

Unlike the other three fundamental forces, which, in one way or another, involve fundamental particles, gravity is yet to be associated with any fundamental particle. Graviton, which is supposed to be a fundamental particle, is still very much theoretical and it is yet to be discovered. Also, among all other fundamental forces, gravity seems to be the weakest. The hand of an average human could hold an apple against the gravity of the entire Earth.

However, gravity has a Universal range and in large distances, gravity reigns supreme as even the biggest galaxy clusters, galaxies, stars, planets, etc could not go against gravity’s influence. On some occasions, like inside a black hole, gravity shows intense and unimaginable strength as not even light can escape its powerful grip. Gravity is holding the Universe together against the powerful effect of mysterious dark energy which is expanding the space-time at a rate faster than the light. Just like gravity, we don’t understand the dark energy.

Some theories suggest that gravity and dark energy might be related and they might be an innate property of the space itself. Some scientists believe that dark energy is repulsive gravity which pushes things away from each other while conventional gravity pulls things close to each other. When the Universe was smaller, gravity was stronger than the repulsive dark energy. But in the current time, dark energy is stronger than gravity and the dark energy, in Trillions and Trillions of years, will cause the end of the Universe means of heat death.

However, if in the future, the strength of the dark energy goes down and gravity becomes stronger, then things could be different. The gravitational force could halt the expansion of the Universe and could start pulling matters together. Gravity will keep on pulling things close to each other and the galaxies will come close to each other. As the matter in the Universe gets closer to each other, the gravity will get even stronger. Eventually, the pull of gravity will smash and crunch all the matter in the Universe into an infinitely small, dense, and hot point – called Singularity. This event is called ‘Big Crunch’.

The ‘Big Crunch’ will cause the eventual end of the Universe. All the matter and the energy of the Univers will lose all its properties and will be crunched into the Singularity. All the galaxies, stars, planets, black holes, neutron stars, white dwarfs, and life will get destroyed and will become part of the Singularity. However, the end of the Universe scenario caused by gravity may have a reassuring twist. Our Universe came into existence from a ‘Singularity’. So if the expanding Universe, which is supposed to meet a grim ‘heat death’ scenario, somehow rebounds and coalesces into a ‘Singularity’, it could start a new Universe from that Singularity.

This new Universe would again form planets, moons, stars, galaxies, and even new life. This way, gravity could cause the end of the Universe through a ‘big crunch’, but may end up reviving it through ‘Singularity’. Of course, it is still in the realm of theory and for this to happen, dark energy has to get weaker and gravity has to become stronger.

3. Dark Energy

Dark Energy is a mysterious repulsive force that may cause a violent end of the Universe. Edwin Hubble discovered that there are other galaxies in the Universe apart from our own Milky Way galaxy. He also discovered that all these galaxies are moving away from the Milky Way galaxy. The further a galaxy is the faster it is moving away. Scientists have figured out that it is the space in between the galaxies that is stretching and pushing these galaxies away from each other. So, a group of scientists set out on a quest to discover the Universe’s expansion rate.

The scientists have used a Type-1A supernova as the standard candle for the experiments. Type-1A is a type of supernova that occurs in a binary system which, along with a main sequence star, has a white dwarf as one of the companions. Scientists expected the rate of expansion of the Universe to be slowing down. However, in a shocking discovery, they found out that the expansion rate of the Universe is not decelerating instead the rate of expansion of the Universe is accelerating. They figured out that there is a mysterious repulsive force that could be an innate nature of spacetime. This repulsive force, termed ‘Dark Energy’, made up 68% of all the content of the Universe.

Till now, scientists have been unable to figure out what dark energy is and how it operates. We don’t know if it is a force field, a particle, an innate nature of spacetime, or just another expression of gravity. The interesting thing about this mysterious force is that even when the Universe expands, it does not get diluted. The expansion of spacetime adds more space in between the galaxies and pushes them apart. With the inclusion of new space, dark energy also appears within the space.

We have discussed in the ‘Entrpoy’ segment of this article that the entropy, coupled with the expansion of the Universe which is instigated by the dark energy, will bring about the end of the Universe in the form of ‘heat death’. But that scenario is applicable if the dark energy remains constant with the latest observation.

However, there is a probability that the strength of the dark energy might not remain constant and it might increase or decrease in the far future. In a recent study by Elisabeta Lusso (Durham University) and Guido Risaliti (University of Florence), it is shown that the dark energy or the ‘cosmological constant’ may not be constant. These scientists have used quasars as standard candles instead of Type-1A supernovas.

If the strength of the dark energy decreases, then emboldened gravity might cause the end of the Universe in the form of a ‘big crunch’. However, there is a probability, slight it may be, that dark energy increases exponentially, and it leads to a violent and scary end of the Universe scenario. In this scenario, the dark energy becomes so strong that it nullifies the effects of gravity completely, even in the close proximity of the matter. In this end of the Universe scenario, dark energy not only pushes galaxies away from each other, but it starts to push the individual stars and black holes away from their home galaxies.

Then as space expands even more, dark energy becomes stronger and pushes planets, moons, asteroids, etc away from their orbits. No object in the Universe remains gravitationally bounded to each other. Meanwhile, the space keeps on expanding and the individual atoms start to break away from each other. The Universe will be devoid of any structures. Even now, the dark energy keeps on getting stronger & stronger and it even invades the space in between the subatomic particles and tears them from each other. Then finally the dark energy gets so strong that it rips apart the fabric of the space itself and brings about the end of the Universe.

This violent end of the Universe is termed ‘Big Rip.’ If any unfortunate intelligent being exists at this time, that being will experience a violent death as the dark energy will shred it to pieces and rip it apart down to its individual subatomic particles. We sure want this never to happen to us.

4. False Vacuum Decay

Of all the possible scenarios of the end of the Universe, false vacuum decay is probably the scariest one. The big rip is surely a nasty and gruesome scenario for the end of the Universe, especially for any living being. No living being, intelligent or not, would want every single subatomic particle of its body to rip itself apart. However, for the big rip to happen, the dark energy has to increase exponentially which seems an unlikely situation in the next few Billion years.

If dark energy does indeed reach a level to cause a big rip, it would take place over Trillions of years, and by that time we humans may not exist and the Universe may not remain conducive for intelligent life or for any form of life. On the contrary, the false vacuum decay could potentially cause the end of the Universe at any time in the blink of an eye. The scariest thing is that we won’t even realize that the vacuum decay happened and we would cease to exist just like that.

In order to understand how the false may cause the end of the Universe, we need to understand the true vacuum state in quantum mechanics. In quantum mechanics, there is activity even in the vacuum. However, in a true vacuum state, the elementary particles and quantum fields remain at the lowest minimum energy level. This represents the stable situation of the quantum field and the elementary particles. However, if a quantum field or an elementary particle, is not in the lowest possible energy level, then it is in a ‘metastable’ situation which represents a false vacuum state.

If an elementary particle or a quantum field is in a ‘metastable’ state, then it can roll over to the lowest energy level and attain a stable state. This event is termed as vacuum decay and it will prove catastrophic to the Universe. Currently, Top Quark, the heaviest elementary particle and a fermion, and Higgs Field, a Boson, are thought to be in a ‘metastable’ state. Both Top Quark and Higgs Field can attain the true vacuum state through quantum tunneling or quantum fluctuation.

In this scenario, it will create a bubble and will engulf the entire Universe at the speed of light, destroying all the elementary particles as we know it and ending the Universe. This will happen instantly and we won’t even know that it happened.

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