One day the universe will end. But why? And how? Will it be dead forever? And how do we know that?
For decades, scientists have studied this subject and developed numerous theories about the fate of the universe. In this blog, we’ll look at some of the most prominent beliefs about how the universe will end.
First and foremost, the universe is expanding, and not only that, the rate of expansion is accelerating and the reason is DARK ENERGY. This energy is an odd phenomenon that pervades the entire universe. The expansion is like us throwing something in the air, but instead of falling, it simply flies away faster and faster. We don’t really know where this acceleration is coming from but we term it “dark energy”. This is all hypothetical, and we don’t know what the properties of dark energy are, but there are hypotheses that point to three possible possibilities for the end of the universe.
End of the universe by the BIG RIP
Since the BIG BANG or the birth of the universe, it has been expanding. For unknown reasons, new spaces are created equally. Space between galaxies expands, so they move apart. The inside of the galaxies also expands, but here the GRAVITY is strong enough to keep them together. The expansion of dark energy continues at an accelerating rate so fast that even gravity can’t compensate for this effect anymore and it could eventually tear the fabric of space-time apart, leading to the annihilation of all matter in the universe. Space between the single objects expands very fast, causing large structures like galaxies to be torn apart.
Next, big bodies like black holes, stars, and planets die because their gravity is strong enough to keep them together, so they disintegrate into their constituents.
In the end, space would increase faster than the speed of light. Atoms would start to disband. Once space expands faster than the speed of light, no particles in the universe can interact with any other particle. The universe would dissolve into countless lonely particles that won’t be able to touch anything else in a strange, timeless universe.
HEAT DEATH/BIG FREEZE
“The only difference between BIG RIP and BIG FREEZE is that in BIG FREEZE, over an extended time period, the universe expands forever and converts matter into radiation while keeping it intact.”
Why does this happen?
Every state tends towards the state of entropy (The second law of thermodynamics, which states that a closed system’s total entropy will always increase over time). For instance, if we mix different liquids of different temperatures after some time the solution will have the same temperature all around and become uniform. The same thing applies to the universe.
So, as the universe gets bigger and bigger the matter also spreads out. After lots of generations of stars, all the gas clouds necessary to form a star will be exhausted. As no new stars will be formed and the remaining suns would die, the universe will turn dark and too cold for life to exist and all matter will eventually break down into subatomic particles. Black holes will slowly evaporate over trillions of years due to what is known as Hawking radiation.
Only a dilute gas of photons and light particles remains, until even this decay. At this point, the universe is at its maximum entropy; everything ceases and the universe is dead forever.
Unless theoretically, it might be possible that after an incredibly long period of time, there might be a spontaneous entropy decrease as a result of something called “quantum tunneling”, leading to a new big bang.
BIG CRUNCH AND BIG BOUNCE
“Stephen Hawking mentioned this in ‘The Theory of Everything’, which might make it the most popular theory.” What if there is less dark energy than we think or it decreases over time, gravity would be the dominating force in the universe.
In a few trillion years, the expansion of the universe will slow down and stop. After that, it will start reversing and galaxies would start merging as the universe become smaller and smaller. At the beginning of the universe, when it was small, the temperature was high, and the same will happen now. The temperature will rise everywhere all at once.
A few hundred thousand years before the big crunch, the background radiation would be hotter than the surfaces of most stars. Minutes before the big crunch happen, the cores of the atoms will rip apart, before supermassive stars devour everything. Finally, all black holes would merge into a supermassive mega-black hole that contains the entire mass of the universe. In the last moment before the big crunch, it will devour the universe, including itself.
BIG BOUNCE theory states that big crunch has happened a lot of times and the universe goes through an infinite cycle of expansion and contraction. This theory is based on the idea that the Big Bang was not the beginning of the universe, but rather the start of a new cycle in a larger, infinite process.
End of universe
While it’s impossible to say for certain how the universe will end, scientists have proposed several theories on the subject. Whether it’s the Big Freeze, the Big Crunch, the Big Rip, or the Big Bounce, one thing is clear: the end of the universe will be a momentous event that will fundamentally alter the course of cosmic history.