How Will the Universe End?
- Brandon Lie
- Nov 24
- 5 min read
There’s a popular saying:
“All good things must come to an end.”
We often say these things about our experiences, our memories, and our relationships, to remind ourselves of the reality that may be waiting for us. But what about the universe? What about reality as
we know it? Will that end?
According to most scientific theories, the answer is yes.
There are many theories regarding the end of the universe, and while we cannot be certain exactly how this may happen, we do have enough information to come up with some ideas.
Heat Death
One of the theories, and most popularly believed, surrounding the end of the universe is known as Heat Death. First developed by William Thomson in the 1850s, the hypothesis of heat death states that the universe will one day achieve a state of maximum entropy.
According to the second law of thermodynamics, entropy of the entire universe, as an isolated system, will increase over time. Entropy is the measure of how energy gets moved around and distributed throughout a system. It’s basically how particles of matter keep transferring energy to each other until the energy is evenly distributed. A hot cup of coffee cooling down and transferring its thermal energy to the surroundings is an example of increasing entropy.
If we assume that the universe will last for an infinite amount of time, eventually maximum entropy will occur, in which all energy of the universe will be completely evenly distributed. In other words, every single part of the universe will be the same temperature, which gives the theory its name: the death of heat.
While this theory remains the most likely to occur based on the knowledge we have at the moment, this doesn’t necessarily explain the end of the universe, merely the end of all life and action. The universe will not just blink out of existence, it will still exist, except all bodies within it will be the same temperature, which means no chemical reactions, no action, and definitely no life.
But like with all theories, this one has some holes in it. For this to be true, we must assume that the universe is an isolated system, which means that there is nothing outside of it, or at least nothing outside that can affect it. However, we don’t have solid evidence that this is true, and that there could be a possibility of a greater cosmos existing outside our currently observable universe.
The Big Rip
This theory is significantly more violent than the previous one. As the name suggests, the universe will eventually tear itself apart.
To first understand this theory, we must first understand that the universe is expanding. We know this because of a concept known as “redshift”. As we observe light waves travelling from space, we can see their wavelength sort of ‘stretch’ out, following the expansion of the universe, and thus their frequency decreases, shifting to the red side of the visible light spectrum.
For a while, it was believed that the universe’s expansion was decreasing, until studies done by Brian Schmidt and Saul Perlmutter. Simply put, they measured how redshift changes over long distances, and while they expected the redshift to decrease over the distance, they found that it instead increased. This means that the expansion of the universe is increasing.
This fits into Einstein’s Theory of Relativity. In order to prevent model universes from collapsing under their own gravity, he included the fact that the vacuum in between bodies of mass may include its own energy (Cramer, 2004). We call this energy ‘Dark Energy’, and it’s basically the opposite force of gravity that balances out or even overcomes the universe’s gravitational force to collapse into itself. Through the study, it was revealed that dark energy produced an anti-gravitational force three times larger than the gravitational force between masses. It was also seen that dark energy increases the greater the distance between two objects.
The force of dark energy causes distance between masses to increase, thus also causing dark energy to increase, causing a feedback loop. It was estimated that in an approximate 22 billion years, the Big Rip will occur. The expansion of the universe will be so fast that it will rip.
A general timeline has been approximated for the events that will take place leading up to the Big Rip:
1 billion years before the Big Rip: galactic clusters will be ripped apart.
60 million years before: the Milky Way galaxy would have dispersed.
3 months before: our Solar System will disperse.
30 minutes before: Earth rips apart and explodes.
10^-19 seconds before: Atoms are ripped apart, and then nuclei are dissociated into simple neutrons and protons.
There will no longer be any structure in the universe.
The Big Crunch
This theory is quite literally the opposite of the Big Rip.
This idea acts more as a hypothetical scenario, rather than an actual theory. Due to the gaps in our understanding of dark energy, there is a possibility that dark energy will eventually weaken, allowing the universe’s gravitation pull to overcome it. According to Alexander Friedmann (1922), after achieving maximum expansion, the gravitational pull of the universe will start to reverse the process, pulling all mass into itself, forming a singularity. Think of the Big Bang, but in reverse.
While this theory doesn’t have evidence as strong as the previous two, recent evidence has shown that it shouldn’t be completely ignored.
The Big Bounce
This theory follows onto the previous Big Crunch scenario. As its name suggests, this theory involves a bounce. After forming a singularity of such high mass and density, gravity will cause all matter to ‘bounce’ outwards (Bojowald, 2024). Einstein’s Theory of Relativity states that, when the universe gets clumped into a singularity, gravity will start acting differently, and thus push everything outwards, exactly like the Big Bang.
If this were true, it proposes the idea of a cyclical universe. A universe of death and rebirth. One with no definitive end.
While I do think that the heat death of the universe is the most likely to occur, I do have a sort of hope that the Big Bounce is true instead. The concept of an infinitely rebirthing universe of literally infinite possibilities just appeals to my fantasy-loving wild imagination.
Reference List
Analog science fiction. (n.d.). https://www.npl.washington.edu/av/altvw126.html
Azarian, B. (2024, May 24). Life need not ever end. NOEMA. https://www.noemamag.com/life-need-not-ever-end/
Bojowald, M. (2024, February 20). Big bang or big bounce?: New theory on the universe’s birth. Scientific American. https://www.scientificamerican.com/article/big-bang-or-big-bounce/#:~:text=Instead%20it%20may%20have%20represented,all%20traces%20of%20this%20prehistory.&text=This%20picture%20of%20the%20big,view%20of%20what%20came%20before.
Heat Death of the universe. (2017). In International Journal of Engineering Research in Mechanical and Civil Engineering (Vol. 2, Issue 11, p. 95) [Journal-article]. https://www.technoarete.org/common_abstract/pdf/IJERMCE/v4/i11/Ext_81294.pdf
Helmenstine, A. (2025, August 17). What is entropy? Definition and examples. Science Notes and Projects. https://sciencenotes.org/what-is-entropy-definition-and-examples
Libretexts. (2025, January 1). 2nd Law of Thermodynamics. Chemistry LibreTexts. https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Thermodynamics/The_Four_Laws_of_Thermodynamics/Second_Law_of_Thermodynamics
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