Polluted White Dwarf. — NASA/JPL - Caltech

Mysteries of Space – How will the universe end?

22nd May 2025
Author: Sean Sweeney

The idea that “nothing lasts forever” is a universal truth but applying it to the cosmos leads us to a big question. How will the Universe end? For centuries, philosophers have pondered what the fate of everything will be. Today, scientists have developed interesting theories, from quick conclusions to slower events that will happen over time. Let me share some of these potential endings for our Universe.

Things We Know Will End

We may not know how the Universe will end but some things in our world are a definite and we have the science to point us in the right direction. Let’s start with the Earth. Yes, the Earth unfortunately has an expiry date, and that is because our Sun is evolving and one day it will become too hot for any life on our planet to survive.

Fortunately, this isn’t for another five billion years or so. Once the Sun runs out of its hydrogen fuel, it will become a red giant - puffing out it's atmosphere. Eventually it will expel its outer layers leaving behind a white dwarf. This remnant core of our Sun will mark the official death of our star.

Then there’s our Milky Way galaxy, which may collide and merge with the Andromeda galaxy, also around five billion years time from now. Thus, leading to the birth of a new galaxy. So, although not technically the end of our Milky Way galaxy, it will still become something different entirely.

Theories On How The Universe Will End

Our Universe is a big place - I mean big! It’s constantly in motion and evolving. On top of this, there are multiple scientific processes happening at every moment and on various scales. These processes range from the small realm of quantum physics to the huge scale of galaxies and the evolution of the Universe itself. So how will all this end, will it end? Science still can’t say for sure but there are a few theories that explore the potential end of the universe.

Alex Mittelmann

The Big Freeze

The Big Freeze, is also known as heat death. It is a scientific idea about the Universe that suggests that the Universe will continue to expand, eventually reaching a state where it is too cold to sustain any form of life. This is due to stars moving farther apart, burning out and no new ones appearing.

Who Came Up With This Theory?

The Big Freeze theory wasn’t created by any one person but by a collective body of ideas from different scientists over time. In terms of

When Will It Happen?

Well not to worry. The Big Freeze isn’t happening any time soon. In fact, it’s estimated that this process could take trillions of years. It won’t be a sudden event but will more likely be a gradual cooling of our Universe over billions of years.
ArtOfAnrach

The Big Rip

In the Big Rip scenario the Universe's rapid expansion, driven by dark energy, becomes so intense that it eventually overwhelms all other forces in the Universe, such as gravity. It would tear apart everything from galaxies to atoms, and even the fabric of spacetime itself.

Who Came Up With This Theory?

The Big Rip theory was first thought up by Robert R. Cardwell, Ph.D. in 2003. He is a professor in the physics and astronomy department at the University of Dartmouth. The theory was later reviewed by Marcelo Disconzi , Ph.D., Thomas Kephart, Ph.D. and Robert Scherrer, Ph.D.

When Will It Happen?

Robert R. Cardwell, Ph.D. came up with a hypothetical answer as to when the big rip may take place. You will all be glad to know this answer was 22 billion years from now.
Nasa

The Big Crunch

The Big Crunch suggests that the expansion of the Universe will eventually reverse, leading it to collapse back in on itself. However, scientists currently observe the Universe to be speeding up in its expansion because of something called dark energy. This makes the Big Crunch unlikely.

Who Came Up With This Theory?

The Big Crunch theory finds its roots in the works of Alexander Friedmann. In 1922 he created equations to show that what happens to the Universe depends on how much stuff (density) is in it.

When Will It Happen?

If The Big Crunch was to happen, it is predicted that it would not happen for another trillions of years, possibly even longer.

One Last Mention - The Big Bounce

Another theory is the Big Bounce theory. It proposes that before our Universe formed there was already one before it. Instead of starting from a single point the Big Bounce sees the Universe collapsing and then bouncing back, expanding again.

Who Came Up With This Theory?

The Big Bounce theory can not be credited to one person, but rather to a group of scientists who have been exploring and developing the concept over time. Some of these key figures include the Loop Quantum Cosmology Researchers, including Abhay Ashtekar, Tomasz Pawlowski, and Parampreet Singh.

Other mentions go to Roger Penrose and Anna Ljjas who in 2019, received 1.3 million US-dollars from the Simons Foundation to help them conduct a research project to formulate and test the big bounce model through different parameters.

When Will It Happen

Because it is an idea about how the Universe might work, we can't be sure when the Big Bounce might happen.

Challenges and Opinion

We have now covered some of the most popular scenarios that scientists think could be the end to our Universe but what challenges do we face in understanding which one is most correct? Accurately coming up with the answer with theories like the Big Freeze, Big Rip, Big Crunch and Big Bounce is challenging because we do not fully understand the mysterious forces that shape the cosmos, especially dark energy.

Our current theories and knowledge of the Universe provide clues but cannot definitively tell us how these forces will behave over trillions of years. Thus, leaving the exact end of the Universe an open question and left for current and future generations of scientists to continue improving upon.

As for me, well… The thought of how the Universe will end, if at all, fascinates me, and I’ll continue to play scenarios in my own head on what its end may be. I inclined to think that the Universe will continue to expand as it has since it's birth. So if I could partially agree with any of the theories we've spoken about it would be the big freeze.