The End of The World as We Know It

Author: Cindy Hu

From: West Orange, NJ, USA

https://pixabay.com/photos/milky-way-universe-person-stars-1023340/

Some say the world will end in fire,

Some say in ice.

From what I’ve tasted of desire

I hold with those who favor fire.

But if it had to perish twice,

I think I know enough of hate

To say that for destruction ice

Is also great

And would suffice.

Robert Frost, “Fire and Ice”

Introduction

The end of our universe is a popular subject for both writers and scientists alike. A quick Google search brings up dozens and dozens of poems, and the Internet is filled with different theories. Some are mundane, others exotic, still others illogically rooted in imaginative fantasies.

Today’s post will explore several different theories about what will happen at the end of time as we know it. First, we’ll consider an infinitely accelerating universe. Then, we’ll cover a recollapsing one. Next, we’ll compare and contrast a critical universe and a coasting one. Finally, we’ll end with a completely hypothetical theory contingent on the existence of multiple universes.

Infinite Acceleration

What does it really mean for a universe to be accelerating? (No, I’m not talking about what happens when you press down on a car’s gas pedal.) Instead, I’m talking about its rate of expansion.

As scientists have continued to gather data on celestial bodies, they noticed that nearby galaxies appear to be getting farther away from us. After graphing some data, they concluded that our universe is actually expanding: at this very moment, everything is getting farther and farther away from us.

We don’t know what’s causing this expansion, so we simply call it dark energy.

Dark energy combined with gravity are the two factors contributing to our universe’s expansion. Gravity is an inward pulling force that works against expansion; dark energy is an outward pushing force that causes expansion.

In this particular theory, scientists predict that dark energy will overcome gravity, causing the rate of expansion of the universe to continuously increase forever. Galaxies will move farther and farther away from us at ever-increasing speeds. Eventually, they might even exceed the speed of light. This may sound bizarre and improbable, but a lot of current data actually support this theory.

The Big Crunch

This is essentially the reverse of the Big Bang and the only theory in this post that involves the universe closing in on itself.

We all know the standard Big Bang model and how the universe came into being: it started from a tiny point of mass and rapidly swelled to become larger and larger. Since natural phenomena often come with a sort of balance - hot and cold, rainy and dry, etc., it only makes sense for us to imagine the universe ending in a reverse Big Bang.

According to this theory, gravity will overcome the force exerted by dark energy, and the universe’s expansion will slow down, stop, and eventually reverse. Everything will come closer together and all matter will collapse into a single point. Current data has not yet ruled out this theory, but it’s quite unlikely as opposed to other theories.

Critical v. Coasting

Here are two more related theories. In a critical universe, gravity and dark energy will remain in a balance that allows the universe to continue expanding forever but at a slower and slower rate. The universe won’t ever stop getting larger, but eventually it will reach a point where its rate of expansion is nearly negligible.

In a coasting universe, there will still be a certain balance between gravity and dark energy that will allow the universe to keep expanding. The difference here is that a coasting universe’s rate of expansion will remain the same. While a critical universe’s rate of expansion will get slower and slower, a coasting universe will continue expanding at the same rate forever. This means that the speed at which galaxies are moving away from us today will remain the same in the future.

Darwin Extended

This last one is my personal favorite, although it may be slightly more philosophical than scientific. In short, this theory is contingent on the idea that we are not alone: there are other universes besides ours and we exist in a multiverse. And not only that, but some of these universes also host intelligent life. Eventually, the intelligent life in those universes will become advanced enough to create their own universes.

As this continues, the multiverse will become populated with all kinds of different universes. Some will host intelligent life, some will not. Those that host intelligent life might have the ability to “reproduce,” leading to more baby universes. The ones that don’t will simply die off, perhaps in one of the four ways mentioned previously. Eventually, this will lead to some kind of natural selection among the surviving universes. Only “fittest” ones - the ones with the most intelligent life that can create more baby universes - will live on.

Natural selection is closely related to Darwin’s theory of biological evolution, which states that favorable genes are passed down from one generation to another. As time passes, those with favorable genes will have more reproductive success and those who don’t will begin to die off. This will eventually lead to the development and creation of new species.

If it’s possible for coexisting species to compete with one another for survival, why wouldn’t it be possible for coexisting universes to do the same? At this point, this is only a hypothetical situation, but if additional universes are ever discovered, we just might have to consider extending Darwin’s theory to extraterrestrial worlds.

Conclusion

Remember that everything that has been presented in this post is still a complete theory. Only time will tell if any of these are accurate, although today’s data largely supports the first one - the accelerating universe. Nevertheless, scientific claims can easily be disproven and more research will definitely help clear things up.

I will end with some food for thought: according to Stephen Hawking, time only exists in our universe. Therefore, it wouldn’t make much sense to talk about what happened before the Big Bang. One way to think about this is to consider the process of change: if nothing ever changed, it would be impossible to verify the passing of time. In a way, the words “time” and “change” are synonymous. If this holds true, it also wouldn’t make sense to talk about anything after the end of our universe.

Whether this is a semantic issue or a scientific one, I don’t know. And maybe we’ll never know. But that’s where the fun begins.

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Author: Cindy Hu

Cindy is a high school junior in NJ who loves math, physics, and biology, among many other subjects. Her hobbies include reading, playing the piano, and learning to crochet.

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Citations:

1. Bennett, J. O., Donahue, M., Schneider, N., & Voit, M. (2018). The Essential Cosmic Perspective. New York, NY: Pearson.

2. Hawking, S. (2018). Brief Answers to the Big Questions. London, UK: John Murray.

3. Melodysheep. (2019, March 20). Timelapse of the Future: A Journey to the End of Time [Video]. YouTube. https://www.youtube.com/watch?v=uD4izuDMUQA