If you look up at the night sky, you will see billions of bright stars illuminating the darkness. Every one of those stars, from the asterisms¹ to those standing alone, are giant spheres of hot gas – also known as suns. Each of these suns belong to their own region in the universe, their own galaxy. Some have solar systems, like our galaxy; others do not. There have been approximately 40 trillion suns found in our universe, and still trillions more to find. Some of these suns are parts of millions of galaxies, Hubble² revealing an estimated 100 million. However, as technology advances, so will our estimations and that number will increase to around 200 million.

Many people believe that our universe has always existed – that it is an unexplainable phenomenon. This is not true, though. The universe began 13.8 million years ago, but what came before the universe? What comes after? While no exact explanation of the origin and fate of our universe exists, there are many standing theories to help the human mind grasp possible concepts.

You may have heard that the universe expands perpetually. It will continue to expand forever, even after everything in the universe dissipates – and eventually everything will. The question then becomes: what happens after everything is gone? Or rather, what happened before the universe, as we know it, existed? 

As many know, scientists often use the Big Bang Theory to explain the massive explosion that created our universe. Even so, scientists do not know what existed before this occurrence. There are two major theories that I would like to explore: The Cyclic Universe Theory and The Big Freeze Theory. Although these are only two of many existing theories, they serve as fundamental [possible] explanations of how the universe was born, and its ultimate fate.

In 2010, British mathematician, mathematical physicist, and philosopher of science Roger Penrose popularized a new theory known as the Cyclic Universe in his book Cycles of Time: An Extraordinary New View of the Universe. This theory states that the universe is subjected to endless cycles of expansion and cooling; each cycle beginning with a “big bang” and ending with a “big crunch.” This “big bang” refers to the commonly known Big Bang Theory, that the universe began with high heat and density and inflated to form the universe – however, Penrose’s theory suggests that the Big Bang was not the beginning of the universe, but rather a part of a repeating cycle- that there was a phase leading up to it. 

The “big crunch” part of the theory refers to the possible fate of our universe, in which the expansion of the universe reverses, causing it to recollapse. This phenomenon would, at length, cause the cosmic scale factor³ of the universe to reach zero, which could potentially lead to another “big bang”, in which the universe would reform. The Cyclic Universe Theory states that this cycle would repeat itself again and again, for all eternity. Although additional evidence showing that the expansion of the universe is accelerating rather than slowing does decrease the likelihood of this theory, a variation in dark energy⁴ could serve as proof of this theory’s existence. Penrose explains this theory much more extensively in his book Cycles of Time.

An opposing theory on the origin and fate of the universe is the Big Freeze Theory. In 1777, French astronomer Jean Sylvain Bailly developed this theory through his writings on the history of astronomy. Bailly believed that all planets had an internal heat, which was increasingly cooling. Further development of this theory has shown that the universe will expand at an increasing pace, as a result of dark energy, therefore causing matter and energy to thin out over an immense amount of time. Under this model, the universe would become so vast and matter and energy so thin that stars would cease to exist, resulting in a universe too cold to sustain life; thus the name “Big Freeze”. The universe would, theoretically, become an endless void, forever expanding, with no cosmic activity.

Although these are some of the more popular theories regarding the origin and fate of our universe, there are a number of others out there. And while there is science that supports each of these theories, they are still just theories. Considering how immense the universe is, it would be impossible to know anything for certain; that is what makes it so compelling, though. We may never truly know the origin and fate of the universe, but it is an intriguing phenomenon nonetheless. 

Penrose stated in his book Cycles of Time, “To before the Big Bang? Surely not: the Big Bang is supposed to represent the beginning of all things, so there can be no ‘before’. Never fear—this is just a mathematical trick. The extension is not supposed to have any physical meaning! Or might it …?” Like Penrose, we should always question our existing knowledge. Possibilities are endless as is our universe; therefore our minds should be, too.

Footnotes:

¹A pattern of stars that is not considered a constellation

²A space telescope launched into low Earth orbit in 1990; a space-based observatory

³ A mathematical quantity that shows the relative change in size of the universe

⁴A counterpart to gravity (“anti-gravity”) force which provides a negative pressure which fills the universe and stretches the fabric of spacetime

Sources:

Roger Penrose Cycles of Time book: https://www.amazon.com/Cycles-Time-Extraordinary-View-Universe/dp/0307278468

https://wmap.gsfc.nasa.gov/universe/uni_fate.html

https://www.apu.apus.edu/area-of-study/math-and-science/resources/origin-of-the-universe/#:~:text=The%20Big%20Freeze%20Theory%20(also,over%20immense%20periods%20of%20time.

https://exhibits.stanford.edu/super-e/feature/jean-sylvain-bailly-1736-1793

https://unsplash.com/@grakozy