Scientists Argue Over How Universe Will End

Scientists and cosmologists have long discussed the origins of the universe, an expansion that occurred when high density and temperatures created an event known as the Big Bang. With that knowledge of how it all started, it’s natural to be curious about how it will all come to an end.

Currently, two leading theories regarding the eventual fate of the universe are known as the Big Rip Theory and the Big Freeze Theory. Both provide potential answers for what may be the ultimate fate of our universe, but that raises the question: which one is more likely? To figure that out, we need to understand what each of these theories entails.

Let’s start with the Big Rip Theory. Physicists have described this as one potential outcome for the end of the universe. To understand it, we need to cover a few important pieces of context. Firstly, the universe is constantly expanding. Over time, the distance between parts of the universe is steadily increasing, a phenomenon that has been occurring since the Big Bang due to the energy from that event.

As a result of this constant expansion, galaxies outside our own are gradually moving away from us, with those further away moving faster. However, these galaxies are not moving through space; rather, the space they inhabit is also expanding. In other words, the universe encompasses everything that exists—our galaxy and others—and everything is gradually spreading itself thinner.

The second piece of context is the existence of dark matter and dark energy. Dark matter is one of the most important cosmic phenomena in the universe, yet it is surprisingly difficult to study because it cannot be detected directly. It is composed of particles that do not absorb, reflect, or emit light. Scientists know it’s there by observing its effects on visible objects in the universe, as it collects around galaxies, affecting gravitational fields and bending light.

Dark energy, on the other hand, is not as well understood. It comprises roughly 68% of the universe and is linked to the expansion of the universe. Current theories suggest that dark energy causes space and the galaxies within it to gradually move apart. This mysterious force is still not fully understood, but it can overwhelm gravitational and electromagnetic forces, causing objects in the universe to keep moving apart.

In short, the universe is constantly expanding, largely due to dark energy. Now, what exactly is the Big Rip? Given that the universe is continually expanding at an accelerated rate, the theory posits that eventually, this force will begin to deconstruct matter and even spacetime itself. Essentially, the universe would be broken down into its basic components, with gravitational forces between objects being pulled apart by rapid expansion. Ultimately, the entire universe would be torn apart, from galaxies to stars, planets, individual atoms, and even time itself, leaving nothing behind.

In 2015, a new model of the Big Rip theory was developed by Marcelo Disconzi, an assistant professor of mathematics at Vanderbilt University, along with physics professors Thomas Kephart and Robert Scherrer. They were able to approximate when the Big Rip might occur—around twenty-two billion years from now. For the Big Rip to happen, dark energy would need to become stronger than gravity, eventually causing single atoms to separate.

Disconzi examined the viscosity of the universe, which refers to how resistant it is to expanding or contracting. He determined that the universe’s viscosity is quite low, meaning it could theoretically expand to a near-infinite size. If dark energy increases in strength as the universe expands, it could eventually become strong enough to pull individual atoms apart.

If the Big Rip theory is correct, the space between galaxies would become nearly infinite, with individual stars drifting away from their galaxies, and planets being torn apart. On a microscopic level, molecules and atoms would split, with electrons being pulled away from atoms. This would reduce the universe to its bare components, potentially leading to a scenario where the very fabric of space glitches as it begins to tear itself apart.

However, the Big Rip isn’t a certainty. There are other predicted models for the eventual demise of existence, such as the Big Crunch. This theory suggests that the universe’s constant expansion will eventually slow down and lead to everything collapsing into a singularity, akin to a reverse Big Bang.

Then there’s the Big Freeze, which suggests a state where the universe becomes so still that nothing can physically happen. According to this theory, as the universe expands, energy will become evenly distributed, leading to thermodynamic equilibrium. This would mean that all heat and energy would be constant across the universe, ultimately decreasing temperature and leading to a state where no new heat can be produced.

When considering which of these outcomes is more likely, it depends on who you ask. Some scientists hope for a Big Crunch, where gravity pulls everything back together, leading to a new cycle of destruction and creation. However, most scientists agree that the universe will continue to expand, making the Big Freeze the more widely accepted outcome.

There is also a less conventional theory known as the Big Slurp, or False Vacuum Decay. This theory suggests that if a part of space transitions from a high energy state to a low energy state, it could create a bubble of vacuum decay that expands at the speed of light, potentially altering the universe as we know it.

While the exact nature of how the universe will end remains uncertain, it is clear that it is a long way off. Understanding these theories can foster a greater appreciation for the universe we inhabit and remind us that nothing is permanent.