How Will Our Universe End?

We're all familiar with the concept of the Big Bang, and it's quite disheartening that the popular TV series "The Big Bang Theory" has come to an end. However, let's steer away from the candy bars and delve into a different aspect – the Big Crunch. While most people have heard of the Big Bang, fewer are acquainted with the Big Crunch. Despite various theories like the Big Freeze and the Big Rip, the Big Crunch stands out as the most plausible scenario for the eventual fate of the universe.

The Big Crunch Theory finds its origins in Einstein's theory of general relativity, which suggests that the universe's trajectory mirrors the ebb and flow of events. Just as actions have reactions, the expansion caused by the Big Bang is believed to eventually reverse, leading to the universe's collapse. Once the universe reaches its maximum size, dictated by its energy content, it will start contracting, eventually forming an immense black hole containing all matter. Within this singularity, everything will be compressed to an infinitesimal size, earning the name "Big Crunch."

While this scenario might not bode well for bacon enthusiasts and those who plan to live for billions of years, there's a silver lining. While calculations imply the possibility and even probability of a Big Crunch, our understanding of the universe is incomplete. Certain variables remain unknown, and this uncertainty affects our ultimate destiny.

The universe's expansion results from the interplay of density and outward momentum. Density influences gravity – the denser the universe, the stronger its gravitational forces. This should theoretically lead to a gravitational pull that counteracts the initial outward momentum of the Big Bang, resulting in a Big Crunch. However, observations challenge this simplicity. Distant regions appear to be expanding at a faster rate than those closer to us, and galaxies are drifting apart. This mystery is attributed to dark energy, an unknown factor in the universe's expansion.

Depending on the amount of dark energy present, two outcomes are possible: the universe's expansion continues indefinitely, leading to freezing conditions, or the forces of gravity ultimately overpower dark energy, prompting a Big Crunch. The prevalence of dark energy has led some to speculate that a Big Crunch is inevitable. A 2015 report proposed that the current accelerated expansion might be the universe's last phase before contraction begins in tens of billions of years.

In the event of a Big Crunch – assuming insufficient dark energy – the process would unfold gradually. Even distribution of matter would result in a relatively even contraction. Over time, galaxies would approach each other, and the pull of gravity would intensify. After approximately a hundred billion years, as temperatures rise, stars would explode and vaporize, reducing all objects to atoms. These atoms would then break down further. In the final stages, all matter would compact into a small space, leading to extreme chaos. Some theories speculate that space-time would become so warped that it shatters, rendering concepts of time, distance, and direction meaningless.

It's crucial to note that living organisms would long have ceased to exist before such a point is reached. Given our limited understanding of the universe's workings, it's impossible to predict its ultimate fate with certainty. The scenario of a Big Crunch involves all matter returning to its point of origin, culminating in a colossal black hole. Beyond this stage, speculation reigns – it could pave the way for the birth of a new universe, or this process might have occurred multiple times already, with our existence being just one cycle in a series of expansions and contractions. Ultimately, only those expecting to live for billions of years need to concern themselves with these considerations.