Imagine standing on the edge of time itself–gazing into the vast, dark expanse of the universe, knowing that its fate (along with your own) rests in the hands of five awe-inspiring, yet terrifying possibilities.
In The End of Everything (Astrophysically Speaking), published on June 9th, 2020, scientist Katie Mack takes readers on an extraordinary journey through the cosmos. She explores the five theoretical ways the universe could meet its end, drawing on concepts from theoretical cosmology and astrophysics. Written during the tumultuous early days of the COVID-19 pandemic, Mack’s book not only offers a comprehensive yet accessible exploration of complex theories. The big crunch, heat death, the big rip, vacuum decay, and the bounce are all different ways the universe could end. Her book serves as a poignant reminder of the fleeting nature of human existence.
In a world grappling with uncertainty and daily struggles–whether it’s the chances of a bird flu outbreak, or political changes–contemplating the distant and unimaginable end of the universe may offer a surprisingly comforting escape. The sheer scale of cosmic endgame scenarios serve as a reminder of how small and transient our individual problems are in the grand scheme of things. Immersing ourselves in the fate of the universe gives us perspective, allowing us to step back from the noise of life and reflect on our small place in the cosmos.
Our lives, in the vastness of time and space, no matter how important they feel, are just a blink in the eye of eternity.
Understanding the Big Bang
Mack describes the universe’s earliest moments following the Big Bang, when the universe was unimaginably hot and dense. In this time the universe was a chaotic mix of energy and particles that laid the groundwork for the formation of the universe as we know it.
In the first fractions of a second, the universe underwent rapid expansion, a process known as inflation. This set the stage for the formation of galaxies, stars, and planets. As the universe cooled particles began to combine, forming the first atoms and eventually, cosmic structures.
This expansion was first confirmed by American astronomer Edwin Hubble, whose observations of redshifted galaxies indicated that space itself is stretching. The discovery of the cosmic microwave background radiation (leftover radiation from the Big Bang, the oldest light in the universe and farthest point in the cosmos we can observe) further solidified the Big Bang model as the foundation of modern cosmology.
The precise rate of expansion in the beginning allowed the fundamental physical constants and forces to be harmoniously balanced and allow life to exist. If the universe had expanded too quickly after the Big Bang matter would have dispersed too rapidly, preventing the formation of galaxies, stars and planets. Conversely, if expansion had been too slow, gravity could have caused the universe to collapse back in on itself before complex structures could form.
Using the James Webb Space Telescope, scientists have confirmed that the universe is still expanding. Modern measurements show the expansion is at an accelerating rate, driven by dark energy (an unknown force that makes up about 68% of the cosmos). This acceleration influences the distribution of galaxies, formation of stars, and the eventual fate of the universe.
The Big Crunch
The Big Crunch assumes that dark energy will behave differently over time, causing expansion to halt and reverse. The Andromeda (nearest major galaxy at 2.5 million light-years away) and the Milky Way galaxy will collide. Stars will be flung out of orbit, and gas will ignite around supermassive black holes. Gravity overcomes the force of the expansion, until all matter collapses back into a single infinitely dense point. This mirrors the conditions of the Big Bang, but in reverse–a colossal “rewind” of cosmic history.
Heat Death
Also known as the “Big Freeze,” Heat Death proposes that the universe will continue expanding indefinitely, leading to a state of maximum entropy (think of it as the tendency for things to become more spread out and less organized over time). Over immense timescales, galaxies will drift apart, stars will burn out, matter decays and the universe will grow cold and dark. Black holes evaporate due to Hawking radiation (a phenomenon where black holes emit thermal radiation due to intense gravity, leading to a gradual evaporation of their mass). Without energy sources, all processes requiring energy will cease, and no thermodynamic work can be done. In this cold, dark future, there would be no energy gradients left to sustain any processes, leaving a barren, lifeless cosmos.
The Big Rip
The Big Rip predicts that dark energy’s repulsive force strengthens, and the universe’s expansion rate could accelerate uncontrollably to the point where it overcomes all forms of gravitational and electromagnetic bonds. All cosmic structures would be torn apart. This includes galaxies, stars, planets, and even atomic structures. This process culminates with the universe being ripped to shreds, ending in an unbounded, infinitely expanding void.
Vacuum Decay
This theory suggests that our universe exists in a “false vacuum,” a metastable state that is not its lowest possible energy state. This could, theoretically, decay into a lower-energy state which would be the true vacuum state. If such a transition occurs, it would result in the formation of a true vacuum bubble expanding at the speed of light, obliterating everything in its path while reshaping the physics of the universe. This concept is rooted in quantum field theory and highlights the potential instability of our cosmic vacuum.
The Bounce
The Bounce Theory envisions that the universe goes through cycles of expansion and contraction. Instead of ending in a single event, the universe would contract into a singular state (similar to the Big Crunch) but then would “bounce” back in a new Big Bang. This cycle would repeat indefinitely, creating a cosmos with no ultimate beginning or end, just endless cycles of renewal. This theory aligns with some quantum gravity models but lacks strong observational support.
New Insight
A recent Big Think article by Ethan Siegel (2024) sheds light on emerging challenges to established theories about the universe’s ultimate fate. Central to this discussion is the “Hubble tension,” a persistent discrepancy between different methods of measuring the universe’s expansion rate. It has called into question the reliability of current cosmological models. Groundbreaking data from the Dark Energy Spectroscopic Instrument (DESI) in Arizona reveals that dark energy might not behave as consistently as previously believed.
If the properties of dark energy evolve over time it could significantly alter scenarios like the Big Freeze or Big Rip, potentially reviving the idea of a cyclic universe. This new data underscores how much remains unknown about the fundamental forces that govern the cosmos, prompting scientists to revisit and refine their theories.
Astrophysics teacher insight on learning and teaching astrophysics
In order to find out the effect of astronomy on society, I conducted an interview with Mr. Neil Farley, who teaches an astrophysics and astronomy class at Bronx Science. In an interview he explained his views on cosmic phenomena.
The Big Bang and Faith: “In the 20th century, this idea of the Big Bang came up—that actually the universe did have a beginning. And you know, they kind of proved it in the 1960s by finding the cosmic background radiation. For me, learning about science has kind of increased my faith.”
Cosmic Perspective: “The Sun is going to burn out in 4 billion years, and when it does, it’s going to expand to the size of the Earth and vaporize it. But when people hear numbers like 4 billion years, it doesn’t seem that urgent—it’s hard to grasp the scale of it.”
Fine-Tuning of the Universe: “If the universe’s expansion had been just a fraction different, or if we were slightly closer or farther from the Sun, we wouldn’t be here. That kind of fine-tuning is amazing—it’s one of the most compelling arguments for the uniqueness of life.”
Hope in Science: “Even when bad things happen, I believe they’re happening for a reason. Thinking about something larger, like the universe and its mysteries, helps me not get too caught up in everyday anxieties.”
Teaching Astronomy: “I never took an astronomy class in college, but when I was asked to teach it, I forced myself to learn because I was already interested. Explaining concepts like the speed of light or the vastness of galaxies gave me an even greater appreciation for the universe.”
How to become inspired: “Growing up, I loved going to summer camp because they had an observatory. Being out in the middle of nowhere, seeing all the stars—it just made me fall in love with astronomy.”
The World Today
Contemplating the vastness of the universe and its inevitable fate could provide a profound sense of relief when faced with immediate, overwhelming concerns. The risk of an Avian Flu outbreak, for instance, has stirred anxiety amongst many Americans due to its potential impact on public health and global stability. Likewise, political controversies and divisive figures can dominate our thoughts, creating a sense of frustration or helplessness.
Shifting our focus back to cosmic phenomena like the Big Rip or the Heat Death, which are concepts so distant from our everyday reality, offers a chance to momentarily detach from the chaos of daily life. The universe has endured for billions of years and will continue evolving long after our current struggles have faded. It is remarkable that life exists at all.
The fine-tuning of the universe is a reminder of just how extraordinary and interconnected everything is and reinforces the preciousness of the present moment. Reflections by Mr. Farley highlights how the universe has the power to shape both intellectual and emotional perspectives. Whether through faith, scientific curiosity, or simply staring up at a star-filled sky, the cosmic offers a profound sense of wonder. Its scale reminds us that human concerns, though significant, exist in a grander framework and learning about the universe can inspire inspiration.
If the universe is destined for an eventual end, then the time we have now becomes all the more precious, all the more worthy of our gratitude.
Instead of being consumed by worry over pandemics or politics, we can focus on the connections we share with others, the beauty of the natural world, and the opportunities we have to make a positive impact on it all.
“Even when bad things happen, I believe they’re happening for a reason. Thinking about something larger, like the universe and its mysteries, helps me not get too caught up in everyday anxieties,” said Mr. Neil Farley, who teaches an astrophysics and astronomy class at Bronx Science.