What Would Life Look Like in a Universe Facing Heat Death?

Everyone from astrophysicists to fiction writers has postulated what the end of the universe could look like. Everyone’s theories range from the fantastical and impossible, based on current scientific understanding, to closer to the possible than humans think. These ideas continue to develop to this day as people further explore the stars and the unfathomable, never-ending stretches of the universe. The heat death theory is one of the most prevalent, and while it sounds impossible — and it might be — there are some reasons to believe the universe could one day be devoid of warmth.

What Is the Heat Death of the Universe Hypothesis?

The heat death of the universe is a hypothesis also known as the Big Chill or the Big Freeze. Despite it sounding like the universe would burn to death because of heat, this poses the opposite — this represents a scenario where all heat in the universe would die, and everything would enter a state of no present thermodynamic free energy. 

This can only happen if the chaotic nature of the universe’s entropy reaches a maximum. No process could continue, and nothing would happen, including heat. The universe and everything in it would act like a hot cup of tea that is cooling. It would begin with low entropy, with hot steam rising into the cold depths of space. As the steam escapes and temperatures regulate, everything becomes uniform, and the heat becomes scattered and random, entering a state of high entropy.

This is one of many ideas put forward in scientific debate about the fate of the universe. While it sounds unlikely given the extremes it would require, there is some scientific backing for it. However, it remains a hypothesis for a reason. There are plenty of sound arguments against and for the idea, making it one of the most interesting debates in space discourse.

How Would It Happen, and Is It a Certainty?

If entropy reaches its maximum, then all temperatures in the universe would disperse. Everywhere would have the same temperature, meaning places that were typically warm would freeze to near absolute zero. 

The Earth is a closed system, meaning its entropy cannot decrease. It can remain stagnant or increase. This is why the hot cup of tea never regains warmth after sitting on the coaster for too long. The universe would never obtain those temperatures again once it was lost. However, the universe is an isolated system because it has no edges and no other entities with which to exchange energy or matter.

The heat death of the universe is not a certainty. However, the universe is constantly expanding, spreading out that thermodynamic free energy to greater lengths. It is one of the more likely scenarios among the popular theories, along with the Big Rip and the Big Crunch. There is no way humans would survive it, as it would be too cold. In fact, humans would need to escape Earth and inhabit other planets first, as the Sun would become a Red Giant before the heat death of the universe.

What Evidence Supports Heat Death?

There are a few prevailing reasons why the heat death hypothesis remains a consideration for the universe’s fate, with thermodynamic laws being the most significant. 

The Second Law of Thermodynamics

This is the foundation of the idea. The second law of thermodynamics states that energy can never decrease over time in isolated systems. Because the universe is regarded as an isolated system, the energy will keep spreading infinitely until it becomes so disordered that it cannot continue. There is an endpoint to this energetic stretching that would take a long time to reach, but it is possible.

The Accelerating Expansion of the Universe

Additionally, the universe’s constant expansion is strong evidence supporting the hypothesis. Everything continues to grow, and over time the pace becomes faster. This has been observed for over a decade, and the discovery earned a Nobel Prize in Physics. 

Astronomers have been observing specific types of supernovae and their brightness levels and increasing wavelength, or redshift. It is proving that more space is appearing between them, causing their energy to decrease.

The Cosmic Microwave Background (CMB)

The CMB is what remains of the Big Bang. The radiation has been pouring into the entire universe for all of time. Its temperatures are almost completely uniform, suggesting there was a time near the universe’s birth that already attained equilibrium. If this is how it was in the early days, then it is not impossible for the end of the universe to revert to this state. 

Lack of Evidence for a “Big Crunch”

The Big Crunch is a theory about the fate of the universe that holds that everything will collapse in on itself. This can only happen if gravity fights back against the continuing expansion. Unfortunately, observational evidence fights this evidence. Many believe the discovery of dark energy directly contradicts the Big Crunch, further disrupting this camp.

While the absence of evidence for one idea does not inherently make other hypotheses more legitimate, it does minimize the number of possibilities humans have conceived for what the end of the universe could look like. Reducing the likelihood of other hypothetical scenarios merely increases the probability that the universe will experience heat death, based on the circumstances humans have postulated to date. It is possible we have not even considered the actual event that will happen, but only continued research will make this even clearer.

The Universe’s Long Goodbye

While there are a few ideas that support the heat death of the universe, experts still do not know for certain whether this will be the event that triggers the collapse, or whether there will be a singular, notable event at all. Everything in space may slowly dissolve or break apart for a million simultaneous reasons beyond humanity’s current comprehension of the cosmos, or all thermodynamic free energy could disappear. All the planet can do is keep questioning the curiosities of the unknown. Maybe it will eventually reveal the truth.