The Morning Ritual

Each morning, I boil water to prepare a hot drink with lime or lemon and a pinch of salt. While some prefer tea or coffee, my preference is a refreshing hot lemon drink to kickstart the day.

Now, consider an interesting scenario: if I place my hot drink on a table, can it become hotter after five minutes without any external interference?

Your instinct might be to say, "Absolutely not, physical laws prevent that." However, the reality is that these laws allow for such a possibility, even if it’s not commonly observed. The reason we typically don’t see this phenomenon is due to entropy.

In a closed system without external influences, entropy tends to increase. In this case, the likelihood of heat from the cup transferring to the surroundings is vastly greater than the opposite. Eventually, this leads to an equilibrium where the cup and its environment share the same temperature.

Keep this concept in mind, as it will be crucial for understanding the cosmic interplay between entropy and gravity throughout this essay.

Gravity: The Cumulative Force

In our earlier scenario, we didn't consider the influence of gravity. Why is that?

Does gravity not play a role in the rate of heat transfer? Does it not influence how steam molecules disperse in the room? Indeed, it does, but scientists often describe its effect as "negligible."

This term reflects the fact that gravity's influence is too weak to make a significant difference in qualitative discussions. The intriguing aspect of gravity is its cumulative nature.

Take a steam molecule, for example. Earth's gravity exerts a slight pull on it from every molecule of the planet. While these forces accumulate, their impact remains minor due to the steam molecule's minimal volume. However, when we consider a large rock, the cumulative force becomes more pronounced, as the greater volume allows for a more substantial gravitational pull.

Yet, in the grand cosmic scale, even this force is trivial. You could easily lift the rock with a hydraulic digger, highlighting how the relationship between entropy and gravity is clearer at larger scales.

The Cosmic Thought Experiment

Imagine a hypothetical cube in space that could contain a million suns. Within this cube, visualize a vast gas ball. Here, the effects of gravity come into play, unlike in our previous scenarios.

As gas molecules within this cube attempt to disperse, entropy operates similarly to the steam molecules from my hot drink. However, they face an additional challenge: the cumulative gravitational pull from other molecules in the gas ball.

Due to the immense size of this gas ball, gravitational forces exert a significant influence, drawing molecules together. Eventually, a dense core of gas molecules begins to form. Meanwhile, gas molecules at the boundary continue to spread, causing the gas ball to expand, which accelerates the boundary molecules.

In a prior essay, I explained that temperature is simply a measure of molecular speed. As the gas ball expands, the temperature at its boundary increases.

In contrast, the core's gravitational forces become so strong that they prevent certain molecules from escaping, causing them to fall toward the core and accelerate, which also raises the core's temperature.

When does this process cease? In the hot drink scenario, heat transfer stops when equilibrium is reached. However, in our cosmic thought experiment, achieving equilibrium is far more complex.

The Entropic-Gravitational Dance

We observe a curious phenomenon: gravity's influence on entropy leads to a core that becomes denser and hotter, while the outer boundary expands and increases in temperature.

In a scenario akin to my hot drink, one might expect the core's heat to transfer to the cooler boundary until equilibrium is achieved. Yet, in this cosmic context, the flow of heat behaves unexpectedly.

As heat moves from the core to the boundary, the boundary expands, moving away from the core's gravitational pull. Consequently, this results in a decrease in the boundary's temperature rather than an increase.

This creates a self-sustaining cycle: the core's temperature rises, releasing heat that expands the boundary, which cools down even further. The growing temperature difference between the core and boundary accelerates this cosmic engine.

Of course, this process cannot continue indefinitely. Nature has a twist in store.

The Romance Beyond Expectations

As the core compresses beyond a certain threshold, nuclear forces emerge. When gravitational pressure becomes intense enough to cause atomic fusion, an outward force is generated that counteracts further compression of the core.

We now witness the birth of a star, an organized entity arising from the chaotic tendencies of entropy, driven by gravitational forces that initiate nuclear fusion at a specific threshold.

This realization is astounding. Before concluding, let’s address a critical question: Does a star reduce or increase entropy?

On one hand, the temperature in the core rises due to nuclear fusion, increasing entropy. On the other hand, as the core's volume diminishes, entropy decreases. The key lies in understanding which effect prevails.

Scientists have analyzed this and concluded that the net result is a reduction in the core's entropy. Conversely, the boundary's volume increases, leading to a rise in entropy. The increase in entropy at the star's boundary surpasses the decrease in the core, indicating that the star ultimately contributes to the system's overall entropy.

This discovery is even more remarkable. The only distinction between my hot drink and the gas ball is that gravity's effect is negligible in the former, while it plays a crucial role in the latter. The outcome is a stunning creation of order emerging from chaos, with the ultimate purpose being to enhance the universe's disorder. This realization fills me with wonder!

This first video titled "The Biggest Ideas in the Universe | 20. Entropy and Information" explores the intricate connection between entropy and cosmic phenomena, shedding light on the principles discussed in this essay.

The second video, "What If Gravity is NOT A Fundamental Force? | Entropic Gravity," challenges conventional notions of gravity, aligning with our exploration of gravity's role in the universe.