Understanding Closed Systems and the Second Law of Thermodynamics in the Universe

At first glance, it may seem like a mere matter of semantics, but the distinction between closed systems and the application of thermodynamics can have significant implications. In particular, understanding whether the laws of thermodynamics apply to the universe can lead us to fascinating insights about the nature of reality itself.

What is a Closed System?

A closed system is a physical system that does not exchange any matter or energy with its surroundings. However, the real challenge lies in finding a true closed system in the real world. Many attempts have been made, but invariably, there is always another factor, whether it's a dependency, a time lag, or an external influence, that prevents certain closed systems from being realized.

The Second Law of Thermodynamics

The second law of thermodynamics states that the total entropy of an isolated system cannot decrease over time. Entropy, in simple terms, is a measure of disorder or randomness in a system. While this law applies to most systems, it becomes particularly interesting when applied to the universe as a whole.

Are We Living in a Closed System?

It is often debated whether the universe itself can be considered a closed system. To answer this question, we must examine the composition and dynamics of the universe. The universe, by definition, includes everything that exists. Therefore, it does not allow anything from outside to enter or leave. This means that the universe is a closed system and, as such, the second law of thermodynamics does apply to it.

Types of Closed Systems

1. Mass Fixed Closed System

A mass fixed closed system is a system where the total amount of mass contained within it remains constant. This implies that no mass can enter or leave the system. The universe can be viewed as a mass fixed closed system. The mass of radiations entering and leaving the system is nearly balanced, making their contribution negligible.

2. Volume Fixed Closed System

A volume fixed closed system is a system that has a fixed volume and does not allow any matter or energy to enter or leave. While the volume of the universe is vast and expanding, it can still be considered a volume fixed closed system in the context of the matter and energy within it.

The Stellar Bubble and the Milky Way Galaxy

Considering the matter within the universe, we can look at the Milky Way galaxy as a closed system. The galaxy, along with the surrounding vacuum, forms a bubble that is relatively isolated from the rest of the universe. The mass and energy exchanges within this bubble are self-contained, making it a closed system. This means that the laws of thermodynamics apply, and the total entropy of this system will not decrease over time.

Conclusion

The universe, as a closed system, follows the laws of thermodynamics, with entropy increasing over time. This understanding helps us better comprehend the nature and behavior of the universe. By recognizing and understanding the boundaries and rules of closed systems, we can gain deeper insights into the fundamental laws that govern our reality.