Primer Home / Entropy / An Explanation of Why Your Bedroom is Messy

An Explanation of Why Your Bedroom is Messy

Topic: Entropy
by Christopher, 2020 Cohort

One might describe entropy as a measure of disorder and point to the second law of thermodynamics which states that the total entropy of an isolated system can never decrease over time. For example, your bedroom always tends towards a messier or more disordered state and castles, built centuries ago, now stand in disordered ruins.

Now consider a container separated into two halves. One of these halves contains a gas and the other is completely empty (a vacuum). If we now remove whatever is separating the two halves, we all intuitively know that the gas would spread out evenly throughout the volume of the container. According to the definitions given above, this means that the state in which the gas is spread evenly throughout the container is the most disordered state. This may seem puzzling, as an evenly distributed equilibrium state does not sound disordered.

Entropy could therefore be more accurately described as a measure of how spread out energy is. Consider a hot water bottle that you fill with boiling water to keep yourself warm. Immediately after filling that bottle, there is a significant heat difference between your body temperature and the temperature of the bottle. This allows the bottle to warm you up. Now imagine that you’ve woken up in the middle of the night to find that your hot water bottle has cooled to room temperature. It now no longer serves any purpose because there is no heat difference between yourself and the water bottle. The entropy (or the ‘spread of the energy’) has increased to a maximum.

Considering entropy from this perspective, we can see that in any system, it is the difference in energy rather than the total energy that is useful. In the previous example, when you wake up to find yourself next to a room temperature water bottle, it is not the case that the bottle has lost all its energy, just its useful energy. All the water particles are still vibrating with an amount of energy equivalent to that room temperature. However, this energy is no longer useful to you as the system made up of yourself and the hot water bottle has reached equilibrium. We can think of the universal increasing of entropy accordingly. Energy (and by extension mass) always works to distribute itself equally and the amount of useful energy in any system therefore decreases.

Another way we can frame entropy then, is in terms of decay. The world as we know it exists because of the various sources of useful energy around us. The sun is one obvious one. However, with every passing day the sun uses more of its fuel and therefore depletes its source of useful energy. We might consider this decay. Using this lens, it may be possible to use the principle that entropy always increases to examine other walks of life. For instance, perhaps one could find a link between the inevitability of conflict or the inevitability of civilisation collapse and this law that says decay is an unstoppable force.

Explore this topic further#

• Wikipedia Introduction to Entropy{.link-ext target=”_blank”}
• Michio Kaku and Morgan Freeman Explain Entropy YouTube{.link-ext target=”_blank”}
• Charlie Lineweaver and Paul Davies provide an excellent discussion about entropy and complexity in Complexity and the Arrow of Time{.link-ext target=”_blank”}
• Arieh Ben-Naim’s, Discover Entropy and the Second Law of Thermodynamics Chapter 1{.link-ext target=”_blank” }
• History of Entropy{.link-ext target=”_blank” }

Return to Entropy in the Primer

Disclaimer#

This content has been contributed by a student as part of a learning activity.
If there are inaccuracies, or opportunities for significant improvement on this topic, feedback is welcome on how to improve the resource.
You can improve articles on this topic as a student in "Unravelling Complexity", or by including the amendments in an email to: Chris.Browne@anu.edu.au

One might describe entropy as a measure of disorder and point to the second law of thermodynamics which states that the total entropy of an isolated system can never decrease over time. For example, your bedroom always tends towards a messier or more disordered state and castles, built centuries ago, now stand in disordered ruins.

Now consider a container separated into two halves. One of these halves contains a gas and the other is completely empty (a vacuum). If we now remove whatever is separating the two halves, we all intuitively know that the gas would spread out evenly throughout the volume of the container. According to the definitions given above, this means that the state in which the gas is spread evenly throughout the container is the most disordered state. This may seem puzzling, as an evenly distributed equilibrium state does not sound disordered.

Entropy could therefore be more accurately described as a measure of how spread out energy is. Consider a hot water bottle that you fill with boiling water to keep yourself warm. Immediately after filling that bottle, there is a significant heat difference between your body temperature and the temperature of the bottle. This allows the bottle to warm you up. Now imagine that you’ve woken up in the middle of the night to find that your hot water bottle has cooled to room temperature. It now no longer serves any purpose because there is no heat difference between yourself and the water bottle. The entropy (or the ‘spread of the energy’) has increased to a maximum.

Considering entropy from this perspective, we can see that in any system, it is the difference in energy rather than the total energy that is useful. In the previous example, when you wake up to find yourself next to a room temperature water bottle, it is not the case that the bottle has lost all its energy, just its useful energy. All the water particles are still vibrating with an amount of energy equivalent to that room temperature. However, this energy is no longer useful to you as the system made up of yourself and the hot water bottle has reached equilibrium. We can think of the universal increasing of entropy accordingly. Energy (and by extension mass) always works to distribute itself equally and the amount of useful energy in any system therefore decreases.

Another way we can frame entropy then, is in terms of decay. The world as we know it exists because of the various sources of useful energy around us. The sun is one obvious one. However, with every passing day the sun uses more of its fuel and therefore depletes its source of useful energy. We might consider this decay. Using this lens, it may be possible to use the principle that entropy always increases to examine other walks of life. For instance, perhaps one could find a link between the inevitability of conflict or the inevitability of civilisation collapse and this law that says decay is an unstoppable force.