Does entropy increase with improbability?

In summary, entropy is defined by the Gibbs entropy equation and is a measure of the spread of probability distribution in a system. A system with more equal probability states has a higher entropy than a system with few probable states. Therefore, entropy does increase with improbability.
  • #1
MeneMestre
1
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Well, maybe that's a simple question, but it has been pissing me off for some time ... Does entropy increase with improbability?
 
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  • #2
What is the definition of entropy (the real one that has an equation in it, not the vague English-language bit about "disorder")? The answer to that question will suggest an answer to your question.
 
  • #3
MeneMestre said:
Does entropy increase with improbability?
Entropy is defined for all systems (whether or not the are at equilibrium) by the Gibbs entropy equation
$$S=-k\sum_{i}^{l}p_{i}\ln p_{i}$$
where ##p_{i}## is the probability for the system to enter the ##i##th state. Notice that the entropy has a minimum value of zero for the delta function distribution ##p_{i}=\delta_{ij}## and a maximum value for the uniform distribution ##p_{i}=1/l##. Thus the entropy is how spread out the probability distribution ##p_{i}## is. A system which has many equal probability states is at higher entropy than a system with only a few probable states.
 

Related to Does entropy increase with improbability?

1. What is entropy and how is it related to probability?

Entropy is a measure of the disorder or randomness in a system. It is related to probability because as the number of possible outcomes in a system increases, the probability of any specific outcome decreases, leading to higher entropy.

2. Does entropy always increase with improbability?

In general, yes. As the likelihood of a specific outcome decreases, the number of possible outcomes in a system increases, leading to higher entropy. However, there are some exceptions to this rule, such as when a system is at a state of maximum entropy.

3. How does the concept of entropy apply to real-world systems?

Entropy applies to all systems, including real-world ones. For example, a messy room has higher entropy than a tidy room because there are more possible arrangements of objects in a messy room. Similarly, a chemical reaction that produces more products than reactants has higher entropy because there are more possible arrangements of molecules in the products.

4. Can entropy be reversed or decreased?

In general, no. The second law of thermodynamics states that the total entropy of a closed system will always increase over time. However, it is possible to decrease the entropy in a local or temporary sense, such as when energy is added to a system to create order. But overall, the total entropy of the system and its surroundings will still increase.

5. Is there a relationship between entropy and the arrow of time?

Yes, entropy is often used as a way to understand the arrow of time, which refers to the one-way direction of time from the past to the future. Entropy increases as time passes because there are more possible ways for a system to be disordered than ordered, and the likelihood of becoming more disordered increases over time.

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