Isolated/Closed Systems: Relativistic Thermodynamics Explained

In summary, the conversation discusses the difficulty in distinguishing between an isolated system and a closed system when considering them in a rest frame. The speaker also brings up the concept of light and whether it can be considered as part of an isolated or closed system. The conversation ends with the speaker realizing that their initial question was based on a flawed definition of the two terms.
  • #1
Twigg
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If you put everything in a rest frame, it seems as if it's impossible to tell an isolated system from a closed system (globally in SR, locally in GR). Am I off my rocker to think so?

There's at least one catch I've thought of so far: light. I can't say for sure that it satisfies either definition because it can't be dragged into a rest frame, but I also can't say it shouldn't be thought of as a closed or isolated system. It's counterintuitive in a 3space+1time worldview, because EM radiation behaves almost like a dissipative transport process as seen in Poynting's Theorem (flow of charges through an E field gives you a work that is distributed in an irreversible fashion as radiation). But could a 4-volume element full of EM radiation be called an isolated/closed system? If so, is the specific internal energy of that volume element defined? Or am I just completely off my rocker?
 
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  • #2
Twigg said:
If you put everything in a rest frame, it seems as if it's impossible to tell an isolated system from a closed system

What are your definitions of "isolated" and "closed"?
 
  • #3
Sorry for the late reply.

PeterDonis said:
What are your definitions of "isolated" and "closed"?

You hit the nail on the head, thanks. I was defining them both to be systems with no flow of invariant mass/energy in or out, so my question was a silly one. My bad.
 

Related to Isolated/Closed Systems: Relativistic Thermodynamics Explained

1. What is an isolated/closed system?

An isolated/closed system is a physical system that does not exchange any matter or energy with its surroundings. This means that the total amount of matter and energy within the system remains constant and cannot be added or removed. Examples of isolated/closed systems include a sealed container, a planet, or the universe as a whole.

2. What is the significance of relativistic thermodynamics in isolated/closed systems?

Relativistic thermodynamics is a branch of physics that studies the relationship between heat and other forms of energy in systems that involve high speeds or strong gravitational fields. In the context of isolated/closed systems, relativistic thermodynamics helps explain how the laws of thermodynamics apply in situations where the effects of relativity cannot be ignored, such as in systems moving at near the speed of light or in the presence of very massive objects.

3. How does the first law of thermodynamics apply to isolated/closed systems?

The first law of thermodynamics states that energy can neither be created nor destroyed, but it can be transferred between different forms. In isolated/closed systems, the first law still applies, meaning that the total energy of the system remains constant. However, since the system cannot exchange energy with its surroundings, any changes in the system's energy must come from within, such as through internal processes or reactions.

4. What is the difference between an isolated and closed system?

While both isolated and closed systems do not exchange matter or energy with their surroundings, the key difference is in their boundaries. An isolated system has no interaction with its surroundings, while a closed system can exchange energy with its surroundings, but not matter. In other words, a closed system can only exchange heat and work with its surroundings, but not particles or substances.

5. Can isolated/closed systems violate the second law of thermodynamics?

No, isolated/closed systems cannot violate the second law of thermodynamics, which states that the total entropy (or disorder) of an isolated system will always increase over time. While the first law of thermodynamics allows for the internal energy of a system to remain constant, the second law dictates that the distribution of that energy will tend towards a state of higher entropy, resulting in an overall increase in disorder within the system.

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