How does the universe expand with the law of thermodynamic

In summary: It's a common misconception that the first law of thermodynamics is being violated in the case of an expanding universe. In summary, the first law of thermodynamics deals with conservation of energy, but when it comes to the universe as a whole, defining and measuring its total energy is problematic and there is no one definitive answer. Therefore, the expansion of space does not violate the first law of thermodynamics.
  • #1
Ekue Kpodar
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If space is expanding wouldn't that violate the first law of thermodynamics
 
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  • #2
Ekue Kpodar said:
If space is expanding wouldn't that violate the first law of thermodynamics
Why do you think it would?
 
  • #3
The first law of thermodynamics has to do with conservation of energy. The problem is that defining the total energy of the universe is problematic and there's no one way to go about doing so if I remember correctly. I don't have much info on this topic, but I believe the answer is that conservation of energy doesn't apply when talking about the universe as a whole. Hopefully someone here can give you better info than I can.
 
  • #4
phinds said:
Why do you think it would?

I'd think so if I'd never read up on the issue before.
 
  • #5
Drakkith said:
I'd think so if I'd never read up on the issue before.
Yes, but I was trying to point him to conservation of energy on his own before spilling the beans the way you did :smile:
 
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Likes Drakkith
  • #6
Thanks :smile::cry:
 
  • #8
Drakkith said:
I'd think so if I'd never read up on the issue before.
I'm not so sure I would (I don't think I did the first time I heard about it). Why doesn't a baseball flying up violate the first law of thermodynamics?
 
  • #9
russ_watters said:
I'm not so sure I would (I don't think I did the first time I heard about it). Why doesn't a baseball flying up violate the first law of thermodynamics?

I've seen that very question asked here on PF before.
 

1. How does the law of thermodynamics relate to the expansion of the universe?

The law of thermodynamics is a fundamental principle in physics that states that energy can neither be created nor destroyed, but can only be transformed from one form to another. This law is relevant to the expansion of the universe because it governs the behavior of energy and matter on a cosmic scale. As the universe expands, energy is constantly being transformed and redistributed, following the laws of thermodynamics.

2. What role do entropy and disorder play in the expansion of the universe?

Entropy is a measure of disorder or randomness in a system. As the universe expands, the entropy also increases. This is because the expansion leads to a more disordered and less concentrated distribution of matter and energy. The increase in entropy is in accordance with the second law of thermodynamics, which states that the total entropy of a closed system always increases over time.

3. How does the expansion of the universe affect the temperature of the universe?

The expansion of the universe leads to a decrease in the temperature of the universe. This is because as the universe expands, the energy and matter within it become more spread out, resulting in a decrease in thermal energy. This is known as the adiabatic cooling effect, and it is a direct consequence of the first law of thermodynamics, which states that energy cannot be created or destroyed, only transformed.

4. Can the expansion of the universe be explained by the laws of thermodynamics alone?

No, the expansion of the universe is a complex phenomenon that cannot be fully explained by the laws of thermodynamics alone. While the laws of thermodynamics play a crucial role in understanding the behavior of energy and matter in the universe, there are other factors at play such as dark energy and dark matter that also contribute to the expansion of the universe.

5. How does the expansion of the universe affect the overall entropy of the universe?

The expansion of the universe leads to an overall increase in the entropy of the universe. This is because the universe is constantly expanding and becoming more disordered, resulting in an increase in the total entropy. However, the exact impact of the expansion on the total entropy of the universe is still a topic of ongoing research and debate within the scientific community.

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