Star and planet formation according to the 2nd Law of Thermodynamics

[mess1n]

In the first part of Brian Cox's documentary series 'Wonders of the Universe', he explains how the entropy of the universe always increases, and that we are therefore headed for a state of total 'disorder' where all is left of the universe is photons and dying black holes.

But wasn't this essentially the initial state of the universe after the big bang? Minus the black holes. If it was, how did stars and planets form from this without violating the second law? It seems to be a situation where the splattered egg reforms into a perfect egg. When stars and planets formed, it seems as though the universe became more orderly. Was matter formation just massively unlikely? Or am I misinterpreting entropy?


Andrew

 

[bcrowell]

But wasn't this essentially the initial state of the universe after the big bang?

No, the early universe was in a very low-entropy state. A maximum-entropy state would have been dominated by gravitational waves. A good popular-level book that covers this is Cycles of Time by Roger Penrose.

 

[bcrowell]

Since this seems to be a FAQ, I've written a FAQ entry for it.

FAQ: Wasn't the early universe in a disordered state?

No. The second law of thermodynamics says that entropy can only increase, so if the early universe had been in a state of maximum entropy, then the cosmos would have experienced its heat death immediately after being born. This contradicts the observation that the present universe contains burning stars, heat engines, and life. These observations imply that the early universe was in a very low-entropy state, which shows that its initial conditions were extremely finely tuned. The reasons for this fine-tuning are not explained by general relativity or the standard model. I'm not an expert on inflation, but apparently adding inflation to the model does not cure this fine-tuning problem.[Penrose 2005]

These ideas are strongly counterintuitive to most people, since we picture the early universe as an undifferentiated soup of hot gas, very much like what we might imagine a heat-dead universe to be like. In what way is the early universe *not* equilibrated?

We observe that the cosmic microwave background radiation's spectrum is a blackbody curve, which would normally be interpreted as evidence of thermal equilibrium. However, this observation only really tells us that the *matter* degrees of freedom were in thermal equilibrium. The gravitational degrees of freedom were not. In standard cosmological models, which are constructed to be as simple as possible, there are no gravitational waves. Although the real universe presumably does have gravitational waves in it, they are apparently very weak. In a maximum-entropy universe, the gravitational modes would be equilibrated with the matter degrees of freedom, and they would be very strong, as in Misner's mixmaster universe cosmology.[Misner 1969]

Even in Newtonian mechanics, gravitating systems violate most people's intuition about entropy. If we psssssht a bunch of helium atoms into a box through an inlet valve, they will quickly reach a maximum-entropy state in which their density is nearly constant everywhere. But in an imaginary Newtonian "box" full of gravitating particles, the maximum-entropy state is one in which the particles have all glommed onto each other and formed a single blob. This is because of the attractive nature of the gravitational force.

Charles W. Misner, "Mixmaster Universe", Physical Review Letters 22(1969)1071. http://astrophysics.fic.uni.lodz.pl/100yrs/pdf/07/036.pdf

Roger Penrose, 2005 talk at the Isaac Newton Institute, http://www.Newton.ac.uk/webseminars/pg+ws/2005/gmr/gmrw04/1107/penrose/

 

[Jamders]

Since this seems to be a FAQ, I've written a FAQ entry for it.

FAQ: Wasn't the early universe in a disordered state?

No. The second law of thermodynamics says that entropy can only increase, so if the early universe had been in a state of maximum entropy, then the cosmos would have experienced its heat death immediately after being born. This contradicts the observation that the present universe contains burning stars, heat engines, and life. These observations imply that the early universe was in a very low-entropy state, which shows that its initial conditions were extremely finely tuned. The reasons for this fine-tuning are not explained by general relativity or the standard model. I'm not an expert on inflation, but apparently adding inflation to the model does not cure this fine-tuning problem.[Penrose 2005]

These ideas are strongly counterintuitive to most people, since we picture the early universe as an undifferentiated soup of hot gas, very much like what we might imagine a heat-dead universe to be like. In what way is the early universe *not* equilibrated?

We observe that the cosmic microwave background radiation's spectrum is a blackbody curve, which would normally be interpreted as evidence of thermal equilibrium. However, this observation only really tells us that the *matter* degrees of freedom were in thermal equilibrium. The gravitational degrees of freedom were not. In standard cosmological models, which are constructed to be as simple as possible, there are no gravitational waves. Although the real universe presumably does have gravitational waves in it, they are apparently very weak. In a maximum-entropy universe, the gravitational modes would be equilibrated with the matter degrees of freedom, and they would be very strong, as in Misner's mixmaster universe cosmology.[Misner 1969]

Even in Newtonian mechanics, gravitating systems violate most people's intuition about entropy. If we psssssht a bunch of helium atoms into a box through an inlet valve, they will quickly reach a maximum-entropy state in which their density is nearly constant everywhere. But in an imaginary Newtonian "box" full of gravitating particles, the maximum-entropy state is one in which the particles have all glommed onto each other and formed a single blob. This is because of the attractive nature of the gravitational force.

Charles W. Misner, "Mixmaster Universe", Physical Review Letters 22(1969)1071. http://astrophysics.fic.uni.lodz.pl/100yrs/pdf/07/036.pdf

Roger Penrose, 2005 talk at the Isaac Newton Institute, http://www.Newton.ac.uk/webseminars/pg+ws/2005/gmr/gmrw04/1107/penrose/

I think we need a new model where Thermodynamics laws are almost perfect. The place where Universes are created and despaired as smooth as a hurricane or Typhons do in our planet. Thermodynamics are ok for engineering inside the planet and when u can have limit (e: gasoline engine). Either the universe is the last frontere or there is other system where it can have entropy almost zero so will increased to the despairing state of max entropy. Observing jupiter. mass gravity and energy such system must exist so the 98 % that was needed to adjust the actual model (dark energy and dark mass?) would not be necessary

 

[sardar]

, thank you for sharing your thoughts on this topic. I can provide some clarification on the relationship between the second law of thermodynamics and the formation of stars and planets.

The second law of thermodynamics states that the total entropy (or disorder) of a closed system will always increase over time. This means that the universe as a whole is moving towards a state of maximum disorder, also known as thermodynamic equilibrium. This is a fundamental principle of the universe and applies to all systems, including stars and planets.

Now, let's consider the early universe after the big bang. At this point, the universe was in a highly ordered and dense state, with all matter and energy concentrated in a single point. As the universe expanded and cooled, it underwent a process of increasing entropy, with matter and energy spreading out and becoming more disorganized.

This is where the formation of stars and planets comes into play. As the universe continues to expand and cool, gravity causes matter to clump together, forming stars and planets. This process may seem to go against the second law of thermodynamics, as it appears to be creating more order out of disorder.

However, the key to understanding this is that the second law applies to the universe as a whole, not just to individual systems. The formation of stars and planets does not violate the second law because the overall entropy of the universe is still increasing. In fact, the formation of stars and planets actually contributes to the overall increase in entropy, as energy is constantly being converted and released in the form of radiation.

In short, the formation of stars and planets is not a violation of the second law of thermodynamics, but rather a result of it. The universe is constantly moving towards a state of maximum disorder, and the formation of stars and planets is just one step in this ongoing process. I hope this helps clarify any confusion about the relationship between the second law and the formation of stars and planets.