Anonymous
Anonymous asked in Science & MathematicsPhysics · 6 months ago

# Why does not the accretion under gravity of the interstellar medium raising temperature to the point of a nuclear reaction violate the 2nd?

law of thermodynamics. It is, after all really a flow of heat from the diffuse to the concentrated?

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• 6 months ago

Ideal gas law and the FORCE of PRESSURE is why the PRESSURE is greatest in the core and the temperature has to be high enough for nuclear fusion to initiate.

PV = nRT

P = pressure

V = volume

n = moles

R = Rydberg constant

T = Temperature.

There are plenty of hybrid dwarf brown star planets where the temperature in the core I'd high enough for fusion of hydrogen into helium to initiate an be maintained fot several thousand to tens of thousands of years, but tthere may not be enough hydrogen or high enough temperatures or PRESSURES in the core for hydrogen fusion to go on long enough for the star to reach hydrostatic equilibrium between GRAVITY acting inward toward the cors and PRESSURE acting OUTWARD from the core.

Hydrogen fusion stops, so the brown dwarf cools down by conduction and convection and chemically differentiates to form a gas giant with an iron nickel sulfur core. Yiu have a rogue planet with no star. That may be where much of that missing dark matter is.

Source(s): None of this violates the second law of thermodynamics. The volume of the of the brown dwarf has decreased along with the pressure and temperature if the CORE.
• oldschool
Lv 7
6 months agoReport

• 6 months ago

diffuse work converted into concentrated work does not violate the 2nd law. Conversion of work energy into heat energy, and heat energy into work energy, is also not a violation. For nuclear fusion, you need both heat and pressure, so you can gather loads of energy that is diffused in space and simply concentrate it. There is an expenditure of energy in the process, so somewhere, there is a loss of energy in exchange for (is the cost of) the localized concentration of energy, and the universe would see a net decrease in total energy as part of the process. The process does not occur in isolation.

Net processes allow for gains on one part of the system with greater loss in another and thus do not violate the 2nd law. The total energy flux is from a higher energy state to a lower energy state.