- #1
jimmy_jollop
- 1
- 0
Any ideas appreciated!
harcel said:It IS, that is, at least in a large fraction of the volume of many stars. And why would it not be? Only in very high densities for example the approximation breaks down...
harcel said:@chemisttree: this really is a question that does not make much sense: the ideal gas equation is an equation of state, relating pressure, density and temperature.
Sorry, I misunderstood your response as being applicable to the "volume of many stars" instead of the volume of gas in the outer atmosphere of a star. Thus my confusion regarding gravity, dark matter and expansion.Gravity is the attractive force between masses, or if you like the curvature of space-time due to the presence of mass/energy, and the expansion of the universe is just one of the solutions to einsteins field equations which happens to describe the evolution of our universe at large scales. The three entities you name can work together to build galaxies and so on, but one cannot be described in terms of the other.
@Dadface: you're right, it breaks down for non-elastic collisions, or actually in any case where interparticle forces cannot be neglected. But, for example in stars, fusion is going on, but at such a low rate, that even the interior of a star is relatively well approximated by an ideal gas.
There are in fect several ways of being more wrong. For example by claiming that an ideal gas is generally a bad approximation of the matter inside stars.You cannot be more wrong than this.
Ich said:There are in fect several ways of being more wrong. For example by claiming that an ideal gas is generally a bad approximation of the matter inside stars.
There's radiation pressure (dominant only in massive stars) and ther'es degeneracy, most important for collapsed stars. Everything else at high density and temperature should be well described by an ideal gas.
Not necessarily for a plasma, with strong magnetic fields around. AFAIK the ideal gas approximation works better inside the star than in the low density regions.Hmm, but the ideal gas law is valid that the low pressure-temperature limit.
The ideal gas law is used to model stars because it is a simple and convenient way to describe the behavior of gases under a wide range of conditions. Stars are composed of highly ionized gases that are constantly undergoing fusion reactions, and the ideal gas law provides a good approximation of their behavior.
The ideal gas law is a good approximation for stars because it takes into account the three main factors that affect the behavior of gases: temperature, pressure, and volume. These factors play a crucial role in determining the physical properties of stars and can be accurately described by the ideal gas law.
While the ideal gas law is a good approximation for stars, it does have some limitations. For example, it assumes that the particles in the gas are point masses with no volume, which is not entirely true for stars. It also does not take into account the effects of gravity and radiation pressure, which can significantly impact the behavior of gases in stars.
To account for the deviations from the ideal gas law in stars, scientists use more complex models and equations that take into account factors such as gravity, radiation pressure, and the finite size of gas particles. These models are constantly refined and improved as our understanding of stars and their behavior continues to evolve.
The ideal gas law can be used to model the behavior of many types of stars, but it may not be accurate for all of them. For example, stars with extremely high densities or temperatures may require more complex equations to accurately describe their behavior. Additionally, stars that are undergoing extreme events such as supernovae may also deviate significantly from the ideal gas law.