Saturday, 22 March 2014

The Second Law of Thermodynamics is not a simplistic rule that heat always transfers from warmer to cooler regions if there is a temperature difference.

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Author :  D J Cotton
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The Second Law of Thermodynamics is not a simplistic rule that heat always transfers from warmer to cooler regions if there is a temperature difference.

In the early pre-dawn hours the lower troposphere still exhibits the expected thermal gradient, but meteorologists know that convection stops. Yes energy flow stops even though there is warmer air at lower altitudes. That is because there is thermodynamic equilibrium, and when we have thermodynamic equilibrium - well, you can look up in Wikipedia all the conditions and things that happen.

The real Second Law of Thermodynamics takes quite a bit of understanding and many hours, maybe years of study. You guys have absolutely no understanding of it, as I can detect from my decades of helping students understand physics.

To understand it you have to really understand entropy for starters. Then you have to really understand thermodynamic equilibrium and all the other states, such as mechanical equilibrium, thermal equilibrium etc which the Second Law embraces. That is why, for example, you cannot disregard gravity and gravitational potential energy when determining the state of maximum entropy attainable by an isolated system.

If you want to stay in the mid-19th century when much of this physics was not widely understood, and if you want to imagine, for example, that radiative heat transfer does not obey the Second Law, then all I can say is that you must live in a strange and isolated planet, because you sure can't answer my questions about other planets with your climatology paradigm.

When you truly understand the Second Law of Thermodynamics then, and only then, will you start to understand how it explains the so-called lapse rate and how the pre-determined thermal profile supports surface temperatures everywhere, not back radiation from a cooler atmosphere. Thus you will understand why it's not carbon dioxide after all.

1 comment:

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