Hello, I was reading Zeh's "The Physical Basis of the Direction of Time" but I just can't understand him in chapter 1 on something really easy: the definition of the phenomenological entropy + second law. Here is a screenshot I took from the googlebooks edition:(adsbygoogle = window.adsbygoogle || []).push({});

Those two lines of formulas really confuse me, for several reasons. The most obvious one:

He says [tex]\left( \frac{dS}{dt} \right)_{int} \geq 0[/tex]

But I thought the 2nd law clearly stated [tex]\frac{dS}{dt} \right \geq 0[/tex]

After all: a system in connection to a reservoir doesn't have to go up in entropy.

Can anybody clear this up for me?

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# Zeh: Basics of Basics of Thermodynamics, yet really confused

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