Wednesday, November 16, 2011


What I did not know about equilibrium:

1. From SciAm (gated):

From the preamble:
… a sad fact of life quantified by the famous second law of thermodynamics …  if the world is steadily becoming more disordered, how do you explain the self-organization that often occurs in nature? At root, the trouble is that classical thermodynamics assumes systems are in equilibrium, a placid condition seldom truly achieved in the real world.

The Achilles' heel of thermodynamics is that, strictly speaking, it applies only when the system under study is in a quiescent state called equilibrium. In this state the system's parameters, such as mass, energy and shape, have ceased to change. Putting two objects together at different temperatures makes heat flow from the hotter object to the colder. This process stops when both reach the same temperature — that is, when the two are in thermal equilibrium. From that point on, nothing changes.

… Thermodynamics therefore deals only with situations of stillness. Time plays no role in it. … In introductory physics classes, students apply thermodynamics to dynamic systems such as car engines to calculate quantities such as efficiency. But these applications make an implicit assumption: that we can approximate a dynamic process as an idealized succession of equilibrium states. That is, we imagine that the system is always in equilibrium, even if the equilibrium shifts from moment to moment.

Describes the current state of macroeconomic dynamics very well.

2. Beer in equilibrium. From Fat Tire (on its label rather than website):

Fat Tire Amber Ale’s appeal is in its feat of balance: toasty, biscuit-like malt flavors coasting in equilibrium with hoppy freshness.

I expected the brewer to be an economist (after all who would use equilibrium to describe beer?)  but he turned out to be an engineer.

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