Ergodic
Ergodic processes (in our new technical use of the term) are those that resist the terrible and universal Second Law of Thermodynamics, which commands the increase of chaos and entropy (disorder). Without violating that inviolable law overall, ergodic processes reduce the entropy locally, producing pockets of cosmos and negative entropy (order and information-rich structures). We call all this cosmic order the Ergo. It is the ultimate
sine qua non.
Our new use of the powerful adjective Ergodic puts us squarely in conflict with an existing term in statistical physics. The term was invented in the nineteenth century to describe the behavior of gaseous systems that were assumed over time to occupy all the possible states consistent with certain macroscopic properties like number of particles, volume, and temperature. This was known to include highly unlikely distributions of the particles, such as all the particles in one small corner of the container, which would have very low entropy.
Think of a small perfume bottle in a large room. Open the perfume and over time the perfume molecules have dispersed throughout the room. Time reverse a movie of what you saw, and in principle all the perfume molecules would return to the open bottle (at least for a moment).
Statistical physics can calculate the practically infinitesimal
probability that the molecules will all return randomly. It is the ratio of all the states of the system with perfume molecules in the bottle to the number of ways the molecules can be arranged throughout the room.
Ergodic was derived from Greek
ergon (energy) and Greek
hodos (path), to get a word meaning "the path followed by energy." And this meaning seems perfect to describe processes that concentrate potential (usable) energy in local pockets of cosmos that resist the general rise of entropy and chaos overall.
There may be deep physical reasons for the perfume molecules never reassembling themselves in the perfume bottle. This is the problem of
microscopic reversibility.
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