The Metric of Our Universe

Entropy: The Metric of Our Universe

Credit: Wikipedia

In the beginning was the event known as the Big Bang. At that initial event of infinitesimal spacetime, the entropy of our universe was at its minimum, corresponding to its maximum organization — at a point in space and at the beginning of time.

Ever since that initial event, our evolving universe (or its current cycle of evolution) has had its overall entropy increasing monotonically, albeit its rate of increase has been nonmonotonic. The nonmonotonic rate of increase has been due to the counter effects of gravity, the emergence (and evolution) of organizational phenomena that create pockets of decreasing entropy in spacetime, as well as the observed (though not yet understood) effects of dark energy.

Thus, we have traversed a chronology of cosmic spacetime-epochs, including the Planck epoch, the cosmic inflation, the Quark epoch, the Photon epoch, the "Dark Ages" (during which the universe was transparent but no large-scale structures had yet formed). Then followed the period of large-scale structure formation, including stellar evolution, galaxy formation (and evolution) and the formation of galaxy clusters and superclusters. The latter period has been characterized by local reductions of entropy corresponding to all the large-scale structure formation, all of which qualified as reductions in the disarray of matter.

The thin disk of our galaxy began to form at about 5 billion years ago. The solar system formed at about 4.6 billion years ago, with the earliest traces of life on Earth emerging by about 3.5 billion years ago. These epochs, up to and including the present time have been characterized by the emergence and evolution of (self) organizations with the concomitant localized decreases of entropy.

That universal metric, entropy, or, what is more nearly correct, its local decrease (called "negentropy" by Erwin Schrödinger), may be viewed as the lifeblood of our existence. As this lifeblood waxes, our existence flourishes. As it wanes, we hurtle towards heat death.

Nevertheless, there may be an ultimate reversal to the expansion of the universe (the "Big 180"), in which the universe (at least its current cycle) will end in a Big Crunch, after which a Big Bounce might initiate another new cycle, in endless repetition ...

It could happen.

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