From the September 2017 issue

Entropy’s rainbow

The statistically likely path to complexity.
By | Published: September 5, 2017
The early universe was remarkably uniform. Today’s universe is anything but. What gives? The details of how we got from there to here form one of the grand themes of science. But viewed from 30,000 feet, the transformation can be summed up in one word — entropy.

“Hold on a minute,” you say. “Entropy doesn’t build stuff. Entropy tears stuff down!” That is certainly the common impression people have about the Second Law of Thermodynamics. It’s also dead wrong.

Rewind the clock to the middle of the 19th century. In one of the all-time greatest advances in the history of science, Ludwig Boltzmann has just used the statistics of how molecules move to explain why heat always flows from hot things to cold things. It is a beautiful, elegant piece of work. It is also counterintuitive to a generation of scientists who are only beginning to get used to the atomic theory of matter.

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