Deep in the rainforest of Brazil, the humid air hums with a chirping of cicadas,

distant bird calls, the babbling of a stream running towards the Amazon,

and the constant quiet dripping of moisture from leaves to the ground cover below.

A morpho butterfly, its vivid, iridescent blue wings spanning five inches, flutters delicately between branches, landing to sip juices from decayed asai buries in the dappled sunlight.

It is a fragile and elegant creature, here among the massive trunks of trees, reaching hundreds of feet into the sky.

And yet, with a particular flutter of its wings, unseen by human eyes, indecifrable to scientists

and meteorologists, a ripple of air extends outward, a minuscule force, but it joins with accumulating air currents that feed finally into

the higher atmospheric systems above. Days later, a storm, a continent away, gathers strength.

Winds build and tornado warnings blair. Meanwhile, this same butterfly flutters onward in its verdant and peaceful habitat,

oblivious to any force it may have exerted. The butterfly effect. The idea that a tiny development

in one location can set off a chain reaction, triggering events in the world at large.

A missed train, a mislaid letter, a misunderstood signal, or one all-too-human decision can profoundly affect the unfolding of events in a place altogether different.

Thank you. It's American History Hit here.

I'm Don Wildman, your host. Welcome back.

Human history can be viewed as one event leading to another, which leads to others, in a constant phenomenon of cause and effect.

That's certainly the view of most historians, I'd say, who work diligently to order events and present a coherent, defensible record of whatever happened and how it came to pass.

But there is another dynamic at play in history, never mind in the whole of existence,

where random occurrence is as much a factor as logical order.

It's the butterfly effect that borrows from the mathematical ideas of chaos theory.

Unicorn moments that just happen because they happen and then steer historical consequence

in one direction or another,

banal or profound.

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