...and all for the want of a horseshoe nail.

For want of a nail, the shoe was lost.
For want of a shoe, the horse was lost.
For want of a horse, the rider was lost.
For want of a rider, the battle was lost.
For want of a battle, the kingdom was lost.
And all for the want of a horseshoe nail.

I have been thinking about this proverb, and how amazing it is that people had such a good understanding of chaos theory on a fundamental level hundreds of years before it ever had been formally described.

What other knowable things about our universe are out there waiting to be harnessed that we just take for granted?