Who Found America First: Columbus or the Vikings?

A thousand years before Christopher Columbus saw a light on a Bahamian beach, a small band of Norse settlers stood on the northern tip of Newfoundland, swinging iron axes against fir and juniper trees, building sod houses that would still be visible in the grass nearly a thousand years later. We can name the year. We can name it down to a single twelve-month window.

The year was ten twenty-one, and we know it because of a solar storm that struck the sun in the year nine hundred and ninety-three, leaving an invisible fingerprint in every tree growing...