Almost any way you look at it, Earth’s surface appears flat. The average adult, standing on an expanse of perfectly level ground, can see just 3 miles to the horizon — not nearly far enough to observe the curvature directly. Even the summit of Mt. Everest doesn’t offer sufficient vantage.
To fully appreciate Earth’s arc with your own eyes, you must view it from at least 35,000 feet above sea level, an altitude only accessible by plane. In other words, no human living before the 20th century had first-hand experience of our planet’s true shape.
Yet nearly all educated people today recognize this apparent flatness as an illusion. We have a single man to thank for that: the Greek philosopher Aristotle, working in Athens in the 4th century B.C. According to historian James Hannam, author of The Globe: How the Earth Became Round, Aristotle was the first and only person ...
