|The world is a ball, sir.|
Dear Mister Trump.
The world is a ball.
Simple geometry would have told the ancients that the world is a globe. In the middle of summer, at this latitude in southern Canada, the sun rises in the northeast and sets in the northwest. Day by day, the angle changes, almost imperceptibly, but over a week or a month it becomes pretty obvious. The stars go around in the heavens, and yet even then the picture changes over the seasons. It is clearly cyclical even to our own personal experience, without getting into any deep analytical thinking.
In winter, the sun rises in the southeast and sets in the southwest. On the solstices, and only on the solstices, the sun rises due east and sets due west.
It would be extremely difficult to reconcile this fact with the notion that those other objects revolved around a fixed, flat Earth. The real question to ancient scholars, astrologers, mathematicians, philosophers, would be why?
Why, sir, should it be so?
Why would the sun revolve around the Earth and yet sunset also go up and down in terms of angle like that. This is especially true when the sun looks like a burning ball in the sky, the moon is not just round, but goes through phases, including a dark, circular shadow on its surface. Then there is the new moon period. It must be accounted for. Because of parallax and the size of the Earth, more than fifty percent of the moon is visible over the lunar cycle. The only way to account for that would be to believe the moon is spherical. Ancient scholars did more than sit around and think. A simple experiment in a darkened room with a couple of spherical objects and a light source would have quickly confirmed a hypothesis: the world might be a ball. It would still only be a theory, although evidence lay all around, if only a man had the wit to see it.
|Archimedes, by Domenico Fetti.|
With a straight edge of sufficient length, easily checked for straightness by eye alone, the horizon can clearly be observed to be curved. This is even more true when the horizon is viewed from any great height. We rarely see the horizon, as most of us live in cities, in the suburbs, or in places with terrain, brush, or even just inland.
In a sense, we accept that the world is round without ever having the ability to verify it by our own observation.
That is the difference between the average person and someone like Aristarchus or Cristopher Columbus. They had the ability to conduct the experiment. In the 1470s, Florentine astronomer Toscanelli clearly believed the world was round.
Aristarchus’ experiment not only showed that the Earth was round, but estimated the distance to the sun. His solution is surprisingly accurate.
Columbus’ experiment was even simpler. If the world is a ball, and if that ball is a certain size, then going west might be shorter than going east.
His math wasn’t so good, and he thought the planet was even smaller than it actually is.
According to Gibbon, the first compasses were used for navigation by the sailors of Amalfi in the thirteenth century. This knowledge may have been brought back from China by Marco Polo.
Sincerely, your good friend and colleague,