Claudius Ptolemy

Chronicled events

1. about 150 CE​·​Ptolemy Puts the Earth at the Center
   #5792

   The Earth stands still at the center of the universe. The Moon, the Sun, and the planets circle it.

   #5793

   Every so often, a planet seems to stop, drift backward among the stars for weeks, and then move on. A planet that simply circled the Earth would never do that.

   #5794

   Each planet rides on a small circle, an epicycle, whose center travels along a larger one around the Earth. On the near side of its epicycle, the planet moves against the larger circle’s motion, so it seems to drift backward.

   #5795

   If the Earth spun once a day from west to east, it would outrun everything not standing on it. Clouds, birds, and anything thrown would always seem to drift westward, and we would never see them move east.

   #5796

   The air might turn with the Earth and carry the clouds and the birds along, so they wouldn’t be left behind.

   #5797

   If the air carried them along, they would never seem to move at all. But we see them move in every direction.