Johannes Kepler

Chronicled events

1. 1609​·​Eight Minutes of Arc Break the Circles
   #5805

   No arrangement of circles fits Tycho’s measurements of Mars. My best one still misses some of them by eight minutes of arc, far more than Tycho’s errors.

   #5806

   No arrangement of circles fits Tycho’s measurements of Mars. My best one still misses some of them by eight minutes of arc, far more than Tycho’s errors.

   #5807

   No arrangement of circles fits Tycho’s measurements of Mars. My best one still misses some of them by eight minutes of arc, far more than Tycho’s errors.

   #5808

   The Earth is a planet. It spins once a day and goes around the Sun once a year, as the other planets do. Mars moves on an ellipse, a stretched circle, with the Sun at one of the ellipse’s two foci, so that the line from the Sun to the planet sweeps out equal areas in equal times, and the other planets, I expect, move the same way.