Physics experiments confirm that many reported trajectories are possible, but not the rising fastball. The present paper shows how the apparent rise may be explained as a perceptual illusion due to the hitter underestimating original speed of the pitch. The illusion of the rising fastball. Top trajectory indicates actual path of a fastball. Bottom trajectory indicates path experienced by a batter who underestimates initial speed of the pitch.
Dotted lines show line of sight to the ball at equal temporal intervals.
Since distance to the ball is ambiguous, the line of site progression is consistent with both actual and experienced trajectories. If correct line of site is maintained, the slower, experienced trajectory will also appear lower. When the ball reaches home plate, its correct location can be accurately perceived.