SNU Professor Haecheon Choi’s Team<?xml:namespace prefix = "o" ns = "urn:schemas-microsoft-com:office:office" />

"It is impossible for the baseball to rise. It is just an optical illusion"

“Third strike for a missed swing and he’s out. The ball spiked up just in front of the batter. Unfortunately some a batter would be unprepared for. What a pitch!’” This type of commentary is something we can hear occasionally in pro baseball. However, SNU Professor Haecheon Choi (Mechanical and Aerospace Engineering) Claims otherwise. “The ‘spiking up’ of a ball thrown by the pitcher does not actually happen” he said last 24^th. What happens is actually an optical illusion.

The pitcher’s mount is actually 25cm higher than the playing field. Hence they would always throw the call towards a lower point at the catcher. At this point, when spin is added to the call the ball’s downward pitch can accelerate, also known as the Magnus effect, named after the German Physicist Gustav Magnus who theoretically proved that spin can affect a ball’s trajectory. If the ball rises up, it is called the ‘Reverse Magnus Effect’.

Professor Haecheon Choi’s Team analyzed the spin and trajectory of a baseball-sized object in their wind tunnel by applying different forces and directions of wind. Upon analysis, it appears for the reverse Magnus effect to occur, one has to throw the ball at speed of 155~270 km/h with the ball revolving at 98 rev/s.

While rare, it is not impossible for pitchers to throw such balls. However, Professor Haecheon Choi claims it is actually impossible in real life due to the threading of the baseball. The Magnus effect occurs due to the turbulence above the ball. Because the threading of the ball disrupts the turbulence and changes the location of the turbulence to other areas of the ball, the reverse Magnus effect cannot occur.

“If the ball thrown by the pitcher travels at a smaller slope than expected, an optical illusion where the ball appears to rise may occur.” The research team plans to present their findings at the KSME Conference expected to be held in May.