MIT Institute Archives & Special Collections

Vannevar Bush Letter
about the Physics of Baseball, 1965

In July 1965 MIT Professor of Electrical Measurements Harold "Doc" Edgerton produced a batch of multiflash baseball photos and sent them to long-time colleague Vannevar Bush for comment. Edgerton was noted for developing the modern stroboscope, which, when employed in photography, could freeze motion and enable observation and analysis of events too rapid for the unaided eye, or standard cameras, to comprehend. Bush had devised early analog computers and had supervised the nation's World War II defense-related research effort. Both men enjoyed tinkering with electrical gadgets and shared a fascination with the unseen. Bush's August 1, 1965, response to Edgerton (from MC 25, the Harold Edgerton Papers) records his thoughts about the physics of baseball.

Part of page 1 of letter

Click on image for complete letter and transcription

Photos from notebook
Click lower picture for a closer look


Two photos of the type sent to Bush, shot in the MIT cage using high-speed-multiple-action apparatus, are included in the sample page from Edgerton's laboratory notebooks. Each print incorporates numerous exposures made by a flash lamp emitting powerful light pulses 120 times per second. The incoming pitch (slower) is represented by the closely spaced balls. The widely-spaced balls indicate the progress of the baseball (faster) after leaving the bat. As Bush notes, "the ball should leave at a velocity equal to the incoming velocity plus twice the velocity of the bat...when there are no losses due to lack of elasticity of ball and bat, rotation of bat when not hit a[t] center of impact, vibration of bat due to bending at time of impact."In baseball parlance the batter has in the top picture "swung under the pitch," resulting in a "pop fly," which is likely to be caught for an "out." She has a better swing in the bottom photo, where contact between bat and ball is solid. There is a good chance that the resulting "line drive" will be a "hit." Note that the baseball collapses upon impact with the bat and springs back into its normal spherical shape as it starts to accelerate. Edgerton also used his multiflash equipment to study golf swings, ballet, juggling, running, and tennis.

In 2008 the Edgerton Family Foundation funded a project to digitize parts of MIT’s Harold Edgerton collections, including his laboratory notebooks, film and video, slides, and negatives, and create a web-based interface for the materials.  Collaborating with the Institute Archives and MIT Libraries on this project are the MIT Edgerton Center and the MIT Museum.

The papers of Bush (MC 78) as well as those of Edgerton (MC 25) are available for use in the Institute Archives and Special Collections (14N-118).

Object of the Month: July-August 2000;
May 2007; July 2008; July 2010

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