Amongst the more interesting topics to discuss, and least understood by the layman (including this author), is the physics of a pitched and batted ball. The forces and measurements at play are numerous: Drag Coefficient, Reynolds Number (Re), Coefficient of Restitution (COR), Spin Rate (in RPM), Muzzle Velocity (in MPH), Magnus Coefficient, Backspin (in RPM), Wind Velocity (in MPH), Altitude (in feet), Temperature and Launch Trajectory (in degrees) are amongst the ordinary banter that physicists use in describing what a baseball does in flight.
For our discussion, the importance comes in determining what can change a baseball’s flight from ordinary (a fly out to the warning track) to extraordinary (a towering home run.)
Baseballs are certainly constructed by a set of rules; yet that is where it begins, not where it ends. The Official Baseball Rules (circa 2001) calls for the baseball to be made specifically:
Rule 1.09: “The ball should be a sphere formed by yarn wound around a small sphere of cork, rubber, or similar material covered with two stripes of white horsehide or cowhide, tightly stitched together. It shall weigh not less than 5 nor more than 5 ¼ ounces avoirdupois and measure no less than 9 nor 9 ¼ inches in circumference.”
From Dr. Adair’s The Physics of Baseball, manufacturing of MLB Baseball has moved around over the years. From Chicopee, Massachusetts (while A.G. Spalding was still the sole manufacturer), it moved to Haiti, then Taiwan and now in Costa Rica.
The making of the ball consists of: A cork-rubber center of a baseball is wrapped by 121 yards of 4-ply, blue-gray wool yarn, 45 yards of 3-ply white wool yarn, 53 yards of 3-ply gray wool yarn and 150 yards of fine cotton then cemented together with the two strips of cowhide .05-.055 inches thick, which was horsehide before 1974, then hand-stitched with 216 red-cotton stitches.  But the storage, shipment and pre-game rituals are not so standard or clear cut. (HOF Manager John McGraw was known to freeze balls for several hours before the game, then “dry” them out so the umps would not notice.)
According to multiple sources, the coefficient of restitution (COR), a measure of velocity after collision to the velocity before a collision must be between .514 and .578 of the initial velocity. (In other spherical sports, this number can be significantly higher…) In 1987, a testing lab in Plainfield, New Jersey (Haller Testing) did a scientific analysis of baseballs collected from all teams – only 116 balls were used – to determine if the balls were a causation of the odd outburst of home runs in the league that year.
Even though studies by R.C. Larsen and Dr. Adair confirm (COR) values nearly equal a decade apart (1988 and 1998), we cannot be completely confident that balls at the stadium are indeed similar unless the testing was done on sight and with nearly identical game conditions in place. Dr. Adair furthers this specific case by suggesting, “ The elasticity of balls stored under extremes of cold or heat can be affected also.”
Meanwhile, at significant altitude, like  A fastball will get to home plate sooner relative to the initial velocity and that also affects the breaking pitches.
The fact the ball has also underwent changes on multiple occasions (1910 – cork center, 1920 – yarn modification & pre-game preparation, 1931 – cushion corked center, 1943 – substandard materials used –“balata ball”, 1974 – cowhide substitution, 1977 – Rawlings made sole manufacturer and moving production around which could effect humidity during processing) is not always indicative of variations in statistical measurements (homeruns), but cannot be completely ignored in the grander scheme of measuring players and their outputs. The following table reflects the studies of Dr. Adair and his measurements of a wide variety of conditions in relationship to baseballs struck.
Other Possible Theories abound about the reasons players are hitting more home runs:
- Energetic Players (less substance abuse of alcohol, not staying out later or prevalent Amphetamines cocktails)
- Improved conditioning (workout regiments, better nutrition, Steroid usage)
- Video taping and gaming (More information game-to-game on other players tendencies, playing hand-eye games improves baseball coordination)
- New hitter-friendly ballparks (Coors, Ballpark at Arlington, Minute Maid, Citizens Bank)
- Altered production methods (change of processing of baseballs & ball bats)
- Climatic changes and favorable wind patterns (El Nino, La Nina. Wrigley Field winds)
- Watering down of leagues (Increased number of teams in ALL Professional Sports has introduced sub-par players that are overmatched by the elite players)
But then again, as Mark Twain wonderfully states, “There are lies, damn lies and statistics.”
 Adair RK, Ph.D. The Physics of Baseball. 3rd Edition. New York: Harper-Collins, Inc; 2002. 5.
 Treat S, Turkin H, Thompson SC. editors. The Official Encyclopedia of Baseball. 5th edition. South Brunswick and New York: A.S. Barnes and Company; 1970. 645.
 Chambers F, Page B, Zaidins C. Atmosphere, Weather and Baseball: How Much Farther Do Baseballs Really Fly at Denver’s Coors Field? Malden, Massachusetts: The Professional Geographer, 55(4); 2003. 502.
 Adair RK, Ph.D. The Physics of Baseball. 3rd Edition. New York: Harper-Collins, Inc; 2002. 28.
 Abid. 83.
 Blanding SL, Monteleone JJ. The Science of Sports: How Things in Sports Work. New York: Barnes & Noble, Inc; 2003. 17.
 Adair RK, Ph.D. The Physics of Baseball. 3rd Edition. New York: Harper-Collins, Inc; 2002. 95.
 Abid. 67.
 Gutman D, McCarver T. The Way Baseball Works. New York: Simon & Schuster, Inc; 1996. 14.