May 25, 2018


Yahoo Sports reports:

A group of scientists tasked with finding the reason home runs flew at a record rate in Major League Baseball last season believe the ball’s aerodynamic properties – and particularly the drag on its surface – are the culprit and not changes to the core that would cause extra bounciness, according to a report the league released this week.

In the midst of a season in which players hit a record 6,105 home runs and emboldened juiced-ball theorists, MLB commissioned 10 scientists to study the source of the spike. Using a combination of Statcast data and laboratory testing, the group found that balls in 2016 and 2017 had lower drag coefficients than their predecessors.

What they didn’t find was why.

“It was something of an unsatisfying result,” said Dr. Alan Nathan, a physicist who has studied the game for decades and chaired the group that wrote the 84-page research paper. “We had a set of baseballs that had a much higher than average drag. We had a set of baseballs that had a much lower average drag. We asked ourselves: ‘What’s the difference between these baseballs?’ ”
Nathan’s conclusion: “We cannot find a single property that we can actually measure other than the drag itself that would account for it. … We do admit that we do not understand this.”

Fans had thought the baseball were juiced, i.e. have a tampered inner core which would give the ball farther distance. Getting more out of a sphere's core is the heart, no business model, in the golf ball manufacturing industry.

When experts cannot find out what the difference between two baseballs, that is very strange.

Some pitchers had indicated that they could not get a good grip on the old ball. There could have been two reasons for this: the height of the seams, or the slickness/texture of the leather.  Umpires still use Mississippi mud to rub up the baseballs to take off the factory sheen and add grip. It could be possible that the balls are fundamentally the same components, but there is a change in either the manufacturing or assembly processes. 

In aerodynamics, a lower drag indicates that an object has less air resistance. This could mean that the baseball may stay "airborne" longer, i.e. less dip or drop in the strike zone. A ball in the strike zone is more likely to get hit. In addition, if there is an issue with the grip, there could be less baseball pitch spin rate which would affect the movement and direction of the baseball.

There is another factor in play: the human pitcher. The way games are now called, pitchers are nibbling at the corners to try to get strike outs instead of "pitching to contact."  By pitchers falling behind in the count, batters can hunt their pitch better. Any advantage to the batter could lead to more contact and home runs.

The home run rate is a puzzle that may have many different elements to solve.