What’s the Deal with the Humidor? 1 Alan Nathan University of Illinois [email protected] El Tiante.
What’s the Deal with the Humidor?
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Transcript of What’s the Deal with the Humidor?
Humidors in the News
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First this
Then this
Some of the News is Controversial
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Tim Lincecum
Even Scientists Get in the Act
Why the Humidor in Denver?
Thin air means better “carry”
•Mile high air density 80% of sea level
•More home runs!
•Let’s take a look
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The “carry” of a fly ball
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• “carry” ≡ (actual distance)/(vacuum distance)for same initial conditions
(379,20,5.2)
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HITf/x + Hittracker Analysis:4354 HR from 2009
Denver
The Coors Effect
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~26 ft
Thin Air More Carry More Home Runs
• Coors Field in Denver:– Pre-humidor (1995-2001):
• Rockies home: 3.20 HR/game away: 1.93 HR/game
• That is a huge effect
• Since 2002, baseballs stored in humidor– What effect has that had on HR’s?
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Home Runs and Humidors
• Coors Field in Denver:– Pre-humidor (1995-2001):
• Rockies home: 3.20 HR/game away: 1.93 HR/game
– Post-humidor (2002-2010):• Rockies home: 2.39 HR/game away: 1.86
HR/game
25% Reduction!
Summary and Outline of Talk
• Thin air results in lots of HR in Denver
• Humidor has reduced HR by 25%
• Two questions:– Can science account for the reduction?– Can we predict what might happen in
Phoenix?
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Effects of Humidity on Ball Properties
• Humid air makes the ball “less bouncy”– “Coefficient of Restitution” (COR) decreases– Ball isn’t hit as hard
• Humid air make the ball heavier– Ball isn’t hit as hard– But carries better
• Humid air makes the ball larger– Doesn’t carry as well
12These effects can be measured
So Here’s The Plan:
• Measure in lab how RH affects ball properties
• Use physics of ball-bat collision to predict change in batted ball speed
• Use aerodynamics to predict change in fly ball distance
• From all this, we can estimate change in home run production
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Physics Alert!!!
• The next few slides will have some details that may bore you
• Hang in and I’ll tell you when to pay attention again
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So this is what we found
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Summary of Findingswith RH increased from 30% to 50%
• Weight increases by 1.6%
• COR decreases by 3.7%
• Diameter change negligible
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For typical long fly ball (100 mph, 30 deg)- Batted ball speed decreases by about 3 mph- Fly ball distance decreases from 415 ft to 402 ft
What about Home Runs?
• We have full record of every home run hit during 2009 and 2010 (336 total)– Total distance– Batted ball speed and launch angle– Good approximation to full trajectory
• With changed balls, can ask whether the ball would have cleared the fence– Only 265 make it
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Final Result
• Actual reduction = 25%
• Calculated reduction = 27.5±4.3 %
• The agreement is amazingly good– SCIENCE WORKS
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And what about Phoenix?
• If RH goes from 20% to 50%– HR reduced by 37.0±6.5 %– A very big effect!
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More Stuff from Nick….
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Final Summary
• Storing the baseballs in a humidor has resulted in a big reduction in home runs at Coors Field in Denver
• We understand very well the effects that lead to that reduction
• We can apply our understanding to predict an even larger reduction if a humidor is employed at Chase Field in Phoenix
• I like to think that our analysis led the Dbacks to postpone their decision
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QUESTIONS?