Cold weather and knuckleballs: R.A. Dickey and the season opener in Chicago

It is a somewhat accepted myth that knuckleball pitchers are doing better in domes (part of the Twins' intrigue by R.A. Dickey.) What is driving this argument is the theory that the lack of wind in a dome would not affect a knuckleball, allowing it to have its fluttering motion that makes it difficult for the catchers to catch and hitters to hit.

So, would it have been better for the Twins to start Dickey in the dome and give someone like Blackburn, Dickey's Cellular Field start tonight?

The answer is no.

There is another physical factor that affects a knuckleball more than the wind: Air density. The colder the temperature, the denser the air, the less the spin. And throwing a knuckleball with no spin, is like throwing a brick to the batters. I am not going to in depth on the physics of a knuckleball, other than try to explain in basic terms what makes it flutter and then I will go into the temperature stuff:

Here is a knuckleball grip (Hoyt Wilhelm):



It is very similar to that of a fastball, but instead of running the middle and index fingers along the seams and trying to hold onto the ball only by the fingertips and thumb tip, the nails of the index and middle fingers dig into the seams, the first knuckles are close on the seams (thus the misnomer; a "nailball" would be more appropriate), which also has the effect of placing the ball closer to the palm, making it more of a change up grip.

the above image shows a knuckleball grip in the manner of a two-seam fastball (sinker), Dickey's grip is across the seams, in the manner of a four-seam fastball:




Both grips have the same effect, with Dickey's resulting to a slightly faster ball towards the plate (low 70s). Dickey, also throws the traditional, two-seam variation that results in a ball thrown about 5 mph slower. So tonight, when you see knuckleballs in the high 60s, low 70s, he is using the 4-seam variation, and when you see knuckleballs in the mid to low 60s, he is using the 2-seam variation.

Why the motion: ideally, a knuckleball from the pitcher to the plate will do only one half spin, moving the seams that held them into the side (90 degrees). The drag (air resistance) of the seams (which increases relatively by the lower velocity of the ball towards the plate than traditional pitches) will cause the ball to have an increased sideways movement, thus "flutter". The argument against the wind is that a lateral (side to side) wind, would exaggerate the natural lateral movement of the knuckleball, making it more "wild".

That's what throwing a knuckleball is all about. How about the temperature effects? Higher temperature decreases the density of air molecules and low temperature increases their density. When it is cold and the air molecules are denser, this has two effects: a. it slows the velocity of the ball which, in turn, b. decreases the spin of the ball, thus making a knuckleball, flutter better. Here is an extreme example to make it clearer: Cold increases water molecule density. Is it easier to push your finger through liquid water, or through ice? The same principle applies to the air.

If you are not yet convinced:

• Here is a New York Times article, where Mike Marshall, the former Cy Young winner, explains why a knuckleball is aided by the cold


• As a further support, Dickey's ERA last season in the open was more than 2 points lower than in a dome (4.48 vs. 6.52), opponents had a .751 OPS in the open vs .952 in the dome, his ERA was 3.66 in night games vs. 8.50 in day games, and opponents had a .715 OPS in day games vs. .980 in night games


• Hoyt Wilhem threw the only no-hitter by a knuckleball pitcher on September 20, 1958 against the Yankees in a cold and drizzly afternoon

Tonight's game conditions are perfect for R.A. Dickey.