According to Wikipedia air pressure within a dome is defined as the following:
The interior air pressure required for air-supported structures is not as much as most people expect and certainly not discernible when inside. The amount of pressure required is a function of the weight of the material - and the building systems suspended on it (lighting, ventilation, etc.) - and wind pressure. Yet it only amounts to a small fraction of atmospheric pressure. Internal pressure is commonly measured in inches of water, inAq, and varies fractionally from 0.3 inAq for minimal inflation to 3 inAq for maximum, with 1 inAq being a standard pressurization level for normal operating conditions. In terms of the more common pounds per square inch, 1 inAq equates to a mere 0.037 psi (2.54 mBar, 254 Pa).
Well that definition only made me more confused but the following easy to understand graph illustrates the effect that air pressure has on a baseball, specifically with a knuckleball:
And a much more detailed description on how a knuckleball works and what it does:
Ideally, we would use real data to determine how well R.A. Dickey can pitch in a dome vs. outside of one. However, he has thrown only once in the past three years inside such a structure. Last year, he tossed nine innings against the Rays in Tropicana Field. The result was a one hit shutout with twelve strikeouts. That simply won't do in terms of sample size, so I decided to take a look at the last four great knuckleballers: Phil Neikro, Joe Niekro, Charlie Hough, and Tim Wakefield.
Phil Niekro 3.98 3.90
Joe Niekro 3.47 4.07
Charlie Hough 4.02 4.29
Tim Wakefield 4.95 5.01
The lowest number of innings in a dome for the above pitchers was 375 innings. Only Joe Niekro exceeded that with over 1,300 IP...thanks to many a game in the Astrodome. That said, Joe Niekro appeared to really benefit from pitching his home games in the Astrodome while Charlie Hough also performed well out of the elements. Wakefield and Phil Niekro did not appear to show much of a difference. It should be noted that the four above never threw a knuckler the way Dickey does. Hough would occasionally try to let go of a hard knuckler, but all four of them typically stayed within the 50-70 mph range with their pitches.
So...what does this all mean? There seems to faint evidence that "knuckleball" throwing pitchers pitch the same or better when pitching inside a dome. It will be interesting to see next year how Dickey fairs inside the Rogers Centre. Some have noted it as a launching pad, but that seems to potentially be hyperbole borne out of a couple of seasons where Blue Jay hitters performed awfully well there while being bookended by relatively average home run seasons. Citi Field actually saw an increase in home runs hit with them moving in their fences last year. Although the first season in Citi Field played about league average for home runs. Below are park factors for HR:
2009 0.99 1.06
2010 1.36 0.72
2011 1.19 0.74
2012 1.03 1.07
If I was forced to guess, I would say that Dickey will be worth anywhere between 3-4 wins next year. Some have called this deal a mistake on the Blue Jays part in giving up an offensive catcher who most scouts feel sure will be a major part of the Mets lineup to come along with a few interesting parts that may boost the Mets pitching or outfield. There is truth in that. The Jays gave up a lot, but when you look at the vulnerability in the AL East at the moment...it is hard not to try to go for it. There certainly is a good deal of risk in the Jays roster with guys who have been somewhat uneven in performance and injured, but, with the money behind the Yankees and Red Sox, if you can strike then you strike. That is what the Jays are doing and, to me, it makes complete sense. As of this moment, they are my favorite for the division.
Another surprise is not the drop in player ranking for Albert Pujols but that the drop was not more. He is currently at #26 only down 19 spots from his pre-season ranking of 7. There is no way you could ever convince me that a player limping after every at bat is one of the Top 30 players in the Majors. I think Matthew Berry's friend said it best it in the video on the page with "Not even close" after receiving a Goldschmidt for Pujols trade request. Performace and youth far outweigh age and potential.