Saturday, May 19, 2012

The Rising Fastball-Myth or Fact?

     "Nolan Ryan has two out in the ninth inning, oh and two on Reggie Jackson.   Here's the windup...and the pitch....STRIKE THREE ON A RISING FASTBALL!!"

 Robin Ventura offers his theory to Nolan Ryan that there is no such thing as a rising fastball. 

    Or was it?  This has been a debate for many years, with technology seeming to support those who believe that baseballs do not rise. Physicists have weighed in the analysis.  Even Mythbusters, one of my favorite shows, did a segment which says that the ball does not rise. 

   However, let me offer a bit of a rebuttal.  First, as a physicist of sorts, let me offer some advice on when to trust physicists.  

   a.  Trust them to determine nuclear transitions, discover quarks, design semiconductors, estimate the age of the universe or measure spectra of atoms.

   b.  Do not trust them to change a light bulb,  select a restaurant for dinner, and never ever let them jump start a car.  And do not trust their opinions about sports. 

   Physicists, you see, do not become physicists because they love physics.  They become physicists because no one will pay them to play sports, and they have no other way to attract a mate.  

   Historically, if you go back 80 years ago, physicists used to argue that there was no such thing as a curve ball, because their simple models didn't predict that.  They tried to argue that it was just an optical illusion caused by the spin of the ball.  Hah!  Later on, the aerospace engineers used wind tunnels and measured the rotation rate of the baseball and calculated that in fact baseballs did curve. Today there is very little doubt that balls do in fact curve. 

    Back in the day, the Village Elliot used to play baseball, as ridiculous as that may seem to anyone who knows the rotund research scientist now.  He never had any real ability to play except for one thing:  he could visually track an 80 mile an hour (amateur level) baseball as well as anyone, and thus was a respectable contact hitter even after age 40.  And I know darn well that there IS such a thing as a rising fastball and that it is not an illusion.  If you don't believe me, go to your local amateur league and try to catch one of these kids that throws at near-professional velocity.  Ask for the four seam fastball and see if you don't wind up catching it in your teeth.
   When I played baseball, we had a kid named Brian Rasay who had pitched for Cedarville University and he definitely threw a hard riser.  I wouldn't catch him without a catcher's mask for that reason.  

   So what gives?  I think first of all, the physicists need to ask what defines the "straightball."   A trivial case would be an underhand fastball, which starts out from a release point of a foot and which can obviously be thrown with an upward trajectory.  But that is not what is meant by a rising fastball.

    The "straightball" would be thrown on a downward trajectory.  
Keeping in mind that the pitchers' mound is about a foot high, the release point may be around six to six and a half feet for a typical (overhand) pitcher, relative to the batter.

Here's a graphic of Brandon Morrow of the Blue Jays, from an excellent article by Mike Fast in Baseball Prospectus,

     Now the batter calls it a straightball if the ball comes in at belt high, or about 3 feet from ground level, without any additional weird movement.  Obviously, the ball is travelling down about 3 or 4 feet.  

    The physicist can note at this point that the actual trajectory is kind of a parabolic path, with some correction because air resistance slows down the ball a few mph on its way to the plate.  Given that a pitched baseball has a speed of 95 miles per hour, the predicted effect of gravity is that it will deviate by about 1 meter (3 feet) by the time it gets to home plate.  The effect of air resistance is that it will slow down a tad as it gets closer to the plate.  So in other words, the initial trajectory is such that the fastball starts out as if it is going to pass six feet above home plate, but it actually winds up at the three foot level.  The baseball pitcher does not need to study physics to figure this stuff out.  He knows from experience where to release the ball to put it where he wants it.  Similarly, the batter is not a physicist and does not get out a calculator to determine the trajectory of the ball.  He knows what the ball looks like and how it should behave.  The point is that "straight" is defined in some kind of modified parabolic coordinate system, which is simple to the ballplayer but very complicated to describe using mathematical physics. 
    What about the effect of spin?  The four seam fastball has maximum air resistance because of its orientation, and if thrown by an overhand pitcher, has a backspin, which results in an aerodynamic force being put on the ball.  The aerodynamicists estimate that the Magnus force on the four seamer is probably about half the force of gravity, and would result in the baseball changing its trajectory by about a foot and a half by the time it crosses home plate.  This is comparable to the distance that a curveball can move, incidentally.  

  The Magnus Force is known to affect the trajectory of spinning baseballs, including the curve ball...AND the rising fastball. 

The Magnus force causes the ball to deviate from the normal trajectory by as much as a foot and a half. This is a real effect, not an optical illusion.  However, since the ball is thrown from a release point of about six feet above the ground, the physicist is probably right that it does not actually have a net rise with respect to ground. 

In Cartesian Coordinates, the normal fastball travels downward from the pitcher's release point to the strike zone, and follows a roughly parabolic trajectory.  The riser has less of a downward break. (the y-scale is exaggerated).

Referenced to the "normal" trajectory, the riser's trajectory can be altered by about 1.5 feet due to the Magnus effect. (y-scale greatly exaggerated). 

   So, the altitude of the baseball does not go from level flight to a rising trajectory.  So if that's how you want to define the rising fastball, it does not exist under normal conditions.  But that is not right way to look at the problem, as baseball players can automatically view the "straight" trajectory in distinctly non-Cartesian systems.  So if you are going to call the rising fastball unreal, the "straightball" or flat trajectory is even more unreal.  
  So I think that the physicists have actually calculated the right answer, but interpreted it incorrectly.  The point is that aerodynamic forces can in fact cause a well pitched four seamer to cross home plate at a higher point than a normal two-seam fastball, by about a foot and a half.  It is not an optical illusion. It is a physical change in the trajectory caused by its spin and orientation.    It is usually not a net rise, however, because the pitcher's release point is about six or seven feet above the elevation of home plate.  

    Let me add one trivial point.  If the pitcher is a submarine (underhand) pitcher, with a release point about two feet above the home plate level, do we mean to say that the ball cannot be thrown up around the letters?  Of course not.  The pitcher can throw the ball with an upward trajectory and the ball clearly rises.  The physicist should not be locked into the math to miss the point that the initial trajectory can be upwards.

     So, in summary, the rising fastball is not quite a myth. The elevated mound and the preferred release point of most pitchers ensures that a pitch thrown for a strike is basically downward.  With a hard backspin, the four seamer can deviate from its normal trajectory by as much as a foot and a half by some credible estimates.  This is rising action relative to its normal trajectory.  Moreover, if the pitch is thrown from a low release point (i.e., underhand), it is trivially obvious that the ball can have a net rise by the time it crosses home plate.  The physicists are correct, however, that a pitch thrown from an overhand pitcher to the belt level of the batter does not actually have a net upwards trajectory relative to the level of home plate.  


  1. You contradict yourself. Dropping less is not the same as rising.

    1. It's not that simple. The point is that the baseball has a normal trajectory, and the pitcher causes it to deviate from the normal trajectory depending how he throws it. It's not just gravity, and if you try to catch a pitcher with a decent riser you may have to catch it with your teeth. The Magnus effect is real.

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