Research Videos
Ball in Flight Animation
The real-time applet shows the occurrence of the physical and optical apeces
for a ball that is directed at a stationary fielder. The up-down motion of
the ball from the starting position to the position of the stationary fielder
shows the physical trajectory. The lines through the ball ending at a vertical
extension of home plate straight up in the air at each point in time designate
the optical trajectory. There are two significant points concerning this.
First, there is nothing notable optically about the physical apex (the highest
point in the air that the ball reaches). At the point where the ball is highest
in the air, there is nothing notable in the optical trajectory that would
indicate to an observer that the ball is coming down (i.e., the ball keeps
rising optically, or against the home plate vertical extension after the ball
is physically coming down). Second, the optical apex (the highest point that
the vertical extension above home plate reaches, or the highest point the
stationary observer is looking) occurs much later than the physical apex.
This is an example in which the optical trajectory is discrepant from the
physical trajectory and, thus, the optical apex is greatly separated in time
and location compared to the physical apex. Optically for the outfielder the
baseball rises longer than it does physically, making accurate judgment of
the physical apex virtually impossible. Observers may think that they know
where the ball is located in space while it approaches, but optically all
they see is a ball image that slowly arcs up.
View of Participants Judging the Apex
The following
video shows five observers attempting to estimate when the apex of a fly
ball coming toward them occurs. On the right, a foot stand holds a green and
yellow light. When the green light comes on, this is when the ball left the
pitching machine located 200 feet directly in front of the observers (as indicated
by the person who was operating the pitching machine flipping a light switch
on that activated the light). A judge 200 feet orthogonal to the trajectory
of the ball (or perpendicular to the plane from the ball throwing machine
to the observers) operates the yellow light. This judge flipped a light
switch on to activate the yellow light when the physical apex (highest point
a baseball reached in the air) occurred. Observers indicated when they thought
the apex occurred by turning on a flashlight that they held in their hand. Because
what the optical trajectory looks like (or where the observer is looking
at each point in time) is dramatically different than the physical up-down trajectory
the ball makes, observers believe the physical apex has occurred long after
it has occurred. For instance, for a ball trajectory shown in the video
the ball comes very close to the observers. In this case observers keep looking
higher and higher in the air (because the ball is getting closer and closer
to them) long after the physical apex has been reached. This is why in
the video the yellow light (indicating the physical apex has occurred) comes
on long before the average response of the observers. Three of the observers
turn on their flashlight just before the ball nearly hits them.
View movie (slow motion)
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Participants View of Ball in Flight
The following video shows the optical trajectory for the ball (what the
ball looks like as it approaches and you are looking at it at each point
in time) for a ball that comes very close to observers (it is the same
trajectory that observers saw in the video showing them trying to estimate
when the physical apex occurs. As can be seen here, it is very difficult
to judge when the physical apex has occurred, and by then it is almost
hitting the fence.
This also shows how we coded what the ball looked like to observers as they estimated when the physical apex occurred.
Human Subjects Review Forms for this experiment can be found in the Kent State University HSRB office under Michael K. McBeath/Dennis M. Shaffer, years 1996-1998. All subjects in the video gave written consent to be videotaped and consent for us to show this video at conferences, on websites, and to classes.
