As the New York Mets and Kansas City Royals face off for the 111th edition of Major League Baseball's championship series, it's not just the players and coaches who are competing. The groundskeepers are vying for a title too: Best Field Design.
We've all seen the interesting patterns displayed in the infields and outfields of baseball stadiums. But do you know how the groundskeepers create such elaborate designs?
Baseball groundskeepers rely on a phenomenon of color science called gonio-appearance to confuse our eyes into thinking we see two different colors of grass. In this case, the grass really is greener on the other side.
Using rollers, they stripe the lawn by forcing the grass to lay in different directions. By changing the direction of the grass against the ground, the groundskeepers are manipulating the way the light reflects to give us a unique perception of color. When it's laying one way, we see more of the flat part the blade. But when they force it in another direction, we see more of the ends.
White light is actually made up of all of the colors of the visible color spectrum: a rainbow that includes red, orange, green, blue, indigo and violet. Objects have properties like dyes, pigments and texture that determine which wavelengths of the visible spectrum are absorbed, and which are reflected back to us. It is this mixture of reflected light that enters our eyes and gives us the perception of color.
When it comes to grass, the way the light reflects off the different areas of the blade causes us to perceive it as different colors of green. That's why we don't see a grassy field as a solid color. Since the flat side of the grass is wider, it reflects more green light, while the narrower sides appear darker.
Gonio-appearance doesn't just happen on the baseball field. You can see it in carpets and fabrics like corduroy and satin when the shade changes as you brush the nap in the opposite direction. It also occurs in nail polish and automotive coatings, which use flecks of metallic paint to create the illusion of different colors depending on your angle of vision. Whenever the color of an object seems to change when the light reflects differently, you're experiencing this phenomenon.
As the rest of the world is watching to see which team will walk away with the Commissioner's Trophy, be sure to take a moment and pay tribute to the hard working color scientists we know as baseball groundkeepers.