Ever wonder what those black streaks under the eyes of athletes are for? Some believe it to be a psychological tactic to intimidate opponents during a game or match while others just think it looks cool. However, there may be more to those black swipes than you think. Among athletes, it is more commonly referred to as "eye black" and was originally used to reduce glare.

Did you know? Eye black used to be available only as grease, but is now widely available as stickers that can be customized and ordered at a cheap price.

So just how does eye black work as a glare reducer? Well, the science is quite simple and it involves a little phenomenon called albedo. Albedo is a measure of an object's ability to reflect solar radiation and depends primarily on the colour and roughness of the object. For example, white snow, which has a high albedo, will reflect more sunlight than black asphalt which has a low albedo.

Did you know? Albedo is a measure of reflectivity. Darker and rougher objects have a lower albedo and will reflect less sunlight. Since less is reflected, more sunlight has to be absorbed.

The albedo of an object is closely linked with two properties: temperature and glare. Because an object with high albedo will reflect more incoming sunlight and thus be less energetic, the temperature of the object will be cooler, but the glare from the object will be greater. You've probably experienced this during the blinding conditions of a sunny day in winter when there's snow on the ground.

The same basic principles hold for an object with low albedo, as in the case with eye black. When football players swipe that greasy black under their eyes, it serves to absorb the incoming sunlight in order to reduce glare received by the eye. So less glare, the better their vision, and the better their vision, the better their game.

Did you know? The use of eye black has been dated back to the 1940s where it was used to reduce glare during an outdoor football game.

Whether eye black really does reduce glare was proven in a study by two scientists back in 2003. In that study, subjects were divided into three test groups and were treated with either eye black, anti-glare stickers, or petroleum jelly. The subjects were then exposed to natural sunlight and properties of vision were then measured. At the end of the study, they concluded that eye black had improved contrast sensitivity by reducing the amount of glare entering the eye.

So the next time you watch a football game and think, "What on earth are those black swipes for?" don't forget that each player wears their eye black for a different purpose. Whether it's for a fashion statement, to appear daunting, or to gain a competitive advantage over another player, eye black is one sports trend that will not fade away anytime soon.

Learn More!

Eye Black and Reducing Glare

2003 DeBroff and Pahk Study

Customize Your Own Eye Black

Huoi Ung is currently studying at the University of Toronto at the St. George campus, completing a bachelor of science and specialize in cell and molecular biology. Huoi’s interests include dining out, playing tennis, drawing and building, and keeping up to date with technology.

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