Today’s Wonder of the Day was inspired by Joe. Joe Wonders, “Are footballs really made of pigskin?” Thanks for WONDERing with us, Joe!

Hut! Hut! Hike! Go long and get ready to soar into the air to catch a flying pigskin for a touchdown.

That's right, folks. It's football season again. In America, that means it's time for high school games under the lights on Friday nights, college games throughout the day on Saturday and professional games on Sunday afternoon, Sunday evening and Monday night, too!

If you've watched much football, you've probably heard the ball referred to as a "pigskin" many times. But if you've ever played with a real football, you probably know it feels like leather. So what's the story?

As it turns out, the earliest form of the ball we now know as a football was more like what Americans now call a "soccer ball." Of course, most of the rest of the world still refers to soccer balls as "footballs."

These early round balls were made of inflated pig bladders. This is why footballs got the nickname “pigskins."

The earliest games of football featured mobs from opposing villages attempting to kick an inflated pig bladder into the balcony of their opponents' church!

Why pig bladders? Before rubber was invented, animal bladders were easy to get. They were basically round, lightweight, easily inflated and fairly durable.

The oldest football ever found was made in the 1540s. It consists of a pig bladder covered with pieces of leather, possibly from a deer. It was found in 1981 at Stirling Castle in Scotland.

Of course, it wasn't always the most pleasant task to blow up a pig bladder to use as a football. So when rubber was invented in the mid-1800s, pig bladders took a back seat to inflated rubber balls.

Eventually, leather coverings were added to strengthen the balls and make them easier to handle.

The shape of the football eventually changed from a round ball to its current elliptical shape with pointed ends (also known as a prolate spheroid). The new shape allowed the ball to be thrown farther with a forward pass.

Modern footballs are about 12 inches (one “foot") long and about 22 inches in circumference (around) at the center. Many people wonder why they're called "footballs" when most of the game is played with the hands.

Even though footballs are kicked occasionally during a game, the name most likely arises from the fact that the game has always been played on foot rather than on horseback, like the game of polo that was more popular at that time.

Modern footballs used in college games and professional leagues are made of leather. Footballs still have an internal bladder, but today they're made of polyurethane or rubber.

Laces hold the leather panels of the football together and provide a good grip for throwing the ball. Manufacturers also usually stamp the leather panels with a grain-like texture to help players hang onto the ball.

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