Apr 02, 2019

The Physics of Puck Luck

Reporting Texas

Joel Hanley. Photo courtesy of Dallas Stars.

On March 13, Joel Hanley, a defenseman for the Texas Stars hockey team in Cedar Park, scored an almost unbelievable goal.

During an American Hockey League game between the Texas Stars and the Manitoba Moose in Winnipeg, Manitoba, Hanley shot the puck into the Moose’s defending zone from about 90 feet away. He was simply trying to get the puck into better scoring position.

“I was just trying to get the red line and get a hard dump-in so the goaltender couldn’t get it,” Hanley said.

According to the laws of physics, what happened next was exceedingly rare, says Jose Alvarado, a physics professor at the University of Texas at Austin

“One in a million would be a good idea of it,” Alvarado said. “Maybe one in a billion.”

The puck took a hard bounce off the backboards behind the net, hit the ice, and bounced into the net for a Stars goal.

The goal was caused by the the conversion of spinning energy — caused initially by the shot, and then by the backboards — into moving energy.

The rubber puck is able to store more energy than a basketball or a football, and that’s what creates the seemingly impossible path.

“Hitting the board first, which creates the spin, allows the puck to pick up more energy,” Alvarado says. “That’s why it follows that crazy path, which is what makes it so improbable and rare.”

Alvarado describes the effect as similar to a coin hitting the floor: Given the right spin, it could bounce anywhere. That’s exactly what happened.

“I was in disbelief,” Hanley said about his goal. “I wasn’t sure how it went in, or what happened, just really excited, shocked that it went in the net.”