Rhys Thomas spun a large rubber ball on the tip of his index finger.

“Why not try to spin the ball at the same time as I spin a ring?” he asked enthralled Hucrest Elementary School students. “Why not spin two tennis balls in my hand to show off my understanding of gravity?”

Living up to the challenge, Thomas kept the rubber ball spinning on his finger while juggling two tennis balls in the other hand and twirling a plastic ring around his arm and another around his leg.

The students let out hollers and whoops.

This trick wouldn't be possible without gravity, Thomas explained.

“Without gravity, there wouldn't ever be juggling,” he said. “Without gravity, I could keep throwing these balls up in the air, and they'd keep going. A juggler tries to keep the balls in the air. and gravity tries to keep them down.”

Thomas visited the Roseburg elementary school Monday to perform his traveling show “Science Circus” on behalf of the Oregon Museum of Science and Industry in Portland. A professional juggler for the past 25 years, Thomas teaches physics with circus tricks.

“It's kind of ‘rah rah' science show,” he said. “Looking into things from a science aspect is actually fun.”

Hucrest Principal Jeff Plummer said the school invited Thomas to perform Monday to kick off preparations for the school's science fair, which will be held in April.

The students saw science in action, as Thomas demonstrated concepts, such as centrifugal force.

He told the students about Italian physicist Galileo, who figured out that gravity pulls at a constant rate of acceleration. “Which means gravity pulls things so that they are going faster as they fall,” he explained.

This concept is evident to a juggler, Thomas said.

“I notice a ball thrown high takes longer to get back and hits my hand harder,” he said.

Galileo also figured that gravity pulls objects down at the same rate no matter how heavy they are, Thomas told the students. Then how come when he dropped a heavy plastic block and a feather at the same time they didn't hit the stage at the same time? he asked.

“There is something else there that is slowing the feather down,” Thomas said.

After several guesses, one student said, “Air.”

“What Galileo figured out if there is no air, you could throw a feather and a block and they would fall the same,” Thomas said.

But since he couldn't suck all the air out of the Hucrest gym to demonstrate, Thomas settled on throwing down the block with the feather on top of it.

“I'm going to let the block push the air out of the way for the feather so they fall at the same time,” he explained.

Sure enough, the feather and the block hit the stage at the same time.

Several student volunteers became Thomas' assistants, including second grader Kylee Haines. Thomas placed a pointed helmet on Kylee's head and had her hold two knitting needles to demonstrate gyroscopic stability, where an object gains more stability the faster it spins.

Thomas balanced three large rubber balls on the knitting needles and the helmet, but they quickly fell off.

“What do I need to do?” Thomas asked.

“Spin it!” the students yelled.

Spinning, the balls stayed balanced on the knitting needles and helmet.

As he reached the conclusion of his show, Thomas brought out his “balancing toy” — a unicycle.

“If I can get the tire under my center of gravity, I should be able to balance,” he said.

First-grader Breydon Church tossed to Thomas a rubber ball, juggling pins and stick to hold in his mouth. While riding his unicycle, Thomas balanced the spinning rubber ball on the stick in his mouth and juggled the pins.

His audience squealed with delight.

“I love juggling,” he told them. “I wanted to learn more about juggling so I studied the science of juggling.”

• You can reach reporter Inka Bajandas at 541-957-4202 or by email at ibajandas@nrtoday.com.