If your children tend to think of science as a school subject, and a boring school subject at that - take them by the Hansen Planetarium and let them play. This holiday season the planetarium has a half dozen toys on display, donated by The Chem Shop. And each one illustrates a different scientific principle.

On a recent Saturday, Stuart Becher, planetarium designer technician, was playing right along with the children. While making sure everyone got a turn, he answered questions as fast as the children could ask them."Oh, how does this work?" someone asked him about the little saucer-shaped disk that looked as if it had money lying on its lid. One person after another reached out to pluck the coins, only to have their fingers pass right through them. The coins were actually nestled down inside the disk. One person after another was fooled by the mirage.

"The Mirage works because of two opposite parabolic mirrors," Becher explained. When you see a mirage in nature, it's a similar principle, he said. "In the desert a layer of hot air actually refracts the light. Down in Arizona or New Mexico, a whole town can appear reflected, upside down, in the sky."

The toys are simple-looking, but children can spend hours playing with them. One of the most popular is a wooden frame from which five balls hang by strings. The Swinging Wonder. Pick up an end ball, let it go, and it swings down and strikes the line of balls and sends the last ball shooting up in an arc.

Click, click, click. All afternoon, children illustrated a basic Newtonian principle, said Becher. "For every action there is an equal and opposite reaction."

The Santa's Toy Lab hands-on display is free and runs through Dec 31. Becher says children of all ages are welcome to play with the toys on the second floor of the Hansen Planetarium (15 S. State) from 5 p.m until 8 p.m. weeknights and on Saturdays all afternoon and evening. "During the weeks the children have off school, we'll have the toys out all afternoon and evening every day," he said.

Becher added, "This first toy display is relatively small. Next year we hope to expand it, to get sponsorship by a large toy company. We'd like to put together a very large-scale Capsela display."

But even the smaller Capsela toys on display this year, Becher said, are examples of mechanical engineering in action. They show the way gears work.

"And I had a great time putting them together," he adds. Which is the main scientific principle the staff hopes to illustrate: Science is fun.