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pennywise1My kids are weirdly consistent in their vocational dreams. They flirt with various ideas, but they always end up whipping back to their respective Norths like compass needles. By the time I was ten, I’d already torn through a half-dozen intended vocations: paleontologist, stand-up comedian, astronaut, clarinetist…stuff like that.

For years, Connor (now 14) has had his eye on engineering, and has recently narrowed it to alternative energy engineering. Erin (now 12) has wanted a career in medicine since she was 8 and has recently narrowed that (through questions like “What do you call a person who studies the way the body works?”) to research physiology.

Delaney (8) has pretty much always wanted to be a scientist of some kind.

A few weeks ago, Erin hunched intently over the kitchen table with a dropper to see how many drops of water would fit on a penny. Cool science project from school involving estimates, observation, averages, graphing. Good stuff.

Delaney suggested expanding the parameters of the study to see if water temperature would affect the results. I was reading in the next room when a small brouhaha broke out between the researchers. As usual, Erin came tromping in to me with a look of righteous determination.

“Dad, Laney and I are doing an experiment to see if a penny holds the same amount of hot water as cold water.”

“And?”

“And I’m trying to tell Laney that we have to use the same penny for both, because one might be a little different, but she…”

“They’re both the same! Shiny 2009 pennies!” whined Laney from the doorway.

I walked into the laboratory and saw two shiny 2009 pennies sitting side by side on the table, waiting for further instructions.

I asked Erin why you need to use the same one.

“Because there might be tiny differences — little scratches or nicks that you can’t even see, but they might affect the water differently.”

“Variables.”

“Yeah, variables.” Erin looked mighty pleased with her middle-school sciency self. I was too. But I wanted Laney to learn a cool thing about her life’s work, not to feel defeated. I told her to imagine that I was a scientist designing a study to see if people with blue shirts could get things off high shelves more easily. I opened the kitchen cupboard and asked white-shirted Laney to grab a cup off the top shelf.

She gave me a fumey look.

Blue-shirted me reached up and brought down the cup. “Well there it is. I’ve learned that people with blue shirts”

“Dad”

“are better at”

“Dad”

“getting things down from”

“DAD!”

“What?”

“You’re taller.”

“I think it’s the shirt.”

“Then you’re a dork.”

“How can you figure out whether it was the shirt?”

“I just wouldn’t use a tall person at all! I’d get two people who were both…” She paused. “Normal.”

I told her she had just removed a variable. She got it.

“But you’re obviously tall. The pennies are exactly the same.”

I admitted that they might be, then motioned her into the basement. We looked at the pennies under our microscope. Sure enough, canyons and craters loomed.

By this time she’d thankfully forgotten that her big sister had ended up right. It was just cool.

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Dale McGowan is the author of Parenting Beyond Belief, Raising Freethinkers, and Atheism for Dummies. He holds a BA in evolutionary anthropology and a PhD in music.