How the car goes, where wind comes from, and other bluffs

We were eleven minutes into a forty-minute drive to my in-laws' when Lucy, who's eight, leaned forward against her seatbelt and asked, "Dad, how does the car actually go?"

Her brother, who's five, came in before I could breathe. "And where does wind come from?"

I said "Great questions" in the voice of a man buying time. My wife looked out the passenger window. She knew. She's known for twelve years. She also knew the little orange engine shape on the dashboard had been glowing since Tuesday.

So, in the interest of honesty, the full list.

1. How does the engine make the car go?

They think I know: Every part, the whole diagram, probably from memory.

What I actually know: Gas goes in. Something goes vroom. I once said "the pistons do the work" so confidently that a waiter nodded.

What you actually need to know: Most car engines are four-stroke. Inside each cylinder, a piston slides down and pulls in air and fuel. It slides up and squeezes them. A spark plug fires, the mix burns, and the blast shoves the piston down hard. Then it slides up again and pushes the exhaust out. Those pistons turn a crankshaft, and the transmission sends that spin to the wheels. Tell an eight-year-old it's thousands of tiny controlled explosions every minute and watch her face. (Electric cars skip all of it. A battery runs a motor that turns the wheels.)

2. Where does wind come from?

They think I know: I have a degree in this. Or a connection.

What I actually know: For one full second I believed the trees waving make it. I didn't say it out loud. Thinking it was bad enough.

What you actually need to know: The sun. It heats the ground unevenly, so some air gets warmer than the air beside it. Warm air rises, and cooler, heavier air slides in to fill the gap. That sliding is wind. Forecasters call it air moving from high pressure to low. At the beach on a sunny afternoon you can feel it happen. Land heats faster than water, so the breeze blows in off the sea. At night it often flips.

3. Why is the sky blue?

They think I know: There's a short answer and I'm withholding it for dramatic effect.

What I actually know: "It reflects the ocean." It doesn't. I said this for about thirty years.

What you actually need to know: Sunlight looks white, but it's every color mixed together. When it hits the tiny molecules in the air, the short blue wavelengths get bounced around far more than the long red ones, so blue comes at you from every direction. It's called Rayleigh scattering, and kids love saying it. Sunsets go orange and red because the light is crossing much more air to reach you, and most of the blue gets scattered away before it arrives.

4. What does that orange light on the dashboard mean?

They think I know: I've diagnosed it and made a calculated decision to wait.

What I actually know: I've been resting my thumb over it at red lights since Tuesday.

What you actually need to know: That's the check engine light. The car's computer found a problem somewhere in the engine or emissions system. A loose gas cap is a classic cause, so tighten it until it clicks and give it a few days of normal driving. A steady light means get it checked soon. A flashing light means a serious misfire that can ruin the catalytic converter. Ease off, skip the hard acceleration, and get it to a mechanic as soon as you safely can. Every car sold in the U.S. since 1996 has a diagnostic port under the dashboard, and many auto parts stores will read the code for free.

5. How much air goes in the tires?

They think I know: I just know, the way I know their birthdays.

What I actually know: I once read the big number on the side of the tire and filled it to that. With authority. In front of other dads.

What you actually need to know: The number on the sidewall is the maximum the tire can hold, not what your car wants. The right number is on a sticker inside the driver's door jamb, sometimes in the glove box or on the fuel door. Check it cold, before you drive or after the car's sat a few hours, because driving warms the air and bumps the reading up. A pencil gauge fits in the glove box. Once a month is a good habit.

6. How do you jump-start a car?

They think I know: I've done it a hundred times, probably in the rain, probably heroically.

What I actually know: Twice. Both times a stranger in a work truck did it while I held the flashlight.

What you actually need to know: No jokes on this one. Car batteries can give off hydrogen gas, and a spark near one can make it explode. Check your owner's manual first, because some cars want the cables on dedicated jump posts instead of the battery. Otherwise: red clamp on the dead battery's positive (+) terminal, the other red on the good battery's positive, black on the good battery's negative (-), and the last black clamp on bare, unpainted metal on the dead car's engine, well away from the battery. Start the good car, let it run a few minutes, then start the dead one. Remove the cables in reverse order and never let the clamps touch each other. If the battery is cracked, swollen or leaking, stop and call for help.

7. How do airplanes stay up?

They think I know: I worked it out on the flight to Grandma's.

What I actually know: I stared at the wing the entire flight, willing it to stay on. That was my contribution to aviation.

What you actually need to know: A wing is shaped and tilted so it shoves air downward as it moves. Push air down, and the air pushes the wing up. That's lift, helped along by lower pressure above the wing than below it. (The old story about air on top having to "catch up" with air underneath is a myth.) Try this tonight. Fold a paper airplane, bend the back edges of both wings up a little, and throw it. It climbs. Bend them down and it dives. You just built elevators, the same control a real pilot uses.

8. Where does thunder come from?

They think I know: I understand it, and also that I can make it stop.

What I actually know: "Clouds bumping." I'm a grown man with a mortgage.

What you actually need to know: Lightning heats the air around it hotter than the surface of the sun in a fraction of a second. That air expands so violently it makes a shock wave, and that's thunder. Count the seconds between the flash and the boom and divide by five for roughly how many miles away it struck. And the rule that isn't up for debate: if you can hear thunder, you're close enough to be struck. Get inside a building or a hard-topped car and wait thirty minutes after the last rumble before going back out.

The one I'm glad they asked

The car one. Not because I suddenly knew, but because the answer was sitting in the glove box in a book nobody in our house had ever opened.

Saturday morning, Lucy and I spread the owner's manual across the hood like a treasure map. She found the door sticker. She ran the tire gauge while I read the numbers back. Her brother checked the washer fluid, found it low, and announced it like breaking news. We pulled the dipstick, wiped it, slid it back all the way, pulled it again and read the oil between the two marks. Twenty minutes, start to finish.

Do it this week. You need the manual, a tire gauge and a rag. Let the kid hold the gauge and hunt for the sticker. You read out loud, and when you hit something you don't know, say so. "I don't know, let's find out" might be the most useful sentence a kid hears from a parent, because they're learning how to find things out by watching how you do it. They pick up your habits long before your advice. And in eight short years she'll be behind the wheel with you in the passenger seat, which is a much better day if she already knows where the tire sticker lives.

On the way home we stopped at Grandma's, and Lucy insisted we top off her washer fluid too. Grandma hadn't asked. Lucy didn't care. Leave it better than you found it.

The check engine light? Gas cap. My wife suggested that on Tuesday.