As I put the kids to bed on a night before Christmas some years ago, and prepared to tell them a good night story, my first-grade daughter Lauren put the inevitable question to me.

“Dad, is there really a Santa Claus?”

I was ready. “Why, yes, Lauren, there is a Santa Claus.”

“And does he really fly around the world on Christmas Eve, delivering presents to all the good boys and girls?” asked my third-grade son Adam.

“Yes he does.”

Both kids looked at me skeptically. I could see little wheels turning in their heads where visions of sugarplums should have been dancing.

Finally, Lauren spoke up. “Dad, there are over 2 billion children in the world. How can Santa possibly deliver presents to all of them in one night?”

I thought I had her there. “Remember, Lauren, Santa only delivers presents to those children who celebrate Christmas. And not all children do.”

Adam said, “But even if we assume that at least 85 percent of all the children in the world are Muslim, Hindu, Jewish, Buddhist or simply non-believers, that still leaves 15 percent of them who do celebrate Christmas, and 15 percent of 2 billion is around 378 million children.”

Again, I thought I had them. “But remember, kids, Santa only delivers presents to kids who have been good.”

Still, Santa would have to stop at almost 92 million houses because even if there was a bad kid there likely was a good kid in the same house.

Now I thought I really had them. “Actually, guys, taking into account time zone changes and the rotation of the earth, Santa really has more like 31 hours to work with.”

Lauren quickly calculated that would work out to roughly 822.6 visits per second, Dad. That means that Santa has 0.001 seconds at every stop to park the sleigh, jump down the chimney, fill stockings, distribute gifts under the tree, eat whatever snacks have been left for him, go back up the chimney, get back in the sleigh and move on to the next house.

Adam calculated that Santa would have to travel more than 71 million miles on Christmas Eve.

Lauren pulled a small calculator out from under her pillow as I silently cursed the success of the Bainbridge Tech Levy. “And that means that Santa would have to be traveling at 650 miles per second.”

Adam chimed in, “That’s 3,000 times the speed of sound.”

“Remember, these are really special reindeer,” I added sheepishly.

“They must be,” Lauren said. “Reindeer on earth travel no faster than 15 miles per hour.”

And don’t forget the reindeer are pulling a sled and carrying, what, say 321,300 tons of presents, Lauren said.

“The sleigh is probably made of titanium,” I bleated pathetically, “You know, a real light metal.”

Adam, who is 9, knows more about reindeer than anyone at his age should. He says regular reindeer can pull only about 300 pounds.

So if Santa’s “special” reindeer can pull, say 10 times the weight a regular reindeer, Santa would still need 214,200 of them for the task, said Lauren, who was really getting on my nerves by now. “If I remember the formula correctly from kindergarten,” she said, the amount of energy produced would cause the two lead reindeer to burst into flames immediately, and would vaporize all of the following reindeer, the sleigh and the gifts in less than four-thousandths of a second.

I thought about pointing out that the fire might be put out by the vacuum created by the constant and deafening sonic booms that would be created in the reindeer’s wake, but on reflection didn’t think it would really help my case.

“Well, right, then kids, bedtime!” I announced precipitously. “Time to turn out the lights.”

The kids settled into their beds as I flicked off the lamp and bolted for the door. But before I escaped the room, I heard Lauren sleepily ask, “Dad, tomorrow night could we talk about the Easter Bunny?”

Tom Tyner writes a weekly humor column for this newspaper.