My knowledge of astrophysics is a little lacking, as our four-year-old has recently discovered.

This week, while we were trying to have a civilised family breakfast, she pestered me with questions about the workings of the universe and I couldn't quite give her the explanations she wanted.

To begin with, she wanted to know where the sun goes after sunset. I started off telling her it mostly went to New Zealand, where her friend Laura lives. But it also called at Australia and South Africa.

My husband, whose understanding of such things is better than mine on account of him once taking, but failing, physics A-level, suggested we try to introduce a bit of modern science instead of perpetuating childish fantasies.

He said this was the window of opportunity to talk about how the moon goes round the earth and the earth goes round the sun.

So while he spooned porridge almost into the baby's mouth, I got an apple, an egg and an orange and began orbiting them around each other on the kitchen table.

"Can you understand this," I said, watching our daughter pull a goblin-like face and then join in with the baby in banging spoons on the tray of his high chair.

"Yesh, marmee," she said in one of that morning's silly voices.

"Okay, so you now explain it to me."

She began a little song: "The moon goes round the sun and the sun goes round the earth and the moon goes round the sun and the earth goes round the moon. La, la, la, twinkle, twinkle, twoo."

"Er ... not quite," I said. "Let's have another go."

"Booorrring," she said, and without giving me a chance, she asked her next question.

"Marmee, why is there a man in the moon?"

"There isn't, sweetie," I said, half relieved she wasn't demanding information about angles, rotations and trajectories.

"So who's face is it?" asked little Miss Galileo.

"It's not a face at all. It's the shadow of mountains, or dry lakes ... I think."

"Or it might be a lady."

"No, I don't think ..."

"I know, I know. The sun could get married to the moon and their babies could be all the little stars."

"Yes, perhaps. But you know, those little stars are really enormous suns in other galaxies, trillions of miles away."

"Would it take about a week to get to them?"

"Much, much longer," I said, searching for a suitable time scale before settling with: "Longer than you could ever imagine."

"The moon's not far," she said. "Can we go there? I like it because it's so shiny and pretty." She had got down from the breakfast table to twirl like a ballerina.

"We'd have to learn how to be astronauts and travel in a space rocket," I pointed out.

"Do rockets have televisions?"

"Well, you couldn't watch CBBC, but ..."

"Marmee, can I have chocolate cake for breakfast?"

My husband stopped spooning for a second. "Oh, is that the end of Learn with Mother?" he said, in a tone of mock disappointment.

"For now," I said. "And I think we've made some progress. Next week, we'll be discussing the rise and fall of the Roman Empire, starting with why togas were such lovely dresses."