🌓 Why Does the Moon Change Shape?

Every night, Comet the kitten looked at the moon from her window. One night it was round and full, like a big silver plate. A few nights later, it looked like half a cookie. Then it was a thin curve, like a smile.

"Grandpa," she asked, "is someone nibbling the moon?" Grandpa chuckled. "No, little one. The moon doesn't really change. Let me show you."

He took a ball and a flashlight into a dark room. "The ball is the moon," he said. "The flashlight is the sun. And you are the Earth." He turned on the flashlight and shone it at the ball.

"The moon doesn't make its own light," said Grandpa. "It shines because the sun lights it up, like the flashlight lights the ball. But only one half is ever lit."

Grandpa slowly walked the ball in a circle around Comet. When the ball was on the far side, Comet could see the whole bright side. "Full moon!" she said. When it was to the side, she saw only half lit up. "Half moon!"

When the ball was between her and the flashlight, the bright side faced away, and she could hardly see it at all. "New moon," said Grandpa. "That's when the moon seems to disappear."

"So the moon is always round," said Comet, her eyes wide. "We just see different parts of the lit-up side as it travels around us!" "Exactly," said Grandpa, with a proud purr.

That night, Comet looked out at the thin crescent moon and smiled. "Goodnight, Moon," she whispered. "I know you're still round." And the wind outside seemed to whisper back, "Goodnight."