Once upon a time, there was a dog named Atlas. He lived with his Mom and Dad in a big red dog house. He liked peanut butter, frisbees, and his blue bandana.

One night, Atlas noticed something strange. The Moon looked like a smile, but Atlas was sure that just the other day the Moon looked round, just like his frisbee!

"Someone must have cut up the Moon," Atlas thought, and he ran inside to tell his parents about the Moon.

"Mom! Dad! Someone cut up the Moon!" Atlas exclaimed.

"What on Earth do you mean, Atlas?" asked his mother.

Atlas explained that the Moon was not round and full, but looked like a smile.

His mother smiled, and said, "Go get ready for bed, Atlas, and I will tell you about the Moon as your bedtime story tonight."

Atlas raced upstairs, brushed his teeth, and climbed into his bed.

"Do you remember how the Sun shines on the Earth, and that's what makes day and night?" asked Atlas's mother.

"Yeah! And when the Earth turns around it becomes nighttime!" exclaimed Atlas.

"Well, the Sun shines on the Moon too, which is why we can see it in the sky. Depending on where the Moon is as it goes around the Earth, we can see different parts of the Moon." explained Atlas's mother.

"But if the Sun is always shining on the Moon, why doesn't the Moon always look the same?" asked Atlas.

"I'll tell you what," said Atlas's mother, "for the next month, let's take a picture of the moon everyday. That way, you can see how the moon changes."