Imagine it is your birthday! You celebrate it at home. There are birthday balloons all around you.

Your aunt is an astronaut. She says that she will take you on a ride to outer space as your birthday gift! You go in her spaceship, carrying one balloon.

You reach outer space and step out of the spaceship with the balloon. You are wearing your space suit, of course!

What happens to the balloon as you enter the vacuum of outer space? Let's find out in this chapter!