Hot air rises up, up, and up.
热空气呀，一个劲往上升。
It is lighter than the cool air around it.
它比周围的冷空气要轻。
A balloon traps the hot air in a big bag.
热气球把热空气装进大口袋。
The light air pushes the bag up.
轻轻的热空气，把口袋往上托。
A burner keeps the air inside hot.
燃烧器一直把里面的空气烧热。
When the air cools, the balloon goes down.
空气一凉，气球就慢慢落下来。
That is how people float high in the sky.
人们就这样，飘在了天空里。
