FLYING garbage (垃圾) bags? That's a funny thought. But it is possible. A garbage bag can become a hot air balloon. You will need to wait for a sunny day with no wind. Shake open a large, dark, plastic (塑料的) garbage bag in a cool, shady (有树荫的) place. Hold it open and move it through the air until it is filled with air. Tie it closed with a long piece of string (绳子).