Things you will need.
1.First you will need a ping pong ball and also a hair dryer that works.
I think this will work because the air pushes it up forcing it to stay up.
You can put two ball at the same time it will stay up but not for long.
If you put a ping pong ball on a hair dryer it will just float because the gravity pulls it down but the air pushes it up float. Air can beat gravity there is the answers.