Bernoulli, an 18th century Swiss mathematician, discovered something quite unusual about moving air. He found that the faster air flows over the surface of something, the less the air pushes on that surface. That means that the air pressure on the object is lower than average.
The air from the straw, as you blow through it, produces the levitating ball phenomenon using Bernoulli’s Principle. The fast air moving that you are blowing around the sides of the ball is at a lower pressure than the surrounding, stationary air. If you look closely, you’ll see that the ball wobbles while it is levitating in midair. The ball is attempting to leave the area of low pressure, but the higher air pressure surrounding it forces it back into the low pressure area.