Every time you toss a ball, you experience gravity. It pulls the ball back down to the ground. Without gravity, the ball would float off into the atmosphere. Gravity is such a constant presence in our lives, we seldom marvel at the mystery of it. It’s considered a natural phenomenon, an observable event which is not manmade -- sunrise, weather, and earthquakes are similar occurrences. But now we’re learning that gravity is actually just all in your head.