This riddle says: A boy throws a ball as hard as he can. It comes right back without hitting anything. How?
The answer is: he throws the ball straight up into the air.
The wording makes most people imagine the boy throwing the ball forward. If that were true, it would usually need to hit a wall or another object to come back.
But the riddle never says which direction he throws it. If he throws it straight upward, gravity eventually slows the ball, stops it for a moment, and pulls it back down toward him.
Nothing has to be hit for the ball to return.
The puzzle works by using an assumption we make automatically. Once you stop picturing a forward throw and consider every possible direction, the answer becomes simple.
