You've just hit a great putt or a great chip. The ball rolls all the way up to the hole, gets to the lip and looks like it's about to go in the hole. Instead, the golf ball hangs over the lip and it stops. Agonizing.
The good news is that, under the Rules of Golf, you have some time to wait to see if the wind, rain, an act of God or some other invisible force will push your ball in the hole.
Under Rule 16-2 of the Rules of Golf, a player can hit their shot, wait for the ball to stop, and then the clock starts ticking.
When any part of the ball overhangs the lip of the hole, the player is allowed enough time to reach the hole without unreasonable delay and an additional 10 seconds to determine whether the ball is at rest. If by then the ball has not fallen into the hole, it is deemed to be at rest. If the ball subsequently falls into the hole, the player is deemed to have holed out with his last stroke, and must add a penalty stroke to his score for the hole; otherwise, there is no penalty under this Rule.
What constitutes "unreasonable delay" is uncertain, but basically it's not lollygagging.
So, the next time your jaw has dropped because that ball didn't go in the hole, you might just want to wait 10 or so seconds.