The Sport Information Resource Centre
The Sport Information Resource Centre

Safe or out? Because the speed of sound is slower than the speed of light, baseball fans in the stands can mistakenly think a player is safe because they hear the sound of the ball hitting the mitt of the first baseman after the batter crosses the base (similar to the delay between lighting and thunder). Umpires, who are much closer to the action, can more accurately assess whether a player is safe or out compared to a fan in the stands 100 or 200 feet away.