Bicycles are easier to stabilize when in motion due to the gyroscopic effects of the wheels and the dynamic balance achieved through steering. When stationary, the lack of forward momentum eliminates these stabilizing forces, making it difficult to maintain balance. The discussion references a comprehensive book, "Bicycling Science," and links to research papers that delve into the mechanics of bicycle stability. Previous threads have explored this topic extensively, highlighting the physics behind bicycle dynamics. Understanding these principles is crucial for improving balance techniques in cycling.