👉 The term "ninety-knot" is a phrase used in physics to denote the speed of sound. In simple terms, it means that the speed at which sound travels through air changes by 90 degrees when you change your direction of travel from one point to another. This concept is particularly relevant in aviation and navigation, where the speed of sound (or, more accurately, its velocity) plays a crucial role in determining the path of an aircraft or ship. The faster the speed at which