Units of speed are always a unit of length per unit of time. Different units of length and time may be chosen depending on the situation. This makes it easier to read the measurements. For example, ...

Cepheid variable stars exhibit regular pulsations whose period directly correlates with their intrinsic brightness (absolute luminosity). The Leavitt law establishes this relationship between ...

Learn how to calculate when and where two trains will meet! This video walks you through the process of using relative speed and distance to find the exact point and time of intersection. Perfect for ...