Light sometimes appears to be "dragged" by the motion of the medium through which it is traveling. This phenomenon, referred to as "light dragging," is typically imperceptible when light is traveling ...

In a “normal” electrocardiogram (ECG), the transition of the QRS axis in the precordial leads occurs between leads V 3 and V 4 (i.e., there is a dominant S in V 3 and a dominant R in V 4).