A shadow is formed when an object blocks the photons that are traveling from a light source. Light travels fast, but not instantaneously. We see because light from a source is reflected from an object to our eyes. Light can be reflected by a mirror, refracted by a lens, or absorbed by the object. Good explanations are based on evidence from investigations.
Energy is transferred in many ways.
Changes might occur, for example, in properties of materials, position of objects, motion, and form and function of systems. Interactions within and among systems result in change. Models help scientists and engineers understand how things work. Models take many forms, including physical objects, plans, mental constructs, mathematical equations, and computer simulations. One way to describe something is to say how it is like something else.