They result from light’s inability to penetrate opaque objects, creating a region devoid ... was chosen for its ability to amplify, absorb, and modify light under intense conditions.

But some objects block light… Seymour: like this wooden spoon… or this bowl of cereal. Albert: We call these objects opaque. If light can’t go through an object, it creates a shadow!

Some objects are opaque such as stone, metal and wood. This means light doesn't travel through them. Light bounces back off the object. On the other side of the object a shadow is formed.