Dissecting the Demon

Observing the cross-section of higher dimensional objects is the most important and direct way to recognize any higher dimensional object. This method is easy to understand when we consider a flat-lander looking at a 3D object.

The flat-lander can see only the plane on which he is situated. That's his universe. So if a 3D object passes through his universe, then he will be able to see only the part that is passing through his universe. He can see only the cross-section of the 3D object. Take an example of a sphere passing through his universe ( plane ) as shown in the figure. As the sphere passes through the plane, the flat-lander sees a series of circles changing shapes automatically. He will see a circle appear out of nowhere and grow bigger and bigger. Then it starts growing smaller and eventually disappears from his universe.

Passage of a sphere though a plane.

Similarly if we ( 3D humans ) pass through the universe of a flat-lander, then the flat-lander will see 2 black circles of cloth appear in his universe ( our pants ) which will join together ( our hip ) and then change color ( from pant to shirt ) and then change to smaller circle of flesh ( our neck and face ) and will disappear in a black mess ( our hair ). So by observing how these circles change for different humans the flat-lander can tell us apart.

Similarly we can see and interpret the 4D objects by looking at their 3D cross-sections. So when a 4D sphere passes through our universe we first see a small sphere appear out of nowhere and then grow bigger and the become smaller and disappear from our universe. Similarly the cross-section of other objects can be studied and using this information we can tell apart the hyper objects. This is a direct method of recognizing higher dimensional objects.