“Seth material” search engine (Jane Roberts)

The projected form does make some impression upon the physical system. It is possible for it to be detected. It is a kind of pseudo-image, materialistically speaking, but it has definite electromagnetic reality and chemical properties. Animals have sensed such apparitions. They react to the chemical properties and build up to the [perception of] the image from these.

These chemical properties are more diffused in such an apparition than in a physical form, however. The chemical composition of a storm, perhaps, will give you an idea of what I mean. … They cause small disturbances in the physical system. As a rule, they are not solid, in the same way that clouds are not solid, and yet they have shape and to a certain extent, boundaries and movement. They definitely have a reality, though you cannot usually perceive it with the physical senses.

Perhaps this diffused quality is the most important difference (from your point of view) between an apparition and a physical form. There is an atomic structure, but in some ways it is less complete than the physical one. There is always a minute difference in the body’s weight when the individual is projecting.