There are three basic elements of matter in the known universe: protons, neutrons and electrons. Protons have a positive charge, electrons have a negative charge, and neutrons have no charge.

It has been determined that, on a sub-molecular level, ectoplasm is made up of almost entirely neutrons and electrons. Thus, the key to catching a ghost lies in the third element: protons.

Protons and electrons naturally attract each other.

In addition, ectoplasmic molecules are spaced far apart, much farther than the molecules of normal matter. This is how a ghost can pass through a solid object. Think of a strainer passing through sand.

Every time a ghost passes through a solid object, some of the ectoplasmic molecules chance to strike the molecules of whatever it passes through. These molecules become more tightly knit and form a thick goolike substance. This substance is called ectoplasmic residue, or as we call it, slime. Keep in mind that there is a difference between ectoplasm in its natural form and the slime residue.

With this knowledge I knew that trapping a ghost with physical means would prove impossible. However, since protons and electrons attract one another, I deduced that if we could somehow use protons as a "lasso", it would actually be possible to catch a ghost. Deducing this was the easy part. The hard part was designing the equipment to do the job.