Do Ghosts Consist of Matter? Ghosts Are Made of What Exactly?
For thousands of years, sightings of spirits have caused people to ask the question, “What are ghosts?” Knowing that interactive ghosts are the disembodied spirits of people and animals, the question remains, “What are ghosts made of?”
Ghosts must be made up of energy; that we do know. Spirits have sometimes been reported by some as glowing, emitting their own light source. This has caused some to wonder if ghosts could be comprised of the basic unit of light, called photons. Photons, however, do not carry an electrical charge but are known to emit different energy forms (infrared light, gamma rays, etc). Many forms of electromagnetic waves, such as gamma and radio waves, can pass through solid objects 
where visible light struggles to do so due to wavelength and frequency. Different wavelengths of photons are actually what allows us to see matter in the visible spectrum. The waves bounce off of atoms, visible light interacting with many solid things.
Since atoms make up the physical world, ghosts, which are capable of passing through solid objects such as walls, must be made of something smaller than atoms. Neutrinos, also called “ghost particles,” are indeed smaller than atoms and are known by scientists to be able to pass through objects. Initially, one might think that ghosts might be fashioned out of neutrinos. The problem with ghosts being neutrinos is that neutrinos, like photons, do not carry any electrical charge. If neutrinos carried an electrical charge, atoms would repel them.
Because atoms are surrounded by electrons, solid items (matter, comprised of atoms) bounce off of one another. If ghosts can be detected by EMF meters and are capable of disrupting electronic devices, then it would make sense that they possibly carry an electrical charge. This is what troubles both scientists and ghost investigators. What, then, are ghosts?
It has also been theorized that ghosts could be made up of plasma. Plasma is the fourth state of matter beyond a solid, liquid or gas. It is comprised of charged particles called ions and electrons. Plasma is a collection of atoms which have absorbed so much energy that the electrons have separated from their nuclei. It is an ionized gas, highly energized, and the most common state of matter in the universe. Neon lights are an example of plasma that is created by energizing gas, within a sealed glass tube, until it glows. What is encouraging about ghosts possibly being a form of plasma is that there are many types of plasma which exhibit different characteristics. In other words, there is a chance that ghosts could be a yet to be understood form of plasma.
One could make a strong argument for ghosts being comprised of plasma bodies, because like ghosts, plasma generates electromagnetic fields. It even conducts electricity and radiates electromagnetic waves. We know that plasma can emit light, as the sun and stars are plasma bodies that do so. The shape of the sun as a glowing orb might reveal the natural shape of plasma. Interestingly, some orbs that are thought to be of ghosts and spirits, are also round and emit their own light source.
Several years ago, Joshua P. Warren of LEMUR discovered that ghost lights (glowing balls of light) seen on Brown Mountain were actually luminous plasma orbs created by electrical discharges created during rainstorms. The LEMUR team was able to prove this in a lab environment. Their finding demonstrates that plasma balls of light can manifest in the natural environment, appearing and disappearing just like ghosts.
If a plasma were of a lower density, it could be capable of slipping through walls. In example, scientists are aware of dark matter, also called “collision-less plasma,” that is an invisible, physical substance that has the ability to pass through other matter like itself. Could ghosts be made of something similar?
What about ghosts becoming visible, then disappearing? It's been noted that magnetic plasma can become translucent or transparent, depending upon its frequency. The lower the frequency, the more translucent and visible the plasma will become to the human eye. In similarity, the opacity of a see-through specter would fluctuate just like eye-witness reports, the ghost being able to appear and vanish right before one's eyes. Even more intriguing, perhaps the frame of mind of a disembodied spirit could change the frequency of the plasma body, making the apparition appear from dark to light!
As of this writing, no one knows what ghosts are made of. Theories abound. It is possible that ghosts are made up of undiscovered particles - a yet to be discovered energy. We'll have to wait and see...