So, in the last post (see PHYSICS OF GHOSTS 101: PART SIX B: WHAT IS IT, AFTER ALL?  CATOPTRIC PARADOX  -  I.) I gave you my explanation to what I call Catoptric Paradox. 

It is a well-established fact that sometimes a ghost can appear in a mirror, while it cannot be observed directly.  Essentially, the observer has to look into a mirror with his back to the room and see ghost in a room, while direct look into the room reveals nothing in it.  From the standpoint of simple optics this effect appears utterly impossible: all light in the room, all objects ought to be reflected in the mirror and hence they ought to be seen just as well as directly.

If you are following all my posts, then you’ve probably seen my previous one, where I’ve decided to leave for a moment the subject of ghosts and to praise the great books of Harry Potter (see HARRY POTTER – FOREVER!).  Now I am back on the subject, which I would like to start with a quote from this marvelous book.  This is a dialogue between Harry Potter and Nearly Headless Nick, the ghost of House of Griffindor, and it is right on the subject:

I just finished my second time reading Harry Potter, all seven books in a row.  Just like the first time, it was … magic.  The images of the novel were invoked so vividly, so truly, that afterwards it feels as if I’ve been there and witnessed it all, either under a cover of the invisibility cloak or from a dive into Dumbledore’s Pensieve.  I only wish it all was real, I wish it lasted longer, but the last book is finished and closed, while I remain where I am – a poor Muggle, locked in Muggle’s Azkaban. 

We have discussed introduction, optics and acoustics of ghostly manifestations, smells and touch/punch. Here are a few subjects which I haven't touched yet about ghosts.

Sometimes ghosts interact with the living, but sometimes they appear unaware of present day observers. They may come in groups wearing old-fashioned outfits. They also can appear with antiquated technical means, like a man riding a penny-farthing bicycle.

Extreme case one: someone gets a witness of a large event (baseball match) in a place where the stadium used to be seventy years ago. The crowds of oddly dressed people are cheering from the bleachers; they do not pay any attention to the intruders from the future: who cares when it’s a perfect home run!?

We have discussed optic, acoustic and, to some extent olfactory manifestations of ghosts, but, as we all know, ghosts also can do things. They can touch you, they can flick a light switch in your room, they can cut you with a razor blade, they can toss a VCR into your head. There are numerous witnesses of such interactions, from a light breeze to a murder by a poltergeist. How can that be possible?We started with the notion that upon their manifestations ghosts absorb energy. I daresay that this absorption of energy can be substantial for a quite brutal demonstration of force, when air gets down more than just a few digits of centigrade and this might be just a side effect. Ghosts also are capable to absorb electrical energy

We have discussed optics and acoustics of ghostly manifestations (see Physics of ghosts 101: The introduction and Physics of ghosts 101: part I – Optics, part II and part III- Optics and acoustics), but what can I say about a ghost, which appears with smell of a rotten flesh? How did that one conjure molecules of ptomaine so the witness could actually smell it? I admit, I have no slightest ideal However, there are some possibilities.

PHYSICS OF GHOSTS 101: PART TWO - OPTICS  I was talking about colors of ghosts. I just went through the gallery of ghost photos in Janet Bord, The 100 Greatest Photographs of the Paranormal from The Fortean Picture Library, from the publishers of #Paranormal and I didn’t See any color picture where ghost would appear in its own color! They all look like semi-transparent monochromatic objects, while their colors are projected from the objects on background (leaves from the trees, church furniture, etc.). Yet, I do believe I’ve seen ghosts in color myself, at least twice. And there is a plenty of written witnesses of that kind. 

The previous post PHYSICS OF GHOSTS 101: PART ONE - OPTICS was concluded with the notion that in terms of optics ghosts likely act as gray (black) bodies, which explains their appearance / disappearance acts, depending on their thermal energy and major spectral characteristics lying likely in near IR area of a spectrum. The latter needs some extra comment.

I will start with a simple fact: the ghosts are gray bodies (in optical terms, not in the terms of appearance). This looks like a plausible explanation to many witnesses, but in that Sense ghosts are similar to us, living humans. 

Looking at ghosts (figuratively speaking) I Would say it is a hell of an undertaking to describe their physics. I, by no means, am going to do it in full, because nobody knows all the answers on that subject, yet it might be helpful to discuss some aspects of ghosts in more or less systematic matter. In this entry I would like to touch the Optics of ghosts.

First of all, let’s review how ghosts appear to us ( See Introduction). To say the least, their appearance is ghostly:

In a dim light ghosts often appear as shadows. And, in general, ghosts have a somewhat limited Visibility: people may not see them at all, but cameras do. And so do animals (dogs, cats). Ghosts also can be seen as 2D reflections in mirrors and in 3D in fog or Smoke. Finally, ghosts can appear to us and then disappear within one occurrence, sort of “dissolve' into thin air. What does this means from the standpoint of physics? 

Let's do a simple thing, a thing so simple that I wonder if anyone has done it before. I guess, it must have been done for sure, but I am not aware of it. But, anyway, ignorance is bliss, so let's list all key elements that are characteristic to ghosts and see if we can come up with a scientifically sound summary on their physics, derived from these characteristics.
1. Ghosts have a somewhat limited Visibility: people may not see them, but cameras do. And so do animals like dogs and cats. Ghosts also can be seen as 2D reflections in mirrors and in 3D in fog or smoke.