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