So I'm sitting in my home office at night, slogging away at my blog (hmm... "blogslogging"? I may have coined a new word here). Even though it is fully dark outside, the window shade is up because earlier I wanted to let in the dying sunlight and cool twilight air, and I simply hadn't gotten up to close it yet. My wife is in the living room reading, and the Little Astronomer is asleep, so I have a sense of being alone. Then, out of the corner of my eye, I see something move outside.
I hate that feeling. The cold wave that goes through me, the feeling of being, well, almost naked, defenseless. I move just my eyes to the window, and see the fence, the neighbor's house (too damn close, I hate California sometimes), the front left corner of my recycling bin, the top of a snapdragon growing in a pot along the fence. I also see the reflection of my office in the darkened window, a Universe where in-and-out is reversed. But in both realities everything is static. There is no motion, no hint of anything having changed position.
I turn my eyes again to my lovely prose, and just as I start to type, I see motion again. This time I move my head, and this time, as before, there's nothing there.
As a kid, my brain went through many years of training as a creduloid, someone who believes just about anything, simply because someone told me so. UFOs, astral projection, the Bermuda Triangle-- at some point, I believed in it. Over time I figured out how to ask for evidence, how to evaluate it, and how to form an opinion based on that evaluation. I've had a long time to make that procedure second nature.
So my skeptical brain kicks into gear easily and smoothly. Nothing's moving out there, my brain reasons. So either something moved in here (unlikely; there is nothing in here that can move), or it's an illusion (likely; I've been fooled before). OK, assume it's an illusion. Can I test it? I need to try to repeat it.
I position myself just as I was when I saw the apparition, and start typing. Suddenly, I see it again! A motion, out of the corner of my right eye. This time, though, I don't move. I sit very still, and then slowly start moving my head, left to right, up and down, just a little bit.
Sure enough, after a few seconds, I know exactly what has happened. The ceiling light above and behind me reflects in my glasses. The light bounces off my glasses and illuminates my right eye. My eye reflects in my glasses and then back into my own right eye. In other words, the motion I see is the motion of my own eye, as seen by my own eye. My glasses act as a mirror, but not a very good one, so the outlines of my pupil and iris are not terribly distinct. And the geometry of the situation is pretty finicky; if I move my eye even a little bit the reflection disappears.
That's why I see nothing when I turn my head, and even when I just move my eyes. If the angles aren't just so, the reflection doesn't manifest itself.
I laugh. My immediate thought, skeptic that I am, is to wonder if this accounts for some sightings of ghosts. I know for a cold, hard, fact that most people are not trained to think critically. Polls show a lot of people believe in ghosts. And a lot of people wear glasses. What is the size of the population who live in the intersection of those three characteristics?
I'd love to see statistics. Have any ghost researchers done that study? It's easy enough: take the number of people who have seen ghosts, and get the ratio of those who wear glasses to those who don't. If that ratio is significantly higher than for the rest of the population, then I think we can explain quite a few "ghost sightings".
But having seen the quality of a lot of ghost hunters on TV, in magazines, and from reading about paranormal/psychic fairs, I can just guess they probably have little or no interest in finding out that ratio. Boo hoo.