As I was putting on my coat yesterday afternoon to head out to my 3:00 PM class, I noticed what appeared to be a smudge or scuff on the wall near my office window. Slightly upsetting. Not only was it unsightly, but I couldn’t imagine what might have caused it. Sort of like walking out to your car after work and finding a big scrape or dent that hadn’t been there when you left it.

But wait. The wall was bathed in bright, direct sunlight. Could that smudge just be a shadow? To test that theory, I held my hand out to block the sunlight—and the smudge/scuff disappeared. Whew!

Pulling my hand away, I noticed a faint, white afterimage of my fingers trailing their shadow. Cool! But immediately I began to doubt what I’d seen. Had I imagined it? I held my hand up a second time and pulled it away. Again, the afterimage.

Then I began to wonder: Was that afterimage visible only to the naked eye? Or, could someone also view it in a video, even if mediated by a screen.

Well, only one way to find out. I pulled out my phone and shot a quick video of my hand’s shadow on the wall. And YES! When I looked at the video, I could still see that afterimage trailing the shadow as my hand withdrew.

(This is all basically happening as I’m buttoning my coat to leave for class, don’t forget. Multitasking 🙂 )

Much later, when got home from work last night and was showing the video to my husband, I had to laugh at the sound of myself murmuring the word “cool” in rather awed tones. I hadn’t intended saying it—wasn’t even aware, in fact, that I had. But clearly, my inner voice has a mind of its own, as evinced by that little whisper of a thought slipping into the air without asking permission 🙂

Some things never get old—like popping bubble wrap, snapping retractable tape measures closed with a “thunk,” and (if you’re from Wisconsin) eating cheese curds so fresh they literally squeak against your teeth. Playing with optical illusions surely deserves a place among this pantheon of small pleasures.

You have no doubt seen afterimages before. (Link to Wikipedia article on “afterimages” HERE.) You’ve probably also played the little optical illusion games like looking at the green, black, and yellow United States flag for several seconds and then transferring your gaze to a blank white wall and seeing the flag in its correct colors. Or viewing a “negative” image of a photo and then, similarly, looking at a white wall to see the correct photographic image.

But have you seen the optical illusion created by pairing the afterimage of swirling spirals with Vincent Van Gogh’s Starry Night ? Click on the video below to give it a try.

It’s really (whispers) C O O O o o ʟ  🙂