"I'll believe it if I see it with my own eyes."
How many times have you heard someone say that? The implication, of course, is that if you see it (or hear it), that you can't get fooled. What your senses tell you, and how your brain interprets those inputs, are pretty reliable.
Enter Kokichi Sugihara of the Meiji Institute for Advanced Study of Mathematical Sciences, who is the master of creating illusions that do things your eyes and brain say are impossible -- and all with no trickery, no CGI, using only cardboard, glue, and other ordinary items. Take a look at this video, in which marbles seem to roll uphill -- until he turns his little structure around and shows you that it's a trick of perspective. (For those of you who usually aren't inclined to check out links in posts, this one and the others in this post are a must-see.)
The thing that makes me watch that clip over and over is how absolutely convincing it is, even when you know what's going on. Something is happening in your brain when you see his little cardboard channels and platforms from one angle that makes it impossible to interpret it any other way than that the marbles are defying gravity. "Stop it," I tell myself. "First, you know that the Law of Gravity is strictly enforced in most jurisdictions, and second, you know how he did this!" But my brain stubbornly refused to cooperate, preferring instead its impossible explanation of anti-gravity.
For more of Sugihara's fantastic structures, go here and here -- I find the second of these so brain-bending that it almost makes me a little seasick.
All of this vividly illustrates a point I've made before; our sensory organs and brain are easily fooled. Just as in my earlier post regarding visual/auditory conflict and the McGurk effect, there are times when our brains can't handle the sensory input they're being given, and amazingly, the brain's response is to admit defeat immediately and say, "Okay, then, I guess the world doesn't work the way I thought it did." Given how easily the brain can be tricked into giving up something it's always been sure of -- gravitation, or in the case of the last video, the properties of structures lying in a plane -- is it any wonder that skeptical people disbelieve eyewitness testimony of the paranormal?
"It was a UFO!" someone says. "I saw it!" Or, "I saw the ghost come into the room and float across the floor and finally disappear through the wall." Well, as Sugihara shows, I might believe that you saw something. But whether your brain was correctly interpreting what your eyes detected is another matter entirely. So don't get grumpy with me if I ask for hard evidence of your UFO or ghost. It's just too simple to trick the human brain -- and scientific measuring devices are a heck of a lot less easy to fool.