Every once in a while, I will discover something that absolutely blows my mind and I will obsess over that thing until I can seem to wrap my mind around it. This thing that I have recently found out about is not only still stumping me, it stumps everybody. Scientists are still unable to figure out exactly why this phenomenon exists. It is called "Benham's disk". It was discovered by a man in 1895 who made a toy disk that looks like this:
A plain black and white disk. But when spun, extremely fast it looks like this:
You can see some color inside the disk when it spins very fast. That's interesting in itself, but there's something far more interesting about this illusion. The color that you are seeing within the wheel is not the same color that everybody else sees when they look at it. I personally see a light brown color in the spinning wheel like this:
Some people see olive green, cyan or yellow, but everybody sees their own color in the wheel, and some people don't see any color (just black and white). Scientists have still not yet determined why this is, but they have guessed that it has to do with the fact that the human eye responds to red, green, and blue at different rates.
This illusion was first discovered by spinning an actual disk very fast, but it can now be viewed with a simple repeating sequence of 6 frames:
