This trick is about the reverse wheel motion, also called the rotating wheel illusion, which falls under the optical illusions. This illusion is making the mind perceive things that are not there. It's amazing how the psychology of the mind works. To see other examples check our Brain Tricks main page.
Tips for the reverse wheel motion: When this page has loaded, the neighboring demo is in “auto run” mode: the wheel rotation smoothly varies between standing still and a maximum speed of 120 rotations per minute (120 rpm, indicated at top right). The wheel rotation, however, looks quite different: it seems to slow down to standstill when the maximum speed of 120 rpm is indicated! It helps to know that the wheel is rendered with standard movie speed: 24 frames per second.
Notes: With the “thumbs” of the two vertical sliders you can set the speed, the right slider is for coarse adjustment. When you begin to adjust the speed yourself, “auto run” switches off. Now you can observe that increasing the rotation speed, starting from zero, indeed initially speeds up the wheel, but then it begins to slow down! Find the speed (≈120 rpm) where the spokes stand still (the left slider helps with fine adjustment) – but observe that the centre, and certain cute irregularities around the wheel still move. This tells you that the wheel still rotates, but because of the simulated slow movie speed of 24 frames per second the spokes seemingly stand still, and can even go backwards if you speed up! There are additional standstills at higher speeds, here you can check this around 240 rpm.
This is what you may have observed in movies (especially in Westerns with prominent spoked wagon wheels). It never occurs in direct observation under daylight (though there is a little discussion in that respect).
Trick of the Day: The moon when close to the horizon looks bigger than when it's in heart of the sky. That's because when it's close to the horizon, your eyes sees it in comparison to other parts of the horizon, such as trees, mountains and houses, and that's what makes it look bigger. For more tricks of the day check Tricks of the Day.
Other than the reverse wheel motion trick, the mind can be fooled in different ways within the subject of the optical illusions. It's no longer accurate to say "what you see is what you get". Now choose a related page, or simply click on previous/ next.