Topic: Rotational Anomaly

[gerhed]

Proceeding forward as the tire rotates backwards--please explain

http://www.youtube.com/embed/zc01wBJsc6k?hd=1

[Duke McDukiedook]

Optical illusion, probably having to do with the limitations on the frame rate the eyes and brain can perceive. I am sure the camera and playback device both play roles in this phenomena.

[Duke McDukiedook]

http://en.wikipedia.org/wiki/Wagon-wheel_effect

Looks like I was kinda right.

[Dusthawk]

Ever looked at a wheel on a car driving next to you and it looks like it's going backwards or turning at a slower speed that it's actually going? A very common phenomenon. Pretty cool to watch sometimes, but careful it doesn't hypnotize you, it's happened.

[333]

How about this explanation;  Ever have a phonograph turntable that had the dots around the perimeter used for getting the RPMs just right?  2 or 3 rows of dots for each speed the turntable was capable of, you would adjust a knob until the dots stayed still.  I seem to remember the phrase "stroboscopic".

[seanbarney41]

works just like a timing light

[333]

Well, not exactly.  A timing light uses a strobe because it can fire at an exact time to show the position of the mark on a timing wheel.  The turntable thing uses a constant light source against a row of dots so when the dots seem to stand still,. the speed is correct.  But it is the same effect.  This link explains it better. 

http://en.wikipedia.org/wiki/Stroboscopic_effect