Science Questions

Burp-related Optical Illusions?

Sun, 1st Jun 2008

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Steve asked:

If youíre driving up a motorway and get a lorry next to you on the front wheel of the lorry the nuts are sticking out. As itís driving it looks like a ring because itís going so fast. If you really burp the nuts then stop whilst youíre burping. Once you stop they start revolving again.


This is a fantastic question!  You can achieve the same effect, not necessarily with an up thrust of wind, but also by crunching your cereal.  If you were to go along in a car and eat some cereal at the same time you would see the same effect.  Also, if youíve got an LED clock radio at home you can achieve the same optical illusion looking at the display - the numbers appear to jump or flicker on and off as you chew.

Whatís happening is youíre creating your own in-body stroboscopic effect.  The vibrations when youíre eating are being transmitted to your eyeballs and theyíre making your eyeballs move very slightly.  This rapid eyeball movement is capturing the movement just the right way of those nuts going round the wheel or the flickering of LED clock lights.  So this creates the appearance of jumping or freezing or switching off for a fraction of a second.  Itís literally your eyes moving together in unison as a result of crunching or burping or making a movement which jolts your eyeballs a little bit in your head.


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