I have been thinking about the plane propellers. Until recently the only way to fly 
out of here was on a propeller driven plane so I had frequently noticed the WWI during 
the start of engines. Clearly, the source of the vibration there would be the engines 
themselves. (Some of those planes vibrate so badly on the ground that it seems they 
should fall apart.) 

That observation has me wondering if there is a relationship between the rate of 
vibration, rotation speed of the "spokes" that produces the illusion. (The electric 
toothbrush might be well synchronized with the refresh rate on the computer monitor. 
At home I have an electric toothbrush and two monitors that might have different 
refresh rates. hmmm) It seems like there should be some measurable relationship here 
that should be easy enough to quantify. We start with the Purves' methodology, add a 
variable speed vibration source, and take some measurements. 

This thread has provided an excellent source of procrastination!

Dennis

-----Original Message-----
From: Stephen Black [mailto:[EMAIL PROTECTED]
Sent: Tuesday, April 20, 2004 1:58 PM
To: Teaching in the Psychological Sciences
Subject: Re: Wagon-wheel illusion again


On 20 Apr 2004, Ken Steele wrote, referring to Purves:
> 
> The original demonstration was actually done inside with 34-W sealed
> beam headlights.

Yes, but in his introduction he said that he became interested in the 
topic after observing "automobile wheel covers, airplane propellers, 
jet engine fans..rotating in daylight". He also said "It should be 
noted that all the effects we describe were equally evident in 
sunlight".

So where were his good vibes coming from?

Stephen

___________________________________________________
Stephen L. Black, Ph.D.            tel:  (819) 822-9600 ext 2470
Department of Psychology         fax:  (819) 822-9661
Bishop's  University           e-mail: [EMAIL PROTECTED]
Lennoxville, QC  J1M 1Z7
Canada

Dept web page at http://www.ubishops.ca/ccc/div/soc/psy
TIPS discussion list for psychology teachers at
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