Topic: Poll: For Fun - Spinning Anemometer Optical Illusion

[galfert]

This is a fun neat trick.

My WS-2902A is temporarily mounted on a 10 foot pole that is only buried 1.5 feet in the ground. This makes it so that the device is only 8.5 feet up in the air. It is just about the right height to play tricks on your eyes. The anemometer sometimes appears to be spinning in the opposite direction.

This phenomenon is something that I learned at a much younger age. It was one of the first neat animated graphics that I did on my Apple IIe computer (it was something similar to the dancer, I think I was a horse running going backwards). To see and experience what I'm talking about you should check out this Wikipedia article.
https://en.m.wikipedia.org/wiki/Spinning_Dancer

Can you see the dancer spinning both ways? Sometimes you need to look away to make it change directions. If you look through your peripheral vision it can help to experience the change in direction.

Once I get my flag pole mounted and move my WS-2902A, I'll probably stop seeing this illusion. At the added height there won't be any confusion as to which way it is spinning. For now it is a neat thing to experience. I should probably take some video and see if I can experience it that way too. Then I'll have it for future reference since I'll be moving it soon.

[Cutty Sark Sailor]

First time my wife noticed this effect on the anemometer ... ... heh...  i almost wound up in the couch.

[nincehelser]

I haven't noticed it with an anemometer, but I've never really tried.

The rotations of the dancer seem to be due to my expectations.  If I expect it to go the other way, it does.