Spinning dancer

AnalogKid

Joined Aug 1, 2013
12,254
Yes it definitely is worth the fuss. So much of what we see is only what we think we see. For example, you cannot see anything you are directly looking at: that's a well known hole in your retina. But your brain fills in that little detail for you.
Uh....nope. The Optic Disc is off-center. The area of the retina with what "your are directly looking at" has the greatest concentration of rods and the only concentration of cones. That's why peripheral vision is monochrome.

ak
 

MrChips

Joined Oct 2, 2009
35,091
She is not rotating at all. It is an optical illusion.
You can demonstrate the same illusion with Lissajous figures on your oscilloscope.
You are seeing a sequence of static images of different poses.
I can make the dancer rotate CW or CCW at will.

Edit: Cover the upper part of her body and just look at the tip the toe.
Pretend that the tip is a sine wave signal on an oscilloscope moving from left to right.
 

ErnieHorning

Joined Apr 17, 2014
65
Maybe my brain is just screwed up, I can easily make it spin both ways. In fact, knowing that it’s just a two dimensional drawing, I can make it just go back and forth too.
 

Georacer

Joined Nov 25, 2009
5,182
She is not rotating at all. It is an optical illusion.
You can demonstrate the same illusion with Lissajous figures on your oscilloscope.
You are seeing a sequence of static images of different poses.
I can make the dancer rotate CW or CCW at will.

Edit: Cover the upper part of her body and just look at the tip the toe.
Pretend that the tip is a sine wave signal on an oscilloscope moving from left to right.
I finally did it! The covering trick did it for me!

I also found out that it's much easier to impose a rotation direction to my brain, if I rotate my finger in my field of view as well.
 
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