by Matthew Cobb
One shows the simple beauty of mathematics, the other shows you can’t believe your eyes.
https://twitter.com/SciencePorn/status/663430553883029504
A mind-bending illusion: Which way are these rings rotating? https://t.co/SLtsaF4TjB pic.twitter.com/Utxn6Xvdx2
— Slate (@Slate) November 1, 2015
Stop da rings – plz!
Love the first one.
And sub
I am all like, ‘can I believe anything I see’? And I am about to go teach a class. This should be interesting…
Interesting. For the record, for me a ring spins CCW when I focus on it, CW when I don’t (and yep, they both spin CW if I focus on a letter or mark just left or right of the video).
Does anyone get the opposite? I.e. CW when you focus and CCW when you don’t?
I noticed the same.
I get the same thing. I get them spinning in opposite directions. When I switch focus from one ring to the other the direction of the spin switches.
CCW is the ‘actual’ direction of rotation. Of course, like any movie, it’s really just a series of still images, but the incremental change from one frame to the next shows the rings spinning CCW*. The illusion is the shading on the dots, so that when you’re not focused on a ring, other cues make you interpret the rings as rotating CW.
*Especially considering this is an animation, not recorded video, where you can get strobe effects when the frequency of rotation is similar to the frequency of recording (or some multiple of it), which can cause the object to look like it’s standing still or rotating backwards.
For me they go widdershins and deasil
1st reminds me of spirograph set I had as a kid. 2nd how suseptible I am to optical illusions.
I just came across a spirograph for the first time in years the other day at a hobby store. I’m not sure how many kids still play with them. Hell, for that matter, I’m not sure how many kids every played with them. I had a set passed down to me from my older brothers, and I never had the patience to spend more than about 5 minutes with it.
If you move your head forward and back you can find the Blind Spot and have the opposite center dot disappear.
That is very cool!
Mental. I’m going cross-eyed.
And the first one just sharpens that pang of regret that I only began to appreciate the beauty of science, and maths/physics in particular, once I was in my mid-twenties. It’s so elegant.
That first one reminded me of locomotive valve gear. Back in the pre-electronic days, before everything was controlled by computer-designed cams and stepper motors, there were many surprisingly sophisticated geometric linkages designed to achieve the desired output motion, often using a subset of the geometry shown in the GIF. Locomotive gears were just the most visible manifestation of that beautiful mechanical engineering.
cr
I think I see what they’re doing there. You’re getting contradictory information depending on whether you’re following the circles or the stripes within each circle. When you focus, you see the circles, and when you don’t, you see the stripes.
In the second one – the dots are rotating anticlockwise (both circles). The background stripes are rotating clockwise.
When looking at a circle, the motion of the dots predominates. When not looking directly (i.e. when looking at the ‘other’ circle), the high-contrast stripes predominate.
This probably has something to do with the areas of the eye, the centre is more attuned to detail and position, the peripheral vision is more attuned to detecting motion.
That’s my initial impression anyway.
cr