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The Jastrow Illusion popped up on Twitter last week, and so Yosup Joo and I replicated it in class with some track that he brought from home. The students’ reactions were pretty funny. Kids were shouting, “It’s sorcery,” “It’s witchcraft,” and “What’s happening to my brain?”
I showed the illusion first, from the front of the class, but students were blaming me for the effect. “You’re holding them at an angle.” “One of them is closer to us.” So then I passed the track around and students replicated the above placement on their desks… and went even more wild.
Then by drawing several curved pieces on the chalkboard, I was able to explain how and why the illusion works.
A good time was had by all… and they probably even learned something!