Are These Two Objects the Same Size or What?

On Twitter, BBC Academy trainer Marc Blank-Settle attracted more than 3,000 retweets for pointing out something strange about the pieces to a wooden train set: Apart, one track appeared larger than the other, but placed atop each other, it was clear they were actually the same size. Settle summed it up for thousands of others: “What is going on here?!”

In the video above, Slate demonstrates what’s known as the Jastrow illusion, a tricky brain teaser that may arise from how two objects’ angles are compared. (No, it isn’t the camera angle.) The objects are in fact the same size, it’s just hard for our brains to see them that way.