After the blue and black (or white and gold) dress split the Internet last year, netizens are scratching their heads again at the latest optical illusion. This time, it's a set of toy train tracks.
BBC Academy trainer Marc Settle posted a clip of his son's toy train tracks on Twitter on Thursday (April 7).
He wrote: "My toddler's train track is freaking me out right now. What is going on here?!"
The post has since been liked more than 2,000 times and retweeted over 1,900 times.
Mr Settle demonstrated in the clip that when placed side by side on the same plane, one track appeared to be longer than the other. But when one was stacked directly on top of the other, they were actually the same size.
Many were confused:
But other Twitter users were quick to suggest explanations for the illusion:https://twitter.com/iMagicTony/status/718145265354600448
Some remembered learning about the mechanics behind the optical trick as children:https://twitter.com/smile_of_decade/status/718200380547538945
The explanation behind the trick is called the Jastrow Illusion, as defined by the American Psychologist Joseph Jastrow in 1882.
When two identical shapes with four sides of different lengths are arranged together, one will appear larger than the other due to how the brain perceives perspectives.
As the longer arc of one track is brought into contrast with the shorter arc of the other, it appears that the one track is longer than the other.
This classic geometric illusion might not have made as big an impact on the Internet as the blue and black dress did, but Mr Settle was still pleasantly surprised to wake up to more than 1,000 retweets.