A dad in the U.K. is stumping people online after posting a video of his son's toy train tracks apparently changing sizes.
Marc Blank-Settle, a trainer with BBC Academy, posted a video of himself playing with his son's toy train tracks. He said he was playing when he noticed something trippy.
When Blank-Settle stacked the tracks on top of each other, the tracks appeared to be the same size.
But when he lined them up next to each other, one of the tracks seemed much longer than the other.
Needless to say, people were sufficiently freaked out.
And some people had some out-of-this-world explanations.
"I don't like things that I can't explain....bloody trickery!" one woman wrote.
But it turns out that the freaky illusion has an easy explanation. As some people pointed out, the phenomenon is called the "Jastrow illusion."
In the illusion, both of the objects are actually the same size, according to the New World Encyclopedia.
"The fact that the shorter side of one figure is next to the longer side of the other somehow tricks the brain into perceiving one shape as longer and the other as shorter, although it is unclear exactly why this is so," according to the encyclopedia.