Like any magic trick, this optical illusion requires careful planning and a particular perspective. A hand places a metal ball at the bottom of a 3D printed slide and the ball immediately rolls uphill. Did a YouTuber figure out how to defy gravity? Is the video playing backwards? There’s a perfectly reasonable explanation of course, but it still breaks your brain a bit to watch. What’s your guess on how it’s done? Watch the video below for the answer.
If you guessed that the slide is not as three dimensional as it seems, you’re right. When the camera is in the perfect spot, it looks like a normal miniature version of a children’s playground slide. But as soon as the camera shifts, you can see that it’s not. The slide itself instead runs the opposite direction and is only slightly sloped. And it doesn’t even connect to the stairs supposedly leading up to it. If the ball were to be placed at the top of the stairs, it would fall straight down.
Some optical illusions are just static pictures that appear to move or pulse. But 3-D printing add another dimension to the mind-bending puzzles. The StruckDuck YouTube Channel shows off other optical illusions and how to design them.
Now that we’ve covered how this illusion works, let’s ask the fun question. Can animals see optical illusions? According to the internet, it seems that otters can see that a rug looks like a bottomless pit. And maybe cats see the illusion too, but the results were less conclusive. We’re not mad at the unscientific approach, it just means more otter and cat videos to watch. And that’s always a good thing.
Melissa is Nerdist’s science & technology staff writer. She also moderates “science of” panels at conventions and co-hosts Star Warsologies, a podcast about science and Star Wars. Follow her on Twitter @melissatruth.