Yo-yos have been around for centuries, and while hundreds of variations exist, they all have one thing in common: string. That is, until now. Gizmodo recently shared a YouTube video from the Veritasium that features professional yo-yoer Ben Conde, who has mastered a yo-yo that detaches from its string in midair. It might look like magic, but it's all basic science.
As the video explains, when Conde releases the yo-yo, the string unspools from the center as the rest of the toy falls, gaining both kinetic and rotational energy. The rotational speed of the yo-yo is around 6000 RPM (revolutions per minute), which gives it gyroscopic stability and keeps it moving fluidly.
With a normal yo-yo, the string is looped at the center so when it reaches the end, it can keep spinning (a trick called "sleeping"), or it can return to the thrower's finger. As Conde demonstrates, his yo-yo continues to spin off of the non-attached string unless it is pulled back in time. Friction pads cause the string to wrap around the center when Conde pulls on it, which then causes the spinning yo-yo to reverse its path. To perform some tricks, Conde allows the yo-yo to leave the string completely before whipping it back into place.
It might sound complicated, but with Conde's many hours of practice, it mostly just looks awesome.