By Mark Jones
The Royal Society’s motto, ‘Nullius in verba,’ translates literally to ‘no one’s words.’ It is taken to mean ‘take nobody’s word for it,” interpreted as verify all statements by experiment. The Society has published many impactful scientific advances over the course of its near 400-year history. It is some serious stuff. Newton’s theory of light and color, Watson and Crick’s structure of DNA, Hawking and Penrose’s work on black holes, and more were all published by the Royal Society. It was not a Society noted for frivolity. “Mastering the Manu — how humans create large splashes” is the rare Royal Society publication that brought a smile. While not likely to win a Nobel Prize, it is fun.
Making a splash what the sport of manu jumping is about. Olympic diving competitions focus on the splash too, with the goal being no splash. Manu is the opposite. The biggest splash wins. Olympic diving is subjective. Manu is far less subjective. MANUTECH determines the score using video to measure splash height. Jumps are captured and a freeze frame used to measure the height. Only in the finals is any subjective scoring added. Noise matters too. Sound is measured by an underwater microphone. The louder the better.
Manu jumping is a New Zealand sport, developed in Māori and Pasifika communities. It dates back only to the 1990s but now is a national pastime with international reach (thanks to the internet). It was posted videos that prompted the researchers to investigate.
Manu jumpers can thank the Worthington jet, the name for a phenomenon we’ve likely all seen but didn’t know it had a name. An object falling into a liquid carries with it a pocket of air. When the inflow of water as the pocket collapses creates a column of liquid that is propelled upward. That is the Worthington jet. It is much larger than the crown splash, the initial splash outward when the object first contacts the liquid. Thanks to the Worthington jet, jumpers from 5 meters can make splashes more than 10 meters high.
Researchers made robots that simulated the motions of manu jumpers. Their research determined that the motion of the jumpers in the air to position the body and movements under water both contribute to maximizing the splash. (In addition to the size and weight of the jumper.)
The researchers found that hitting the water butt-first in a V-position at an angle of about 45° was important. Even more important was the timing and execution of stretching out under water. Stretching out makes a larger air cavity. A larger air cavity makes a bigger Worthington jet. Stretching out too early releases the air cavity before it completely develops. Straightening out too late, and the cavity has already started to collapse, weakening the splash. Milliseconds matter.
Thanks to the research, there is now a blueprint for maximizing splash height. The trial and error of the early contests, with a variety of approaches, are now well behind us. There is now a correct way. It also shows that mastery of form and action are still required. I liken it to many other sports that have been put under the proverbial microscope, like golf. Knowing the right way to manu jump is no guarantee of success any more than knowing what a perfect golf swing looks like. Execution is still required.
I hope manu jumping spreads; only through wide adoption will it ever make it to the Olympics. Looking at the videos, it is a far more fun event than competitive diving.
Pool weather is gone here in Michigan. I’ll have to wait until next summer for my testing of the results.
Filed Under: Commentaries • insights • Technical thinking
