The basilisk lizard, often nicknamed the “Jesus lizard,” is renowned for its remarkable ability to sprint across the surface of water. When threatened, it can switch from running on land to dashing over water, despite weighing about four ounces far too heavy for surface tension alone to hold it up.
In the 1990s, Harvard scientists Tom McMahon and Jim Glasheen investigated how this was possible. By studying video footage, they developed a mathematical model showing that each step of the basilisk’s water run involves three phases: the slap, the stroke, and the recovery. During the slap phase, the lizard’s foot strikes the water much like a sprinter’s foot hits the ground, creating an upward force. The faster and larger the slap, the more lift is produced. In the stroke phase, the foot moves backward quickly, forming an air cavity that helps lift the foot out of the water. The final phase, recovery, involves lifting the foot out in preparation for the next stride.
But could a human do the same? According to McMahon and Glasheen’s calculations, a person weighing 175 pounds with an average foot size and elite sprinting speed would need to move at roughly 98 feet per second to stay above water. That would demand energy output far beyond human capacity about 15 times more than what we can sustain. So, running on water on Earth remains impossible for humans.
However, researchers from the University of Milan explored the idea under altered physical conditions. In a 2012 experiment, volunteers were equipped with a harness system that mimicked lower gravity and wore large fins to increase foot surface area. Attempting to “run” in an inflatable pool, they could stay partially above the surface for several seconds when gravity was reduced to 10% of Earth’s.
This finding led scientists to speculate: could water running be feasible under extraterrestrial conditions? Physics World noted that Titan, Saturn’s largest moon, has gravity at about 13.8% of Earth’s and surface lakes similar to ours. Under such conditions, even world champion sprinter Sha’Carri Richardson could potentially dash across the water. She’d need to hit the water at roughly 28 feet per second within the speed range of her racing performance and generate enough upward force to stay aloft.
So, while water running isn’t realistic here on Earth, in the right corner of the solar system, it might just be possible.
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