WHAT IT IS Keeping your feet as well as your head above water
WHY YOU WON’T DO IT It is an occupation best practised by deities
Ever since the the gospel tales of Jesus Christ miraculously walking on water, it has been a metaphor for virtually any apparently impossible act. Though the internet is awash with clips of humans seemingly defying the laws of physics to traverse lakes and rivers, none has so far proved anything more than a hoax. But with a little bit of science, you too could at least appear to achieve the impossible…
The idea of being able to walk on water has long fascinated humans, with the concept appearing in a number of classical and religious texts. Even Leonardo da Vinci sketched out an idea for a system of floats that could be worn on the feet to allow travel across the water’s surface. Sadly, though, the brutal facts of biology mediate against us ever accomplishing such a thing without artificial aid – we simply weigh too much, and all our mass pushes down through our relatively small feet, resulting in a lot of pressure that ensures we get that sinking feeling.
Nevertheless, there are several animal species that can walk on water. One of the most interesting is the common basilisk Basilicus basilicus, a lizard hailing from Central and South America that is somewhat irreverently nicknamed the Jesus lizard. It can run across water for distance of several metres, avoiding the wet stuff by rapidly slapping its feet on the water’s surface, to provide lift and create air cavities which they have moved on from before they can close up.
The lizard will take as many as 20 steps per second to keep up momentum. For humans to replicate this, we’d need giant feet that we could bring up to our ears in order to create sufficient ‘slap’.
But fortunately there is an alternative: cornflour. By adding sufficient amounts of this common thickening agent to water (and it does take a lot), you can create a ‘non-Newtonian’ liquid that doesn’t behave like normal water. Now, if the surface of the water is hit hard enough, particles in the water group together momentarily to make the surface hard. Move quickly enough and put enough force into each step, and you really can walk across the surface of a sufficiently dense cornflour solution. If you have a sweet tooth, then you could achieve a similar effect using custard.
Fun though all this may sound, it’s still rather messy and better read about in theory than demonstrated in practice. If you must do it, then keep the water wings handy in case you start to sink – and have a shower afterwards!