Guest Writer Feature: Walking on Water by Charlotte Marmonier


Our guest writer for this article is MindMover intern Charlotte Marmonier, a Year 11 student from International School Manila. 


[Photo credit: Bence Mate, Nature Picture Library/Corbis]

       "Walking on water" is a phrase that has been extensively used by humans to exaggerate or enforce one's achievements, success, or great breakthroughs. Although it has been used metaphorically, physically it is an impossible task for people and most species on Earth to accomplish. Throughout the years, and as science has evolved along with species, certain beings have achieved what once used to be a great mystery, and studies of their locomotion have allowed us to understand how it is physically possible to walk on water.

       An example of this in an experiment (or an object acting in this way), would be a paperclip resting on water. Although paperclips are made of steel, a metal whose density is far greater than water, it is still able to sit on top of the liquid. Similarly, certain species are able to do so, by making use of the tension present in the surface of the water. 

[Photo credit: Colin Barschel, Photo.net]

        Before we dive into this subject, understanding the principles and properties of water is essential in order to observe how it is physically possible for some creatures to achieve this phenomena. In doing so, one must make sense of two concepts: surface tension and cohesion.

          Without going into extensive depth, this common yet intricate concept of surface tension is that it acts like a layer of skin on top of water. The reason for this skin is because the water molecules on the surface hold onto molecules that are like them, which can only be found on the surface as well. This concept is known as cohesion, and cohesive forces are present in between all nearby molecules in a liquid. 

          Since the surface molecules do not have neighbouring ones above, they have stronger bonds between the ones nearest them on the surface. As a result, this acts as a barrier, in which the water molecules are held together tightly and can thus resist outside forces, like the paperclip.

          In everyday life, there are two types of animal locomotion on water. The first follows the rules of surface tension that have been explained, where the species, like a paperclip, is able to rest on top of the water without having to exert any force. Examples of organisms that behave like this are water striders, fishing spiders, and mosquitoes. 

[Photo credit: Mats Halldin, Wikipedia.com]

           The second, which opposes the idea of surface tension, is that animals must exert large amounts of force so that they can glide or run across a body of water, and are unable to remain on top of water unless in motion. Examples of these animals are the basilisk lizard, western grebes, and even walking dolphins, such as those that we see performing in ocean parks.

[Photo credit: Greg Gillson, Pacific NW Birder blog]

      From studying how living beings move, we can find infinite demonstrations that can be done with this concept to help visualize the process in an interactive manner. Whether we have an ardor for the sciences, or detest the feelings they bring back from school projects, this is just one of the many topics science has involved itself in with our daily lives. 


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