While students often see the summer as a time to leave the classroom behind and head for the beach, lake, or pool with their friends, I always like to remind them of all the scientific principles they’re unknowingly learning about while cooling off. Whether its simple ideas like the “every action has an equal and opposite reaction” that propels them forward as they push water back, or more complicated concepts like buoyancy that keep us afloat, what they learn in class can inform their understanding of the active world around them.
Now, as the New York Times Science Section recently reported, a group of scientists at the University of Amsterdam have turned this flow of information on its head. Taking inspiration from large sand castles, Physicist Daniel Bonn and his colleagues have discovered the ideal ratio of water to sand in order to make strong structures. Surprisingly, it’s much lower than the usual gloppy stuff we concoct on the beach to fuel our visions of castles, forts, and dream houses, with the best mix found to be about 99 parts sand to 1 part water. In this mixture, the water acts like a weak but sufficient glue holding individual sand grains together from intermolecular forces (an example of these forces is surface tension). Any less water, and there is not enough glue, the sand grains simply slide past each other. Any more, and the mixture gets a soupy consistency which flows easily, the sand effectively drowned.
It’s projects like these that make me love tutoring physics. A simple observation and some lazy summer pondering led a curious scientist to yearn to understand something so present in our everyday lives, yet complex in its workings. And from these investigations we come out with both a new conceptual understanding of the physics at play, and a practical knowledge to do something we actually enjoy and care about. This is the serendipity from which physicists, engineers, biologists, or simply curious and engaged youth are formed. Teachers always hope their students stay engaged over these long summer months, and teaching them how to approach the world in this inquisitive way is the best way to ensure they do.
By Erik Lessac-Chenen, Private Tutor