Have you ever been told not to play with your food? Perhaps been told that it isn't polite or disrespects the other people at the table?
I have a confession: sometimes I play with my food.
I can't help it! There are certain things I have learned throughout my life, in science classes or otherwise, that just stick with me - and I just can't help myself. Three of the worst offenders have been outlined below.
Yogurt Tension Gashes
Context: As a structural geologist I have spent a fair amount of time staring at deformed rocks and trying to figure out how they ended up that way. Huge tectonic forces over time, moving of faults, etc. Now look at the example below. How do you think that those cracks could have formed in the darker sandstone so that they could be filled in later with the white minerals? Why did they form all lined up in a row like that? What possibly could have caused a feature like this to form?
The food: A nice, freshly opened container of yogurt (preferably plain and without very much added sugar). You have just peeled off the top of the container and are staring at undisturbed surface, as tempting as freshly fallen snow. You might be tempted to just dig in and start eating, but my structural geology professor taught me that this undisturbed yogurt is so much more than a snack: it is a miniature laboratory.
Playing with your food: By placing your thumb and pointer finger on opposite sides of the yoghurt container and squeezing them gently towards each other, you can create some bands of tension gashes of your very own! They might not be quite as pretty as the ones in the sandstone, but they sure are a heck of a lot easier to make. Look at the angle between the direction that your fingers have applied the force, and the angle that the cracks opened up - you might be surprised!
Ice Cream on a Windy Day
Context: It is a hot day and you are lucky enough to be eating an ice cream cone. Everything is going well. The day may be uncomfortably warm, but the ice cream is helping you feel a little cooler. Suddenly, there starts to be a breeze. How wonderful! The wind blowing past you feels a little better than the stagnant hot day. But wait, it seems like your ice cream is now melting faster than you can eat it! What is happening? You feel cooler with the wind, so why is your ice cream now all over your hands?
The food: As this example is about ice cream, you might be surprised that the food in question is not the ice cream itself. As this involved leaving something to melt, using ice cream is too much of a tasty loss. Instead, this involves two ice cubes.
Playing with your food: I typically do this on windy days by pulling two ice cubes out of my glass and setting one out in the open and the other blocked from the wind by a glass or something. For the example below, I placed two ice cubes of roughly the same size on matching plates and put them in the living room. One was able to sit out undisturbed. The other was placed ~4 feet away in front of a fan set on its highest setting. For the undisturbed ice cube, the air around it started to cool down creating a barrier between it and the warmer air that might cause it to melt. But the ice cube in front of the fan had no such chance. Exposing it to a constant flow of room-temperature air without giving it a chance to cool that air means that the ice cube starts melting significantly faster that its counterpart. See the comparisons at 2 minutes and 6 minutes below.
Torsion Testing Pretzel Rods
Context: When engineers and material scientists want to understand the properties of a material, they put it through a series of tests. These tests help engineers to understand what these materials can be used for - in buildings, vehicles, electronics, etc. While these tests are typically conducted in a laboratory with specialized equipment on pieces of steel, aluminum, or iron, there isn't any reason you can't test other materials as well - like your food.
The food: Our household typically uses pretzel sticks or the thicker pretzel rods, but it is possible that it may also work with crunchy breadsticks or any other long, brittle food that you can twist to the breaking point with your fingers. Please note that this one takes some practice. After multiple failed attempts to create a photo-worthy sample, I brought in my husband who - trained as a civil engineer - compulsively torsion tests every pretzel before he eats it. Every single one.
Playing with your food:
Hold the pretzel at the two ends and twist, trying not to bend or pull the pretzel at all. Pretzels and other brittle materials easily break in tension, so if you pulled really hard or bent it, the pretzel will crack with a flat edge. If you just twist the long pretzel rod, the tension in the pretzel is at an angle of 45 degrees from the orientation of the pretzel stick. Therefore, the crack will want to grow along a spiral that runs down the length of the rod. You can see in the picture that if you twist just right, the crack corkscrews the whole way around the pretzel before it breaks.
While I am not recommending that you interrupt a formal dinner to narrate the rate that your ice cubes are melting, I am acknowledging that I also know that playing with your food can be informative - and, yes, fun.
All other images are my own