If this isn't a question you've been pondering on pasta night, do a little experiment with me. Go to the kitchen, grab a piece of dried spaghetti and, one hand on each end, bend it until it breaks. If you thought it was going to snap into two clean pieces, and you're halfway through the box and it still hasn't happened yet, you're not alone.
A piece of uncooked spaghetti rarely breaks in half, and usually breaks into three or more pieces instead, with several small pieces flying from the middle (my record is seven). Beyond puzzling the average person in the kitchen, the question of why and how this happens has kept (at least two) great scientific minds awake at night.
Fortunately for us, Doctors Basile Audoly and SÃ©bastien Neukirch, both physicists from the Pierre and Marie Curie University in Paris, did a lot of work (and wasted a lot of noodles) to find an answer. Their research was published as "Fragmentation of Rods by Cascading Cracks: Why Spaghetti Does Not Break in Half," in Physical Review Letters (Volume 95, No. 9, August 26, 2005), and won them the 2006 Ig Nobel Prize for Physics.
After breaking strand after strand of spaghetti (they used Barilla, in case you were wondering), taking high-speed images of the process and applying the Kirchhoff equation (which relates to how waves travel through an object that's put under stress), they concluded that spaghetti fragmentation is caused by flexural waves traveling through the pasta after the initial break. Once the spaghetti is bent to a critical point, it breaks. This causes a flexural wave to travel down each of the resulting pieces before they have time to relax from the strain and straighten out. The wave causes these pieces curve more, which leads to more breaks.
Audoly and Neukirch refer to this whole ordeal as a "cascading failure mechanism," which makes a night of snapping spaghetti sound pretty exciting.