Particles!

[eve_prime]

Tonight we attended a Science Pub that was the best we’ve seen so far. Eric Corwin, a UO physicist, explained about “jammed particulate systems” – when you get a bunch of objects, from oranges to marbles to grains of sand, there are different ways they organize themselves when they’re dumped together randomly. We learned why, when you pack a bunch of peas or marbles into a container, they each touch six others, on average. And in a way, a bunch of sand can be described as a solid, a liquid, and a gas! In other words, the typical “reductionist” style of science that starts with the behavior of one object and builds from there doesn’t work when you’re dealing with these aggregate behaviors.

Also, we learned the scientific meaning of “foam” – when you have a collection of objects together, the inverse of those objects (the space between them) forms a “foam.” If you drive a nail into a block of concrete, it will make cracks or shatter, but if you pour concrete around a bunch of objects that you can then dissolve, the remaining concrete foam is easy to drive a nail into, because it’s so much more stable, and only a few threads of the concrete are damaged.

And there’s an experiment we have to try – you dump a bunch of corn starch, baking soda, or flour rapidly into a cup, then drop a marble into it from about a foot in the air, and if you can watch carefully enough, you’ll see that the marble sinks to the bottom of the cup and a thin jet of the powder will burst several inches into the air.

So this guy stayed on topic, explained things clearly, and made his topic fascinating. Yeah!