I have been doing some house cleaning. In cleaning the counters, I noticed a coffee spill that had dried. It had formed a dark ring, with almost no coffee stain in the center. This reminded me of an article that I have read on the science behind coffee rings, giving me the idea for this experiment.
This experiment comes from a recent event in the science news. Researches have discovered that cats drink in a very different way from dogs and other mammals. Now you might think that things like this had been completely explored decades or even centuries ago, but high speed photography has shown us things that we did not suspect before.
One of the interesting things at St. Augustine, Florida's Oldest House is a large stone bowl with a bucket underneath. The stone bowl is half full of muddy water and there is a slow, steady drip of water from the bottom of the bowl to the bucket. Although the water in the bowl is a bit muddy, the water in the bucket is clear. Why?