It's still cold here in the Midwest and not yet through our arctic winter, but with all the cold has come this beautiful array of icicles not yet melting. I have just learned that icicles are smooth if they are made from distilled water. And they are rippled if the water has minerals and salts. This rippling, in fact, occurs at the same wavelength, world over. Nobody claims to know why the wavelength is the same, or even how why the ripples form as a result of the impurities.