Category Archives: Phenomena

Many times after a rain, there is a distinctive odor in the air — a sort of musky smell. This pleasant fragrance is most common in rains that follow a dry spell.

The phenomenon is referred to as petrichor, from the Greek roots petra (stone) and ichor (the blood of gods in Greek mythology). If you are a gardener, you may find this smell similar to the smell you sense when you turn over your soil. Good organic soils contain bacteria, and a bacterium that is abundant in damp warm soils is actinomycete. Continue reading →

What is brontology? Brontology is the scientific study of thunder. All thunder results from lightning. A bolt of lightning rapidly heats the air around it, which causes the air to quickly expand and generate a sound wave we call thunder. … Continue reading →

How do we gain knowledge about the atmosphere? It is easy to assume that current, well-accepted scientific knowledge about anything was originally discovered by the grace of inspired geniuses armed with vastly superior intelligence than the average thinking person. In … Continue reading →

There are spring and summer afternoons when very thin clouds appear overhead and turn the sky a bit white. These types of skies are physically interesting in at least two ways that are worthy of note.

First, the whiteness is a function of the fact that the cloud cover is a thin cirrus cloud. Cirrus clouds are composed of tiny ice crystals that scatter visible light without preference for any of the colors of the visible spectrum (the colors of the rainbow). This particular property is shared by snowflakes as well as by haze droplets. Individual snowflakes look clear but even a small collection of them is white since all of the light that hits the collection of snowflakes is scattered in all directions equally. The same is true of haze droplets which are most common in the summertime in southern Wisconsin. Continue reading →