Daniel smells rain coming through the window and asks why. Rain is just water. Water doesn't have a smell. So what is he actually smelling?

At least three things. And none of them are the rain itself.

The main one has a name: petrichor. Coined in 1964 by two Australian scientists -- Isabel Joy Bear and Richard Thomas -- who published a paper in the journal Nature. They built the word from two Greek words. Petra, meaning stone. And ichor -- the fluid that flows in the veins of the gods in Greek mythology.

So the smell of rain on dry earth has a name that means the blood of the gods.

Petrichor comes from two sources mixing together. First -- oils that plants release during dry periods that soak into rocks and soil. When rain hits, the impact releases them into the air. Second -- a chemical called geosmin, produced by certain ...