Ah, summer: sunny days, heavy storms. Sniff sniff.. smell that? That delightful rainy odor?
“Oh please, rain is simply water, which has absolutely no odor to speak of”, you say. Indeed you’re right! But it’s not the rain that smells rainy, but rather the soil; more precisely, that beloved characteristic smell is attributed to an organic compound named geosmin, produced by the bacteria Streptomyces coelicolor (how I adore biology and its poetic monikers!).
What’s more, the human nose is ultra sensitive to this molecule- the infinitesimal amount of a few nanogams is sufficiently strong for our olfactive apparatus to register.
This discovery is due to six years of research by a team of chemists at Brown University. You might suppose that knowing that geosmin is responsible for that musky smell wouldn’t really advance humanity; au contraire, finding easier and more efficient ways of detecting the molecule has lead to the development of quicker ways of rendering water potable.
And that’s already much more scientific than your grandfather’s prescient rhumatism foreseeing the falling of rain.