What is that odor in the air, the science behind the smell of fall

It’s chemistry, biology, psychology and a little bit of nostalgia

Smell happens when the receptors in your nose pick up aromatic molecules in the air. These molecules ooze out of objects and living organisms in the environment around you.

You smell more aromatic molecules during the summer because hot, muggy air holds more of the molecules and enables them to move through the atmosphere more quickly. The opposite happens when it’s cooler and drier in the fall: air molecules contract together and leave less space for odour molecules to move through. The dominant earthy smells of fall are largely the product of plants hunkering down for the winter. Fallen leaves begin to decay and their sugars and organic compounds in the leaf break down, creating the classic musky-sweet smell of a leaf pile.

Our emotional reaction to any smell comes from the personal meaning we’ve assigned to the scent — typically stamped on your brain when you’re young. (It’s why so many people associate the smell of fall with Thanksgiving and Fall Fairs……Ed

Source: Rhianna Schmunk · CBC News / Photo: Emcmahon