by Ruth Griffiths
We stepped out into the parking lot and noticed our heightened sense of smell. It was one of those moist, warm winter mornings after a long stretch of frigid temperatures. Why does warm air smell differently from cold air? It seemed like a good topic for research.
I discovered that odours are produced by airborne particles released by things in the environment around us. When we breathe in the air, these molecules are detected by receptors in our noses.
The odour molecules become airborne more quickly in a warmer environment than a colder one, so there are more smells available on a warm day than a cold one.
Humidity is also a factor. Pamela Dalton, a senior scientist at Monell Chemical Senses Center in Philadelphia: “Warm and humid air enhances our sense of smell, because the humidity carries odour molecules to our noses.”
Temperature and humidity affect odour because they increase molecular volatility. For a chemical to have smell, it must spread its molecules in the air. That’s why a cold dish smells less than a heated one: the vapours carry more of the scented molecules from the food. Warm air holds more moisture than cold air.
It seems that hot or cold air temperature can affect our preferences for foods. The temperature to which food is heated or chilled also affects our enjoyment of it. Think of hot apple pie versus room temperature pie.
Air temperature can also affect our sense of hearing. Sound sometimes seems to travel farther on cold days.
I remember a crisp morning on the farm when we could hear the neighbour’s dog barking. Ordinarily, sound did not travel that far. My father explained that the sound had “skipped off the clouds.” He was mostly right. It was due to thermal inversion.
Wikipedia explains: When a layer of cold air close to the ground is covered by a layer of warmer air, sound waves travelling upward may be bent, or refracted, by the difference in temperature and redirected toward the ground. An observer standing where the descending sound is focused may therefore hear a sound he would not ordinarily have heard because of his distance from its source.
Air temperature can also affect what we see. Again, as a child on the farm, I witnessed a mirage. We clearly saw in the sky the image of a forest over 50 miles away.
Wikipedia explains: A mirage is a naturally occurring optical phenomenon in which light rays are bent to produce a displaced image of distant objects or the sky.
In contrast to a hallucination, a mirage is a real optical phenomenon that can be captured on camera, since light rays are actually refracted to form the false image at the observer’s location.
We tend to think of our senses are static and defined, but it appears the ocean of air around us can change what we smell, taste, hear and see.