When you smell something, does that mean that little particles of what you smell are going up your nose, or is it gasses given off by the object that we smell?
Cindy, Mira Mesa
Technicallly speaking, those options amount to the same thing, if we can stretch �little particles� to an extreme. The answer to your either/or question is yes. So why doesn't granite stink like garlic? Well, a few conditions must be met in order for something to produce what we detect as an odor. First, the potential smell source must be made of volatile components; its molecules must be able to be released in the form of a gas. And the molecules must be released rapidly enough to become airborne and reach your nose. The faster the molecules are released, the more pungent the smell. And the molecules must be a type that can react with the mucous membranes in your nose and stimulate your scent detectors.
At the back of your nose you have a yellow, postage-stamp-sized membrane that contains many nerve endings connected directly to the smell center in your brain.. When you take in a good snort of air laden with smelly molecules (20 miles per hour, for the average sniff), the molecules bash into your olfactory cleft, and then you hear the faint sound of scientists arguing. Some say it�s molecular vibration that stimulates the nerve cells; some say it�s changes in electrical potential or chemical reactions. Others think the molecules fit into prescribed slots in your olfactory cleft. At present the exact method of interface is a mystery. But however it works, it really is vaporized microscopic bits of the smelly substance that you suck up your nose that make you stop and check your shoes.