So if you did your preliminary reading, you’re up to speed on the theory. In the same way that snakes and cats use their eyes to hone in on prey, humans can use them to enhance their sense of smell.
As long as even a single molecule reaches your nose, it’s potentially something you can sense. For a neural system that can detect s, it shouldn’t be surprising that the nose is incredibly sensitive as well. Some odors can be detected when there is only a few milligrams per thousand tons, or a drop in an an Olympic-size swimming pool. Substances with stronger odors have odor thresholds [how much of something you need to smell it] in parts-per-billion.
How does it work?
The infrared radiation heats the object [if your eyes are on it] just a very small amount. No one has discovered this yet, because it doesn’t happen all the time, and it doesn’t happen to everyone.
Does all of this sound ridiculous to you? Here’s how you can prove it to yourself: take your phone, your drink-whatever is closest-and hold it up to your nose. Note the smell. Now look down at the part you are smelling and continue. You should notice more depth to the smell. Like you took something out of the fridge and put it in the microwave, but on a much smaller scale. Why does that happen? Because your nose is sensitive to chemicals that make up things. When you heat it up, it gives off more of those particles, so the smell is stronger, and more accurate. So your eyes heat up your food ever so slightly, giving your nose just a little bit more information. With an organ that is sensitive to parts-per-billion or even parts-per-trillion, just a couple more molecules can add much more depth to the smell.