How does smell work The Weird Quantum Connection

imagine taking a walk through your favorite park you can smell the morning dew the unique smells of plants soil and distant flowers a feeling of calm and relaxation saturates you all these sensations are due to the very special nature of your sense of smell what you may not realize is that inside your nose rests a very sensitive quantum device that uses complex physics to give you the ability to distinguish according to the latest estimates one trillion different smells how does your sense of smell actually work and what does quantum mechanics have to do with it that's coming up right now in order for you to smell anything molecules from that thing have to make it to your nose everything you smell is volatile in some way meaning it is giving off molecules that float into the air and land inside your nose so whether it's the morning flowers or your coffee or bacon or the foul stench of dog feces the molecules from that source are floating in the air and entering their nose but how did these molecules trigger the sensation of smell at the top of your nasal passages behind your nose there's a patch of special neurons about the size of a postage stamp called the olfactory epithelium they have here like projections called cilia that increase their surface area any molecule from anything with a smell binds to special smell receptors on these cilia and triggers the neuron causing a signal to your brain this signal ends up in a primitive part of the brain called the limbic system which is associated with emotions and memory so that's why smells can trigger strong memories and emotional reactions these neurons are unique in that they come directly from your brain and are out of the open where they can come into contact with the air so this is the only place on your body where your central nervous system is directly exposed to the environment now the question is how did the neurons get triggered the standard explanation going back to the 1950s had been that the receptors and the ends of these olfactory neurons and there are about 400 such smell receptors can only accept particular shapes of molecules and the exact type of smell is determined by how the molecules from the smelly compounds fit in the set of receptors of the receiving factory neurons by triggering a particular combination of the 400 smell receptors the brain interprets a particular kind of smell it's like a lock and key the key is the shape of the molecules of the smelly compounds and the lock is the olfactory receptors one combination can trigger the smell of a rose another combination can trigger the smell of rotten eggs and so on so the thought is that what you are really smelling are shapes of molecules this was the standard explanation for the mechanism of the smell until researchers discovered that you can have molecules of different shapes that have the same smell so for example cyanide smells the same as benzaldehyde a bitter almond smell but they're vastly different shapes so scientists concluded that there must be something more than just the shapes that determine smell well it turns out that although the shapes are different cyanide and benzaldehyde had the same vibration a new research suggests that it is indeed not just the shapes of the molecules but also the vibrations of these molecules that determines how we perceive smell all molecules vibrate with a certain frequency and temple based on their structure bonds and weight it's analogous to sounds coming from various instruments due to their various shapes Luca Turin a bio physicists at the Alexander Fleming Research Centre in Greece conducted experiments using the smell of sulfur compounds he identified molecules that have the same vibrational frequency as sulfur but with completely different molecular shapes than sulfur what he found was that these compounds with the same vibrational frequency of sulfur do indeed smell like sulfur even though their molecules are shaped completely differently Turin's research is not accepted by all olfactory researchers but if he's right how is our nose able to smell the vibration of molecules in quantum mechanics so-called particles like electrons are really waves of probabilities until the moment they're measured the probability wave is such that when the particle encounters a barrier the probability wave does not stop at the barrier but continues through for a short distance so there's a nonzero probability that the electron will go straight through the barrier and show up on the other side of the barrier or the tunnel through that's why this is called quantum tunneling in classical physics this would be forbidden but it is observed in nature due to the laws of quantum mechanics it is theorized that the vibrations of certain molecules might allow electrons from certain smell receptors to tunnel through to other small receptors and trigger signals in the neurons and then subsequently to the brain different molecules with different vibrations can cause different rates of tunneling when the molecule of the order has a certain frequency that matches the energy of the receptor quantum tunneling works in such a way that it opens a gateway for an electron to tunnel more preferentially than went the molecule and it's vibration is not present in a way you might say our noses not only small shapes but here shapes too using the complex physics of quantum mechanics to do it how could our noses have evolved its sophisticated sensory mechanism turing has an interesting answer he says four billion years of R&D with unlimited funding it's a long time indeed evolution is a process we've probably greatly underestimated far vanish here if you like our videos please support us by subscribing subscribe and cost you nothing it just means that you're going to be informed whenever we put up a new video we make about one to two videos a week we'll see you in the next video