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  • Hey, Vsauce. Michael here. And our faces

  • have a lot of holes. We have two ears and two eyes.

  • It makes sense, because the difference in time it takes for a sound to reach one ear

  • and the other,

  • allows us to localize where the sound is coming from.

  • And having two eyes gives us two slightly different perspectives that we

  • can put together

  • in order to perceive depth. But why do we have two

  • nostrils? I mean, our sense of smell isn't good enough to localize

  • one nostril over the other, why not just have a big hole in our nose,

  • like we have a mouth. Well, Stanford University's olfactory research

  • project

  • investigated this and they found that throughout the day

  • one nostril inhales air better and faster

  • than the other. Now, which one is dominant changes throughout the day, but having

  • a good air sucking nostril and a not so good

  • air sucking nostril is important. We need both,

  • because you see, odorants and molecules are absorbed by our skin and snot

  • at different rates. Some things are absorbed so quickly

  • they need to be rushed on the olfactory receptors before they're

  • absorbed earlier on in the nose. Other

  • molecules, other odorants, are slowly absorbed

  • and they need to be given time to get to the receptors and not just rushed right

  • to the lungs.

  • And so having two nostrils allows us to smell

  • more things. Alright,

  • so let's smell some weird stuff, like

  • outer space. What would space smell like?

  • Okay, right, it's a tough question, it actually doesn't make much sense because

  • space

  • is a mere vacuum. If you went into space and took your helmet off to

  • smell it, well, all of the air in your lungs and throat, nose would be violently

  • sucked right out. In fact, even if you really tried to get some sort of

  • olfactory sensation, about all you would feel is the quick evaporation of

  • water coming out of your mucous membranes

  • and you might smell, for the few seconds that you were conscious,

  • nasal fluid and blood. That doesn't sound fun at all.

  • But here's the thing. Objects

  • that have been taken out into space and then returned to a

  • habitable atmosphere, like inside a space station,

  • smell differently than they did before

  • they went into space. Astronauts report that their suits,

  • after being in space, have a strange metallic

  • burn meat arc welder fumes smell.

  • It's believed that the odor is caused by high energy particles

  • that cling to the suit and then, once brought inside,

  • react with the air, creating a burning

  • smell. One particular type of high energy molecule found

  • all over interstellar space are polycyclic

  • aromatic hydrocarbons. These guys are the result

  • of combustion. And in 2004, the University of Toledo, Ohio found evidence

  • that those very molecules may exist in old

  • nebula. The result of convection currents cooling carbon and hydrogen

  • allowing them to bond into giant shapes.

  • Polycyclic aromatic hydrocarbons are also formed,

  • when cooking meat at high temperatures.

  • So, in order to train astronauts even more realistically here on earth,

  • NASA actually reached out to Steven Pearce of Omega Ingredients

  • to replicate the smell of things that have been to space

  • as a perfume. If we know the chemical makeup of something,

  • even something light years away from us, we can assemble those ingredients

  • here on earth and get an idea of what it would

  • smell like. Recently, researchers have discovered

  • Ethyl Formate in the dust cloud Sagittarius

  • B2. Now, again, if you were to go there

  • and lift up your space suits visor and take a whiff,

  • you would die. You wouldn't be able to take a whiff, all of the air in your nose and

  • lungs and throat would be

  • immediately expelled. But if you were able to take a

  • bucket of Sagittarius B2 home with you to earth

  • and then give it a smell, because of the ethyl formate

  • Sagittarius B2's stuff

  • would smell like raspberries and rum.

  • Pretty neat, right? But let's get closer to home.

  • What does the inside of your nose

  • smell like?

  • Well, it's kind of hard to know because we are smelling it

  • all the time and our bodies become desensitized

  • to constant stimuli to keep us from being overloaded

  • and to keep us prepared to sense any out of the ordinary smells that

  • we might need to know about. This happens to us all the time.

  • When you first step into a restaurant, you can smell all the food,

  • but halfway through the meal you're no longer aware of the smell.

  • It's called neural adaptation. I guess the point I'm trying to make

  • is that in order to figure out what the inside of a nose smells like

  • you'll need to smell a novel one,

  • like, for instance, smell the inside of your friend's nose.

  • It might seem weird at first, but it could be a great way to form

  • new memories. Our sense of smell may not be as acute as our other senses,

  • but it seems to be tied to memories very very closely.

  • A single whiff of an odor can instantly remind you of where you used to smell

  • that smell

  • and maybe even who you were with. This may be

  • because of the olfactories' connection to the limbic system

  • in the brain. Olfactory information is sent

  • through the limbic system, which is known to be involved with

  • emotions and memories. No other traditional sense is connected

  • to the limbic system in this way. We've also found

  • that patients who have memory loss caused by brain damage

  • tend to also have an impaired ability

  • to smell. So treasure your sense of smell,

  • because it not only keeps us safe from gross

  • odors or rotten food, it can also keep us safe

  • from incest. Individuals who are

  • raised together in the same home for the first few years of their life,

  • whether they are genetically related or not,

  • will tend to be less physically attracted to each other

  • later in life than they are to strangers. This is known

  • as the Westermarck effect and one of the main mechanisms it works via

  • is the olfactory system. Us humans have an interesting ability to

  • distinguish the smell of a stranger

  • from someone that we are genetically related to or

  • grew up in very close proximity with. This entire phenomenon may be a

  • natural way for us to avoid inbreeding.

  • But what about someone who can't smell?

  • What do we call them? Someone who can't see is blind,

  • someone who can't hear is deaf and someone who can't speak is mute,

  • but what do you call someone who can't smell?

  • Well, there's a word for the inability to smell - anosmia.

  • Now, even though the adjective form is very very rare,

  • it exists. A person who can't smell

  • is anosmic.

  • There's another word we should have investigated a long time ago.

  • Olfactory. What does is it come from? Well,

  • the "ol" part comes from odor and from smell,

  • but "factory?" Well, factories make

  • things, but the nose doesn't makes smells,

  • it smells smells.

  • Right? Well, here's the thing. We

  • smell objects because molecules from those

  • objects react in certain ways with our olfactory

  • receptors. And molecules have

  • specific shapes and vibrations and ways of behaving,

  • but the smell is not actually

  • intrinsic to the molecule. The smell is merely a

  • consequence of how that molecule reacts

  • with us. No us,

  • no smell. So, olfactory

  • is a fantastic word. Every sight

  • and feeling and sound and smell we get from our universe

  • is actually just the universe reacting with

  • us. Everything we know about the universe we know

  • because it has already been processed and changed and analyzed and filtered

  • inside the factory of our sense.

  • And as always,

  • thanks for watching.

Hey, Vsauce. Michael here. And our faces

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為什麼我們有兩個鼻孔? (Why Do We Have Two Nostrils?)

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    林宜悉 發佈於 2021 年 01 月 14 日
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