The Suspicious Smell

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I'm Dr.

Adam Adam Rutherford.

And I'm Dr.

Hannah Fry.

And you are going to send us your everyday mysteries.

And we are going to investigate them.

Using the power of science.

Science.

Science.

I like it.

Welcome back, Curious, to the next episode of Curious Cases of Rutherford and Fry.

What is going on with your voice?

I'm not sure, but I notice...

Because I'm very observant like this, I notice you've got some new face furniture.

Is that what you call it?

Yeah.

Because I've had my nose pierced.

Yeah, nice.

I think I'm having a midlife crisis.

You're not even in your midlife yet.

Well, it depends, depends how long my life is, doesn't it?

You're not even 40.

You know what?

Actually, this is

sort of related to today's show because when I had my nose pierced,

all I could smell was blood for three days.

That was it.

Constant.

And actually, that is loosely related to today's show.

It is very specifically related.

Because it's all about smell.

Today, we've got an absolute stinker for you.

For which I can only apologise, it's my new deodorant.

Lol.

No, actually, listeners have been sending in lots of questions about smell to curiouscases at bbc.co.uk, and we've bundled them up all into a delicate bouquet for your delectation.

Okay, so Alice Taylor asked, why do our bodies smell?

I know the reasons behind body odours, such as not washing and fungal or bacterial infections, but there must be a reason in our evolution as to why this happens.

Well, adding to the potpourri of pongs was this question from Lorena Busta Hottado, who had gotten to know some people through an online book club and wondered whether their in-person smell might affect how much she likes them.

Which is a

puzzling question because I would be...

I'd be smelling the books themselves more than the people if I

smell of a book.

And finally, to add to the Schmorgas Board of Stinks, Brookhan Davies from Wales asks, why is it that if I eat garlic, it makes my breath smell of garlic.

If I eat curry, it makes my fart smell of curry.

But if I eat asparagus, it makes my wee smell of asparagus.

I mean, this is a little bit more scatological than I was hoping for.

He goes on, is there something inside me making these decisions?

If you cannot answer this, I can send samples.

Please, Brucken, and I cannot stress this enough, don't.

Yes, I've checked with the BBC lawyers, and we believe that sending bodily fluids by post is a violation of the Malicious Communications Act 1988 and is therefore a crime.

Anyway, we've got two expert smellers in the studio today to sort this out.

We've got Matthew Cobb, Professor of Zoology at the University of Manchester and author of Smell: A Very Short Introduction.

And Barry Smith, Professor at the Institute of Philosophy, Director of the Centre for the Study of the Senses, and a regular guest on radio, fors the Kitchen Cabinet.

Okay, Matthew, I'll tell you what, why don't we start with some of the basics here?

Does everything have a smell?

Well, everything is quite a tall order, but lots of things do.

I mean, basically, a smell is a molecule that is in the air.

Or if you're a fish, it's in the sea, in the water.

So it's in the medium in which you are moving.

And animals and some plants can detect these volatile molecules.

And so, yeah, lots of things do.

So anything that's sort of small enough and volatile enough that it can end up in your nose, you would be able to smell?

Potentially.

There are only some things that we can smell.

So

there are some odors that we differ in our individual differences, have individual differences in what we can smell.

So in principle, something like most small molecules, we should be able to detect.

But there's lots of ifs and buts there.

Is there a relationship between certain molecules and the way that they smell?

Yes, but I don't know what it is.

And neither does anybody else.

Not really.

So, there's a general principle.

So, things that have got sulphur in them and in rings tend to smell a bit farty.

But that's not an absolute

rule.

You can't go from looking at what a molecule, the structure of a molecule, and then being able to know what it smells like.

But we do presumably know that actually quite a subtle change to the structure of a molecule can fundamentally change our experience of it.

Yes, I can show you that if you want.

Oh, yeah, go on.

Okay, so what you've got to do is just tell me whether you can smell the difference between these two molecules.

Okay, so this one smells...

oh it's quite don't smell it too hard it's quite pungent it sort of smells like

washing up liquid on steroids there you go so this is we've got a little flask here with a tissue in it, and

yeah, that's washing up liquid.

It's all right.

Okay, but this one, though, this one is like much grassier, sort of sweeter.

They're not wildly dissimilar, but that's definitely sweeter.

That is more perfumey, isn't it?

Okay, so what you have just smelled are two alcohols: octanol, which has got eight carbons, and the one that you thought smell of washing up liquid has got nine carbons.

So, that difference, and you said they're the same, but they're different, there's something similar to them, that's the alcohol.

But the chain length, the number of carbon atoms produces that difference in perception.

So your noses have just detected the difference of a single atom of carbon.

That's very cool.

I want to know about, okay, so if you're looking at something, I know that our eyes have different types of receptors to detect red, green, and blue light.

Is it a similar thing in your nose?

Do you have like a number of receptors and the sort of flavor that you're smelling is on some sort of spectrum?

It must be said that we don't really understand how it works, but the basic idea is you can imagine it being a bit like playing a chord on the piano.

So if your fingers are a smell, you press down on the keys and it produces a particular odour.

And what that shows is that each odour

can activate more than one of your smell receptors.

You have around about 400 kinds of smell receptor in your nose.

So each smell can activate a series of different receptors.

And it's the way that they they activate those receptors that's what produces the perception.

Do we all have the same receptors?

No.

So, does that mean that people can smell different things?

There's huge variability between individuals.

For example, and this is a very rare example in the human olfactory spectrum.

This is an odour, I'm going to let you smell, which only activates one receptor.

Ooh, so that's unusual.

It's about the only example we know.

And we know that variability between individuals in the gene for that receptor alters how they perceive.

So, this is like a particular case where we have good understanding of it.

Yeah, well, ish.

We've got better understanding elsewhere.

So, what it tells us is that we can go from this smell, if you respond in a particular way, I can tell you what your genes are.

Similarly,

if I'm C1R all over, I know it.

If we were to see your genes, I could then predict what you will think of it.

Get on with it.

I want to see a reaction.

So, let's see.

Ryan.

There you go.

Give it a go.

It's like a...

Goodness.

It feels like, you know, when you take

when you've got the beginning of a cold and you use a nose squirter and you sort of squirt saline up your nose, it feels like that.

It feels like that.

Yeah.

And I can't smell anything.

Really, really?

That smells like an empty bottle to me.

Okay.

What?

But is it a proper reaction to that?

So it's going up your nose and it's making your eyes water, but is it nice?

Is it nasty?

It's it's like medicinal.

Okay, so it's medicinal.

So this is stuff called androstenone, which in certain shops and in certain parts of the internet you can buy as a pheromone, supposedly, that attracts women fast or attracts men fast.

Give me that bottle.

In fact, but that's a load of hogwash, isn't it?

Hog is the absolute right word because it is in fact a pig pheromone.

So it's water, isn't it?

It's made me snort.

Pig.

But it only works in pigs.

When you give it to a pig, the female pig adopts the prone position straight away.

That's the pheromone that gives you an immediate behavioural reaction.

She also starts to ovulate.

So

it's a pheromone in the farming industry, very significant.

But for this bizarre reason, it happens to be that it's kind of a legacy in the humans with this single receptor, with this variability.

The fact we've got variability and the fact that Adam can't smell it at all, you think it's medicinal.

I think it's quite sweet.

And I think it's a bit sweaty.

You think it's a bit sweaty.

Okay, so those are the main variants.

And there is a fifth variant which nobody ever admits to, which is, hmm, that's nice.

So there are a very small number of people who are...

Are those the ones that are descended from pigs?

No, well, we're related to pigs.

Nobody's descended from pigs.

And our response to that determines whether we'll like pork, because there's a little tint of that.

So

where you are on that genetic profile will determine your acceptability for pork and pork chops.

All right, well, let's address Brucken's question about

the foods that smell in different ways.

What is it about asparagus that makes our pea smell?

Asparagus is just a wonderful example.

So we metabolize it very quickly and we turn it into methane thiol.

Thiol is a particular sulfurous compound, it's got a very potent smell usually.

Methane thiol is the one that appears in farts, it appears in garlic breath, it appears in your urine.

And that, of course, is the one that smells rubbery, sulfury, bit like boiled cabbage.

But the nice fact about this is that many people thought, my wee doesn't smell of asparagus.

And a very clever olfactory scientist took the wee of the people who said it didn't smell of asparagus to the people whose wee usually smelled of asparagus and it smelled of asparagus.

So what it turned out was it wasn't so much a difference between whether they produced the smell of asparagus and their wee, but whether they could detect it.

Oh, I see.

So, so you could, it, it's a, it's, there's a two, there's two components to this.

It's whether you can smell the chemical that is the metabolite from

asparagus, but also whether you're producing the...

Does everyone produce it?

Not everybody produces it.

Very small numbers of people don't, but very large numbers of people say, I don't smell any asparagus in my wee, but if you take it to people who do, they'll say, oh, yeah, there's the asparagus note.

Got it.

And what about his other questions?

And let, you know, family-friendly show, this is the last time we're allowed to mention farts, but are curry farts a real thing and is garlic breath a real thing?

Garlic breath is a real thing.

So you, again, you metabolize it in your gut and then you get these thiols coming into the mouth.

But actually, the lingering thiols in the mouth that give you garlic breath, you can solve that.

You can make that go away.

Because Japanese scientists found out that if you use the browning enzyme of a bruised apple, that turns these sulfur molecules into something odorless and it just disappears.

I did this with a bunch of chefs and it it was particularly successful.

They had it all over their fingers, they rubbed it on the bruised apple, no smell, and they realized I can clean my knives with this.

Yeah, I actually like the smell of garlic on people's breath.

If you like the person themselves.

Quick question for Hannah.

What is the correct number of garlic cloves to put in the recipe?

Is it

a factor more than it says in the recipe?

It's 10 times what it says in the recipe.

So

what about curry farts?

Curry farts, I mean, whenever you're getting all those wonderful ingredients in your stomach, and remember, some of of them are chemical irritants, so they're going to get the system a little bit jazzed up.

So you're going to produce a bit of gas, a bit of odor.

I think we release about 1.5 liters a day on average.

But sometimes...

You might do.

Wow, I think some of us even more.

1.5 liters?

Apparently, yes.

Even the Queen.

Who knows?

Who knows if the Queen does?

I think suppressing is not a good idea, though.

I want to know a bit more about the experiment when they work that out.

I don't think you need to be a rocket scientist to imagine how you did it.

Maybe a balloon scientist.

Did it involve a bath?

Delightful.

On the point about

taste and smell here, given that we're talking about food, Matthew,

what's the balance

between those two when it comes to assessing our food?

Well, you've got...

maybe five, six dimensions of taste.

So salt, sour, sweet,

bitter,

always gumami, gumami, and kind of hot, cold.

Smell, on the other hand, what is the dimensionality of smell?

That's almost a philosophical question because if you think about it,

what are the words we use to describe smells?

In virtually all exceptions, apart from things like dank, there is no special word to describe a smell.

It's going to be, it smells woody or like an apple.

It's going to be using another term, another smell, to describe a smell.

That's particularly true, actually, when you think about wine tasting

and the sort of absolutely ridiculous words that they come up with to describe.

Maybe this is, I'm just showing my lack of class here.

But it's like, oh, it's a grass.

Leather.

Grass and leather.

It's very difficult to describe smells.

And we know what the dimensionality of sound is, of vision, we can measure it.

But the dimensionality of smell, for the moment, that's something we have yet to really discover.

But the key point is you've got taste, you've got smell, and then there's something else which is a mixture of the two, and that's flavour.

In general, when people talk about taste, they're really talking about flavour.

They're not got those crude five, six, seven dimensions.

They're talking about something much richer and I can show to you that most of what you think is taste is in fact smell.

Go on.

And the listeners can join in if they want.

Okay let's do this.

Let's do this.

Okay.

Right, so I'm going to going to give you a little sweet, chewy sweet.

You've got some rather fetching medical nose clips that you're going to put on your nose.

I want you to take this sweet and then chew it with your mouth shut

for about 10 seconds.

So, probably a good idea to take a breath before you start to chew the sweet.

Okay, this is, um, I realise now that getting my nose pierced about three weeks ago was a terrible idea.

This medical nose clip is not gonna

be particularly difficult.

You did not plan ahead there, did you?

Okay, all right, okay.

Oof.

So, put that in your mouth, chew with your mouth shut, and now think about what you can taste.

Okay, now take your fingers off your nose.

Oh my lord.

That's extraordinary.

So what did it taste like when you had your nose?

It tastes nice and sweet, deliciously sweet.

And then the second that you open are like really lemony.

So you couldn't taste the lemon until

you got your nose.

I've done this demo with Matthew before.

It's very nice.

That's extraordinary.

So it's really only when you can smell it that you suddenly get that whoosh.

Because what's happened is all the volatiles you've been chewing up have gone roaring over your smell cells which are about the level of your eye they're really high up in your nasal cavity they're not in down your nose they're way up here okay so far we've been talking about individual smells but we also spoke to dr ann sophie barwich from the university of indiana she runs a lab called the stink tank and she says it's the blend of molecules that really counts So when you want to study how people respond to smells, in the lab you often test them on individual molecules.

That makes for more controllable conditions.

But in everyday life, you almost never or hardly ever smell individual molecules.

You smell hundreds of them.

Even your ordinary things like coffee, wine, tea contains hundreds of aromatic molecules.

And it's the combination of these molecules, called odorants, that matters.

By combination, I do not mean you just simply add up the odor of the individual small compounds, but more like Aristotle said, basically that the whole is more than the sum of its parts.

There's a good example for that, although I might ruin the morning coffee for you.

If you drink your coffee, well, this coffee aroma consists of several hundreds of molecules and a small percentage, about 3%,

is indole.

And indole is an odorant that on its own smells very strongly of, well, feces.

It smells of poo.

Which you don't smell, of course,

if you wake up and you get this glorious whiff.

You don't smell the poo, but trust me, it's in there.

Similarly, jasmine, beautiful flower, great perfume ingredient.

Well, also, again here, a small percentage of its smell is also indole.

And even a couple of well-known perfume brands, and I can't say the names, but they contain indole.

This is why some olfactory scientists kind of like to make jokes about that, that certain perfumes stink of poo, quite literally.

Well, that puts a whole new spin on the method of attack if you don't like somebody's perfume.

Yes.

I mean, it might make buying perfume much cheaper, although probably a lot worse.

Is this a common tactic, Barry?

Do people use Indole a lot?

Yeah, just a little bit.

You don't want to overdo it, or you're going to get the smell of poo.

But I do think you want that contrast.

Smell is a contrastive sense.

It tries to figure out when something has changed.

So if you've got a cliff edge of something nasty and something nice, it probably amplifies what's nice.

So natural jasmine, as Anne Sophie just told us, has got about 2 or 3% indole.

Now if you give somebody a synthesized jasmine and you leave that out, at first if they're novices, they might not notice the difference.

But if you ask them forced choice, which do you prefer?

They prefer the one with the indole in it.

So I think you need something a little bit nasty, a bit of pain with your pleasure to really enjoy it.

A little bit of poo.

This program is not how I thought it was going to pan out.

It's much more

scatological, is the word I was aiming for.

Right, let's move on to the next smell.

This is a nicer smell.

So, and you can see what these, these are rose petals

taken from my garden this morning.

These are my daughter's favourite smells.

She told me the other day.

So, what I want you to do is to guess how many different molecules there are in that bouquet.

Oh, it does smell nice.

I mean, it's hard to know because it's sort of like the sweetness of the petals and then like the grassiness of the stems.

I'm gonna say two.

Two.

Okay, do you have a garden?

Well I'm gonna take the sort of trivial pursuit tactic which is when they ask questions where there's a number involved the answer is either zero or a million.

So yeah it smells like roses to me or it does nothing but I'm gonna go with a million Barry

30.

Well there's two problems here.

How many molecules are there and how many molecules can we detect?

So if you do a chemical analysis of a rose bouquet, there are about 220 different molecules in it.

Now, I doesn't mean to say we are actually smelling all 220.

My guess is that Barry's 30 is much more about right in terms of what you're actually getting in that bouquet.

And if you were a skilled perfumer, you'd be able to, which I'm not, you'd be able to break it down and analyze it.

Essentially, then, I was out by 28, and Adam was out by 999,970.

That's often the way in this, in this show.

Many orders of magnitude.

We'll call it a draw.

You know what though?

Okay, so far we have been talking about how we smell, but I actually want to go back to Alice's question as well about why we smell.

See, those are sort of why questions they come up

from a philosophical and from an evolutionary point of view.

And I think there's two layers to it.

Now, the first is she alluded to it: we have bacteria in our skin, and there's a particular type of staphylococcus which lives

on our skin and on the hairs on our armpits.

And they digest proteins that are secreted in sweat and they break off amino acids and they release a part of the molecule that contains sulfur.

So you're getting that same sort of sulfury smell from

I actually gesticulated to my armpit.

So I'm sorry about that.

The second layer, and I think this is what she's alluding to in the question, is a sort of evolutionary angle.

Why have we evolved to smell?

Is this beyond finding people with bad hygiene just less attractive?

Well I think that is an important part of it.

But Matthew, we do have subtly different smells that we produce.

Not everyone smells the same and we can detect that.

Yes, absolutely.

So we've all had people who we've loved dearly and we've recognised their smell and that's very, very important.

And that's going to be a mixture of what they're eating, their genes and their overall habits over a very long time as well as washing and whatever perfume they may have put on and our noses are sensitive enough to really make those distinctions that we can actually possibly not identify individual people but but you know we know the smell of people that we we like yeah you know the smell of your the your baby's the back of your baby's neck you know that smell compared to anything else yes you can identify particular individuals who are close to you barry does it have an impact on on relationships which was part of Lorena's question?

Yes, I think it does.

So we're chemo signallers.

We send out messages from our smell, and other people are picking them up all the time.

We don't know we're doing it, but we were sensitive to it.

So a lovely piece of work by Noam Sabelle from the Weissman Institute, showing that maybe, like dogs, we also sniff other people out.

So how would we do that?

Well, not the way dogs do, obviously, but we have a tendency when we've just shaken hands with a stranger to then put our hand towards our face.

Maybe we just swipe our nose, maybe we just rub our mouths and we're able to smell what's on our hand.

So lovely experiment done by Nome Sabel where the experimenter invites the participant into the lab, shakes their hand and said, I've got to go and get a piece of equipment.

And then while the participant is sitting there being filmed, they start putting their hand towards their face.

Now, independent people coded this to say, was that a sniffing of a hand, hand, touching the face and sniffing a hand?

It's a very nice illustration of why we might do what dogs do.

I would quite happily never shake anyone's hand again.

I'm all for fist bumps from now on in.

The other thing to say, I remember soon after I had my

second child,

my second baby, and there would be some times where I would be working and like my husband would be holding the baby.

And I forgot that babies are not dogs.

And so

was almost like hiding from her and expecting her to be able to know that I was there.

But I mean, you're saying that we're more sensitive than perhaps we might realise.

Oh, I think there's lots of unconscious processing going on all the time of odors and smells, and that's having an effect on mood, it's modulating our decisions, our perceptions.

I mean, even looking at food.

When you're hungry, your threshold goes down.

You can smell food odours more keenly.

When you're sated, your threshold goes up.

You don't notice them as much.

Matthew, your take on all of this?

Well, I know the handshake work and the videos are very convincing, but it's yet to be replicated, which is one of the problems there is in studying human behaviour.

And I have yet to

see anybody smelling my hand after I've shaken it.

I shook hands with the producer.

He didn't smell it.

I didn't smell my hand after I'd shaken him.

So whilst it's absolutely right that there are lots of unconscious ways in which we are sampling smells from around us and from the people near us, I'm not sure that we're doing it on quite the extent.

That's a healthy degree of scientific skepticism there.

What about sexual and romantic attraction?

This is a big area which has been quite controversial in the past.

Yeah, so we asked cognitive neuroscientists, author of The Scent of Desire, Dr.

Rachel Hers, what the evidence suggests about the influence of bodily bouquet on the attractiveness in heterosexual relationships.

So I like to say that there's no Brad Pitt of body odor.

This may be dating myself myself

since there, you know, Brad Pitt may not be the number one, you know, male sexual icon these days, but your body odor, your true natural body odor, is actually the representation of the genetics of your immune system, and everyone is actually unique.

What we're really doing when we're being attracted to somebody's body odor is actually sensing a compatibility immunologically with that other person.

And when I say compatibility, that means not actually identical to me at all, but not a a million miles apart either so this sort of sweet goldilocks spot of having the right amount of potential doubling up on good things but avoiding any doubling up on negative things so what we are really doing is we're sensing not family because this is sort of almost the olfactory incest avoidance mechanism but we are also not necessarily wanting someone who's so different from us that there's nothing that's good that's going to be potentially doubled up and so something that I've kind of cautioned about when people are potentially looking for their perfect mate with whom to have a family is to ask, you know, your dates to not overuse these sort of, you know, fragrances that are not part of their own natural bouquet.

Because, well, it could be that if you would have smelled what they really smelled like initially, that you would have been not quite as attracted to them.

And that may have been a signal, actually, that biologically you're not quite as compatible.

Now, Matthew, I know that this is an idea that's quite popular in the press, but how plausible do you find it?

How much evidence is there for this idea?

I think it's possible, and there are some animal studies that suggest that it is the case, but there are also many other studies which undermine that confidence.

So my feeling is that if it isn't a very strong effect, if it isn't coming through clearly, then perhaps it's not quite real.

What are the studies that have looked into this, Barry?

Nice study in Germany of finches, where you're able to keep and breed the finches.

So you know their genes, you know what they're eating, and you maybe know about the bacteria on them.

Now, when they breed, they will pick a finch whose genetic profile, whose immune system is far away from theirs, histocompatibility complex, different from theirs.

Question is whether that goes further into humans.

And how about when it comes to studying humans?

Do we have any suggestion that this is actually an effect that exists?

Well, the funniest one was when people were asked to smell t-shirts of different males and find them attractive or less attractive and to rate them, they threw in a ringer and they put a gorilla t-shirt in there.

And a lot of the women find that more attractive than the males.

That sounds like compelling evidence that this might be a house built on sand.

Matthew, your take on this?

I think it's a house built on sand.

Thank you.

That was my polite way of saying

something rather more strongly worded.

So let's leave it there.

Thank you very much to Matthew Cobb.

Thank you very much to Barry Smith and to our contributors and Sophie Varich and Rachel Hurst.

So Professor Fry, when it comes to why you smell, can we say case solve?

Why do people smell, you mean?

Yeah, sure.

Okay, well, old faction is an ancient sense, much older than vision.

It's a mechanism for detecting chemicals and it has a resolution at the level of a single atom.

Bacteria that live on our skin break down proteins in sweat and that's what gives us smelly pits.

But when it comes to how smell actually works, the answer, the definitive answer, is the three most important words a scientist can ever say which are, we don't really know.

That was four.

Okay, well that was a much more scatological show than I thought it was going to be, but that's what happens if you're dealing with two smell experts.

Matthew Cobb, you came armed with a lot of Tupperware and small tubes.

We've only managed to get through a couple of them.

I think now is the time to reveal all.

Well, I'm not going to open this one too much because it is pretty stinky, but there you go, Hannah.

Have a whiff of that.

See if you can identify it.

What's that?

Quite like that.

It's a bit like TCA.

What is that?

I recognise that.

It's like incense, but mustier.

Is it elephant feces?

Wow.

Yeah.

Incense.

I'm a moron.

Yeah, I liked it.

There we I was going to seal that one.

So that's that's elephant.

I mean, I have many questions.

Where do you get elephant feces from?

There's a company, well, I mean, that's what it claims that's what it is.

But I will say that I did have a student once who I was doing this smell test, and they had just come back from the zoo and they went, that's elephant poo.

Wow.

So there you go.

I did a TV program years and years ago, before I did anything for the BBC, where I had to go around to one of the big safari parks and collect tiger urine from the straw and sorry from the straw as in you i see not with a straw that's honest to god

honest to god that was what was going on in my mind uses of a straw that's pretty no no the straw that the tiger had weed and okay the tiger wasn't present during this but i feel like that was a low point in my uh i think it would have been lower if you had to collect it by hand with the straw and also probably terminal let's move on

so i'm not sure this is going to work you've got two smells here and i want you to see whether you can.

You're going to have to squeeze them a bit because they're getting a bit old.

Squeeze them as you smell them.

See if you can identify them.

Haven't you given me this one before?

No, no.

Are they the same?

Are they different?

Good luck.

They smell quite similar.

Come on, give us a go.

I'll do one nostril each.

That's confusing.

I can't smell the difference.

You can't smell the difference, okay.

Squeeze them.

Squeeze it.

Squeeze the bottle.

That's.

I've been a bit too hard there.

I got a bit of tissue in there.

I might sneeze now.

I mean, this is thrilling radio.

No, I can't tell the difference.

Oh, okay, right, it's failure.

Seal,

very careful.

I think it's going to be mint and caraway.

That's it.

He's got it in one.

So that is Wells Cumin.

Mint.

Yes, cumin.

Come back here.

So these are

mirror images.

The molecules.

I think I'm just smelling the plastic box.

I think you probably are.

The key point is that the molecules have got exactly the same composition, but they are like two isomers, they're two isomers, two hands of a glove.

And so one of them smells kind of hot, and the other smells kind of cold.

Oh, I can smell cumin now.

There you go.

And we've done chirality on the programme.

Yeah, we are.

They are.

So these are...

Identical molecules, but mirror images.

And your nose, those receptors, can detect that shape.

So it's not just an extra atom that you can smell, but also the orientation of the molecules produces a different perception in your brain.

I remember about

more than two decades ago when I went on a school trip and

the only thing I remember about it, I can't tell you where it was, I can't tell you what the school trip was about, but I remember there was someone there who said that actually the shape of the molecule changes how sweet it smells.

but specifically that like i think they were saying like hexagonal shapes end up being quite sweet is there anything in that?

The ancient Greeks thought that.

They were really convinced.

I mean, look, I am old, but I'm all out.

You know, you might have had a classicist alongside you in a school time.

That's what Democrit said.

So Democritus is the first atomist.

And he says, everything's made out of atoms.

I'm made out of atoms.

The Ritsina and Swilling's made out of atoms.

And then he started thinking about smells.

And so what he said was, well, something that smells sweet must have a round atom.

And something that smells unpleasant must be kind of pointy.

And that's still where we are today.

So there's some link between the shape, the molecular orientation, composition, structure of a smell and how we perceive it.

But what that rule is, what the rules underlying that, we don't have any precise detail.

And it's not as simple as smooth and spicy.

It's not, but if you think of it, we change into another sense because we struggle to describe smells.

So saying something is round makes you think it's sweet.

And also, notice that we use sweet as a description for a smell, but sweet isn't a smell, it's a taste.

If I give you a vanilla pod to smell, you'll say, smells sweet.

But then, if we cut a little bit off and get you to eat it, it tastes bitter, licorice-like, no sweetness in there at all.

It's because we combine the aroma of vanilla with things that are sweet, chocolate, ice cream, that's why we think it's sweet.

All right, well, thanks again to Barry and Matthew.

And we should also mention that there's a couple of charities that deal with

problems with smell, and they've received an enormous enormous boost in the last couple of years because everyone's been so aware of them.

And those charities are AbScents with a C in it and FifthSense.

And so, if you've got any issues with your smell, you should probably look them up.

Hannah, I'm gonna fill in for Hannah because she's eating the sweets that Matthew brought along with us.

It's now time for Curio of the week.

Fast and curious, occasionally spurious, totally geek chic,

Rutherford and Fries, Curio of the Week.

Okay, so we have two Curios of the Week in what is becoming a great tradition on this programme.

One of them is very short, and it is a musical performance of our theme tune.

This time from Evelyn Shaw, she's 10 years old, she lives in Australia.

And

here it is.

Evelyn, that is brilliant.

I think we know what that is as well.

Is it a carrot kazoo?

It's a carrot kazoo.

So,

listeners might remember that probably about five years ago, goodness only knows we did make the character.

I think I had at least two less children and more organs.

So, yeah, well done, Evelyn.

That's that's the carrot kazoo.

Uh, I think we need to retire the carrot kazoo.

Now, you are for our first curio of the week.

Now, the second one came in a package,

and I opened it and hasn't seen this yet.

And it contains two large wooden objects, and I have got no idea what they are.

Can I just show you?

Yeah.

Okay, so they look like they're wheels.

So they have,

they're beautifully round with epoxy resin, I think this is.

I think this is a wood and epoxy resin.

They'd be obviously put on a lathe.

And then there are one, two, three, four, five, six,

seven holes.

Is this a seven hole?

Hang on a minute.

Is this a wooden and epoxy resin seven hole donut?

Well, it certainly is.

Dear Adam and Hannah and the team, I've been a huge fan of Curious Cases since you first started broadcasting.

Well done, Gareth.

And he's training to be a carpenter.

And he's bought himself a huge wooden lathe.

Oh, my lord.

To learn how to make bowls for friends and family.

And then an idea occurred to me.

He says, whilst revisiting some of your earlier episodes, what better challenge than to make something that you've brought up a couple of times, Hannah?

I'm so excited.

Okay, but you know, do you remember that this is a human, the human form?

Seven holes.

Topologically, we're equivalent to this.

I literally have no idea what you're talking about.

Yes, look, mouth,

other end.

Anus.

Thank you.

We can say that.

Can we?

It's a biological.

I think only bum hole is allowing.

Okay, bumhole.

Bunghole.

Mouth's a bum hole.

Eyes.

Tear ducts.

Yeah.

In your eyes.

But the eyes aren't holes.

You do in your tear duct.

Oh, that is a tube, isn't it?

Yeah, eyes.

So you've got one.

Uh-huh.

One.

Nose.

Because you can go from one nostril through to the other nostril.

Yes.

Mouth.

Yes.

And then, I can't remember the other one.

Nipples.

Maybe nostrils too.

Is nostril two?

Well, wait.

In and out, in and out, innocent.

You can go from nostril to nostril and you can go from nostril to mouth.

So that is too.

So it's about five inches wide.

It's a disc and it's got seven holes in it, like a doughnut, and it's a topological version of humans.

Yes, exactly.

Do you know what?

In the Venn diagram of things that I enjoy, epoxy resin is up there.

As is mathematically profound and beautiful objects.

As is

things that mean stuff that is very niche.

As is free gifts.

And believe me when I tell you that I'm going to put this on my wall.

You will.

I'm going to do it at my house right now, and it's going to go on a shelf.

So, Gareth goes on.

He says, He's got his own YouTube channel, which is called Seven Driftwood.

And the video of your donut is the first item I've created in this way, and it's the first video to be uploaded.

I really hope you enjoy.

Hannah's googling it right now, and we're going to have a look at it.

I mean, it is absolutely lovely, beautiful craftsmanship, and some quite good maths, I suppose.

I don't know.

It's important.

You need to know, sometimes when I can't sleep at night, I literally spend hours watching videos like this.

I mentioned this before you met you.

When we did the ASMR video, you watch

lathing videos.

So here is

the first video that Garris upsloaded.

It's labelled The Curious Cases of Rutherford and Fry Seven Hole Donuts.

So far it's had 26 views.

So listeners, you know what to do.

Hannah, get a load of this.

Now you need to know.

Actually, because she's gone off into her special place now and won't be back for several hours.

We have now lost her for this episode.

So all that remains...

It's 18 minutes long.

I'm not coming back.

I will see you in 20 minutes.

All that remains is for me to say goodbye on behalf of me and Hannah and we'll see you next week.

Sucks!

The new musical has made Tony award-winning history on Broadway.

We demand to be home!

Winner, best score!

We the man to be seen!

Winner, best book!

It's a theatrical masterpiece that's thrilling, inspiring, dazzlingly entertaining, and unquestionably the most emotionally stirring musical this season.

Suffs!

Playing the Orpheum Theater, October 22nd through November 9th.

Tickets at BroadwaySF.com.

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