Q&A: Greedy Guts & Useless Numbers

27 March 2018

It’s Q&A Time! The Naked Scientists gathered a panel of experts to tackle your sci-curious questions; geneticist and food neuroscientist Giles Yeo, biologist and insect expert Chris Pull, material scientist Rachel Oliver and mathematician Bobby Seagull. So if you have any foodie thoughts, mathematical musings or an insect-ious thirst for knowledge, then this is the show for you. 

In this episode

Raw Vegetables

06:18 - Is raw food healthier than cooked food?

Genetists, Giles Yeo, crunched the numbers...

Is raw food healthier than cooked food?

Chris Smith asked geneticist Giles Yeo, from Cambridge University, to crunch the numbers on this question posted on The Naked Scientist Forum. 

Giles - I think it depends on what you mean by better for you. If you talk about calories, then it is true that cooking increases caloric availability. Briefly, caloric availability is how many calories you’ll get out of the food rather than as compared to how many calories are actually in the food, so 100 calories of sugar is 100 calories of sugar. But if you take 100 calories of sweet corn and you look in the loo the next day, you clearly haven’t absorbed anywhere near to 100 calories of sweet corn.

With regards to cooking: if you ate raw celery, that’s 6 calories pretty much for a medium stick of raw celery, whereas if you cook it, you get 30 calories just by cooking the celery. So, if you are looking to reduce your calorie intake then yes, cooking it you get more calories but if you don’t cook it then you get less. But then cooking also does a lot more: for example it kills parasites and also there are certain minerals and vitamins that are only made available from the food after you cook it.

So, I think the answer is from a pure caloric point of view maybe, but is it necessarily better for you? That depends.

Chris - So the whole argument about how many calories you burn off in your jaw muscles crunching things up, which is another consideration?


Rachel - I’d heard, actually, if you eat celery, you’re using up more calories eating it than you get from your stick of celery, is that really true?

Giles - No, no. It is a myth but it’s 6 calories per stick; it’s just barely a myth.

Chris - Is that 6 calories per stick how much you consume eating the stick or how much you obtain by eating the stick? When I say consume, as in how much you burn off eating the stick. How many calories do you need to munch it up?

Giles - It depends how many calories are in a stick of celery. It’s probably about 6%, broadly speaking, from eating a stick of celery compared to 100% when you eat 100 calories of sugar, for example.


08:22 - Why do I hate maths?

It's not *that* bad, Cambridge University's Bobby Seagull explained why.

Why do I hate maths?

This question came in from one of our very own Naked Scientist, Katie. Chris Smith put this question to Mathematician Bobby Seagull, from Cambridge University. Turns out, Katie's not alone, as the rest of our panel showed: that's geneticist Giles Yeo, material scientist Rachel Oliver and insect expert, Chris Pull. 

Bobby - No. She’ll join armies of people, sadly. Actually, being a maths teacher and not an english teacher I consulted Wikipedia to see what “hate” means and let me read you definition of hate. “It’s deep and extreme dislike, especially in working feelings of anger or resentment.” So that’s a strong word. It’s not dislike or it makes me a little bit queasy, this is like an intense feeling.

Chris - But lots of people have had the “double maths” feeling. Who here had double maths at school? I bet you all had double maths and who really really looked forward to it?

Rachel - I liked it.

Chris - You’re a material scientist Rachel. Maths is at the heart of everything you did. Did you like maths Chris?

Chris P - No, I hated it.

Chris - Giles?

Giles - Awful at it.

Chris - There you go. All the bio people in here, the biologically focused people..

Giles - Fluffy science we called it.

Chris - Yeah, the fluffologists like me and Giles and Chris, we’re in Katie’s camp Bobby.

Bobby - Yeah. There are different types of mathematicians. I think everyone here is probably competent at maths, but I think there’s one startling fact. I work with a charity called National Numeracy and they said that 50% of working adults in the UK had the numeracy skills of an 11 year old. They asked them to work out a 10% increase in salary. With or without a calculator, half the working population can’t work do that so that’s a really daming statistic of  where maths is in this country.

Chris - So what are we going to do about it?

Bobby - I think partly it’s cultural, partly it’s reputational, so I think it’s easy to trash maths again. If you go with your friends to the pub and have a drink and you say that you do maths, everyone starts patting each other on the back saying I couldn’t do maths at school, I was terrible. But if you said you couldn’t read, people look at you like - “what, you’re a cultural philistine - you can’t read!”.

Chris - They say that about opera don’t they? I’ve noticed that if you admit to not liking art or sport or opera or something, people will look at you like you’re some kind of cultural pariah. But if you turn round and say, I don’t like science, then people do actually laugh. They say, oh well you know, it’s all a foreign language to me. It’s interesting how there is that distinction.

Bobby - Again, I do there are elements of cultural aspects to this. I’ve got cousins who are living and raised in India and I’m ethnically Indian. I compare my cousins attitudes in India to my cousins in the UK’s attitude to mathematics and in India. When people do well at maths they seem to say “oh, you’re doing well at maths because you're working hard”. Whereas in England, if kids do well they attribute it to talent and flair. And I think as a society, as soon as we attribute mathematical competence to flair, it’s easy for the rest of us to say “oh, I don’t have any flair so I can never be good at math”.

Chris - Do you think, to a certain extent though, it’s down to the teacher? Because someone like you who stands up in front of a class, does a rap, engages the class, gets their attention from the get go like you’ve got all of our attention in here. You may just laugh and then begin to think that’s the critical thing isn’t it, we need more good teachers?

Bobby - Yeah. I think teachers definitely play a role, but also parents play a role. Again, at parents evenings: every time a mum or a dad says to their child “don’t worry, you’re failing at maths - I failed too”. So, as a society we need to stop accepting that maths failure is a good thing. We need to start saying “well actually, it’s not a good thing; what can we do to turn it around?”

Chris - It’s like the social norm. It’s okay to be a little bit on the large size these days? Giles, you’re nodding. I’m not saying you’re a bit on the large side. You’re interested in people who gain a bit too much weight and people have shown that the social norm has crept up that it’s okay to not worry about your diet so much as perhaps we did historically, and it’s the same with this, isn’t it?

Giles - Yeah, I think so. It’s because it’s acceptable and I say it, I’m equally to blame to say I’m terrible at maths. I hated it at school. Now, am I terrible at maths? I hope not otherwise I wouldn’t be able to end up getting a PhD. But you’re absolutely right: just in what we said, we have immediately painted ourselves into a terrible at maths corner, even though I don’t think we’re going to be terrible at it.

Chris - It’s not just maths things people hate is it, Chris? Because insects have a bit of a bad wrap too don’t they?

Chris P - Yeah, definitely. This is also probably quite psychological; I know my sister was terrified of spiders and I think that comes from my mum being terrified of spiders. I think it is this inherited cultural phenomenon but, at the same time, I do think some spiders and other insects evolutionary might have posed a threat to us, and maybe there is…

Chris - Malaria: hundreds of millions of cases a year. Dengue: 50, 100 million cases a year of that. The mosquito spread diseases so I suppose we have a reason to hate these things?

Chris P - Yeah, definitely.

Giles - Plus they’re hairy and scary.

Stacked dots

What's the smallest material we can build with?

Chris Smith put this question from listener Janet to material scientist Rachel Oliver, from Cambridge University. 

Rachel - Well the smallest building block of any material is an atom and I guess that’s the smallest thing you can build things with. You hear about splitting the atom; it’s totally true you can split an atom. But if you have a brick which is something you’re used to building things with and you split that brick, you kind of get two small bricks. If you split an atom into two pieces, it’s like splitting and brick and ending up with say two balls of cotton wool or something, you end up with something completely different.

So our smallest building block of material is a single atom and people do build things with single atoms. There are technologies whereby you can take a tiny tiny needle, really really sharp and essentially use it to push materials around. There’s some guys at IBM in the US, and they use single atoms on surfaces to build what they call quantum corrals. Now a corral, I guess is in old west terms is basically like a fence, so they build a fence out of atoms on a surface and you can actually look at pictures of them with every atom in a circle. They’re not enclosing little tiny cows, like a corral would have done in the old west, they’re enclosing electrons, which are negatively charged particles and then looking at how the electrons behave in that little fence they’ve built.

Chris - Why is it useful to be able to fiddle with atoms like this though? Is this actually going to help us in the future if we can engineer atoms in this way?

Rachel - Potentially. Everybody uses, I’m sure, laptops and tablet computers and all this kind of thing, and those computers have been getting smaller, and smaller, and smaller, and as they get smaller and smaller they get faster and faster. The reason the computing companies like IBM, Intel, anybody like that are really interested in building with atoms is they’re pushing the size of these little switches inside computers right down to the atomic scale; it’s a tough thing to do though. But there are, even now, companies out there who are developing industrial scale technologies building at the atomic scale.

Chris - Is it also relevant that - I think it was Chris McManus - who came on this programme; he wrote the book about being right and left handed and said that “asymmetry begets asymmetry”, so if you want to build something asymmetric you start with particles themselves that are asymmetric. So if you want to build a really strong component for a jet engine then you have to start with the right things in the right configuration down at the atomic scale so that you get something on the big scale that has those properties, it’s just amplified up to a big scale that we can see.

Rachel - Yeah. In terms of things like a jet engine you need exactly the right ingredients, but the metals that are used in jet engines they’re the important length scale there is very very tiny so down at what I would call the nanometre scale. People might be more happy in millimetres and a nanometre is like a millionth of a millimetre, and you have to engineer the structure of that material right down at that scale in order for the jet engines to work. The thing that’s tough about jet engines is that they have to keep working at really really high temperatures, and you can’t let the material get longer, expand by even very very small fractions at those high temperatures otherwise the blades of the jet engine will start bumping into the casing and the aeroplane goes slightly bang, which is not really what you want.

Chris - The claim that’s made by companies that make and engineer these jet engines is that the gas stream that’s running through the middle of that engine is about 1500 degrees centigrade. And the materials that the engine itself is made of will melt at less than that temperature so you’re actually containing and constraining and using a gas stream that’s at more than the melting temperature of the thing you’ve made your engine from and you have to engineer it to withstand that, which is just phenomenal work really, isn’t it?

Rachel - Yeah, it’s amazing. And there are different ways that materials can deform and expand and change shape, and some of those we have to worry about at normal room temperature, but some of them only start when you get close to the melting temperature. So that means that you have to really be very clever about how you engineer stretches right up at those very high temperature.

Ant near a white flower

17:18 - Are ants telepathic?

How do they know if their queen dies?

Are ants telepathic?

We had this question sent in from Caitlin in Nottingham. Chris Smith put it to ant expert Chris Pull, from Royal Holloway University. Material scientist, Rachel Oliver, then had a colony query of her own. 

Chris P - Well, to be honest, it’s not a far cry from what they’re able to do. I guess if telepathy is being able to sense someone’s emotions or their internal state of what they’re thinking, ants kind of do have a way of being able to do that. They use chemical smells - pheromones and queen’s emit what we call a queen pheromone in the colony. What this pheromone does is it tells the workers in the colony that she is the queen. And it has another role as well so it acts as an infertility sort of signal so it suppresses the ovaries of the workers and stops them from reproducing. So, if the queen dies, she obviously stops emitting that signal and that’s how they are able to tell whether or not the queen is present any more and the workers themselves can start laying eggs and try to get some reproduction.

Chris S -  Is that what happens: if the queen is lost for whatever reason, will a new queen emerge from amongst the ranks if you like?

Chris P - It really depends on the species, but in your average ant then generally no, so the queen once she’s lost, she’s lost. And in bumble bees as well, once she’s lost, she’s lost.

Chris S - So what happens to them? What happens to the colony, does it just sort of go into anarchy or something?

Chris P - Again, it depends on the species. If it’s a species where workers are able to still lay eggs, then they can lay male eggs. They haven’t been fertilised so they’re not able to make males or females but they can lay male eggs which will disperse and mate with another queen, so it’s an opportunity for, if the queen dies, a second resort for the workers to get some reproduction in.

Chris S - Ah. So the genes live on even though the colony itself maybe the end of the road for them? Rachel?

Rachel - If they’ve made some great structure that they live in, in the end does everybody in that one die and then that’s left empty? Is it just left forever or does another team of ants move in?

Chris P - As I said, the workers can only produce males because they haven’t been mated and without the queen there producing more workers then, obviously, the colony eventually just dwindles; the workers die off and that residence is empty. In honey bees you might get colonies moving in and trying to utilise that space. In ant colonies, because they’re just made out of soil they’ll eventually collapse or another colony might use it.

Box of tissues

19:44 - Are vaccines bad for you?

Caller Richard had a question for our own Chris Smith

Are vaccines bad for you?

Chris Smith took on this infectious enquiry from caller Richard. 

Chris - First of all, thank you for an interesting question Richard. The flu vaccine in an average year is about 75% effective. Now what that means is that if you take an average person, with an average dose of flu, and an average dose of flu vaccine, they’ll be protected 75% of the time. But flu isn’t just one single entity, there are many different strains of flu. There’s two different types of flu A: there’s H1N1 swine flu and there’s also H3N2, and there’s also another form of human flu called flu B. All of them can cause epidemics and all of them are represented in the vaccine. All of them continuously mutate and change and, therefore, you have to update the vaccine year on year on year. You have to keep having the vaccine every year in order to make sure your immunity stays current.

Now, the other problem with this is that not every years the vaccine is 75% effective. Some years the vaccine may not be as effective as others. This year has been a particularly bad year for the flu vaccine. In fact, one of the types of flu that was in the vaccine - the B strain - didn’t actually work at all because the virus had mutated. And changed and the other type of flu A - the H3N2 - that was in the vaccine, that didn’t work very well either; it was about 20% effective for various reasons.

So, therefore, people who had had the flu vaccine this year were protected against one of the circulating strains but not the other ones. And that meant that they might go around thinking that they’re protected from flu and it’s not going to be a risk for them and for anybody else and, therefore they’re more likely to be spreading flu.

There was an interesting study that got done by the British Medical Journal about 10 - 15 years ago - it got published in the British Medical Journal - and what they did is to ask people “have you had flu this winter?”. And then they took samples from those people and tested their blood for antibodies against the flu and what they found is about half the people who said they didn’t have flu that year, had had flu as proved by the antibodies that were in their bloodstream.

In other words, you can probably get people who have a low level infection with flu. They don’t know that they’ve got it. They don’t feel ill because they’ve got partial immunity to the flu but they’re nonetheless fully infectious and they go about their business potentially infecting other people and spreading flu around, and they don’t know they’ve done it.

One the whole summarising: flu vaccines are very good; they’re money well spent; they do save lives and the help to protect patients in hospitals and care homes and they help to protect kids in schools. They help to protect people with serious illnesses like diabetes, kidney disease, heart disease and so on. But, at the same time, we have to make sure everyone has one because otherwise you’re leaving a gaping gap in our defences. And anyone who hasn’t been vaccinated then catches the flu and then they’re fully infectious and they give it to other people.

So it is effective; we do like the flu vaccine but, at the same time there has to good compliance and uptake in the population or it’s not going to work.

Birthday Cake

22:54 - What are the chances of sharing a birthday?

Mathematician Bobby Seagull stuns us with stats.

What are the chances of sharing a birthday?

Chris Smith asked mathematician, Boby Seagull, to breakdown the birthday paradox for listener Liz. 

Bobby - You might think that the most recognised song in the world might be a Stormzy rap or a Taylor Swift song, or Ed Sheeran who seems to be everywhere all the time. But actually, according to the Guiness Book of Records, it’s Happy Birthday which is the most recognised song in the English language. So it’s only appropriate that the birthday paradox is something which is important to maths.

So the question is: what’s the minimum number of people required, let’s say in a room, for the chance of two people sharing the same birthday be more than 50/50, and obviously it means the same day and month, not the year.

Chris - Shall we ask the crew? Giles, what do you think?

Giles - 50/50?

Bobby - The chance of two people in a room having the same birthday being more than 50/50; how many people do you need in a room to guarantee there is more than a 50/50 chance.

Giles - Oh my goodness. About 180 people.

Chris - Chris?

Chris P - About 250.

Rachel - I reckon it’s quite low. Maybe 30.

Bobby - Rachel’s pretty close. Intuitively we seem to think it’s quite a high number but actually it’s 23 people. With 23 people, mathematically, the chances of two people in that room sharing the same birthday is slightly more than 50%.

Chris - Are you going to show your working as all good students should?

Bobby - We’ll try to. This is one of the things where, with a whiteboard and paper this is quite easy to demonstrate, but without we’ll try. A good analogy is…

Chris - I’m going to write this down as you go.

Bobby - Let me just give you an analogy first before you start. One way to think of it is imagine a 365 sided dice and after 23 throws you’re more than likely than not to get two of the same numbers the dice land.

Chris - Where does the 23 number come from?

Bobby -  The 23; we’re about to get there now. Step one: the probability of two people sharing the same birthday in a group is 1 minus the probability of no-one sharing the same birthday. So we’ve got that yet?

Chris - Right.

Bobby - So it’s 1 minus the probability of no-one sharing it. So let’s work out the probability of no-one sharing the same birthday. In a group of 2 people, firstly it’s 365 out of 365, that’s essentially the first person can be born on any day. Then you multiply that by 364 out of 365. I’ll explain the second fraction. That second person can be born any day apart from the first day that the person…

Chris - That you’re born in, yeah?

Bobby - Yeah. So that’s the 364 choices; that’s for 2 people. If we expand it to 3 people now we’ve got one less option so that original multiplication we multiply that 363 over 365. If you keep on doing that, adding 362 over 365, all the way to 23 people at this stage you get this multiplication to be 0.493. If you cast your mind back a minute…

Chris - You wanted 50/50?

Bobby - Yeah. So it’s 1 minus that. So once you get to 23 people, the chance of....

Chris - 51%?

Bobby - Yeah.

Chris - Rachel’s going to dispute your maths now.

Rachel - No, I’m not. I’m just going to point out I’m not nearly that clever but I am basically an engineer by training. So my pragmatic version of answering the question is that I know that in a typical school class, you quite often get two kids sharing the same birthday, so therefore 30 was a good guess from that point of view.

Chris - That’s the benefit of wisdom see.

Rachel - So no maths really, just common sense.

Bobby - On the birthday paradox, if anyone’s a football fan here?

Chris - Giles, you look like a footballer. Are you not a football fan?

Giles - American football fan.

Chris - Chris, are you a footballer?

Chris P - No.

Bobby - Can you indulge me on my football related birthday paradox?

Chris - Go on then.

Bobby - We’ve got the World Cup coming up and this is a great test ground for the birthday paradox. Because, coincidently, the number of people in every World Cup squad is 23 people and there are 32 squads in the World Cup. So if people want to test if this theory is true, I think the World Cup squads get announced on the 4th June. Go on the FIFA website that day and check up all the squads - be a nerd like me - and see how many squads. And in the last two World Cups, I think in the 2014 World Cup there were 16 squads out of 32 that had 2 people sharing the same birthday. And the World Cup before, there were 15 out of 32, so just under 50%. So it does work.

Chris - I’m guessing, but I think people will be looking at the FIFA website for reasons other than who’s got a birthday in common.

hanging lightbulbs

Can we use light to store information?

Chris Smith asked material scientist Rachel Oliver, from Cambridge University, to light up an answer for Helen on Facebook. 

Rachel - That’s a really cool question. Storing information with light is actually quite hard because storing light; keeping it kind of stable in one place is difficult. But transmitting information with light is something we do all the time. You can take this back a really long time, so I guess, even in ancient times people used fire to send signals. And certainly in Elizabethan times, there were these beacons set up all round the country which were there to be lit if they saw an invading armada coming from Spain. Eventually they did and they lit their beacons and warned London and Dover of what was happening and what they needed to do.

In the modern world: you hear adverts on the telly for superfast fibre optic broadband. That’s a slightly more sophisticated way but it’s basically sending pulses of light down long thin pieces of glass to send information about the internet.

There’s the question: how small can we go with light? How little light can we use? We talked before a little bit atoms as the smallest piece of a material you can have. The smallest piece of light you can have is something called a photon: it’s what we call a fundamental particle of light and it’s a really amazing thing. We can actually do experiments which show that light is a stream of particles and, at the same time, light is also a wave which sounds completely contradictory, and we can transmit, store, or move information on a single photon. Interestingly, you can think of photons not just as being particles, but a point in a specific direction; that’s the property of the light called its polarisation. For example, a light putting up is a one light pointing sideways as a zero would work and then you can transfer information like that on a single photon. The tiniest possible particle of light.

Chris - In essence, this is how we’re transmitting data at terabit rates all over the world now and fibre optics for the internet isn’t it? That’s how programmes like this are streaming all over the world at the moment?

Rachel - Yeah. We’re not using single photons yet. We’re using pulses with lots of photons in. That’s partly because when it goes down the fibres, quite a lot of the light gets absorbed into the glass, so if we only send it on single photons, we would lose out. But there are schemes for using single particles of light to transfer information perfectly securely so you can use it then to basically keep really really valuable information very very safe. There’s even then schemes for how you deal with the fact that you lose large chunks of photons down your fibre that gets absorbed into the material.

Giles Yeo's gut

30:32 - Getting quizzical and spilling guts in the studio...

Our panelists go head to head and a lifesize (knitted) gut is passed round the studio.

Getting quizzical and spilling guts in the studio...
with Giles Yeo, Chris Pull, Rachel Oliver, Bobby Seagull

Our panelists battled head to head for the Q&A Big Brain Quiz. Team One was mathematician Bobby Seagull and geneticist Giles Yeo. Team Two was material scientist Rachel Oliver and biologist Chris Pull. 

ROUND #1 - What happened first?

Team One - Bobby and Giles

QUIZ Q1 - Which happened first: The year that Fluorine was discovered? Or the only draw in the history of the Oxford-Cambridge boat race? What do you both think.

Bobby - Boat race started about 1880s.

Giles - I think so it’s the 160th birthday.

Bobby - Yeah. So fluorine must have been discovered. Is it fluorine?

Giles - Fluorine.

Bobby - It must have been discovered before.

Giles - We’ll go with fluorine.

Bobby - Yeah.

Chris - So you’re going fluorine was first?

Giles - Yeah.


Chris: I’m sorry to say the only draw in the history of Oxford Cambridge boat race history occurred in 1877. Fluorine was discovered 9 years later in 1886.

Chris: Over to Team Two - Rachel and Chris

QUIZ Q2 - Which happened first: The invention of a catapult, or the first use of negative numbers?

Rachel - The catapult: it strikes me as something kind of medieval.

Chris - Yeah.

Rachel - People throwing rocks at castles. Negative numbers: do we think the Romans could do negative numbers? They understood about zero - maybe the could do negative numbers?

Chris - I feel like numbers have been around a really long time.

Rachel - Numbers have been around a really long time. We’re going to go with negative numbers.


Chris - Did you know that Bobby?

Bobby - I was thinking of negative imaginary numbers, not negative integers.

Chris - The answer is the catapult. That first came about in 400 BC, whereas negative numbers were used in the Han Dynasty in China from 200 BC.

So both teams are doing very well at the moment. Your net score is zero.

ROUND #2  - What’s bigger?

Chris - Round two is appropriately named “what’s bigger?”... Hopefully your score by the end of this round! Back to

Team One - Bobby and Giles

QUIZ Q3 - Which is bigger: The lifetime of an adult house fly or the time taken for the Apollo astronauts to reach the moon?

Bobby - How long does it take? Three days, four days to reach the moon.

Giles - It took three days or four days. The average house fly right? All the way from maggots or are we doing the fly-y bit?

Chris - No we’re doing the fly-y bit.

Giles - Oh, just the fly-y bit. I think we’re going to have to go with the moon. Because if you include the maggot stage then it’s definitely longer.

Bobby - It’s just the flying annoying part.

Giles - Yeah, just the fly annoying part. So we’re going to go with the moon.


Chris - Lifetime of a fly. An adult house fly lives for 2-4 weeks; it took the Apollo team about 3 days to get to the moon. The New Horizons Pluto probe, launched in 2006, did it in just 8.5 hours...

TEAM TWO - Rachel and Chris

QUIZ Q4: Which is larger: The average length of the small intestine or the length of nose hair grown by a human over a lifetime?

Rachel - I know that the small intestine is surprisingly long.

Chris - Yeah.

Rachel - But I have no idea how much nose hair a human grows in a lifetime.

Chris - Something like a few millimetres a day. Not a day.


Rachel - It would be like down to our feet quite quickly. How long your hair is also depends on how often your hair falls out but I’m also not sneezing that much nose hair.

Chris - I know that as men get older it grows longer right?

Rachel - It does but do you get quite hairy.

Chris - Sprouting it like yeah, so.

Chris S - Sincere apologies to our older audience. What are we going for then nose hair or small intestine?

Chris - I think it must be nose hair because so far the obvious answers have been the wrong ones.

Rachel - Okay. I got the last one wrong so let’s go nose hair.

Chris S - Giles do you know the answer to this one?

Giles - I did not know that. I know the gut is pretty long but I have no idea about nose hair growth.

Chris S - I think you should get out what you’ve got in your bag under the table.

Giles - What I have got with me is a life sized knitted gut.

Chris S - Who knitted this Giles?

Giles - This is knitted by a consortia of professors and secretaries and research managers at the Institute of Metabolic Science. This is a life size knitted gut, also known as the “food to poop tube.” This is the mouth bit.

Chris S - Oh that’s fantastic.

Giles - Then if I can hand it around so.

Chris S - I’ve got the anus. I’ve got the tongue - that’s okay.

Giles - There we go, that’s the size.

Chris S - Goodness this is huge. It’s all the way round the studio. I’ve got the tongue at this end, and esophagus and then what’s this bit? This is the stomach is it?

Giles - That’s the stomach and attached to it will be the liver, the pancreas, the gallbladder.

Chris S - A green gall bladder: it’s all colour coded as well. It’s great. Because bile really is green isn’t it. It comes up the gallbladder then into this first bit of the small pink tube. What’s that?

Giles - This, the whole thing is the small intestine where all of the digestion actually happens. Depending on how far down the food goes is how long it takes to digest, and the further down the food goes, the fuller you actually feel.

Chris S - So before it breaks down?

Giles - Before it actually breaks down to its constituent parts to be absorbed, the longer that takes the fuller you actually feel.

Chris S - What should I be swallowing to get as much food as far as possible down my small intestines so I feel as full as possible then? What’s a good foodstuff to do that?

Giles - One thing is actually protein. Protein to fat to carbohydrates in that order takes the longest to digest. That’s how the Atkins diet works for example. When you eat a lot of protein in the Atkins diet, so much of it travels further down the gut, you get fuller, you eat less, you lose weight. 

Chris S - On that note, if you are intrigued as to how long the intestine really is. The average length of the small intestine, including Giles’ knitted gut, is 6 metres. But over a lifetime, on average, a human will grow 2 metres of nose hair.

ROUND #3 - Science Fact v Science Fiction

Chris - Over to Team One - Bobby and Giles

QUIZ Q5: True or False: Ants have two stomachs?

Bobby - Cows have two stomachs.

Giles - Cows have two stomachs.

Bobby - Why would cows need. Cows have two stomachs because they eat grass.

Giles - Right. So they need a rumen in order to ferment the grass.

Bobby - What do ants eat?

Giles - Grass.

Bobby - Grass. So they would probably need.

Giles - I’ve eaten the bottom on an ant in Australia once. It was very, very…

Chris - That’s a lemony flavour isn’t it?

Giles - Very lemony flavour, yeah yeah.

Chris - Slightly off topic here though. What’s the answer to the quizz?

Bobby - Do you reckon it’s true?

Giles - I’m going to go with true.

Bobby - Shall we go with that? Our finals answer’s true.


Chris - It’s true, they can have the main course and the “anty-pasta”. No, but really, one of their stomachs is for holding food for their own consumption, whilst the second one is to hold food to be shared with other ants. This process is known as trophallaxis.

Chris - TEAM TWO - Rachel and Chris, it’s a pressured moment of you.
QUIZ Q6: True or False: Triskaphobia is the fear of the number 30.

Rachel - He’ll know that one. Trente is French for 30 but is there really a word for the fear of the number 30? I don’t know what else it means though so what do you think?

Chris S - What do you think true or false?

Rachel - I’m going to go true.


Chris - Oh wait, sorry. It’s this…


Chris - I pressed the wrong button. It’s actually false. It’s actually the fear of the number 3!

Chris - Would you like to hear the tie breaker because it’s quite interesting

To the nearest 10, how many multiples of their own body weight can a dung beetle move at one time?

Chris - I’ll ask you one at a time so you can all speculate. It’s quite amazing this and we’ll come to Chris last because he’ll probably has the best chance of getting it right.

Giles, what do you think? Dung beetle; how much poop can they move in one go?

Giles - A hundred times.

Chris - Giles is going a hundred. Bobby?

Bobby - I’ve written down 200.

Chris - Bobby’s going 200. Are we going up? Can you see Bobby’s 200 and raise him at all Rachel?

Rachel - No, I’m going to go 30. I think it’s a good number.

Chris - 30. Chris?

Chris P - Yeah. There was just a talk on and I’m trying to remember what she said.

Chris - It was a good lecture.

Chris P - Yeah. I’m going to say 50 times.

Chris -  1,140. A dung beetle is not only the world’s strongest insect but also the strongest animal on the planet compared to body weight. They can pull 1,141 times their own body weight.

Chris - They follow the stars to work out which direction they’re going?

Chris P - Not quite. They can’t quite see the light from the stars; it’s not strong enough, but they can see the the Milky Way. That’s bright enough for them to navigate by.

Chris - And they use that to roll their ball of dung in the right direction.

Our big brains of the week: Giles and Bobby had one point. You only got one right. Before you celebrate too much.

And ours losers, but nonetheless they redeem themselves by knowing a bit more about dung beetles was Rachel and Chris.

Girl eats milk and cereal

41:12 - Can food allergies be inherited?

What's the difference between allergy and intolerance?

Can food allergies be inherited?

Chris Smith asked geneticist Giles Yeo from Cambridge University to break down this question from James in Oxford.

Giles - The answer is yes, but it’s more complicated than that. The first thing I want to do is that there’s a big difference between “intolerance” and “allergy.” An intolerance is almost like you can be lactose intolerant because you lack the enzyme to break down lactose. An allergy is when you have an immune response to the protein within milk, for example, for milk allergy. An intolerance can be inherited and that’s almost going to be mendelian. So, for example, because a very specific gene needs to break down alcohol and needs to break down lactose and that’s inherited. Allergy is more complicated because it’s an immune response. So while there is a genetic element to it, it’s not like Mendel's peas. You can’t say for sure if my parents were allergic then I’m going to be allergic, so there is a genetic element to it but it is not mendelian. So, in other words, it’s not for sure that you’re going to inherit it if your parents happen to be allergic to a given product or item.


Could we store light forever?

Chris Smith asked materials scientist, Rachel Oliver, to shine a light on this question from listener R. Middleton...

Rachel - The difficulty is storing the light without absorbing it; so you can do that in a thing called a "cavity". In the simplest sense, a cavity could just be two mirrors and you reflect the light backwards and forwards, and backwards and forwards. We can make cavities that will store light, but probably not for very long, so fractions of a second might be the amount of time that we could store a single particle of the light that I was talking about earlier. So you can store information in the form of light and there are ideas for using that, but the problem is the storing part not the information part.

Chris - So if you had a box which is entirely mirrored on its interior, and you put some light in there, would it not just ricochet around forever in the box?

Rachel - Your problem is the "entirely mirrored". You don’t ever manage to make a mirror which is 100% reflective that always bounces back the light. They’re always going to absorb some of the light as well, or some of the light's going to leak out of the box. So, in your theoretically perfect mirrored box, yeah you’re doing great. But actually making one of those is so difficult that the word "impossible" is probably quite relevant!

Race track

43:45 - Why do we count in tens?

Is there a better number to count in?

Why do we count in tens?

Chris Smith asked mathematician Bobby Seagull, from Cambridge University, to drum up an answer to Tim's question on Facebook.  

Bobby - Good question. Demonstration: put your hands up, count how many fingers you have - digits. There we go. I’m hoping all of us have ten.

Chris - What about toes?

Bobby - Yeah. You could do. The reason we count in tens historically, is because we have ten fingers. But other cultures, other civilisations use different things: Aztecs use 20, the Babylonians have used 60. There’s some indigenous groups of people in South America who use 3 or 4. And again, if we happened to be based in the Simpson’s land, Homer has eight fingers so he could equally count in base 8. So really it’s just a quirk of our ten fingers being there.

Dragonfly on leaf

Why don’t insects grow as big as dogs?

Chris Smith asked biologist Chris Pull from Royal Holloway University to expand on this question from Heather on Facebook. 

Chris P- The largest insects today are about 18cm. A few years ago, there was a stick insect in China which was actually 60cm long. Back in 500 million years ago there were insects the size of seagulls flying around. There was a…

Chris S - The size of Bobby Seagulls?

Chris P - Haha. There was a dragonfly which was flying around, and you had millipedes, which obviously aren’t an insect, but they go grow up to 2 metres long. The prevailing theory is that back then there was just a lot more oxygen in the atmosphere, and because they breath passively through the networks of air filled tubes, the larger you get, the harder it is for that defusion based respiration to work. It’s kind of like if you were to snorkel near the surface it’s easy for you to get enough air, but if you were sitting on the bottom of a swimming pool with a 3 metre long snorkel, you could imagine how much harder it would be to get enough oxygen and enough CO2 back out. That’s essentially why we think insects are limited because today the levels of oxygen are much lower than what they have been back in very ancient times.


45:50 - Will nanobots destroy the world?

Do we need to start panicking, or what?

Will nanobots destroy the world?

Chris Smith put this somewhat apocalyptic question to material scientist, Rachel Smith, from Ted on Facebook. Starting with, what is a nanobot? 

Rachel - This, I think, comes from an idea which was originated by a guy called Eric Drexler who is one of the fathers of nanotechnology. Nano is this millionth of a millimetre length scale and Eric Drexler came up with the idea of these tiny little robots that he hoped would be really useful so they could essentially make things for us on that tiny scale. He thought well, what you need is the robots to be able to make more robots, and then they can make more of the useful things.

But then he started to worry about maybe if the robots can make more of themselves, then they can make more and more of themselves, and kind of eat up everything of the lab they’re in. Then having eaten the lab they’re in sort of set off across the city consuming, and as there’s this idea of the grey goo where everything in the world gets turned into nanobots.

Having said all that, I should probably reassure your listeners that I don’t think it’s very likely to happen. In terms of stuff that scientists can make at the moment, we’re talking about things that don’t self-replicate, they don’t re-make themselves. But they can self-assemble; they can build themselves in the first place. Those sorts of processes: they‘re workable - we do them in my lab. But you have to provide very much exactly the right ingredients and exactly the right conditions. By which I might mean the temperature or the pressure, those kinds of things.

So with current technologies I don’t think we need to be scared at all. However, it would be stupid to say oh, this is physically impossible, because we know about self-replicating entities, but what we’d have to design deliberately is something that comes with its own powerpack. That is completely adaptable to all sorts of of different environments, too different chemical sort of species being available that also carries all the information it needs in itself. And yeah, we’re starting to design life, and life did evolve but it took quite a long time for life then to start from some kind of puddle on the barren Earth and turn into what we have now. And it’s not turned out to be grey goo so I think we’re probably safe.


48:03 - What's the most useless number?

It's like the reverse of asking a parent to select their favourite child...

What's the most useless number?

Chris Smith asked mathematician Bobby Seagull, from the University of Cambridge. Surely all numbers are precious to a mathematician?

Bobby - Asking a mathematician what is the useless number is always the reverse of asking a parent to select their favourite child but if we must, we must give an answer. Let’s take a time machine back to 16th century Italy. Let’s go to Lombardy and let’s meet Gerolamo Cardono. This mathematician was a polymath; he actually did biology, physics, chemistry, philosophy, writing. He even had a dabbling in gambling. And he was looking at solutions to cubic equations.

For our listeners: we have linear equations, like the straight line like my rap: y = mx = c. Then we’ve got our quadratics: that’s x squared - looks like a smiley face. And then the cubics where it’s an x cubed type graph. He was looking at solutions for these. He came across some solutions which were imaginary. An example that he gave was: what happens when you expand (5 + sqrt(-15)) and you multiply that by (5 - sqrt(-15))

If you can mentally picture that, you multiply the 5 and the 5, so a double bracket expansion boys and girls, you get 25.

Chris - Giles has done it already!

Bobby - So you get the 25 there so we get a minus of 5 lots of root minus 15. We get the opposite a plus 5 lots of root minus 15 so they cancel out. At the end we get minus lots of the root of minus 15 squared. So now we’ve got 25, we’ve got a minus, minus 15, so that gives us 25 plus 15 gives us 40. So what Cardono said was, in italian… I’ll do it in English “Thus far does arithmetical subtlety go of which this, the extremes as I have said, so subtle, that it is useless.”  So he thought that the minus squared of 15 imaginary number was useless. But interestingly, over time, imaginary numbers became very useful.

Who’s planning on going on a holiday this summer?

Chris - Pretty much everyone I think.

Bobby - Taking a plane I guess? Actually, air traffic relies on radar, and radar uses complex computations where they distinguish stationary objects and moving ones and for this they use imaginary numbers because it makes the calculations a lot more manageable than if you just had straightforward, standard, real numbers. So there you go, imaginary numbers are real and not as useless as Cardono thought.

Chris - So there are useless numbers but they’re not really useless?

Bobby - Exactly.

Woman asleep

50:33 - Why can't I hear myself snore?

But I can CERTAINLY hear my partner snoring!

Why can't I hear myself snore?

This question came in from caller Stan. Luckily, Chris Smith was able to dream up an answer. 

Chris - Brilliant question. The answer is Stan that when you go to sleep your brain diengates a lot of the flow of sensory information coming back into it. A good example of this is why you don’t act out your dreams for example. We know that we all dream; we do it every night and we dream many many times a night. Probably about 20 times a night you have a dream, but you don’t find yourself stalking people round your house, jumping out the window, that kind of thing because there is a specific structure in your brain stem, which is called the sub-coerulea region. And when you go to sleep and start to dream, this activates, and it disengages the flow of information coming back out of your brain to tell you muscles what to do, and it also damps down the flow of information coming up your spinal cord coming into you. So you’re effectively disengaging your sensitivity to the things that you do yourself.

There’s also another region of the brain which is where what’s called the parietal lobe, and the occipital lobe, and the temporal lobe all meet this area of the brain. This has a strong ability to suppress any sensory information coming into your body. You can’t tickle yourself, for example, because this area knows that you’re about to tickle yourself and it says to your brain, to your consciousness, in a minute I’m going to tickle myself. When you feel the tickle sensation coming in it won’t surprise you; you’re expecting it, and because you’re expecting it it doesn’t arouse you. It’s the same with your snoring. You’re making those noises yourself; you’re suppressing your own sensory system so you are not aroused, or woken up, or stimulated by that sensation. But when someone else does it, because it’s unpredictable and unexpected, we notice it.

Box of Donuts

52:26 - Why does food make me happy?

Geneticist and Neuroscientist Giles Yeo was able to cook up an answer...

Why does food make me happy?

Chris Smith asked neuroscientist Giles Yeo, from Cambridge University, to cook up an answer and Rob in London. 

Giles - I think, first of all, we feel happy when food arrives because the anticipation of food and when the taste of food will tickle a set of neurons in the brain that releases dopamines that makes you feel happy. Now why would this be the case?

You eat, I think, primarily to fulfill a metabolic need, so that is I’ve burned a thousand calories I need to eat a thousand calories. The problem is that you need to eat more than a thousand calories - say 50,000 years ago in the Serengeti - because you’re not guaranteed your next meal. So what happens if you have to eat more than you need to buffer against the time when you actually don’t have enough food. In order to make your body fight the ‘I’m slightly full’ feeling to eat more of the chocolate cake when it arrives, for example, it makes the chocolate cake taste so good.

It’s the so-called dessert tummy. Dessert tummy is actually in your brain. The dessert tummy are actually the dopamine neurons in your brain making the chocolate cake taste good so that you’ll continue to eat it even though you’re stuffed with 2,000 calories of venison.

Chris - That’s the making room even though you’re full feeling? That circuit in process when you say to the kids eat your greens and they say, “No, I’m full”, and then you say “would you like some chocolate cake for afters?”. And they suddenly have room for it. That’s that system?

Giles - It’s that system and the key thing there as well is caloric density. For example, when you’re actually thinking about eating your greens, and because they're packed full of fibre the number of calories for every given gram of celery - as we talked about is not that high. Whereas chocolate, which is high in fat and sugar, then for every given gram you get a lot of calories which means that you can stuff them in all the little areas of your full stomach to make sure that you eat as much as possible. But the problem is there came a time when there was feast and famine. The problem is this has become toxic in our feast environment and part of the problem with obesity today.

Chris - And just finishing the show where we began Giles, you began and I took you to task about Monster Munch and things - I was just kidding. But how is the vegan diet working out for someone who normally eat a normal western diet and you’ve put yourself on this vegan diet regime? How’s it working out?

Giles - It’s very interesting. I can’t eat enough and so I’ve dropped half a stone in three weeks.

Chris - I was going to say you do look like you’ve lost a bit of weight. Are you saying you cannot physically eat enough to feel full?

Giles - Ah, no. So what happens is I get full when I’m eating, but the food I’m getting full on is calorically less dense, so lentils and celery or something. I’m just eating the stuff where I’m mechanically full, but because I’m getting less calories out of it, then I get hungry quicker. I don’t tend to be a grazer; I don’t tend to snack a lot and so I’m getting into caloric deficiency.

My wife’s very excited about this that I’m losing weight, it has to be said. So it is very interesting for me I have to say and so I have lost the weight even whilst not cutting down on my food. I’ve been eating: I’m going to go home tonight and I’m going to have a great big bean burger, but I’m going to feel hungry later in the evening because I can’t eat pudding. I can’t have apple pie; I can’t have anything with eggs or butter in it, and I’m not going to be able to have pudding to get my dessert tummy to tickle my dopamine neuron.

Chris - How have you coped with it? Because a lot of people say when they change their diet quite radically all of a sudden they find that they do not feel right for a while. Probably because their microbiome is a bit upset and they’ve tuned their microbiome to eating what they normally eat, and then they suddenly make a diet switch and they say it takes a while to settle down. Are you coping okay with the total diet switch?

Giles - I’m coping okay. I have to say that the first week, week and a half, I realised I’m only a few weeks in and I got a bit ‘windy’ shall we say, but the windiness has gone away. So no, there was definitely an adaptation of my gut microbiome to this drastic change in my diet.

Chris - Do you think you’ll carry on doing this afterwards or are you going to be so glad to get back to a bacon sandwich?

Giles - There are a lot of people out there who are getting all ready to be offended by me doing this, but the reality is I think I’ll probably stick to vegan two or three times a week. I think it’s been good. I do think I eat too much meat - I do. And now that I’ve actually spent nearly a month learning vegan recipes, I’m excited and I’m not as scared to cook the food. I think two to three times a week vegan is something that I probably will stick to.


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