Naked on a Punt!

28 August 2018
Presented by Chris Smith, Georgia Mills.

Join the Naked Scientists for a leisurely ride on a punt, past Cambridge's picturesque riverside colleges.  At each stop the boat picks up some of the brightest brains from the University and hear about their cutting edge ideas, from fraud-preventing holograms to driverless punts. Plus, the team find out it's not always the best idea to perform chemistry on your drink supply.


In this episode

The truss structure of the Mathematical Bridge

04:13 - The bridge that Newton didn't build

What makes the infamous Mathematical Bridge so special?

The bridge that Newton didn't build
with Max Thompson, Rutherford's, & Graham McShane, University of Cambridge

The Mathematical Bridge in Cambridge is famously (and incorrectly) said to have been built by Isaac Newton. But the structure itself is of interest to engineers, like Graham McShane, as it has very useful properties for things like bike helmets. First, Rutherford's punter Max Thompson tells Chris Smith about Queens' college.

Max - At the moment we’re at the mill pond area as you mentioned. It is one of the major hotspots for punters to have their tours begin. But we’re also next to Darwin College just over there. One of the newer colleges on the river, of course named after Charles Darwin. And then to my right hand side we have the old Anchor pub as well, formerly known as the Jazz Club and it was actually where a small band you may have heard of, Pink Floyd, played their very first gigs back in the 1960s when Syd Barrett was the lead singer.

Chris - We’re now going under the bridge. This is the bridge next to the pub. Which road is above us now Max?

Max - It’s Silver Street. This will be Silver Street Bridge, hence the association. This will often be where most tourists will be standing to view the Mathematical Bridge. And also to watch the most punts crash into one another because this is a turning point for most chauffeurs to go down to the other side of the river. And so they’ll be bumping into self-hires and everyone bumps into one another so it gets a little bit chaotic shall we say. We’re now arriving at Queen’s College here founded back in 1448, in part, by one Margaret d’Anjou, the wife of King Henry VI who founded King’s College which we’ll see later on. We’ve just gone underneath the Mathematical Bridge here designed back in 1749 by a student of Isaac Newton’s called William Etheridge and build by David Essex. So if anyone tells you it was designed by Isaac Newton, they’re lying. We’re about to pick up our first guest so I’m going to find ourselves a nice spot to park up and get him on here safely.

Chris - We’re just maneuvering into the side here. And there is teetering on the bank above us our first passenger. Welcome aboard.

Graham - It’s a long way down.

Chris - It’s a very long way down.

Georgia - Welcome to our studio.

Graham - Thank you. My name’s Graham McShane. I’m a Fellow in Engineering at Queen’s College. And I’m an academic in the Engineering Department so I lecture and do research in topics in engineering materials.

Georgia - We’ve just travelled under the very famous or infamous Mathematical Bridge that Max was just telling us about. Unlike most of the bridges which are kind of solid, this one is like a crosshatch kind of design with lots of wood and poles. Loads of geometric shapes. They look like sort of folded up like a duplex kind of structure. So why is the bridge, apart from looking great, why is it special?

Graham - It’s very unusual amongst the bridges that you see behind the colleges on the river. As you mentioned, all the other bridges are solid stone arches, but the mathematical bridge, is made out of wood. It’s the first thing to notice about it. and the reason you can get away with making it out of wood is that it’s a totally different kind of bridge. It’s what’s known as a “truss structure.” A truss structure is made up of a whole series of bars which are linked together and they transmit the forces very efficiently to the supports. And so by using a truss structure, you can create a structure which isn’t necessarily as strong as a solid stone arch but it uses little material. It uses the material very efficiently, and so it transmits the forces to the supports very efficiently so you have a very lightweight structure.

Georgia - This is why it can be not so solid as all the others?

Graham - That’s right, that’s right. And what’s also unusual about the Mathematical Bridge is not that it’s just a truss structure but it’s an arched truss structure. You very often see trusses used to build things like railway bridge. In those cases, it’s a flat truss structure that goes straight across the river, but the Queen’s Mathematical Bridge is an arched truss structure and that’s quite difficult to achieve. And so the bridge uses a very distinctive way of arranging the bars called “radius and tangent trussing,” and that’s a way of achieving this curve to truss shape.

Georgia - Ah, oh. Being attacked by another punt. We’re trying to have an interview here.

Chris - We’re going to be boarded in a minute.

Georgia - Do you get punt pirates? Is that a thing? It’s a very impressive structure and it seems like it’s a great idea if you want to save material. You’re an engineer, do you use this structure in your work?

Graham - Well, truss structures are obviously of interest for efficient lightweight structures. And saving weight is very important in mechanical engineering design because people want lighter aircraft, lighter cars, lighter trains and so there’s a whole area of research looking at how you can create materials using the same concepts. If you imagine taking a truss structure like the Mathematical Bridge and miniaturising it down until the bars are a few millimetres in length and you’ve got a material that’s called a “lattice material.” A lattice material’s a type of material where it’s made up of an array of bars distributed to transmit forces very efficiently through the structure. And so this allows you to create very stiff, very lightweight materials that are very good for lightweight engineering design. They also have other interesting properties, so when you crush these lattice structures they absorb energy very efficiently. So they can also find uses in things like crash protection and also in helmets.

Georgia - Ah. Another Cambridge favourite - cycling then?

Graham - Absolutely. People want lightweight, efficient helmets for sports and for cycling and all kinds of other applications, and so we’re very interested in using lattice materials to create the next generation of protective equipment and helmets. Maybe in future you might see a helmet that when you cut it open it looks like the Mathematical Bridge inside.

Chris - Graham, do you see the same sort of structures cropping up in nature? Has nature engineered its own solution using the same physics?

Graham - Absolutely. If you look at the structure of the bones in bird’s wings for example, those are very stiff, very lightweight structures where they’ve got a complex network of bones within the bone. You’ve got this truss like structure that give you that stiffness and lightweight, so you do see it evolved in nature in any application where you want to save weight but still has to be stiff and strong at the same time.

Georgia - Max eluded to the fact that there’s an often heard rumour that Newton built this bridge. What is that rumour and why do we know it’s not true?

Graham - Well, it’s a good story but, unfortunately, it doesn’t have any basis in fact. The main reason why it can’t be true is that the bridge was designed and built long after Newton died so he couldn’t have had anything to do with it, unfortunately.

Georgia - He was clever but he wasn't that clever.

Graham - He wasn’t that clever, that’s right. There’s also stories that it was designed by a student of Newton, but that’s not true either.

Industry and air pollution

09:21 - Carbon emissions, past and future

How have our carbon emissioned changed over the last ten years, and what can we do about it?

Carbon emissions, past and future
with Professor Herbert Huppert, University of Cambridge, Max Thompson, Rutherford's

Ten years ago Chris Smith interviewed Professor Herbert Huppert about the growing levels of carbon emissions. A decade later, have we got any closer to solving the crisis or is it looking worse than ever? First, Rutherford's tour guide Max Thompson gives us the low down on King's College.

Max - We’re now arriving at King’s College founded back in 1441 by King Henry VI. Also known as the mad young King. He was often thought to be the inspiration for King Joffrey in Game of Thrones. Ironically the College itself was first set up as a finishing school for Eton graduates, but these days it actually has the highest population of state school students in Cambridge.

We also see the King’s College Chapel just here looking rather splendid and glorious. It’s actually the second largest chapel in Europe only being beaten by the Sistine Chapel at the Vatican because everything's bigger at the Vatican, of course. It was meant to take only ten years to build but thanks to said War of the Roses it took 90, which isn’t as bad as Sagrada Familia in Barcelona, but still nothing to brag about either I suppose.

Chris - Anything else notable about King’s?

Max - Well, the most notable alumni from King’s is, of course, Alan Turing known as the father of artificial intelligence and modern day computers, and basically helped us win World War II.

Georgia - And we have some people waiting for us on the lovely lawn in front of King’s College next to the giant sign saying no mooring. We have two more special guests so let’s find out who they are.

Herbert - I’m Herbert Huppert. I’m a theoretical geophysicist here in Cambridge and I’m interested in the environment, and how volcanoes erupt, and how we’re putting in far to much carbon into the atmosphere and will live to regret it, or I hope we’ll live.

Chris - Funnily enough, when we were announcing our arrival we phoned you up and we said we were going to be a little while. And you said I’m a geologist, that could mean millions of years.

Herbert - Yeah. Well you know, the Earth has been around for quite some time. You and I are very recent, even humanities are very recent introduction and timescales differ from the Earth to what you and I are used to thinking about.

Chris - And who’s our other passenger?

Jules - Jules Griffin from the Department of Biochemistry here at Cambridge. I work on aspects of type 2 diabetes, in particular the interactions between our diet and relative risk of developing type 2 diabetes.

Georgia - So we’ll be toasting our alcohol and talking about our health later?

Jules - Yes indeed.

Chris - So Herbert, let’s talk about the health of the planet first before we talk about the health of the people on this punt and the wider society. Amazingly, ten years ago you and I did almost the same thing as we’re doing today because we did a punt trip down the Cam and we chatted about the subject of carbon in the atmosphere, carbon sequestration and so on. How has your view today, ten years later, compare with your views ten year ago? Has it sort of  played out the way you expected?

Herbert - I remember the punt trip but not what I said ten years ago.

Chris - I was going to say it’s age.

Herbert - I’m only 21! But things have got much much worse. I don’t remember the exact figures 25 years ago, but something like 27 billion tons of carbon dioxide were put into the atmosphere by mankind. Now it’s 37 billion tons and increasing all the time.

Chris - Every year?

Herbert - Every year. The mean global surface temperature is increasing all the time and we’re seeing great problems. There’s not a great problem but we see how dry and hot it was this summer and the King’s lawn, which is just on my right, was absolutely parched. Well do we want to be parched? Do we want to have a parched Earth?

Chris - Many people argue that the Earth goes through cycles; that it’s been doing it for millions of years; this is just one of it’s cycles that the tiny contribution of humankind is not driving that process?

Herbert - Well those people that argue that, I’m afraid, are not correct. It’s true it goes through cycles but this is a manmade cycle. This is putting a huge amount of carbon dioxide into the atmosphere. Much more than volcanoes do or natural events and it’s putting it in very quickly. There’s a dramatic rise over the last 100 years, which is a timescale…. As I said, I’m a geologist, before the timescale was a million years and now it’s a hundred years, getting much worse over the last ten years.

Chris - If we keep going like this and releasing carbon dioxide, what will be the consequence?

Herbert - First there'll be larger variations in weather going from hot to cold. The general temperature will increase by a few degrees. Also what’s a problem is that the sea level will rise and it will make life very difficult. And now we’re in Cambridge, this used to be pretty close to underwater in the 1400s. We could end up in the 2100s being underwater. A bigger problem of course, I’m just talking about Cambridge, places like Bangladesh that could be totally flooded. Immigration’s not liked, how would it be when thousands, millions maybe even if people lose their homes and their countries, who’s going to take them in.

Chris - Now one of the things that we know has had a profound effect on the climate over long term geological timescales on Earth is things like tectonic plate movements which make mountains and this displays to the atmosphere minerals that can pull down carbon dioxide, and that changes the CO2 level in the atmosphere. Is there a way that we could mimic that process to wind the clock back and undo some of the damage we’re doing and is it practical?

Herbert - Well, that’s a brilliant question if I may say. Over the last 40 years or so people have talked a little bit about taking carbon and storing it in the earth - sequestration. But just very recently it’s been suggested, and I want to do some research on this, whether mineralisation could be speeded up. We know that rocks take in carbon dioxide, just as you say, but that’s on a geological timescale. Millions of years for which we had to wait for this punt. But the question is whether we can influence things so that mineralisation can happen much more rapidly. And that’s an interesting question - please invite me in ten years time and I’ll give you a very positive reply I hope. But I don’t yet know, other than I have a very capable geological colleague at Columbia with whom, just over the last few weeks we’ve been talking about whether we could do something together in just that area.

Chris - Also the question of whether we can draw the CO2 out, and rather than turn it into minerals, put it underground in places like where the oil and gas came from which, obviously, is geologically very stable; it lasts for millions of years and would be able to hold it and hold it safely?

Herbert - Well, that had been the idea for some time of carbon storage. There’ve been a number of experiments; they’ve all been pretty successful when they’re field experiments. We’ve done lots of laboratory experiments and by and large they’ve been successful. But laboratory experiments are not meant to be successful all the time. We often learn from what isn’t successful, but the field experiments have been successful. The total amount at the moment of carbon dioxide that’s taken out of the atmosphere and stored in reservoirs around the world is ten million tons a year.

Chris - Ten million?

Herbert - Ten million.

Chris - So we’re releasing on the scale of billions but we’re drawing down only on the scale of millions?

Herbert - That’s right. 10 million verses 37 billion, and one of those figures is rather smaller than the other.

Chris - Three thousand times smaller, give or take, isn’t it?

Herbert - Yes.

Chris - So it’s not practical?

Herbert - No, no. Well that’s an interesting question. Could it be done? Yes. Could countries get together and companies get together and store carbon dioxide successfully at a rate of say 20 billion tons a year, yes, I think it could be done. There’s easily enough space, reservoir space in the Earth. Nobody seems very enthused. Ask Mr Trump and he’d say under no circumstance. Ask Mrs May and Boris Johnson, they wouldn’t be in favour.

Chris - On that gloomy note…

Herbert - Oh, let me tell you some good things.

Chris - Well good things, these strawberries look rather good. Do you want want one?

Herbert - Oh yes, I’d love one.

17:38 - Diet and diabetes

Are we eating and drinking all together too much?

Diet and diabetes
with Jules Griffin, University of Cambridge

How does our diet affect our lievs, and how are our collective waistlines looking? Georgia Mills and Chris Smith share a glass of fizz with researcher Jules Griffin, and find out how much it will hurt their health.

Jules - I think the basic message is that, as human beings, we’re probably eating too much in the western world at the moment. My research is looking at the interactions between diet and chronic metabolic diseases. So diseases like type 2 diabetes, cardiovascular disease, and fatty liver disease, and diet is a major component of those diseases at the moment.

Georgia - Why is eating too much food bad for you?

Jules - As animals, we’ve adapted very well to storing food and going through periods of relative famine and fasting. And the body’s geared up for doing fasting and conserving those carbohydrates and fats until we need them. The problem comes, though, when we can eat continually and we can basically graze or have much bigger meals. That we’re still very good at storing fats and carbohydrates, and probably the limiting factor is what our skeleton can actually cope with in terms of that storage, and this has dramatic health effects if we eat to excess.

We’re also not doing as much exercise, unlike the chap that’s punting us along at the moment.

Georgia - Not like us though, we’re being lazy.

Jules - Exactly. And I think that’s really the key thing is, that we’re drinking things with plenty of sugar in them or eating things with high saturated fat and we’re not doing enough exercise.

Georgia - So how are you looking into this?

Jules - We look at blood plasma and urine samples from people. Blood plasma is basically the bit of blood after you’ve taken out all the cells. This carries a lot of nutrients around the body, so sugars, in particular glucose, fats, and also amino acids. And the body needs these things in order to cope with the day actually, and get you through the day, and also during processes like growth but, at the same time, you don’t want to have too much of these because they have to be stored somehow and if you have too much of these they get inappropriately stored across the body. So you tend to see them less in our fat cells and more in things like the liver, and muscles cells and that’s how we get insulin resistance, and then type 2 diabetes.

Georgia - So how does looking into this help us - I don’t know, can we stop diabetes in its tracks?

Jules - Actually, there is some good news there. I think if we’d have been conducting this interview five or ten years ago we would have said that type 2 diabetes is largely a one way street. But there’s been some really interesting research into gastric bypass surgery where you can show that just by the fasting associated with gastric bypass you can reverse a lot of the effects of type 2 diabetes as part of this.

We’re interested in trying to understand why certain people are predisposed for developing aspects of metabolic disease and other people are protected. So we’re looking at some of these small metabolite markers to try and pick out populations that are either at risk or are protected, to understand those protective mechanisms.

Georgia - Is that a sort of genetic thing or environmental?

Jules - We know it’s partly genetic and we know it’s partly environment as well, so with food being the biggest component of that environmental factors. We’ve done quite a lot of work in terms of fatty liver development and the bad news there is that alcohol is a big risk factor. But also...

Georgia - Oh oh.

Jules - Yeah, I’m guilty of that as well. But also just sugary drinks as well. Potatoes and crisps based products as well.

Chris - The thing is a lot of what you’re saying hasn’t really changed dramatically in the last five, ten years. And if you look at children going to school, a record number of them, like a quarter in western countries are now overweight or obese at the time of starting school. It’s a really frightening number. So what has changed that we are so dramatically different than we were when young people say 40 years ago were going to school when that number was a fraction? It was a very tiny number that were overweight.

Jule - I think there’s been two big effects that we’ve seen sort of happening. One is a reduction in the amount of exercise. Exercise is amazingly protective even if you don’t reduce weight, actually, in terms of protecting against type 2 diabetes, and the complications associated with type 2 diabetes. I think the other big problem is just the availability of foods that are very high in sugar. The good news is that we’ve probably done a pretty good job as a nation in reducing some of our saturated fat content intake. We need to go further in terms of that, but the bad news is we’re probably eating more calories, and the body’s very good at storing those calories, so that’s how you see more people being overweight and more obesity.

Chris - So if you’ve got this fatty liver change and then you embrace a much more healthy lifestyle, will it go away?

Jules - That’s the good news yeah, it does go away. In terms of, if you can do things in reduce your food intake, or I try and go out on a run a bit more often and do it the other way round as I’ve got quite a healthy appetite.

Punting pile-up in Cambridge

Clever machines and driverless punts
with Amanda Prorok, University of Cambridge

Could machine communication help our transport systems be more efficient, and could we ever have driverless punts? Georgia Mills and Chris Smith chat to Amanda Prorok of the Computer Science Department...

Amanda - I work in an area called multi-robot systems. I deal with the development of algorithms that allow multiple mobile robots to operate in a coordinated manner.

Georgia - Wow! So like a swarm of bees all moving and not crashing into each other?

Amanda - In a certain sense, yes. Some people like to call this collective intelligence. Basically, the idea is if you have multiple intelligent entities communicating and cooperating with each other you can achieve things that are more than just the sum of the individual parts.

Georgia - What kind of applications could you have for a system like this?

Amanda - I think that traffic and transport is currently a very interesting application. There’s a lot that we can do to improve traffic as it is given today. I mean, you look at what’s going on on the river today and you see everybody just kind of doing their thing and we’re randomly avoiding other boats. Nobody has a clue of what optimal manoeuvre here would be and if we would just add a little bit of intelligence to this system we would probably be manoeuvring in a much more smooth, efficient, and actually also safe manner.

Georgia - No offence Max.

Amanda - No offence at all.  Basically, you can think about how humans navigate traffic and there are two ways we do this. Either we have reactive behaviours, which is we, kind of, detect what’s happening around us. There are boats, vehicles to the left to the right, to the front to the back, and we either nudge a little bit to the left to the right, we brake or we accelerate. So that’s one manner.

The other way we deal with traffic is in a little bit more of a deliberate manner. So I can see a boat coming from the front or I can see a boat coming on the left and I can try to make a guess or estimate about where I think that that boat is heading. And based on that I can kind of make a little bit of a plan towards where I want to head so that I will probably not collide with that other boat’s plan which I have kind of mapped out in my mind virtually.

And so this kind of deliberative thing is what we can take many steps further if we actually add technology. So you can imagine that these boats here could be planning their paths all the way from the start to the end, to the goal, and they could communicate these plans to all the other boats that are in the vicinity, and you wouldn’t even have these manoeuvres that you see happening here because the plans are all laid out and they’ve all kind of smoothly negotiated how they’re going to be getting around each other.

Georgia - What are the big challenges involved in systems like this either for punting or for cars.

Amanda - I’d say there are two: one is scaling these systems up. So obviously, if this punt or this boat here has a plan, where it wants to head, it’s not going to communicate this plan to all the other hundred boats on the Cam, so you have to decide whom you want to communicate this plan to. Obviously, communication bandwidth is one issue here and also computational resources are another.

The other aspect is actually when we communicate our plans to other vehicles, we’re assuming that they will take these plans into consideration and they will cooperate with these plans. I’m saying I’m going to go this way, the other car will then try to find a path that goes around that path and not into that path. So we're assuming implicitly that everybody else is going to cooperate with us.

This underlying assumption that everything is cooperative is somewhat of a strong assumption for two reasons. Other boats or other vehicles can be compromised maliciously, or other boats or other vehicles can simply break. The communications may suddenly not be up and running any more and so we can’t really ever assume that other boats are always receiving our plans and act upon them as we think or hope they would be.

Georgia - Right. And no offence Max - don’t listen. But could we use technology and robots to replace our punter do you think?

Amanda - It would be a very sad thing. Actually replacing the punter with a similar mechanical design is probably not the most efficient thing to do. You’d probably want to put a motor into the water that propels us forwards. If you would want to have some sort of robotic arm that pushes down into the water and hits the ground and pushes forwards. I do think that would be quite challenging because you need to have precise force feedback and I’m not quite sure what the sediment looks like at the bottom of the river, but I don’t think it’s solid. So this would involve sensing technology that is resistant or capable of functioning in those kinds of environments and able to give feedback.

Georgia - So your job is safe for now I think.

Chris - Amanda, can I ask you will I still be sitting in a traffic jam on the way to work if we implement your system? That’s what’s going through everyone who’s listening to this minds I’m sure.

Amanda - Throughput and congestion control is one of the things that we can get rid of with more automation in traffic. And it’s not only about making cars autonomous, it’s also about connecting cars to people and deploying a ride sharing system where we’re better using the capacity of cars that can carry more than just one human driver. We can do this by implementing systems where cars are not actually privately owned any more but are similar to what we see happening with Uber and Lyft, being driven around cities in a shared kind of paradigm, and humans can just hop on and hop off on routes that coincide with the routes they would be driving normally with their own private cars.

I think this is a much more efficient usage of the actual resources that we need to produce cars. It’s a better resource of real estate because cars don’t need to be parked anymore. So I think there’s a huge potential to improve over multiple dimensions here if we would implement such systems.


33:02 - Fraud-preventing holograms

How science moves from the lab into the home...

Fraud-preventing holograms
with Chris Lowe, Institute of Biotechnology the Cambridge Academy of Therapeutic Sciences

Science doesn't stay in the lab forever - a lot of it ends up being spun out into technology companies. Chris Lowe has created many of these companies, and joined Chris Smith on the punt to discuss a few of his spinout companies.

Chris L - I’m on my twelfth one now.

Chris S - What do they all do?

Chris L - They’re in various sectors. My research area has been healthcare by technology in general so that covers both diagnostics and therapeutics so the companies span that thing. We have one company working exclusively in the area of diabetes. We have others that are looking at other types of therapeutic modes. Others are in diagnostics area and so forth.

Chris S - I did read somewhere that haven’t you got a contact lens that monitors blood sugar for diabetics?

Chris L - Yes. We were the first group in the world to actually test it with a real person. We gave that person 180 grams of glucose, which is the standard glucose tolerance test, and then we monitored both the blood glucose and tear fluid glucose, which is where the contact lens comes in, and we demonstrated there was a correlation between the two. We’ve only ever done it with one person and that was published in 2006 and nobody’s ever done it since.

Chris S - What does the contact lens do and how does it signal to the person what their blood sugar is?

Chris L - Well, you’re well aware of a soft contact lens presumably - a daily wear contact lens. That’s made out of a polymeric material, and what we do is we incorporate into that a volume hologram. Now a volume hologram is not like the one you find on a credit card, which is a surface relief one. With a volume hologram we can produce layers of metal particles or layers of polymer which create a diffraction grating, so when you put white light in it only releases a single wavelength back out of it, and therefore it looks a coloured one.

Now if we can change the spacing of those fringes within the hologram, within the grating, we can change the replay colour. So the idea is that we put the hologram into a smart polymer, which has a receptor for binding the glucose. That binds the glucose, you get a change in fringe spacing, and hence a change in wavelength that’s replayed out of the hologram. So, in other words, the hologram looks a different colour and we monitor that colour.

Chris S - So the diabetic would have some extra sugar in their blood, that would end up in the tears? That would then enter the contact lens and change the thickness or the size of this grating which would affect the way that the light that’s going through it bends and you’d end up with them seeing a colour, presumably?

Chris L - Yeah. The patient won’t see it because it’s in the eye don’t forget, so we’re using a mobile phone then to actually monitor the colour in the contact lens and then convert that mobile phone response into a concentration.

Chris S - So they know how much insulin to administer or not?

Chris L - Exactly, that’s the idea.

Chris S - Does it work?

Chris L - It works in principle. And I say, we have tried it with one person. But, of course, you’ve got to do major clinical trials on this because people’s lives depend on it so you’ve got to do a significant kind of trial which we’ve not done yet, but we plan to.

I did bring some of our sensors along with us if you’re interested.

Chris S - have you got some?

Chris L - I’ve got some in my pocket. This is one of our holographic systems we’ve been developing. It’s the same sort of hologram that we put into the contact lens but, you see, this is used for a slightly different thing, it’s an authentication sensor. So if you got an expensive piece of...  I don’t know, you might have an expensive handbag for example. Not that you have.

Chris S - Oh I definitely have, Chris. I do have an expensive handbag, especially at weekends.

Chris L  - If that’s an original one you could put a hologram like this on it. This is a breath activated one. In other words, it changes as you breathe on it. If you see it on there it has SH on there. Now that’s one of the companies I was involved in - smart Holograms. If I breathe on it… you see it’s got little...

Chris S - It’s gone green with little ticks.

Chris L - With little ticks on it, exactly. That’s changing one hologram for another.

Chris S - Go on then let the cat out of the bag, how does it work? Because all you did was you went sort of “huh”, and huffed a couple of breaths onto the red colour which says SH, it turned into a whole bunch of little arrows looking green.

Chris L - This actually has two holograms in it. One starts off in the ultraviolet and the other one starts off in the visible region. This first one which says SH on it, that’s in the visible region. Now what happens is when you breathe on it the moisture in your breath, which is water, actually expands the holograms slightly. One hologram moves then from the visible into the infrared so you don’t see it, and the one that’s hidden in the ultraviolet moves into the visible, so you get the replacement of one hologram for another.

The Naked Scientists and Alex Thom enjoy a glass of Reisling

37:47 - Cheers! The chemistry of wine

How does acidity make a wine taste better?

Cheers! The chemistry of wine
with Alex Thom, University of Cambridge, Max Thompson, Rutherford's

Would a punting trip be complete without a tipple or two? Georgia Mills and Chris Smith are joined by theoretical chemist Alex Thom from the University of Cambridge, who is a keen onoelogist. But before the wine drinking starts, they learn a little about the scenery from Rutherford's tour guide Max Thompson. 

Alex - Theoretical chemistry tries to do chemistry mostly in a computer. That is quite hard because there’s a lot of atoms involved in chemistry usually. And so I work on making that better basically by designing algorithms to enable us to solve the problems more easily and on today’s computers.

Georgia - Why does it help to do chemistry on a computer instead of a dish?

Alex - Sometimes you just can’t do the experiments. Let’s say you want to look at the chemistry in the atmosphere of Jupiter or in the Sun, or even let’s say you’ve got a lot of different materials you want to screen for some exciting property like a solar cell. It’s just not economical to do these experiments or not possible, so if you can get answers from a computer that can at least help.

Georgia - And why is it difficult?

Alex - It’s all to the blame of physicists really. We need to solve the quantum mechanics underneath chemistry and, basically, every electron in a molecule is entangled with every other electron and you need to take into account all of those correlations and that gets really horrible very quickly.

Georgia - It sounds like tricky work which might bring us on to your other interest which is also chemistry related. So tell me about that.

Alex - Yes. I’ve had an interest for some time in wine and oenology which is the sort of study of winemaking and tasting wine.

Georgia - So does that mean that inside this basket there might be some wine?

Alex - There are a few bottles of wine in here, yes.

Georgia - Ohh! Hello!

Alex - And other jolities. I’ve brought a few bottles of different wines and it’ll be nice to try them and possibly even do some science on them.

Georgia - Possibly, maybe. Mainly drink them. How does chemistry come into wine tasting them?

Alex - Certainly in winemaking there’s a great deal of chemistry. A lot of vineyards will have their own oenologist, who’s basically a chemist.When you start making the wine from the grape juice a lot of things can go wrong and you need to be able to study it quite quickly and fix them. And to make products that are nice to drink isn’t easy so the more you know about what’s going on in your wine the better.

The flavour profile is made up of hundreds of different molecules. The main components are alcohol and some acidity and water. But the interesting bits are the flavour molecules which are very difficult to isolate and put together and they vary from year to year, and grape to grape, from wine to wine.

Georgia - And these are things when someone will say oh yes, it’s got hints of oak or something, that’s the flavour molecule doing that?

Alex - Exactly. You know it’s taste of guava, or pineapple, or even smell cut grass or that sort of thing. All of those are volatile molecules that you get when you smell it and also when you taste it.

Georgia - This has all got my mouth watering so perhaps - what’s the first one we’re going to taste?

Alex - I’ve brought an interesting wine here called a Reisling - that’s the grape, and I chose it because one of the important constituents of wine is the acidity. That’s what often makes the juicy feeling in the mouth for wine and I wanted to play with the idea of changing the acidity of wine and to see what the flavour changes.

Georgia - Oh, so we can actually change the acidity even though it’s already been made, put in the bottle, we can tinker?

Alex - The joy of chemistry is that we can play with some of these elements in a controlled fashion. Let’s try it as it is and we can comment on it, and then I can tell you what the official tasting notes say.

Chris - I love this. You can tell you’re a chemist, Alex, because you’ve got a pyrex beaker that you’re going to drink this out of.

Alex - Actually I got this at the International Chemistry Olympiad this year, so that was a gift there. It’s great.

Chris - It’s fantastic. It’s literally a pyrex like you would put on a retort stand on a gauze and boil away in a laboratory but it’s got a handle on the side.

Alex - I’m going to put a little of the Riesling in the glasses first. This is the unadulterated wine, as such, and we’ll taste that. Give it a swill in the glass maybe, get some of the flavour out.

Georgia - I think it’s a bit smokey. It’s a bit flowery and maybe a bit of citrus?

Alex - Yes, there’s citrus in there. The flowery is good. I can’t get the smoke myself but.

Georgia - Maybe someone went past smoking.

Alex - Yes, exactly. All manner of things in the atmosphere. But again, everything’s very original.

Chris - It is quite sharp. I’d say that’s quite an acid wine.

Alex - It is, yes. I picked it because it’s a Riesling which is known for one of the most acidic wines. That can be good and bad. People like acidity because it means they keep longer, they age longer, but if it’s too acidic it becomes sharp and horrible. So this is wine you might have on a hot summer’s day - a bit like today and the acidity makes it feel more refreshing.

Georgia - Very very nice. Can we see what happens when we change that acidity then.

Alex - Yes. I’m going to do a little modification to the acidity here so I’ve poured some of the wine into my beaker and we’re going to add to it some bicarbonate of soda. Now this is an alkaline salt basically. It’s just a standard kitchen chemical but… Because we’re on a punt it’s quite difficult to judge quantities and do this correctly, so into this wine I’m going to cheat and add a little bit of a homemade indicator. I’ve made this out of red cabbage last night. Hopefully it won’t change the flavour too much. But this wine is currently a nice sort of yellow colour and if I add a bit of this it should change to a startling pink colour, hopefully. And I can use this indicator to tell me how acidic the wine is, so this very pink colour means it‘s pretty acidic at the moment.

Georgia - it goes bluer when it’s more alkaline?

Chris - It currently looks like rosé doesn’t it.

Alex - Yes, exactly. I’m going to now add to it some bicarbonate of soda and hopefully that should fizz quite happily there, and it’s gone a bit darker purple. So we’re looking for a purplish colour rather than a green colour. If it’s gone too green it’s gone too alkaline.

Georgia - If feels like the acidity might have changed but we’ve also put in cabbage and a lot of soda. Is this really going to tell us anything?

Alex - I chose this partly because I had a red cabbage in the fridge last night. Yes, it’s certainly changed colour now. It’s gone a sort of salmony, maybe very light rose colour rather than the bright pink. It should now smell a lot less as I…

Chris - Yes. It certainly doesn’t smell the same.

Alex - Feel free to spit this out if you don’t like it.

Chris - Have we got a spitoon?

Alex - There’s a jug her we can use as a spitoon.

Chris - Oh god. That was grim. Ah man.

Alex - What's happened to it.

Georgia - It’s ruined! That’s what happened. Ugh.

Chris - That was rank.

Alex - It’s taken all that acidity away. What we’ve now got is a…

Chris - It hasn’t just taken the acidity away. It’s taken any semblance of wine away.

Alex - Yeah. And it basically tastes horrible.

Georgia - It’s like drinking washing up liquid or something.

Alex - Yes. I may have added a bit too much of this. The flavours I can still get - you can still taste the alcohol in this. So it tastes like a shot of alcohol but without anything much else.

The next experiment is to see if we can put the acidity back with a different acid. And so acidity is really really prized in wines because it gives them flavour, so most of the flavours disappeared as well. And if you’re in a really hot climate the grapes tend to turn all that acidity into sugar and they lose a lot of the flavour. This is an acid which I’m going to add which is a different acid from the one we had before. Most of the acid in the wine would have been an acid called “tartaric acid” which I’ve got somewhere in here and malic acid.

Chris - You’re making what lysergic acid? It’s a bit different kind of acid isn’t it?

Alex - Lactic! So this is stuff that builds up in your muscles when you exercise too quickly and it tastes a bit like yogurt.

Chris - Well, it’s gone the right colour again hasn’t it?

Alex - It’s gone a nice pink colour again.

Chris -  It’s back to pink so we know it’s more acidic again. I’ll give it a go. Go on then.

Alex - It’s pretty tart.

Chris - The smell is back.

Alex - The smell’s back.

Chris - Yeah. The smell, it’s wine again.

Georgia - Yeah, I can smell the wine again.

Chris - It’s back to Riesling that we had before. I tell you what, it’s a lot less disagreeable than what we did with the first effort with the bicarb.

Georgia - It’s like one of those sweeties that's super sour. So the flavours weren't destroyed by that red cabbage goop we put in, they were there?

Alex - Just hidden by changing the ph. As you can see, having a more acidic wine gives the flavours more of a chance.

Chris - You’re really enjoying that Georgia.

Alex - That was a very fine face.

Chris - Do you want some more? A top up?

Georgia - I’m quite alright.

Alex - So that’s what you can do and, of course, winemakers do this on a much more careful scale with acidity rather than just pouring a few things together in a punt.

Georgia - That's a really interesting example of how acidity is really important. I have new appreciation for acidity because it did taste absolutely awful and then the flavours did just sort of come back to life.

Alex - Exactly yes. I’ve got one more. We don’t need to finish all the bottles immediately.

Chris - There’s one each.

Georgia - Oh, I spy a word - champagne.

Alex - Yes, yes.

Georgia - Oh my goodness. You’re treating us.

Alex - Yes. It’s a good name in wine. I might just have a glass to catch if any champagne comes out... Oh no, not quite.

Georgia - Ahh!

Alex - Sorry, I put my finger over the bottle to stop it all from squirting out. And I managed to get….

Chris - This is Lewis Hamilton experience there for Georgia.

Alex - Cheers.

Georgia - Cheers.

Chris - Cheers Alex. Now what’s interesting about this is it’s got very tiny bubbles.

Georgia - Do the bubbles change the chemistry of the flavour? Does that make sense? Do they change how we perceive that chemistry?

Alex - Yes. The bubbles when they’re on your tongue and in your mouth they act as little pockets of air and it’s like swirling you glass. They produce these pressure gradients as they’re forming and they make the wine a lot more flavoursome effectively, so you taste the flavour molecules. If you leave champagne out for a day, you can get a nice wine but it doesn’t taste quite as nice after you’ve left it for a day.

Gut Bugs

49:46 - Bacteria: What lies beneath

A jaunt with Claire Bryant, who tells the team about ancient mariner traditions and cutting edge bacteria research...

Bacteria: What lies beneath
with Claire Bryant, University of Cambridge

You're going to need a cleaner boat. Chris Smith and Georgia Mills pick up vetenary scientist Claire Bryant, who warns them about the nasty bacteria lurking in the river, and discusses her own research into salmonella. But first, why do maiden voyages often smash bottles of champagne?

[transcript to follow]


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