Do squirrels ever forget where they hid their nuts?

10 November 2015
Presented by Kat Arney.

The Naked Scientists and some special guests team up to tackle your science questions head-on. Do squirrels ever lose their nuts? Is cracking your knuckles bad for you? And could your gut bugs turn you to crime? Plus, a look at this week's science news.

In this episode

01:28 - Is cracking your knuckles bad for you?

Is cracking your knuckles bad for you?

We put Eva's cracking question to Chris Smith...

Kat - Let's draw a quick straw poll in the studio. Who can crack their knuckles? I can't I've got kind of clicky wrists, but anyone?

Max - I can crack my knuckle.

Chris - Go on max.

Kat - Anyone else?

Ginny - I can't crack my knuckles, but I can crack my big toes.

Chris - Go on then.

Ginny - I'd have to take my shoes off.

Kat - The magic of radio. It's not going to work for this one. How about you Chris, you're a knuckle cracker? Is it bad?

Chris - I'm no good at this actually. I can't make my joints crack at all. Very, very occasionally they do it, but I can't actually make them do it. Is it bad? Scientists don't actually know if it's bad. There's anecdotal evidence that it isn't. The anecdotal evidence has won an Ig Nobel Prize so that's probably how reliable the research is. Donald Unger did an n of 1 experiment on himself. He was a gentleman who for 60 years - there's scientific dedication for you - cracked the knuckles of one hand, but not the other and he wanted to see if there was a difference in his rates of arthritis and there wasn't. So, on the basis of his sample size of one, there doesn't appear to be a problem. Why do we get the cracking noise when you move your fingers and digits? Well actually, that was the work of British scientists in 1947 who first began to speculate what might be going on. But they had no way of proving whether or not they were right at that time. They speculated that what was going on was that when you bend your joint, you drop the pressure in the fluid - the synovial fluid - inside the joint. The drop in pressure causes gas that's dissolved in the joint fluid to come out of solution and form a bubble, either that the bubble popping into existence or collapsing in on itself would produce the energy that makes the sound. No one knew for sure what was the answer but then Greg Kawchuck who's a researcher at the University of Alberta in Canada, he and his colleagues did an experiment that will probably get another Ig Nobel Prize earlier this year. They published it in PLoS One in April. They persuaded a member of their team to get into the MRI scanner. They put a rope around their index finger and pulled and because they had microphone in there too, they could see when on the time course the pop occurred and they could tally that with what the MRI scan showed at that time. And in sync with the pop occurring is a bubble appearing in the joint. Not disappearing, appearing. So, it is the existence of that bubble popping into existence which takes up lots of space in the joint and therefore pushes all of the ligaments and everything else out of the way as well and that creates this expanding pop that you hear. The bubble then hangs around for a while and takes a while to dissolve naturally into the joints which is why you can't pop your fingers again. They reckon that the collapsing force of those bubbles is about 7 per cent of the energy that would be required to damage cartilage anyway. So we don't think, even if the bubble did then collapse again, it's likely to do you very much damage.

04:26 - Could I construct a dome to cover a whole city?

Could I construct a dome to cover a whole city?

Engineer Hugh Hunt answered Heather's question... Hugh - Domes made of masonry, the kind of ones that the Romans built never got much bigger than about 30 metres diameter if we're lucky, modern domes, 300 metres diameter. I think the largest in the world is in Singapore, 330 metres diameter. So, to get to covering a city, my guess is that it would have to be quite a small city. 300 metres is not very far, but I think the biggest thing you have to remember is that it's not so much the forces required to make a dome that holds up its own weight. It's all the extra forces like weather, wind, snow. Even my cat Charlie, if it runs over the top of a dome, if the domes a really big, lightweight dome, that cat suddenly becomes really heavy. The other thing is that when the dome is half built, what happens if there's a big storm then?

Kat - Yeah, you can't just kind of drop it on top.

Hugh - So, you've got to think about how you build something.

Kat - Where would the key kind of stresses be? Would it collapse in from the top, in the middle, if you did manage to get it built?

Hugh - Well, that's an interesting question. If you think about a rugby scrum, that's a bit like a dome and how does that collapse?

Kat - Dome made of big men.

Chris - What about chickens and eggs because they have obviously come up with a way of making something which is extraordinarily strong in one dimension admittedly which is pole to pole? Georgia our producer made me stand on a box of eggs as an 'eggs-speriment' for Easter earlier this year. It did take my weight. There must therefore be a strategy that the chickens use to stop their eggs imploding on themselves. Can we do something similar?

Kat - Well chickens are a lot smaller than a city, Chris.

Hugh - That's it. It's quite a small structure. It's quite a small structure. It's made in really very well-controlled circumstances. So, when it then has to deal with the main forces of being an egg in the nest, it's pretty perfect. You probably don't want your dome to collapse on your city so that the.

Kat - It's risky, isn't it? It's a risky strategy so it's not looking like this is a good idea for Heather's novel, I don't think.

Hugh - Well, it's not bad if it's a small city.

Kat - So, it needs to be a small city made of really good engineers.

Hugh - And of course, if you're trying to make a big dome or a sports stadium, one thing is you're not allowed to have a pillar in the middle. That kind of spoils the game a bit. Now, these big domes for sports stadiums, the criterion is no pillars. But if you were going to do it for a city, maybe you don't mind having pillars. In which case, it then becomes a matter of, "Okay, how big do you want it?"

Kat - So, it's just like a marquee basically. So, I think there's your answer Heather. You can't have a dome, but you could probably have a really big marquee.

07:25 - What makes a good leader?

This week scientists have picked apart the qualities needed to make a good leader in both humans and the animal kingdom.

What makes a good leader?
with Ginny Smith, Science communicator

Do you have what it takes to be a good leader? The traits looked for in people in a Meerkatpower aren't too far different from the traits found in animal leaders too, scientists announced this week. Ginny Smith explained to Kat Arney how you get to be king of the jungle...

Ginny - Well, I've seen a really interesting study that looks at how animals choose their leaders and whether they do it in the same way that humans do. So, this was a study published in Trends in Ecology and Evolution and they used a mixture of mathematical models and experimental studies to examine that question. They got together experts in a huge range of different disciplines from loads of different universities including Oxford and California. They examined a range of different animals. So they looked at elephants, dolphins, lions, chimps, meerkats, zebras, hyenas, and capuchin monkeys. They compared them with 8 different human societies who live in groups ranging from 10 to 25,000 people. So, they were looking at how these different societies chose their leaders because they're all societies that live in groups. They have to make decisions about where to move to, where to forage to find food, how to resolve conflicts. So, they all need leaders of some kind.

Kat - But meerkats don't vote, so how are they choosing their leaders?

Ginny - Well interestingly, there weren't that many differences particularly when you looked at how the leaders became leaders. Okay, so there isn't a voting system but in most of the animal societies and most of the human societies, it's based on the individuals with the best skills. It's based on experience. As those individuals gain experience, gain more skills, they become leaders. There are a couple of interesting exceptions. There was one human society and then also hyenas where leadership is inherited. It's automatically the daughter of the previous hyena leader who becomes the leader and I guess, that's a bit more like our royal family for instance. But I think what's really interesting is that actually, there were more differences within the two groups, within the groups of non-human animals, and within the groups of humans than there were between the two groups. One difference was that actually, human leaders surprisingly tend to be less powerful than animal leaders. So the leader of the animal groups tend to wield more control and more power than our human leaders do, except for one area which was in food gathering. This was another area where there was a big difference in that the non-human animals tend to find their own food and keep it whereas in a human society, the food is all shared so the leaders then have a bit more influence on where that shared food goes.

Kat - So, you can either eat or you can have like a skilled leader.

Ginny - I think that's maybe stretching a little bit too far, but those were two areas where there were some differences.

10:03 - Why do boat trails last so long?

Why do boat trails last so long?

Les' question was put to Cambridge University's Chris Smith and Hugh Hunt...

Hugh - Well, the wake that comes off a boat is turbulence. It's swirl that's generated by the boat and the only way you can get rid of swirl is by that swirl meeting another solid object because conservation of angular momentum says that that swirl doesn't disappear. Now, if the water is quite deep and the boat was away from a shore and there weren't other big boats around then that swirl will last for a long time. It's the same problem you have when a turbulence left from a plane that's just taken off sticks around for quite a long time.

Chris - One other thing to bear in mind is that when a boat goes across the surface of the water, it disturbs or perturbs the surface of the water, and there's a lot of proteins and surfactants which are a bit like washing up liquid in their action chemically in seawater. That's because of plants and other microscopic organisms and sewage. And the effect that that has is to reduce the surface tension of the water so it makes making bubbles much easier. And so, you tend to see little layers of foam or bubbles where boats have gone. And so, one of the things that Lez may also have been noticing is a little trail of spume or the white material that you see as a raft of little bubbles and disturbance on the surface.

11:49 - Can dogs really smell cancer?

Can dogs really smell cancer?

Dogs have an extremely strong sense of smell but do they have a role to play in advancing medical science? Kat Arney and Chris Smith sniffed out the answer to Destiny's question...

Kat - This is one of my favourite things because I've actually been to visit the medical detection dogs. They have a little centre outside Milton Keynes. And yes, there are chemicals. They call them volatile molecules that are given off by cancers and dogs can detect them. And there's various anecdotal stories about owners who noticed their dog kind of pawing at them or worrying at them, and then they were diagnosed with cancer. There are also some experiments, lab tests, if you will, that have been done showing that dogs can pick up some of the smells given off by tumours - various different types of cancers. If they're highly trained - we're talking about highly trained sniffer dogs here - they can be trained to reliably sniff out cancers. There's currently a clinical trial going on in the UK looking at big things like prostate and bladder cancer by getting dogs to sniff people's wee. The thing about the dogs though is that it's all very interesting, but you can't imagine a dog in every surgery up and down the country because these are very highly trained dogs. They're highly trained to certain types of cancers because different cancers will give off different molecules. So, the universal lab test (I just like saying that, better than a CAT scan) is not going to be really practical. But what could be really useful is if we can work out, what are the molecules that these dogs are smelling? because at the moment, it's really hard to tell the difference between aggressive tumours and tumours that aren't growing very fast. If we could work out, what are the dogs smelling? and then develop an electronic sensor, kind of an e-nose that could sniff out those molecules then that is the basis of a much more widely applicable test. So, I think the dog stuff, it's really interesting and they're very, very cute and they work really well. But I think certainly, if we can find out what they're telling us, that could be extremely useful.

Chris - This is sort of the field of metabolomics, isn't it? scientists are now beginning to detect various diseases by not looking for individual genes or individual markers in and of themselves related to a disease. They're saying, "Let's measure lots of chemicals all at once in lots of people who have a condition" and what we'll see is that in people who have that condition, there may be some of those chemicals that are changed just very subtly and individually, very small change, but taken as a population of changes, you've actually got a very sensitive test. When I was in Geneva a couple of weeks ago at a conference run by the drug company Merck where they were bringing research scientists together from across Africa, I met a chap from South Africa who had invented a breath test for TB and a blood test. The way this works is that when you have TB and you come in to the laboratory, and you give samples to try and tell if you've got tuberculosis, it can take a month before you get the diagnosis which if you've already had to trek along way from a remote area, a doctor to get the diagnosis, that's a problem. His technique means you take a blood sample, you look at lots of different markers in the blood, and he can tell with more than 99.9 per cent sensitivity whether or not a person has got tuberculosis just from a blood sample and he can do it in 15 minutes.

Kat - Yeah. The idea of breath tests and blood tests for cancers are certainly very exciting. I think it's definitely one to watch over the next couple of years.

15:24 - If humans went extinct what would take over?

If humans went extinct what would take over?

The world has been dominated by different groups of animals over time but undoubtedly humans have a huge impact on the planet today. If we were to disappear could you think of any obvious contenders to take our place? Zoologist Max Gray had a go at answering Gary's question...

Kat - That's a good one, isn't it? who's going to be the next king of Earth?

Max - That's a great question. Mostly in fact, it's almost impossible to come up with an accurate answer for. It's very difficult to say?

Kat - What about cockroaches? Everyone is like cockroaches. When the nuclear apocalypse comes, it's going to be the cockroaches.

Max - Yes and that cockroaches can survive radiation quite well, but that doesn't mean they're going to become super intelligent. I mean, the whole thing about radiation altering your anatomy or giving you super powers is obviously a complete myth.

Kat - In terms of thinking about what might takeover though. You think you need something that's smart but the primates aren't very widespread individual species.

Max - It's almost impossible to view it from a non-human standpoint like when the way you're asking the question is, what would take our place which isn't necessarily what would happen at all. That's not how evolution works. There might not be a next most dominant species.

Kat - Well, it might be cats. I think they can probably use a kettle.

Max - Really?

Kat - Well, I think they could learn.

Max - Depends on the kettle. You have to have people designing a kettle that could be used by cats. And so, this is one interesting question about all of the ways we interact with the world is mitigated by tools and by our technology which is all very much geared towards our manual dexterity. That's what sets us apart. And so, to replace us, kind of to have a dominant animal so to speak in the way that we fit in the world, you'd need an animal that could develop technology to then devote a lot of time to things other than hunting and reproducing which is what all animals spend most of their time doing, either struggling to survive or struggling to reproduce.

Kat - Not speak to yourself.

Max - Whereas humans don't do that. We've developed the means of surviving largely by spending an hour a week going to the supermarket and then that's about it and then we're all alright, and can spend the rest of our time doing whatever else we like. That's where technological advancement and literature and the arts, and everything that's why we have that.

Kat - I mean, there's a slightly philosophical thing about, "are we the dominator of the planet" because something like bacteria, arguably probably more successful than we are in terms of where they've got to and what they're up to, apart from their lack of literature and all that kind of stuff.

Max - But again, is that dominant? I mean also, bacteria are.

Kat - They never made Breaking Bad.

Max - You're saying bacteria as if that's an animal and it's not right. I mean, bacteria is an entire kingdom of species of which are innumerably more populous than the animal kingdom. I don't know if there's one bacterium that you could say that about.

Kat - I think we can't really answer your question Gary, but nice and speculative.

Max - The short answer is, I have no idea.

18:23 - Has there been new water created since the world began?

Has there been new water created since the world began?

Today, water makes up a huge 71% of the earth's surface but has all this water been around from the beginning? We put Declan's question to Naked Scientist Chris Smith...

Chris - New water being made all the time. First of all, where did all the water on Earth come from in the first place? Because the Earth is about 4.5 billion years old, the stuff that it was made from which was a ring of dust and gas which was forming around the early sun, we've got models of that environment and there's probably not very much water in that. So, all the water on Earth at the moment must have come here from somewhere. The most likely source is comets which are dirty ice balls and also asteroids. Now people have measured the biochemical and chemical makeup of the water on Earth and compared it to the water measurements from comets. The comets they've studied don't seem to have the same chemical makeup. So, we think asteroids, which do appear to have a much closer makeup in terms of the isotope ratio as it's known between the asteroid in the Earth does appear to match much better. So we think that probably, the water we've got, most of it came to the Earth from things hitting the Earth in the first billion years or so after the planet formed. But at the same time, there's a lot of hydrogen here, there's a lot of oxygen on the Earth. The two can react together to produce water which they do all the time. In your body for example and in anything that's alive and respiring, we can take an example. If you burn a molecule of sugar, glucose - C6H12O6 and you burn it with 6 molecules of oxygen, 6O2, the product is some energy. That's what keeps you going plus, 6 molecules of CO2 (carbon dioxide) that you breathe out, plus, 6 molecules of water. You pee those out and you also breathe them out because you breathe out maybe half a litre or so of water every day. So, everything that's alive is doing that process. So, there's lots of water being made every day. So, the water molecules that are here are not the same water molecules but the chemicals that they're made from, the Earth is pretty much a closed system. We're losing a bit of hydrogen off into space which is rearranging molecules to make new ones all the time.

20:26 - Could bacteria affect criminal behaviour?

Could bacteria affect criminal behaviour?

So, could people say, "Oh, it wasn't me. It was my bugs."? Psychologist Ginny Smith took a stab at answering Paul's question... Ginny - That's a really interesting question. So I think the parasite that he's referring to is toxoplasmosis which is a parasite that's very, very common and it lives out its life cycle in rats, but then it has to be passed into a cat to complete its life cycle. So, what it does is it controls that rat's mind and it makes the rat less scared of cats. In fact, it's even attracted to the smell of cat faeces. So, it goes out into the open, it's more likely to be eaten by a cat and that helps the parasite complete its life cycle. Interestingly, lots of humans are carrying this parasite. Most of us, we don't think it causes any harm. Most people don't have symptoms, but it does stick around in our bodies for a long time after we've had it and they found that people who have toxoplasmosis latent inside them are 2.5 times as likely to get into car accidents. So it seems like it might be having some kind of effect similar to the effect it has on rats on us as well. So, could bacteria have the same sort of effect? Well, we're learning more and more about our microbiome, the microbes that live inside us and how much of an effect that can have on all sorts of things. It could affect sleep, mood, memory. It can cause illnesses, it can cause depression, all sorts of things. So, there's a chance that your microbiome could be having an influence on perhaps your risk taking behaviour, perhaps your mood, perhaps making you more aggressive. I haven't found any studies that have been directly looking at that yet. But I did found an interesting one that looked at anti-social behaviour in prisons including violence, and found that by supplementing the diet with vitamins, minerals, and fatty acids, it improved that kind of behaviour. They didn't really mention how that improvement might have been coming about but we know that your diet has a huge effect on the bugs that live inside you, on your microbiome. So, it's not too big a jump to say that it could've been the microbiome that mediated that effect, but we just don't know yet.

Chris - Ginny, you beautifully answered Bhavish's question on Twitter because he said @nakedscientists, "How does the food we consume affect our genes but also our gut brain? in other words meaning, the microbiome." So, you've addressed that one. One point about the toxoplasmosis, everything that does carry it carries it for life and the French have some of the highest rates of toxoplasmosis carriage in the world. In fact, up to 80 per cent and that's probably because they subscribed to cooking things at room temperature a lot of the time, but they also have very poor driving record. And so, some scientists have speculated that the poor driving record and therefore, high insurance premiums in France may be directly corelated with toxoplasmosis.

Ginny - The really interesting point from that is what Kat said. Can we say if your microbiome is having that effect? Is it really you that did the crime? But actually, another interesting study is looking at the opposite way around because of course, our microbiomes are signatures. They are as unique to us as our fingerprints. They've recently found that you actually leave that signature behind you. So, they're starting to look at whether you could use microbiomes to solve a crime by looking at who had been in the area.

Chris - And the whole question of, if you have a 'transpoo-sion', are you potentially at risk of acquiring someone's dodgy behaviour because there was an editorial in the British Medical Journal a couple of weeks ago asking that very question? Wasn't there, Kat?

Kat - Yeah. I interviewed Tim Spector about that. It was really interesting because I think they gave someone who was thin. She had a 'transpoo-sion', a poo transplant from someone who was larger and put on weight. But it's a bit difficult to say if that's really the case. But we won't go down that road. I think we've talked about poo enough on the show and now, I want to hear some news. I want to hear some news this week from Max. what's caught your eye?

24:28 - Forest fire devastates Indonesia

A forest fire of enormous proportions is devastating the people and biodiversity of Indonesia.

Forest fire devastates Indonesia
with Max Gray, University of Cambridge

A perfect storm of weather, farming practice and deforestation has resulted in oneforest fire of the most devastating fires the world has ever seen. Max Gray explained to Kat Arney what had caused this fire in the first place, and how it impacting the surrounding people and environment...

Max - Well, the biggest new story in zoology and conservation world at the moment is the fact that vast amounts of Indonesia are on fire. If you've come across this new story, there's huge numbers of forest fires in Indonesia. Partly because it's an El Nino year so the weather has been drier, the monsoons haven't kicked in very early, and small holdings where they burn parts of the forest to clear the land for farming which is often for oil palm plantations have spread to huge phenomenally large areas of rain forests.

Kat - How big are talking here? It's a chain of islands, isn't it?

Max - It is and so, there's fires everywhere essentially. They're visible from space. There's huge amounts of smoke going across the entirety of Indonesia.

Kat - This sounds horrific. What's it doing to the ecosystem there?

Max - It's destroying a huge amount of habitat which is always a problem and unfortunately, this isn't necessarily news in itself because rainforest destruction in that part of the world is always an issue. Unfortunately this week, it seems to be coming to a close mostly because the rains have started kicking in rather than because of any effective human action. But it has had all sorts of horrible effects on human health because of just the shear amount of smoke and haze in the atmosphere. It's even caused a huge amount of carbon emissions as a result unfortunately. This and other forest fires over the course of this year in Indonesia have released 1.6 billion tons of CO2 which is, to put that into perspective, that's about twice the annual carbon emissions of Germany. This is a horrible, horrible thing going on unfortunately.

Kat - Hugh.

Hugh - Is it just the forest that's on fire? Isn't it that there's also the peat in the ground which is on fire.

Max - That's exactly true. So, most of these forests are...

Kat - So there's loads of carbon in there.

Max - Yeah. So these peat forests, some of the most diverse habitats on the face of the planet. Because the peat is very, very dense, there's a huge amount of carbon stored there. It burns very readily. It used to be very common. There's a lot of peat swamps up in Scotland and that has historically in the UK been used as fuel for fires when people couldn't get access to coal in the 19th century.

Kat - This kind of fire situation, is that part of the natural cycle because I know in places like California, they have fires, it's kind of okay, and everything is kind of cool, and that's part of the circle of life?

Max - No. unfortunately, not. This is really a direct consequence of human action where people have set these fires to clear land so that then they can then be planted. And that has gone out of hand. So, a lot of the products that we consume on a day to day basis contain palm oil and a huge quantity of which is grown in this part of the world. There is a divide in oil palm between what we would refer to as a sustainable palm oil and the other kind of palm oil, which nobody ever refers to as unsustainable palm oil, but it is.

Kat - Naughty palm oil.

Max - Exactly and the sustainable palm oil does have a condition of not using this burning technique. And so, although it's a slowly growing movement, essentially, by seeking out sustainable palm oil, even people on this side of the planet can potentially make a difference or be it, somewhat small to stopping this from happening in the future.

Chris - Hugh.

Hugh - Getting back to the peat though, I mean, we could in theory stop pulling down these forests and maybe grow more trees. But we can never replace that peat. That peat has been there for millions of years.

Max - So, people have done calculations about this and theorised that once it's gone, it could come back but it might take on the order of 400 to 700 years

28:01 - Could we dispose of nuclear waste in an active volcano?

Could we dispose of nuclear waste in an active volcano?

Frank asked "What would happen if you tried to get rid of spent nuclear fuel rods by just docking them into an active volcano? Would this work? Is this even a good idea?"

Hugh - Well, it's an interesting idea. I mean, I think we do need to find a safe place to keep nuclear waste for thousands of years really. Some of the materials in nuclear waste are man-made. They just don't exist in nature. So, one of the things we got to be very careful about is not putting really nasty materials in places which where they might end up affecting the biodiversity.

Kat - And also, where they're not going to come back out again and that seems to be the trouble with volcanoes.

Hugh - It is a bit of a trouble with volcanoes, but that's not entirely the case. If it's a volcano that's not going to erupt then maybe what you're doing is because of the natural circulation of the magma that can go in and out, up and down deep into the Earth, maybe it is a good place. But you have to have certainty in this. And certainly, one of the issues we would face is how would you transport these very dangerous materials from where they are in these safe stores, up the side of a mountain.

Kat - This sounds like kind of a James Bond thing, isn't it? he's going to fly a helicopter directly full of nuclear fuel into the volcano.

Hugh - But there is a serious side to this that it has been suggested that a really good place to put nuclear waste would be at the subduction zones of geological strata.

Kat - So, like down by the oceans or the sort of trenches and stuff like that.

Hugh - So that it means that actually, gradually over time, these nasty materials do get taken down into the Earth. But a lot of this is very politically charged. Could you ever get permission - whatever that means on a global scale - to do anything safe with nuclear fuels? I think that's one of the biggest challenges facing the nuclear industry.

29:59 - Are roads made of the safest materials?

Are roads made of the safest materials?

Engineer extraordinaire Hugh Hunt answered Joe's question...

"Are roads made of the safest materials?" Hugh - Well, they're made of a very convenient material because when you're extracting billions of tons of fossil fuels out of the ground, some of the stuff that you extract is this thick sticky liquid tar which is quite expensive to turn into anything useful. And to be able to use your sticky gunk you waste to make roads is very convenient.

Chris - People were using telephone directories as well. They found that if they chewed them up and laid them down underneath the road then you had a very good way of attenuating vibration. So, it soaked up some of the shocks and sounds, and noise pollution.

Hugh - But there's a huge array of wonderful things you might do to make roads better, cleverer. For instance, you could embed solar panels in roads that would run the streetlights and we've seen those sort of things. But ultimately, what happens is that the yearly cycle of freezing and thawing, and frost heave and the heavy loads from trucks. Roads crack up, and the biggest challenge is making roads that don't crack up. We've come to the conclusion really that flexible bitumen works and inflexible materials are not so good. And maybe ultimately, we're stuck with bitumen.

Ginny - I was interviewing someone last week who was looking at putting little pieces of graphene, graphite, so somewhere between the two, not the kind of really expensive single-layer graphene, slightly chunkier stuff, like smashed up pencil leads into road surfaces and it makes them tougher and less likely to crack and less likely to end up with pothole problems, and extends the life of the roads.

Hugh - Those kinds of ideas are absolutely fantastic but what's interesting is that over the last however many decades, engineers have been trying to figure out actually, what does cause roads to break up. It's a very difficult problem. There is this thing called the fourth power law which says that the rate at which roads breakup is proportional to the fourth power of the load. But this is terribly approximate because it depends so much on weather and frost heave and there are so many factors. There is not a simple answer.

32:32 - Does drinking milk increase the chance of cancer?

Does drinking milk increase the chance of cancer?

We put Patrick's question to Kat Arney, and also asked about the recent news of red meat's status as cancer-causer... Chris - Do you eat sausages and bacon? His question is, "Does drinking milk increase the chance of cancer?" Should I be avoiding bacon and sausages or should I just take a reality check and probably, the risk is relatively light?

Kat - Okay, so I'm going to put my work hat on here because from my data, I work for Cancer Research UK and we do have a lot to say about diet and cancer risk and there have been a lot of studies done. So, there was always stuff in the news recently about, "red meat is as bad as smoking and it's all really terrible!" When you look closely at it, there's a really important difference when you're looking at components of the diet and cancer risk, about the strength of the evidence versus the size of the risk. Now, all the red meat stories came about because IARC, the International Agency for Research on Cancer which is part of the World Health Organisation, they basically said that there is strong enough evidence on red and processed to put it in the same category as smoking in terms of it causing cancer or increasing the risk of cancer in humans. Now, this doesn't mean that a sausage is as bad as smoking a fag. This isn't the same thing at all.

Chris - So, what about if you smoke the sausage?

Kat - Well, smoked sausages are possibly worse than normal sausages. But basically, we know for example that certain amounts that you smoke increase your risk by certain amounts which is much bigger than the increase in risk in eating certain amounts of red and processed meat. So basically, it's about the strength of the evidence is very strong. We definitely know that if you eat certain amounts of red and processed meat, you will increase your cancer risk by a certain amount. The more you eat, the bigger your risk, the less red and processed meat you eat, the lower your risk. Chris - The fact is there are billions of cigarettes being smoked all around the world every day.

Kat - Exactly. I mean certainly, your risk from being a regular smoker is going to be a bigger cancer risk than being a regular meat eater but there will be a risk associated with eating red and processed meat.

Chris - And does milk come under red and processed? Is the same sort of envelope?

Kat - So basically, the evidence on milk and dairy increasing cancer risk is very, very mixed. It's kind of a bit of an internet folklore that dairy is bad for you and it will increase your risk of cancer, particularly breast cancer. The studies have been very mixed on it so some have shown that eating lots of milk and dairy increases your cancer risk. Others have shown that it decreases your cancer risk. So certainly, the weight of evidence there is all over the place. But more broadly, when you're talking about diet and cancer, we don't just eat one thing. You just don't live on steak or on cabbage. You need to have a balanced diet that's kind of rich in fruit and vegetables, less red and processed meat, if you're a meat eater, more chicken and fish. It's risk. It's not a yes, no, black, white. The more of one thing you do, the more it will increase your risk, the more something else you do, the more it will decrease your risk. It's the same with alcohol. The only thing that's really kind of really, really bad for you is basically smoking, so don't do that.

35:55 - Do squirrels ever lose their nuts?

Do squirrels ever lose their nuts?

We put Vinnie's question to zoologist Max Gray... Max - Yes is the short answer, but not as much as people seem to think they do. It's quite a common mistruth that squirrels forget about 50 per cent of their nuts which is not quite how it works. Squirrels are actually very good at remembering where they've left their nuts.

Kat - How do they remember? Do they mark it out?

Max - They remember. Exactly the mechanisms involved in this has been studied in a lot more detail in birds, in a bird called the Florida scrub jay by somebody called Nicky Clayton here in Cambridge actually. They used a combination of both relative and non-relative directions and cues and landmarks, and that kind of thing. But we also believe that squirrels use their sense of smell to assist them. They may be able to smell because they don't bury their nuts very deep as they may still be able to smell the acorns. But they inevitably don't retrieve some of them. But the important point is that if they don't retrieve the nut, that's not necessarily because they've forgotten where it is.

Kat - They're saving it for later.

Max - Well, you would imagine a squirrel going about preparing for winter is frantically running around in oak forests, stealing all the acorns and burying them all over the place. But you're going to prepare as a squirrel, you're going to want to prepare for an unusually long winter or a winter that starts earlier or in case some of your acorns get dug up by other squirrels which happens.

Kat - They get nicked. Do they nick each other's acorns?

Max - Yes. Actually, there's some evidence that squirrels will fake-hide their acorns. They'll kind of scurry about in the Earth and not put an acorn there if there's other squirrels watching them.

Kat - They're like.ooh!

Max - Yeah. It's called tactical deception which is quite a fun term.

37:43 - Can science tell us if free will exists?

Can science tell us if free will exists?

Ginny Smith went to the world of neuroscience to answer Steve's question....

Ginny - The first thing to say is "what exactly is freewill?". We all have this feeling that we are agents, that we make our own decisions, but what do we really mean by that? What do we even mean when we say 'we'? I guess we mean our brains because that's kind of where us comes from, but it all starts getting quite philosophical. To take you back to the neuroscience side of things, there's a very famous experiment by a guy called Libet who asked people when they were in an EEG machine to move their finger whenever they felt like it and remember what time it was. They were looking at a clock when they decided they were going to make that movement. But he was also looking at what was going on inside their brain. He found that there was a 200-millisecond delay between the urge to move and when they actually made the movement. But 550 milliseconds before the urge, before they've even decided, he could see a specific pattern of brainwaves that predicted they were going to make a decision. So that suggests that actually our deciding to move comes after our brains have already done something that's going to make us move. So, he was saying that this suggests that freewill is actually a complete illusion and we don't actually have it.

Kat - So, what is controlling us?

Ginny - So, we're not 100 percent sure. What we think is that.

Kat - Is it the parasites?

Ginny - It could be the parasites. But basically, our neurons start to fire when enough input has built up. So for example, if you went outside and it's a sunny day, you're getting input from the sun that's going through your eyes to your brain and it may be that you decide to put your sunglasses on when that input has built up enough to make your neurons fire then your freewill kind of comes after the effect and creates this idea that you thought you were going to put your sunglasses on. We know that our neurons aren't quiet. All the time, stuff is going on in our brain. Even when we're relaxing, we've got this default mode network where things are firing, stuffs going on, and it could just be that our decisions when that kind of random firing has built up enough and freewill is an illusion.

40:07 - Tomorrow's Engineers Week

Tomorrow's Engineers Week aims to inspire the next generation of engineers.

Tomorrow's Engineers Week
with Hugh Hunt, The University of Cambridge

Tomorrow's Engineers Week aims to get young people to consider engineering as Engineering drawinga future career. Cambridge University engineer Hugh Hunt explained the importance of such campaigns to Kat Arney..

Hugh - Last week was Tomorrow's Engineers Week and I think it's really important to recognise that if you're doing maths or physics or science at GCSC at school, you could carry on with your maths and physics and maybe go on to study engineering and become an engineer. Because I don't think there is a very strong link at school with the idea that engineering needs maths. So last week there was lots and lots going on in schools and outside of schools to try and show how engineers out there in the real world use what they learned at school. It was just fabulous to see just how much excitement and interest there is in engineering.

Kat - When we think about maths, there is this kind of almost this joke that you learn about this stuff at school and then you never use it in the rest of your life. What kind of jobs come under the banner of engineering because I think people think maybe it's just someone building a bridge or digging a tunnel?

Hugh - I think it's a very interesting thing to think about. The Philae lander that landed on the comet recently and thpses remarkable photos that came back from Pluto. I think it's estimated that 90 per cent of the people that worked on those projects were engineers and a lot of that engineering isn't the engineering of the lander itself or of the devices that are going to space. But all of the ground engineering, how do you receive the signals, how do you analyse, how do you process them. And I think every object that you see in your room, if you look around, there's a chair, there's a light bulb, there's paint on the wall, there's carpet. It's an engineering marvel that all of these things are there.

Kat - And I know certainly from the campaign for women in science engineering, trying to get more girls to go into engineering as well.

Hugh - And it's interesting that in some countries like France, engineering is perhaps about 50/50 men and women. There's absolutely nothing at all that says that engineering should be a male domain.

42:17 - Why do I wake up before I need to?

Why do I wake up before I need to?

Chris Smith held the answer to Renny's question... Chris - The reason this happens is that we're actually extremely good at keeping time. In common with pretty much every living process on Earth and I'm including in that bacteria even, we have body clocks. Bacteria have a body clock. They know what time of day it is chemically speaking. In us, the seat of that body clock is a small cluster of maybe something like 20,000 nerve cells which is in a part of the brain called the superchiasmatic nucleus. It's in the bottom of the centre of your brain. These nerve cells are running a genetic programme where gene 1 turns on and that turns on gene 2 which in turn, turns on gene 3 and feeds back and switches off gene 1. And this genetic clock ticks around taking about 24.5 hours to complete its cycle. As it does so, it changes the activity of the nerve cells in the superchiasmatic nucleus and because they are connected to lots of other bodily systems, they can influence how different parts of your brain function and critically, they influence other parts of your so-called hypothalamus including the part of your hypothalamus that produces the hormone cortisol which comes out of your pituitary, goes around your bloodstream, and visits every cell in your body. And this is how your brain's body clock then sets slave clocks which are running in every single cell pretty much in your body. So, every cell in your body knows what time it is. When you get into a rhythm of always waking up at a certain time, your body has to anticipate that it's going to need a big surge of energy at a certain time of day because that means that when you leap out of bed in the morning, you're ready to go. Your metabolism is fired up, you have energy on tap, you're enthusiastic, rearing to go because you want to get to work because it's Monday morning. And the way it does that is by learning that process and cortisol setting all those clocks. Now, what that does mean is that when you change time zones, it's all off-whack and out of kilter because that learning needs to be relearned and readjusted. It also means that because your body clock hasn't catered for weekends, it still thinks it's going to be Monday to Friday. And so, your body clock gets you out of bed even on the weekend, and at least alerts you and wakes you up, and prepares you for the day ahead before you actually need to. It takes a little while to overcome that effect and try and drop off again, and by then of course, you should be rearing to go again. unfortunately, there's no simple answer apart from learning to get up later during the week which is not always possible.

Kat - I have seen some quite interesting stuff about schools and workplaces. It should be more catered towards people who have different sleep-wake cycles because I'm a real night owl. I struggle to fall asleep before about 1:00 o'clock in the morning. Luckily, I've got a bit of flexibility. I don't normally have to get to work until about 10:00. But I don't even wake up until at least lunch time in my brain.

Chris - The thing that's really making a difference now though is screens. The change and the revolution in technology means that many, many people are sitting in front of computer screens, and flat screens which are LCD until well into the night. Social media have got very good data on who's using it, what they're logged into and.

Kat - It's basically all me I think.

Chris - The reason these screens are important is that they are using blue LEDs to produce the white light that you see from the screen. The blue is critical because it goes out of the screen, into your eye, and at the back of your eye is a population of retinal ganglion cells and they're called intrinsically photosensitive retinal ganglion cells. They're important because although you don't see with those cells, they contain a pigment that's very sensitive to blue light and they're connected to your body clock, and they're used to reset your body clock and tell it when it's bright light coming in early in the morning, must be wake up time. So, by basting yourself in rays from your screens at night, you're actually sending a really strong wakeup signal to your brain which is what you shouldn't be doing last thing at night. As a result, you're actually waking yourself up and making it harder to fall asleep and people are robbing themselves of sleep chronically this way.

46:49 - How is it determined that an organism is a new species?

How is it determined that an organism is a new species?

[transcript to follow]

49:11 - How do creatures in sub-zero environments keep their metabolisms working?

How do creatures in sub-zero environments keep their metabolisms working?

We put Bruce's question to Kat Arney...

Kat - This is a great question basically because I like polar bears. There's kind of a difference between hot blooded and cold blooded animals. Now, the hot blooded animals, they need to keep a constant body temperature and you tend to get more hot blooded animals in colder places. So for example, they will keep their body size, they have big body size because that means they lose less heat, they have things like fur, lots of blubber. They'll try and eat as much as they can and this helps to keep them at this temperature where their metabolism will work. Cold blooded animals, things like snakes, salamanders, all these kind of things, they will just be the temperature of their environment. So, as the temperature gets colder and colder, and colder, they basically just kind of shutdown. So, turtles and things like that will effectively, if it gets really cold, they'll just stop working. Bigger animals and mammals, they can hibernate and their body temperature does drop. That kind of gets them through the worst of the winter. Scientists are really trying to study this phenomenon to find out, can we maybe put people into a kind of suspended animation if they've had an accident or potentially, as we've talked about, going to Mars. Could that work? Another thing is that the genetics of individual organisms affects their metabolism. So for example, you might make slightly different enzymes that work better at different temperatures. And also, there's different molecules in your cells that can act as anti-freeze and try and keep all your cells and everything going at lower temperatures. So, there's lots of different ways that animals do it. obviously, evolution is a wonderful thing and will adapt each organism to the niche that it lives in. Lots of ways that different animals do that - polar bears mostly by being cute and furry.

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