Why is There Always Room for Dessert?

We pick apart the questions you wanted to ask, about space, food and mental health.
08 January 2019
Presented by Chris Smith
Production by Georgia Mills.


Do astronauts get WiFi in space? What is the speed of gravity? Why is there always room for dessert? Giles Yeo, Anne-Laura Van Harmelen, Richard Hollingham and Francesca Day gather round the microphones to answer your need-to-know questions about space, food and mental health.

In this episode


New year, new science

Chris Smith asked Richard Hollingham, Anne-Laura Van Harmelen, Giles Yeo and Francesca day what breakthrough, development or discovery, they would really like to see happen in 2019.

Richard - I would really like to see Virgin Galactic succeed in flying space tourists or maybe even Richard Branson into space properly. Just before Christmas they managed 50 miles high in their test spacecraft. I hope they can keep doing this successfully, so the whole space tourism market starts to take off. This isn't just a plug for Virgin Galactic. This is because I have a bet with a friend that Virgin Galactic are going to do it because he was convinced they never going to do this. But also the more companies that get involved in space, particularly these more innovative space plane type technologies, then that's going to really drive down the cost of access to space and maybe one day we can all go into space.

Chris - I used to think I really wanted to go into space, but then since I met you and I've thought about it a lot more and you introduced me to the exigencies of space and you put your wife in a human centrifuge etc., I've lost the inclination.

Richard - Space is horrible, really really really horrible. My favorite quote is from Star Trek, from McCoy in Star Trek, “Space is disease and danger wrapped in darkness and silence.” .

Chris - Francesca you work on things in space, you’re an astrophysicist, so what would you like to see happening in the year ahead?

Francesca - Well if we're wishing for things, I would like to see one of the many experiments that are searching for the identity of dark matter come up with a positive signal and then we might finally find out what it is.

Chris - Why does it actually matter that we understand this? If we know we've existed,
we have no problem existing in our cosmic neighborhood, why do we need to know what this mystery stuff is all about?

Francesca - Well firstly because I really want to know and I think a lot of other people feel the same way. There's just this real drive to uncover how the universe works. Secondly, on a more practical level. Anything we can do that helps us uncover the laws of physics I think it's actually very likely to have technological applications that at this stage we could really only dream of.

Chris - Talking of brains and dreaming, terrible segue I know, but Anne-Laura, anything you would like to see solved and in 2019?

Anne-Laura - Yeah. Good segue-way. I'd like to see scientists use or harness social media in order to better identify adolescents who are at risk for mental health problems.

Chris - Why is this an issue? Not that they have a problem but why is it an issue spotting them?

Anne-Laura - It's an issue spotting them because we don't really know what makes adolescents vulnerable to mental health disorders and especially we don't know what the critical at risk behaviors are. And we haven't really been looking at social media in order to answer that question. I think that that is a really new thing that we can harness and it will give us lots of new information.

Chris - A radical change in the way that we all live our lives isn't it.

Anne-Laura - Yes.

Chris - And Giles?

Giles - I'd like to see us better model the human brain in a dish, like converting stem cells either into neurons themselves which we can do now or actually make brain organoids. The reason why is because I study obesity, that's what I study, and obesity, as we'll talk about perhaps later, is a brain disease, it involves genes within the brain. And obviously if we're trying to study it, at the moment we're using models, we can't legally get into a human brain while they're still alive for obvious reasons and so we need better technology in order to ask the questions in a human context.

Chris - And ask a petri dish why it wants to get fat?

Giles - Exactly. We get Anne-Laura coming in and saying why do you think you're getting fat?

Chris - Giles thank you. While you sort of think about all of that, we have a little guess who game, which we're going to play right across the program for everyone at home to listen to. What we do is give you a sequence of clues as the hour unfolds and you have to try and work out what this thing is. I'll tell you for free it's an animal. The first clue is: this is what it sounds like. Any clues? We'll give you a bit more information later on as the program goes. But for now let's start with this question for you Richard.


Do astronauts have WiFi?

Chris Smith put Rhian's question to Space Boffin Richard Hollingham...

Richard - Well sort of. There is wifi on the space station. You'll probably see pictures of the space station, you'll see astronauts with iPads or laptops not connected by cables. So they have wifi but it's not really connected to the internet as such. So they can access the internet, but mostly they are accessing NASA's communication system, which is provided by these satellites called TDRS, which are tracking and data relay satellite. You mention the International Space Station spinning around the Earth in low-Earth orbit.

Chris - It’s an orbit every hour and a half isn’t it?

Richard - Yeah, every 90 minutes. Then above that, in geostationary orbits, are spinning at the same rate as the Earth, so they’re just sitting there above the Earth, there are these 10 satellites which act as a data relay to the ground. So using those you can get HD video, you can get pictures, you can get mostly all the data that NASA uses. You see pictures or videos of astronauts on the space station, it’s pretty good quality. That also means you can send up movies. So yes they have a movie night, usually I think on a Saturday or Sunday night, so they have movie night on the space station. They have a screen, they have a projector and they can all sit around in the sort of dining area watching movies, but it's not Netflix.

Chris - You’ve interviewed a lot of astronauts haven't you? What do they tend to watch? Because there are a lot of sci fi films, space films out there that's a little bit kind of pathetic if you're actually up there doing it for real.

Richard - They do. They love their sci fi. They love Apollo 13. You know, they love a disaster. They love a disaster in space.

Chris - Is that the sort of visual equivalent of sort of masochism?

Richard - I was intrigued, the other day I was on a plane and I watched an aircraft disaster movie. You can do that on planes. Same way in Antarctica. So Antarctic midwinter, they watch the Antarctic horror film ‘The Thing’ and that's the annual movie in Antarctica. There is this, I think you know, they’re astronauts aren't they, I mean they're not afraid of anything.

A peeled banana

07:35 - Am I half a banana?

Do we really share 50% of our DNA with bananas?

Am I half a banana?

Chris Smith put Sam's question to foodie and geneticist Giles Yeo...

Giles - We clearly share 50 percent of some of the genes with the banana because we're all living beings on Earth and we effectively evolved from the same primordial soup. And so there are going to be enzymatic reactions, things that actually happen with us that are going to be shared. But clearly just sharing the DNA does not make you 50 percent a banana. I mean it's like saying that we share 98 percent of our DNA, complete DNA, with chimpanzees. Does that make us 98 percent chimp? I think what is critical is not only the stuff that is there but how it's turned on and how it's actually turned off. And I think that is probably what is the biggest differences there. So no, I mean we're not 50 percent banana per say even though we share half our genes with the banana.

Chris - Is it really coming down to the distinction of what is a gene? Because a gene is essentially a block of DNA that does a job in a cell and that gene is made of genetic letters, which is how it's spelled out. So I could have a gene in a banana that does a similar job to a gene in a human, but the actual genetic spelling of those two genes, they do a very similar job in the two contexts, but actually they're spelled quite differently. So it's actually down to semantics, what actually is a gene compared between two species.

Giles- That's absolutely right.

Hubble Telescope image of distant stars showing diffraction artefacts.

Can dark matter make dark stars?

Chris Smith put Eva's question to Cambridge University astrophysicist Francesca Day...

Francesca - Dark matter is matter that we know is out there in our galaxy and in the universe because we can see its gravitational impact on other matter, it makes other matter move faster from its gravitational pull, but we can't see it at the moment in any other way. We can't see any light or anything that it emits, as far as we know it doesn't emit any, and we can't detect it in any other kind of lab based experiment on Earth. So most of the matter in the universe we don't understand even though the regular matter we understand really really well. There is this kind of big tension within physics that there is this small group of stuff, the stuff that the Earth is made of, that we really know what we're doing and then most of the stuff out there we've just got no clue.

Chris - Could it though, because it's gravitationally active like the matter we're made of is gravitationally active, could it all clump together and make a huge great dark matter star, which is what the question is all about?

Francesca - Maybe. It depends what exactly dark matter is. In some models of dark matter you do get things called dark stars and by stars what we mean here is an object that has an inward force, so it's a clump of dark matter, there's an inward force set up by gravity and there's an outward force set up by some kind of pressure. So if dark matter interacts with itself, if it interacts with other dark matter, then it could form a star like object, but the star wouldn't shine in the way that our stars do.

Chris - I was going to say, what color would it be?

Richard - Well that was my question actually, is dark matter necessarily dark?

Francesca - It has to be darkish. There are limits on how much it can interact with visible light, but it doesn't have to be completely non interactive with visible light. And indeed we hope it interacts a bit otherwise we’ve really got no chance of discovering what it is.

mental health

11:25 - Is mental illness really on the rise?

How commonly are young people suffering from mental health issues?

Is mental illness really on the rise?

Is mental illness on the rise? Cambridge University neuroscientist Anne-Laura took on this question.

Anne-Laura - Right. I think the answer is both really. Adolescence is a really important time period for the emergence of mental health disorders. And we know that by age 14, 50% of all mental health disorders have emerged. And by age 18 it's about 75%. So adolescence in itself is a really important time period where the majority of mental health disorders first emerge. And what we also know is that about 1 in 10 children in adolescence have a diagnosable mental health disorder but in the last couple of years the number of children in adolescence with a mental health disorders has been rising and this is particularly prevalent in girls. And a good example of that is that there is a 68% increase in the number of adolescents hospitalised for self harming behaviours and the self report of self harming behaviour has increased substantially from 1 in 20 to 1 in 4. So there's definitely a very clear pattern of emerging and increasing mental health problems in youth.

Giles - How much of this do you think can be social media driven. You know because you know, orthorexia, where you actually are, this eating disorder where you like to eat perfectly from Instagramers and things. I mean how much you think is driven by social media.

Anne-Laura - So there is actually really good research done in the last couple of years about the effects of social media on adolescent mental health. And actually the effects are really really little and it seems to be the case that little use of social media is actually beneficial. But then a lot a lot of use is not beneficial but social media use research is really complicated by the fact that most studies actually look at screen time now, what what does screen time mean, they count chatting with your grandma on the face time is the same as looking at a pro-ana website for instance. So you have negative interactions and positive interactions that are all kind of cluster together. So it isn't social media in general that we need to look at but it's what are they doing on social media.

Chris - Returning to the original question do you think then that we are seeing a big increase in mental illness in young people or we are just becoming much better at spotting. I know you said is a little bit of both.

Anne-Laura - No there is, there is a really clear evidence really that the prevalence of mental health disorders in youth is increasing. So and it's definitely also the case that we're more aware of it and we're talking more about it but that is unrelated to the increase.

baby mice

Can animals mate in space?

Chris Smith put Simon's question to Space Boffin Richard Hollingham...

Richard - It is a good question, can I break that down into two things. So let's talk about the animals that we know have mated in space. So we know frogs have mated, salamanders have mated, sea urchins have mated, fish have mated. We're not sure about humans. So they're the animals that have mated in space. Then you have to look at offspring. So there are some have given birth in space and there are some that have conceived in space and then given birth back on Earth. So we know frogs have successfully reproduced, salamanders, sea urchins not so much, fish have successfully reproduced. I was looking at this and the best research seems to be done on mice and they had mice conceived in space and then they brought the embryos back to Earth watch their development, not as successful. So not so many successful healthy mice were born as would have been born on Earth. So this is almost certainly down to lack of gravity.

Chris - Really not just radiation, isn’t there incident radiation in space?

Richard - There is but that's unlikely.You know when you’re only talking a few days on the space station which is shielded and in low Earth orbit. So anyway it's got the protection of the Earth's magnetic field, certainly the conclusion of that paper was that there's some gravity factor acting on the embryo.

Anne-Laura - How is that the fact that they are in space it must be really stressful for these animals. How is stress being taken into account?

Richard - Well they probably haven't. If you were a mouse floating around in a windowless box,you know, that's not an unstressful environment. So yeah absolutely it could well be that it could well be that. I think there is a bigger, if you going to talk about stress is a bigger moral issue with the point of doing this research is so humans can reproduce and live in space. Either in an orbit around a planet in zero gravity, or on the moon, or Mars in lower gravity, then what are the morals of actually raising a child in that sort of environment? For the same reason we don't raise children in remote Antarctic bases. Should we actually be raising children on Mars? And I think that's a more interesting question almost.

weight loss

Is liposuction better than a gastric band?

What's the best way to lose weight? Chris Smith put Mary's question to food expert, and author of Gene Eating, Giles Yeo...

Giles - I'm going to give you the short answer and the short answer is liposuction is no good for us at all, because it's cosmetic; whereas the gastric band actually tackles the source of the problem, which is food intake. Okay, so in order to unpack this the first thing we've got to know is fat gets a bad rap but it's actually its job is to store energy. And when we gain weight we don't get more fat cells, not largely speaking, but your fat cells get bigger, like a balloon. And the problem is, when you actually get to a point where the balloon gets full, then the fat goes somewhere else and it's when it goes somewhere else - such as your muscle and liver - that you end up with type 2 diabetes; you know increased risk of cardiovascular disease blah blah blah...

Chris - Okay. So liposuction is the metabolic equivalent of sweeping dirt under the carpet. Basically, you suck out the fat you can see, but it doesn't take away the bad fat that's doing naughty things in other parts of the body that you can't see?

Giles - It's even worse than that, because the problem with liposuction is it removes your safe fat-carrying capacity; so you can imagine of all these balloons - you know going bigger smaller bigger smaller - the more of these balloons you have, actually the safer; you may not look as good okay, and that's fair enough, but at the end of the day you're less likely to actually tilt into disease. Liposuction may give you a nice booty, but the problem is it actually increases your risk of disease, so it’s even worse than sweeping under the carpet. It's actually giving you more and sweeping it under the carpet. So a gastric band should be the way to go if you're looking at the two of those.

Chris - And what's the book called?

Giles - The book is called “Gene Eating”, which is a play on “clean eating”. It's called the science of obesity and the truth about diets. And, largely speaking, what it’s looking at is the diets that are out there. Now some of them are very faddy and have no scientific basis to them at all. But most diets work to some degree. And the question is what the kernel of truth is; where does that kernel of truth come from, and where the fantasy has actually emerged is what the book is about.

Chris - Most people say that most of these faddy diets work because what they do is make you more calorie conscious. So you pay more attention to what you eat more of the time and you're therefore a bit less likely to overeat.

Giles - At the end of the day a diet that works is a diet that reduces your caloric consumption, right. I mean, it's physics. We can’t actually get away from physics, but different people are going to have completely different strategies of reducing their caloric content. So my wife, for example, bans me from buying chocolate in the house -  there's a plate of chocolate in front of me at the moment! - because she loves it.

Chris - We just wanted to see we've done the experiment the psychologist to the room will say there's a place actually Mr. treats including a cherry Bakewell in front of jars and we're just seeing how many we're going to weigh the plate at the end and we'll see how many have you have consumed.  I've given the game away.

Giles - I know you have you have but but I can't buy chocolate in the house because my wife says “I'll eat it! Don't buy it now!” That's fine. But I have no problems with chocolate but with pork scratchings!

Chris - You can't resist that?

Giles - I can't resist those! But, I imagine a government edict comes down to say ban chocolate so we can lose weight. It'll only work for my wife and not for me because we're not tackling the reasons why we're going to eat more. Diets, if you are to lose weight are going to be personal. You have to do you. There is no magic one diet that works for everyone.

Chris - So that's “Gene Eating”; it’s out, by Giles, at the moment.


21:56 - Quiz: Glow in the dark cats!

We put the panel to the test with our own cunning questions...

Quiz: Glow in the dark cats!
with Richard Hollingham, Boffin Media; Anne-Laura Van Harmelen, Cambridge University; Giles Yeo, Cambridge University; Francesca Day, Cambridge University

We put our own questions to the panel, to see who will be crowned The Naked Scientists' Big Brain of the Week! On team 1, Richard Hollingham and Anne-Laura Van Harmelen, team 2 Giles Yeo and Francesca Day...

Chris - Round one is an old chestnut an old favorite. It's called Tech yes or techno.
Team one. Which of these is a real piece of technology, vacuum cleaning shoes or ironing gloves?

Richard - Vacuum cleaning shoes would be great!

Anne-Laura - Well maybe vacuum cleaning shoes could be on wheels, like roller skates, and then you could roll around your house! I would say that the gloves are actually more realistic.
Yeah I think for the gloves.


Chris - Actually that you were right Richard. the vacuum cleaning shoes are a real piece of tech. Someone's probably not far behind with the gloves. Team two: which of these is real: jeans that double as a keyboard, or a wallet that gets scalding hot when it's stolen. And that forces the thief to drop it?

Francesca - So how does the wallet know when it's been stolen? It would have to be it's far enough away from some phone or something I guess.

Giles - Genes as a keyboard?

Francesca - Yeah you do get these like flexible plastic these days right.

Giles - Genes like DNA?

Chris - Not those sorts of genes. Jeans!

Giles - You see now we got to start from the beginning! We've got to go with the jeans.


Chris - Yeah it is the jeans, that double as a real keyboard are actually a real deal. You can buy jeans they've got a keyboard on the crotch area so you can if you're in touch with technology. You can tap away to your heart's content. You stay in touch with the social media with your friends and get any likes.

Giles - This is a family program!

Chris -  It's as you say flexible plastic type technology. Okay team two are in the lead at the moment, round two. Round two is called Weird Science.

Team One which experiment has actually been done -  genetically engineering glow in the dark cats or genetically engineering ducks, so they have chicken’s legs. What do you think?

Richard - That's not ethical. You can't do that can you? I think glow in the dark cats. I think that's doable. Yeah I think that's quite straight forward, doable, ethically not so dubious. Let’s go for cats.


Chris - Genetically engineered cats are real. They used the same gene that makes jellyfish grow GFP green fluorescent protein to make them glow in the dark. Team 2 it's level pegging now. You gotta get this one right. Have scientists trained dolphins to sing a national anthem or have they trained bees to play football?

Giles - I think it's the bees to play football. A bee-sized football, not an actual football!

Fran - If there were enough bees, and there are good at that, it could be an actual football.


Chris - Yet it isn't 11 aside. Actually these are individual bees that were trained to move a ball and they learned to move a ball by watching what other bees did. So it was bees learning socially from other bees which as you say Fran is what they do to make their hives a success.

In terms of dolphin singing the national anthem the Miami Dolphins do of course sing the national anthem but that's at their football game and they're not an animal, they're human.

Round Three this is called beastly lies which animal super power have we made up and which is the real deal?

Team 1 the naked mole rat can survive being driven over by a Mini or the cockroach can survive being put in a microwave?

Richard - I mean it depends how long we put it in the microwave for doesn't it? Could probably survive a couple of seconds? Nothing can survive that long in a microwave!

Anne-Laura - We’ll go for the cockroach.


Chris - The cockroach is the one that can survive. naked mole rats can survive being submerged in water for an extended period. They can survive high temperatures and even acid. I think that's as low pH not LSD, but they unfortunately are not capable of surviving being run over. So that's the point for team one. Team two, which animal super power have we made up here? Can a pistol shrimp snap so quickly it generates a temperature equivalent to the surface of the sun or kind of type of sea sponge become so acidic that it can dissolve out of the sea creature that just tried to eat it?

Fran - What's a pistol shrimp? Is it like a mantis shrimp?

Giles - Does it look that mantis shrimp thing? I'm guessing, we're guessing. The acidic thing sounds more plausible. Let's go with let's go with acid sponges.


Chris - No you got that wrong. Actually it's a pistol shrimp. The duration of the click that they make with their pincers is less than one millisecond the snap produces what's called sonoluminescence from a collapsing capitation bubble. So they produce an area of very low pressure this causes a bubble to pop into existence which then implodes on itself and as it does so it unleashes a thermal pulse which is of more than 5000 degrees, the surface of the sun is about 5000 degrees. It was the pistol shrimp that actually carried the day there.

Right. That means you're at a tiebreaker situation. So who's going to win this? Now the way this works is that the two teams will discuss between yourselves. When I read out this question you have a very short time ago to work out what you think the answer is. And the team that gives us the closest answer are going to get the point.

Okay so the world's fastest animal is the peregrine falcon. How fast can it go?
Richard - We're going for 200 kilometres an hour.

Chris - Giles and Fran?

Giles - Somewhere close to 160 kilometers an hour.

Chris - That means Richard and Anne-Laura you are the winners, the answer is 390 kilometers an hour. Well done Richard and Laura. Congratulations to you and commiserations to our very worthy losers. I mean that in the nicest sense as in losing the competition.

Binary Stars

How fast is gravity?

Astrophysicist Francesca Day took on this question, put to her by Chris Smith...

Francesca - When we say light can't escape a black hole that's absolutely true. And that's to do with the way that a black hole warps the space in which the light is travelling. Such that, whatever happens to it, it ends up going closer to the black hole. Since the observation of gravitational waves we know very precisely that gravity travels very, very close to the speed of light. We observed an event in which two neutron stars merged and we saw both gravity waves and light emitted from that event. And based on the arrival times of the gravity waves and the light we know that they travel very very similar speeds.

Chris - So basically it goes at the speed of light. But how is it travelling? Is it ripples in the fabric of space that are propagating along? If so, why should they travel at the speed of light? Is that a coincidence, or is there a physical reason why that should happen?

Francesca - There's a physics reason. So one of the great mysteries that we're trying to solve in particle physics at the moment is how quantum gravity works; how we can fit a picture of quantum mechanics and particle physics with a picture of gravity portrayed as spacetime. But we do know almost certainly that there is also a particle associated with a quantized theory of gravity and that's called the graviton. So, in the same way that the photon carries the electromagnetic force, the graviton would carry gravity; and because we think the graviton is massless like the photon, it travels at the speed of light.

A child's drawing of a family

30:32 - How does upbringing affect your mental health?

Can life in your early years affect your risk of mental illness?

How does upbringing affect your mental health?

 Chris Smith put this question to Cambridge Unviersity mental health expert Anne-Laura...

Anne-Laura - So, we know that your childhood is actually really important for your mental health risk. One important clue is that mental health risk often emerges still in childhood. And we know that negative experiences in early life are really, really important for making you more vulnerable to develop mental illness later on in life. The idea is that if you have lots and lots of stress when your brain is developing and when your cognitive functioning is developing still it will impact or so the stress will shape your development. And an example of this is for instance that your brain is really able to quickly detect threatening things, stimuli, in the environment which, from an evolutionary point of view is really important because, when you're walking around in the woods seeing a bear will help you to respond to that quickly right, but when the bear’s in your home environment day in day out this chronic level of stress might lead to your brain to be developed slightly differently making you hyper vigilant to threatening experiences in the real world.

Chris -  So if someone has had a very traumatic upbringing or a bad series of life events when they're little, what should they do to make sure that they do reinforce the positives and don't slip into this vicious cycle of developing the risk factors that would put them at risk of a mental illness later.

Anne-Laura - It's a whole multitude of things that can help and we call them resilience factors. So resilience factors are things that help if you've experienced really negative things to make you more resilient in the future and we know that self-esteem and once your self-esteem is high it helps and we know that when you have really good support from your friends it helps we know that when you have a caring loving family that that helps. So there are lots of different things and there are things within the body within yourself but there are also things in your environment and you don't have to have all of them. You can have one of them in order for it to be beneficial for you in the future.

The red planet

32:38 - When will humans be living on Mars?

When are people actually going to get to Mars, if ever?

When will humans be living on Mars?

Chris Smith put Hannah's question to Space Boffin Richard Hollingham, asking if we really would want to go to Mars in the first place...

Richard - This is my basic thesis space is horrible. Don't go there. Yeah it's really it's interesting. So a few years ago if you went and did an interview at NASA they would talk about journeys on the way to Mars. All this was on the way to Mars, space station was a stepping stone to Mars. You won't hear that anymore. They now talk about going back to the moon. So that is the new destination. As we're celebrating you know this next year in 2018 2019 50 years since the first man on the moon to walk on the surface of the moon. Now talk about return to the moon rather than Mars. And that's hard enough got to go back and recreate these technologies but I'm pretty certain that's going to happen. Pretty sure we will see people whether they are NASA or Russians or Chinese perhaps on the moon within the next decade. I'd confidently say that I was so confident. You're right. I only got to invite me back in 10 years on the naked scientists and I will either be proved right or wrong. Mars is, really, I don't think I can say quite safely, I'll say 2040 right now there'll be people on Mars at the moment we can't even get a coffee cup size sample of Martian soil back from Mars to Earth. That is the problem. We can land on Mars. We can't always land on Mars successfully as the Europeans failed to land on Mars with their Lander last year. So you know it's not always easy to land on Mars. It's really difficult. We don't know quite how to get off Mars again. So maybe a one way trip. I don't think that's realistic.

Chris -  So yeah why do we even want to go.

Richard - I don't know. You know could the pictures from Mars it's really horrible. There might once have been flowing water, now, I think, that it's pretty certain there was water flowing on the surface of Mars once. You know the idea that you can turn it into some new earth. I mean that this goes solely the realms of science fiction from what I understand it for most of the time if you were standing at night on the surface of Mars because of this hazy dusty atmosphere you wouldn't even see the stars. So you know it's a grim cold horrible place to be. Why would you want to go.

Researchers are developing technology to use alongside therapy in order to support eating disorder treatment.

Why do I always have room for dessert?

Speaking with Chris Smith, Giles Yeo answered this question from Rosie...

Chris - Indeed. Now we've all been there haven't we; absolutely stuffed, and then someone comes along with the sweet trolley and then says, "would you like some of this delicious chocolate cake?" you miraculously find a sort of cream-cake-sized corner that's vacant in your stomach... How does this all work?

Giles - So I mean, we know this "dessert-tummy-phenomenon". We go out - I bet you - by the middle of the second course of a meal that you're actually eating - you will have reached your metabolic need for a day! Which means that you would have made up the calories - you know a big meal, not a Michelin star fancy fancy...

Chris - "Nanofood!" 

Giles - Exactly. Exactly. 

Chris - So a decent portion!

Giles - Yes really full... yet, when dessert comes, we actually eat it. The more important question actually about that is, why is it specific to desserts? Because if, say, you had steak and chips and you're really stuffed, and the waiter comes by and says, "More steak? More chips?" you go "dude, no, I feel like puking!" and I won't actually eat it. Yet, we'll actually have the dessert! Well here's the point right when we actually throw back to the Serengeti, when we're dragging an antelope back, and you had to eat more than you needed, because you would never guarantee to get the antelope.

Chris - There's no "Serengeti supermarket". 

Giles - There's no Serengeti supermarket. The problem is something like protein is very bulky. Right. So it goes in. So what happens? Your brain begins to change the quality of the calorie that it actually likes to eat. It begins to increase the caloric density of the food that you eat. So therefore, for every given gram you'll get more calories. You can stuff it into all the little nooks and crannies. What is calorically dense? Fat and sugar. What's high in fat and sugar? Desserts! It's a hold-back from the Serengeti to keep yourself alive even when you've had so much food. And lest you think it's human-specific, look at the grizzly bears doing the salmon run. Okay. So they start getting ready for hibernation. They start by eating the whole salmon, like Garfield right, the whole thing. But, again, as they get fatter and fatter they only eat the skin and the fat underneath it. They increase the caloric density. They don't have dessert but that's the phenomenon!


Could a hidden planet share Earth's orbit?

Speaking to Chris Smith, Francesca Day answered this question for Hannah...

Hannah - Could another planet exist on the other side of the sun that shares our orbit but we never actually see it?

Chris - It's like in the pantomime where the person is always behind the other person it's behind you. Could there be such a planet.

Fran - Probably not. Because even if you didn't see it because the sun was always in the way, we would notice its gravitational effect.

We've measured the orbit of the Earth and other planets very precisely, so we can actually map the influence of the planet on all the other planets. And, if there was an extra one, then even though its gravitational effect is very small compared to that of the Sun, we would still have noticed it...

A depressed woman

41:47 - When does sadness become depression?

What's the difference scientifically, between being sad and being depressed?

When does sadness become depression?

Chris Smith put this question to mental health expert Anne-Laura van Harmelen from Cambridge University...

Anne-Laura - We know certain things about what's going on in the brain when people are more depressed. One of the things is for instance the serotonin system is a neurotransmitter system that makes you happy and that system is shown to be there's a bit less serotonin in the brain in certain regions.

Another thing that is kind of well replicated or well known now is that there are certain networks of brain regions that are working differently or they're more or less active in people with depression. For instance the ventral limbic system is elevated in its connectivity and that means that it is excessively actively giving you negative mood. We also know that the frontal striatal network is lower and that is related to loss of interest and motivation and less pleasure in activities we also know that the default mode network is more active and that is related to more negative thinking about yourselves. But the problem is that you can have different kind of sorts of depression and a researcher has shown that there are over a thousand different types of depression.

So we know that there are lots and lots of different types of depression that also means there are lots and lots of different types of depression in the brain. And in addition to that you can have the same type of depression but with different reasons for that depression. So you can have depression because you had really severe stress in early life or you can have depression because you have financial difficulties. So even if you have the same type of depression or the same symptom clustering, you can still have different causes and therefore different mechanisms through which you get to these systems. So we don't really know yet and the reason for that is is that it's so multifaceted.


Is obesity genetic?

Chris Smith put Omar's question to food expert Giles Yeo, from Cambridge University...

Giles - Written is a very strong word. I think what is undoubtedly true is that our body shape and size, of which being obese is one element of that, has a powerful genetic element. Okay but everything all our traits have a genetic element the question to ask is how much of it is genes and how much of it is the environment? And your body weight and shape and size is a very very typical thing in which genes interact with the environment.

The bottom line is we know that obese people put very simplistically are obese because of a number of genes within the brain that make them more susceptible. You can't go against physics you have to eat more. But what happens is these genes tend to influence your feeding behaviour, your behaviour around food, making people slightly hungrier or slightly more driven to forwards food, they eat more, they gain more weight, therefore our difference in body shape and body size.

Chris - Do we know where in the brain those genes are exerting their effect? In other words biochemically if you're a carrier of a form of a gene that makes you more prone to overeating, where is that gene manifesting its influence?

Giles - Because there are now over 200 genes that we know of that each subtly influence our interaction with food, they exist all over the brain. I mean some exist in an area called the hypothalamus in which it actually influences your actual hunger for food. So just tummy grumbling, I'm hungry. Others can sit actually in your higher your hedonic areas of your brain, your reward function, which influences the amount of reward the pleasurable feeling you actually get from food and others are going to be in areas of responding to stress and we know some people eat in response to stress, other people stop eating when they respond to stress. Same hormone, but yet we actually respondent in different fashions. And so all over the brain.

Chris - One question that springs to mind though Giles is that we're not evolving at a genetic level very fast. But in the last 50 years we've gone from the world population obesity being a rare phenomenon to obesity and overweight being a very common phenomenon as in some populations is more than half the population. That cannot be accounted for by changes in our genes. So what does account for this change in the prevalence of obesity in the population?

Giles - So undoubtedly the environment and I use that loosely for anything that's not genetics so your lifestyle, your socio-economic class, what have you, that has undoubtedly driven the obesity. But what are our genes for other than to respond and adapt to the environment?

I'll give what one simple example, if there were two people. Okay. Two of me. And we stood next to each other and we looked exactly alike. We stood up, there is no difference between us but say we changed the environment and the environment is suddenly someone came along and pushed us both. Shoved me shoved my twin next door to me and I managed to tense my calf muscles up and stand still. Whereas unbeknownst to anyone the person next to me has no calf muscles. So the moment they're actually pushed they collapse.

So in one environment where they're not being pushed we look exactly the same. Whereas when you change the environment when the push comes when our food environment is in now suddenly the genes become unmasked. So the genes haven't changed they've always been there. It's just the way they react to the environment.

Chris - So returning to Omar's question which can we do anything about it. Is the intervention one not of a genetic intervention or some kind of drug but it's the environment that's to blame. That's what's changed. That's what we've got to change back.

Giles - Yeah. We have to fix the environment that we actually living in. I mean there are drugs that are out there that can actually work for some people. And I think for the extreme cases in which you're Mrs. Smith you're type 2 diabetic if you do lose weight you'll die. Then I think there is a case for pharmaceutical intervention but for the most of us I'd like to think that we can really have a concerted effort to try and fix the environment that we're actually in.

Female body builder

How quickly do your muscles waste in space?

Chris Smith put this question to space travel guru Richard Hollingham...

Richard - He'd be fine on a Virgin Galactic flight journey in space for, sort of, 10 minutes or so they'd be fine for that but essentially as soon as you remove gravity your muscles start wasting away. There were studies, I mean lots of studies, in humans because now humans have lived on the space station for more than a year at a time. They did a study in rats. So within 10 days the rats lost a third of their muscle mass. And that includes heart muscle. Now none of this would be a problem if you were going to stay in space forever. So if you go up to space and you live on the space station you can spend the rest of your life on the space station floating around being this idea of this extra-terrestrial human. That's absolutely fine. Trouble is when you come back to earth and you've lost that muscle particularly something damaging like heart muscle you see the astronauts getting out of capsules staggering. Normally they're lifted out of their carriage because no matter how much exercise they do on the space station, they do a lot you know, a couple of hours a day. They're still weakened. They also lose bone density as well. So you can imagine a mission to Mars and you get to Mars. You climb down the steps, fall over and break a leg. That's the sort of, these are the sort of problems so it's more when you stop rather than when you're in there that it's a problem.

Chris - Indeed, among the astronauts to whom you have spoken when you've interviewed them. What is it like when they take those first faltering steps out of the capsule and return to Earth? Do they feel exhausted? Do they absolutely hate it? And how does it take them to rehabilitate themselves after say six months on the ISIS to get back to their full fitness?

Richard -  Actually it takes a year. That's what they allow for most of them because they’re really fit. I mean every astronaut I've met they are kind of superhuman. You know they're really bright. They're really pleasant. They are really really strong. You know it's sickening but yes. So they get back to fitness pretty quick but it does I mean to get back to that full physical fitness that they go into spaces at. It can take you know up to 12 months.

Chriss - And that means for your average Joe like me then I'd be really really up the Swanny without a paddle if I if I were to. I mean I'm not superhuman.

Richard - I mean if you did your exercise every day you'd be okay. I mean you know it's shown when John Glenn had his second mission on the on the space shuttle. He was in his I think his 70s or even his even 80s. There's no there's no reason why a moderately fit person cannot go into space and stay moderately fit in space if they follow Giles’ advice about what they eat if they take exercise and they come back to Earth. They won't be quite as fit as they were when they went up but they will be fine.

Can astronauts cook on the ISS?

Space Boffin Richard Hollingham answered this question, from Gail...

Chris - Can you actually cook food in space what is an astronaut diet like?

Richard - They've got better and better. Essentially, you are heating up components of food. So there's still heating up things in an enclosed environment; and almost everything - so the things you miss - I think from what I can gather from astronauts, taste is affected the same way if you're in a pressurised environment of the aircraft: things don't taste the same. So they do tend to prefer spicier foods. They've also got to gel together, because crumbs are a real problem! So you don't want you know crumbs of your food getting into a crucial instrument! So this actually happened on a mission in the 1960s - one of the Gemini missions, before the Apollo missions - that went to the moon, John Young smuggled up a corned beef sandwich in his capsule, which was all a great joke and everything... until crumbs started getting into the instrumentation! 

Chris - What happened?


Richard - Well it was fine, but it might not have been; so, you know, as a result of taking up a sandwich with with crumbs in, it could have been a real problem!

Chris - What appeals to me - because I like dunking, and that's a big problem because if you "over-dunk" and then your biscuit goes "flop", you've got an issue with your tea haven't you? Whereas, in space, I could dunk with impunity couldn't I, for much longer potentially...?

Richard - But you'd have to do that within a bag, because you can't obviously have a cup of tea...

Chris - If you didn't accelerate the fluid it would stay in the cup wouldn't it?

Richard - Yeah. Well try doing that! Try lifting up a cup of tea without accelerating the fluid! So you lift up a cup of tea and the tea comes out. So it just floats around around you. So yeah it's the sealed environment; so for obvious reasons there's no deep-fat fryer on the space station! It's more a question of heating up things but heating up components of a meal so they can put together a meal - they could heat up, for example, a stew and then heat up some bread, or have some pasta and a sauce. So it's kind of pulling the components together. There is also coffee maker on the space station, so there is espresso coffee!

Chris - I never thought I would learn about corned beef sandwiches on the Naked Scientist so thanks very much for that Richard!

lights in the universe

What is the universe expanding into?

Chris Smith put this simple query to astrophysicist Francesca Day...

Francesca - Yeah. This is actually a very good question. People often say that the universe is expanding and this means that there are galaxies in it are getting further apart. And the analogy people use is if you put a lot of dots on the surface of a balloon and those like the galaxies and as you blow the balloon up the universe is the surface of the balloon all the galaxies the dots get further apart from each other. And this is a very good analogy but it naturally begs the question well the balloon is expanding into the room. What's the universe expanding into. Unfortunately this is where the analogy ends. The universe the space we live in has the mathematical properties or some of the mathematical properties of the surface of the balloon but it has those properties without there being something it's expanding into. In math-speak we say that the manifold doesn't need an embedding in a higher dimensional space. That might not mean much to most listeners.

Chris - Oh I don’t know I thought that was really simple, thanks for that, moving on. In strict terms then does this mean that because one philosophical answer I heard to this question was to say well the universe is everything if that's your definition so therefore the universe is everything so it's not expanding into anything because it is everything. But that's sort of a get out clause isn't it because our human brains have not evolved to grasp but the idea that there could be something that's everywhere and everything all at once and getting bigger. But is everything. It doesn't quite sit with our perception of how the world works and the universe works.

Francesca - Yeah I think that might be the philosophical answer from my point of view as a sort of practising scientist I have some observations. I do some math which describes this expanding space which doesn't need to include what it is expanding into, the maths doesn't require that to be an outside the universe. And then I get an answer right, I compare the answer with data and it matches the data. So that's the sense in which the universe is expanding as far as I'm concerned.

Chris - If you look at where the universe is expanding is it expanding everywhere by the same amount and if I look at say the patch of space between the Earth and Mars, has that expanded a bit in the same way that the patch of space between us and the Andromeda galaxy has expanded, but obviously there's a lot more of that so it will have relatively speaking that would've expanded more.

Francesca - This is also a very good point. It's really only the bits between galaxies that are expanding the bit between galaxies are what governed by the overall motion of the universe within a galaxy the gravity of the galaxy is kind of holding stuff together so it doesn't expand and one way to see that is if absolutely everything was expanding by the same amount we wouldn't notice because anything we could use to measure it would also be expanding.


I always enjoy hearing Giles Yeo on the program. Next time he is on, would it be possible to ask him about the following?

In the past, we were given dietary advice to reduce fats as much as possible, but that complex carbohydrates were fine.

Now, some "experts" are telling us that fats are good (even saturated) and that we should avoid carbs at all costs.

What does Giles think about these opposing views?

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