Naked Science Christmas Party

16 December 2007

Ho Ho Ho! This week on the Naked Scientists we're celebrating the festive season in style, with a party right here in the studio. From Christmas crackers to Brussels sprouts, we'll be looking at some of the science behind Christmas. We'll be learning about snowflakes and how these sub-zero designs are created, we'll find out what your choice of Christmas card says about you, and we'll reveal the best way to cook your sprouts, ensuring your family get all the nutrition they can this Christmas. Also, in Kitchen science we'll be getting you to butter bread and throw it off your kitchen counter in the name of science!

In this episode

Space Ships like Table Decorations

A real threat to astronauts are cosmic rays, these are very high energy charged particles originating outside of our solar system which can pass straight through a spaceship and astronauts possibly giving them cancer or even radiation sickness. It is actually quite possible that if we could get astronauts to Mars by the time they got there they would be so damaged by the radiation there would be no point in sending them.

The International Space StationIf you are on the ground you are protected by the atmosphere and the earth's magnetic field. Astronauts on the Space Shuttle or International Space Station are still protected by the earth's magnetic field, but as soon as you get beyond this you are in much more danger.

An engineer called Ram Tripathi from the Langley research centre in Virginia may have the solution. Make the spaceship look like one of the table decorations made from a pineapple surrounded by cherries on cocktail sticks.

The idea is to charge up the cherries (which would be made of metal) to enormous voltages some positive some negative , this means that the cosmic ray particles which are charged will be attracted to the cherries and hit them rather than the astronauts.

Clone Alone, and it's the real "macaque-oy"

Researchers in America have produced the world's first primate stem cell clones in a move that could ultimately see patient-specific stem cells on offer in the clinic.

A Rhesus MacaqueOregon-based researcher Shoukhrat Mitalipov and his colleagues successfully transferred the genetic material from the mature skin cells of a nine year old male rhesus monkey into egg cells collected from 14 "donor" female monkeys.  The egg cells used in the experiment first had their own genetic material removed, and then the adult skin cell nucleus was delicately re-injected into the egg.

After a short incubation period drugs were added to chemically kickstart cell division in the injected eggs.  A small number (0.7%) subsequently began to divide, yielding embryonic stem cells (ES cells) that the researchers were able to grow in the dish.  The technique works because eggs contain a cocktail of chemicals that re-programme DNA by switching on the correct combination of genes that are required for embryonic development.  But despite huge effort, until now, scientists had not succeeded in making cloning technology work with primate cells - Dolly the sheep and Snuppy the dog were the farthest that they had progressed along the mammalian cloning path.

Exactly why the technique should be so difficult in primate cells is a mystery, but Mitalipov and his team think that they key to their success was a more gentle approach to handling the egg.  They avoided using ultraviolet light when removing the egg's own genetic material, and kept the concentrations of calcium and magnesium very low in the culture medium used to handle the cells.  The results, they say, prove that the technique can work in primates (and hence humans) and it should theoretically be possible in the future to produce stem cells tailor-made to an individual to repair damaged tissues and organs but without the risk of immune rejection.

Ancient rainforest found in a coal mine

A 300 million year old fossilised forest has been discovered in a coal mine in Illinois, USA. Covering an area of 10 square kilometres, it's the largest fossil rainforest ever discovered and contains a diverse selection of extinct flora.

So how does a forest end up in a coal mine and what can the extinct flora tell us?

Researchers from the UK and US team believe that a large earthquake shook the forest causing a large area of it to fall below sea-level it became peat and then coal.

Dr Howard Falcon-Lang from the University of Bristol, UK, said "It was an amazing experience. We drove down the mine in an armoured vehicle, until we were at a hundred metres below the surface. The fossil forest was rooted on top of the coal seam, so where the coal had been mined away the fossilized forest was visible in the ceiling of the mine. We walked for miles and miles along pitch black passages with the fossil forest just above our heads."

The find will have two major implications for current knowledge; the first concerns the coal in the mine and the other the plants. Not all coal is the same - coals are formed by different plants in different environments and this also effects the way they burn.

By studying the coal from the mine, geologists will learn more about the period when they were buried, which happens to be at the height of peat formation. The plants in this rainforest are an unusual array of club mosses, over 40 metres high, which tower over a canopy of tree ferns; there are also shrubs and tree-sized horsetails. It reveals information about the ecological preferences and community structure of such ancient plants; something which hitherto unknown.

It been a big fortnight for archaeological news as some 68 million year old T. rex bones has been found to contain protein - changing current thinking on the fossilization process and proving birds are dinosaurs.

Scientists from the US have found collagen proteins in the bones, which when compared to those of living animals showed it to be structurally similar to chicken collagen. This finding has major implications for fossilization theories as up until now it was thought that organic matter would have decayed completely after a maximum if 100,000 years, the proteins gradually being replaced by mineral.

Comparison of the fearsome T. rex's protein sequence have shown it to be structurally similar to the modern chicken, this provides evidence for the long-standing idea that birds are a group of dinosaurs (known as 'avian therapods') who survived the mass extinction which wiped out the other types of dinosaur. To date, this supposition had been based on the similarity of the architecture of their bones rather than, know researchers know this is true on the basis of related sequences.

King of the Swingers

As a famous character in a great Disney cartoon once sang about, it turns out that Orang utans really are king of the swingers because they know just the right way to swing their way through the forest without wasting too much energy.Sumatran orangutan

That's according to a new study published this week by a team of scientists from Birmingham University, here in the UK.

To get around the forest and move across the gaps between trees, orang utans can't simply climb along to the end of a branch and grab onto another branch of the next tree because they are too big and the thin branch ends wouldn't hold their weight.

Also, dropping down to the ground, walking along to the next tree and then climbing up another tree or a vine is also not a great option either, because it exposes the orang utans to predators on the ground like tigers.

Instead, what scientists watching orang utans in the wild have discovered is that the great orange apes bridge the gaps between trees by choosing young trees with springy bendy trunks which they rock backwards and forwards in any direction they want - a technique known as tree sway. If they swing far enough they can then grab onto the branch of the next tree and relatively effortlessly continue their journey.

The researchers estimated that the orangutans use about half the energy using their tree sway method compared to jumping directly between trees and only one tenth the energy they would have to use if they climbed down to the ground each time they wanted to move across a gap.

Gold, frankincense and myrrh

It may seem unlikely, but the first Christmas gifts of gold, frankincense and myrrh have a connection to today's cutting edge cancer research, according to the science charity Cancer Research UK.

FrankincenseFor example, Gold holds exciting potential for use in cancer research.  Scientists are investigating the potential of gold nanoparticles for cancer imaging, and in treatments that specifically target cancer cells.  And if you're into medically useful bling, you could also try platinum, which is a fundamental component of the cancer drugs cisplatin and carboplatin.  In fact, Cancer Research UK was heavily involved in the development of both of these drugs.

Frankincense is a plant extract, and we all know that these can be rich sources of biologically active molecules. Some scientists funded by Cancer Research UK are currently involved in chemoprevention research, which aims to identify chemicals in plants that have the potential to prevent cancer. These can then be tested further in the laboratory and in patients, and could one day prove to have an important role to play in both the prevention and treatment of cancer. 

For example, researchers in Leicester are investigating specific compounds in plants that could be purified and turned into cancer-preventing drugs. These include Resveratrol, found in red wine, silibinin from Milk Thistle, and curcumin, usually found in the curry spice turmeric.       

myrrhFinally, myrrh is a tree extract.  In the same way, the molecules that led to taxane drugs for cancer, including Taxol, were isolated from extracts from yew trees.  Cancer Research UK is now funding work to find out why some people with ovarian cancer develop resistance to taxane treatment, and who will benefit from the drug. 

And if you're stuck for a last-minute gift idea, you can actually help to support Cancer Research UK's work by buying one of the charity's virtual gifts - you can clothe a scientist, support a clinical trial or research in a UK town near you, or even buy some food for lab yeast! Check our for more ideas.

Gotta Lotta Bottle

Diet-conscious New Zealanders may soon be able to tuck into naturally "skimmed" milk thanks to a programme set up to breed a herd of cows that produce milk containing less than a third of the nomal levels of fat.Bottle of Milk

Scientists from a Biotech company called Vialactia discovered a Fresian cow, christened "Marge", that carries a mutant gene.  As a result she produces milk containing only 1% fat, compared with the 3.5% fat normally found in whole milk.  Her offspring also produce naturaly low-fat milk, indicating that the trait, which the scientists have yet to identify, is dominant.  Another bonus is that the milk also contains high levels of omega-3 fatty acids and makes butter than spreads as easily as margarine even when it's cold.  According the Vialactia chief scientist Russell Snell, the company expects to have the first commercial herd of cows supplying naturally low-fat milk and "ready-spready" butter by 2011.

What is pins and needles?

The nerves in your body have an incredibly high energy requirement so they have a big supply of blood and sugar to keep themselves going. If you lie on you arm when you go to sleep then the common place for this to happen is in your forearm or under your armpit. There is a condition called Saturday Night Palsy. This is where people go up the boozer and have a few. They come home and they fall asleep with their arm over the back of the chair. The arm of the chair pushing up under the arm compresses the nerves supplying their arm against their humerus (the upper arm bone). It squashes the nerve flat and you can actually get a nerve palsy because of it. Normally when you go to sleep at night, when you squash a nerve flat, you squash the arm but reduce the blood flow down the nerve. This means the brain doesn't get signals back into the spinal cord from the nerve because the interruption of the blood flow because of laying on your arm or just physically pushing on the nerve stops the flow of information. The brain starts wondering where the signal has gone from that bit of the body and so it increases sensitivity to whatever that nerve was supplying. You start to get spurious signals as though you could really feel that bit of your body. It's a bit like phantom limb pain you get when you have apart of the body amputated. When you restore the blood flow by moving in your sleep or rubbing or elevating the bit of the body that's starved of blood such as your leg then all the blood rushes back in. The pressure's taken off the nerve as well and it starts to work again. So you get your sensation restored. Thankfully, it's not harmful. But, it can also be assign in people who have other diseases like diabetes that the nerve is deteriorating. As long as you're getting pins and needles that's good news. If you had it all the time then that might be a sign that something bad is happening. If you're just going to bed and laying on your arm it's nothing.

20:09 - The Science of Snowflakes

Now, we all know what snowflakes are, but have you ever gone out and looked at them properly? They’ve got extremely intricate designs and symmetry that both scientists and artists have...

The Science of Snowflakes
with Professor Kenneth Libbrecht

natural snow crystalMeera - It's that time of year again, when we're all secretly hoping to wake up on Christmas morning to see a nice layer of white coating our Christmas streets. That's right, the pleasurable sight of snow that makes the cold so much more bearable. But have you ever thought about the structure of the snowflakes that actually make up some of that snow and how those intricate patterns were created that we see printed in our Christmas cards every year? I spoke to Professor Kenneth Libbrecht at Caltech University and picked his brains about what snowflakes actually are.

Kenneth - They're basically made of ice. What makes them unique is they form from water vapour in the air. When water vapour is condensing into solid ice it forms beautiful patterns.

Meera - Snowflakes form in a really distinctive way. That's how we all recognize them. Why do they form like that?

Kenneth - What makes them interesting is they're a very complex shape but they're still symmetrical. The real reason that works is the growth of the crystal is very sensitive to temperature and humidity. When the flake is falling and it's forming in the atmosphere they will start out growing into a small hexagon because of the way the water molecules hook up. The crystal lattice will form a small hexagon. Then the corners of the hexagon kick out a little further into the air. They'll tend to grow a little faster and the crystal can develop branches. Then as the branches grow, their growth is very sensitive to the conditions of seed. The crystal's falling through the cloud the temperature of the seed changes slightly all the time with the humidity. Even very small changes can change the way the crystal grows. As this thing is falling the growth of each arm will be very complex because of the path it takes through the cloud. The final shape of an arm reflects the whole history of its growth. Each arm has the same history as they're all connected together. Each arm grows, more or less, in synchrony and what you end up with is something very complex yet still has this six-fold symmetry.

Meera - But can you believe there are over forty different classes of snowflakes? What causes these differences?

Kenneth - They really grow in a remarkable variety of different types: columns, branch structures and one of my favourites is a capped column - where there's a column with plates on either end. They all grow at different temperatures and the growth can oscillate between plates and columns as a functional temperature. Plate-like crystals are just below freezing and then columns are a little colder still than the plates. No one quite understands why the crystals grow that way but that's what they do. The conditions do vary a lot in the atmosphere so you get lots of different types.

Meera - The actual change in temperature to create these structures is actually really small, sometimes even just one or two degrees.

Kenneth - That's right. The plates grow around -2 Celsius and columns at -5 and plates again at -15.

Meera - So with just a few degrees causing all these changes, which temperature gives us the best looking snowflake?

Kenneth - Well, the really nice-looking crystals tend to grow when it's pretty cold, around -15 Celsius. Those are these large stellar dendrites (stellar crystals): the ones you really associate with crystals when you think of them. They're very thin plates and they have beautiful branches and lots of structure.

Meera - What about the myth that there aren't any two snowflakes alike?

Kenneth - When you are growing a snowflake the growth is so sensitive to temperature that it tends to form a lot of different possible shapes. If you add up the number of possible ways of making a snowflake you usually find that it's far greater than the total number of atoms in the universe. So it's fair to say that if you go out looking you'll never find two that are exactly alike.

Meera - To finish off, I asked Kenneth for some tips on how we can make the most out of any snow we get this Christmas.

Kenneth - It's really fun to go looking for snowflakes. You don't need any real equipment. A little magnifying glass should help. You can even see quite a bit with the naked eye. You'll find all sorts of different shapes. One of the places I like best is the windshield of a cold, parked car. It has a nice slope and you can brush the crystals away and look at them. Better make sure it's your own car though!

Meera - So there you go. A nice family activity to do together over the Christmas period. That's if we manage to get any snow. To see the different classes of snowflakes to aid you in your snowflake spotting, or simply just to find out more information about these structures, you can go online to Kenneth's website at

Kat - That was Naked Scientist, Meera Senthilingham talking to Kenneth Libbrecht at Caltech University. If you want to find out more about snowflakes and the physics behind their design we do have an article on our website. To find it just go to

Why is it that when you see pictures or photographs of stars they always appear as crosses?

This is to do with how big telescopes are made. They're actually two mirrors and we have one big primary mirror and there's a secondary mirror held above that primary mirror. That reflects the light back down where you'd put a camera. The secondary mirror is in the middle of the tube with the big one on. They've got to support it somehow. They tend to have four supports, vertical supports that hold it up or else it's gonna fall down. That star shape you see round the stars is basically a really, really out of focus picture of this star shape. It's also called diffraction pattern and that's what's producing all these star shapes.

How does a depleted immune system bring on cancer?

This is a really interesting one. It's something that's only started to become clear relatively recently - the role of the immune system in preventing cancer.

For example, patients with HIV can have a very depleted immune system. This leaves them vulnerable to infections like viruses that can cause cancer, like human papilloma virus (HPV) and Epstein-Barr Virus (EBV); so one of the reasons why HIV-infected individuals have higher cancer rates might be because they succumb to cancer-causing infections more frequently. Indeed, the rates of lymphoma, a type of blood cancer linked with EBV infection, are about 100-fold higher in HIV positive individuals.

Also, it's thought now that the immune system actively patrols your body, spotting dodgy-looking cells that are destined to become cancerous and getting rid of them. So it follows that a disease that disables the immune system - like HIV - could increase the likelihood of a cancer developing. Indeed, it's the question of how the immune system may be able to recognise some cancer cells is a hot topic in research now. And whether we can turn it into overdrive and use "immunotherapy" to kick-start the immune system into killing cancer cells in patients, that's a very active area of research.

Another thing that's quite interesting is that the whole role of the immune system first started to become clear, partly through studying people with HIV and also through studying patients who've had transplants. They take immuno-suppressing drugs and are also more likely to get certain types of cancers. That started to make a link.

Also, there have been some interesting observations in patients with melanoma: doctors have occasionally noticed that some people with melanoma just spontaneously get better. That's thought to be their immune system waking up, recognising and then attacking their cancer. Scientists are now working on ways to stimulate this process to happen in everyone. So it's a really active field of research studying how the immune system is involved in this and we'll probably, in the future, see a lot more coming out about it.

29:20 - Quirkology

Are Christmas cracker jokes really funny? What does your choice of Christmas card say about you? We've got Professor Richard Wiseman, from the University of Hertfordshire, on the...

with Professor Richard Wiseman

Chris - Professor Richard Wiseman joins us from the University of Hertfordshire. Do you know the answer to, 'why are ghosts bad liars?'

Richard - Ghosts are bad liars because you can see right through them.

Chris - Boom boom. Now, look these are all rubbishy cracker jokes.

Richard - They're terrible.

Chris - It's something you've been looking at. You acknowledge yourself they're terrible but you've been researching all about the subject of cracker jokes. Why do we have this obsession with them?

Christmas crackerRichard - I think they're really interesting from a social psychological perspective. One of the key questions is, why aren't they better? What is going on that we all want to tell each other these terrible jokes? I think that's the real key to their longevity. If you open a cracker with a good joke and you tell it and it falls flat, clearly it's your problem as a joke teller because you had good material and you failed. If you've got a bad joke and you get no laugh, in fact you get a groan, well you can just blame the joke. There's nothing embarrassing going on socially. I think they're actually rather clever. What they're doing is about a group experience. We're all going, 'oh my goodness, that's terrible,' but it's not putting any pressure on the person whose job it is to tell the joke.

Chris - You've done some actual physical research on types of jokes that get told and the types of people that like and don't like telling them. What did you find?

Richard - Well we asked people, 'do you enjoy telling cracker jokes?' It was the people that were the self-confessed poor joke tellers that said, 'yeah, that's what I really enjoy.' Part of it is that the joke's written down for them and they're pretty short jokes so you don't have that terrible moment when your uncle at the dinner table has just gone on for twenty minutes and has forgotten the punchline of the story. They're short jokes and, as I say, they're not putting the joke teller under any pressure. It's the poor joke tellers that tended to like them.

Chris - Was there any correlation with the cost of the cracker?

Richard - There wasn't. We had some very expensive crackers. We had some very cheap ones and we asked people to come online to rate how funny they found the jokes without knowing whether they were looking at a expensive or cheap cracker. We found no correlation at all. If you're after good jokes there's no need to spend big bucks on the expensive crackers. That's the scientific breakthrough we can say is official science.

Chris - Tell us about your work on Christmas cards because you've been looking now at how the kinds of cards people send can tell you something about their personality traits.

Richard - Absolutely. This was another online experiment. We carried out with the Daily Telegraph and some of the previous research had looked at the size of the card and how much you were spending on it. Again from a social psychological perspective you were saying a lot about yourself. If you were saying look, here's a really expensive card you're saying, ' I'm the sort of person who can afford a card like that.' Second you're saying, 'you're the sort of person, as a recipient, that I think is worth that sort of card's money.' There's a lot of previous research in the area. What we did was ask people to fill out a basic personality questionnaire that told us whether they were an extrovert or an introvert, creative, not creative and so on; and then tell us what type of Christmas card they tended to give. Whether it was one with a traditional design on the front such as a religious scene or a more abstract one, perhaps some holly in a rather abstract pattern, we could match those two up. When you get a Christmas card you can get an insight into their personality.

Chris - What did you find?

Richard - Well, the most traditional cards - the typical religious scenes were associated with people who weren't quite so emotionally stable as most. This is a level of what's called neuroticism.

Chris - That's not good for Christmas, is it? If the religious people are unstable!

Christmas cardsRichard - That's what most of the research shows. Not so much that they're unstable, rather that they're anxious about the world. That's why they come to believe in religion in part because it provides a big comfort blanket for them. Deep down, they're quite anxious about the world. That fitted in with some previous research. We found with the very abstract designs that these people scored highly on a scale which is known as openness to experience. It's those people that tend to be more creative, open to new experience in their lives, people who would really like to look at an abstract pattern and try and find meaning within it rather than being told rather obviously by the artist what that meaning is.

Chris - I like to send funny cards so what does that say about me?

Richard - That says a lot. We did have a lot of people in the 'cute dog with santa hat on' or funny card.

Chris - I had one with Father Christmas sitting on a chimney, using it as a toilet. It said underneath, 'You know when you've been really bad this year.'

Richard - I think that's just sick. I think that's terrible you should send a card like that but you know, each to their own. People who tended to send those cards were the extroverts rather than the introverts, so people who were more socially orientated. Also, if you've got any glitter on the card that was heavily correlated with getting the card from an extrovert because we know that extroverts' brains tend to be under-stimulated so they're constantly looking for other people, noisy environments, bright environments: in this case with glitter on the card to stimulate them a bit more and get them into that comfort zone.

Helen - Richard, I make my own cards. What does that say about me?

Richard - That means you're very mean and you should get out. Very, very mean. I can tell you as a psychologist, you need to get into the shops. Just throw all that card stuff away.

Helen - I put a lot of my own energy and my own thought process into it.

Richard - Yeah, but not your own money interestingly enough!

Chris - She has to buy all the materials, doesn't she?

Richard - That's true and these days it's expensive. I think what's interesting about that he says, backtracking, is you're saying a lot about yourself. You're saying, 'I'm a person who's investing my valuable time in making this thing. I'm a creative type of person.' You're telling us a great deal. You're not just going to the high street and buying something from the shops. It's about creating something individual for the people you know.

Chris - It's quite interesting, what you can get out of cards but lets move it on a bit because the wise men allegedly followed a star to find where Jesus was. Lets look at astrology for a minute. What does astrology tell you? Is there any basis in that at all?

Richard - I don't think so. One of the chapters in the Quirkology book is devoted to looking at some of the evidence for astrology. Certainly people believe it's the case. Certainly when they read their horoscope they go, 'oh my goodness! That describes me.' But of course that's not science, that's not a controlled experiment. Lots of those horoscopes, even if you employ a professional astrologer, will give you a reading which lots of people think, 'that's true for me.' There's nothing special about that reading. There's nothing idiosyncratic in there for you it's just that you read meaning into these fairly general statements. Some of the statements will be double headers such as, 'sometimes you enjoy going along to parties, other times you want to be alone.' Well, of course that's true of everyone. Nobody always wants to be at a party or always be alone. Other times they're statements that we really like to believe about ourselves. So if someone says, 'the stars suggest it's going to be a great week for you and you're the sort of person that's got a lot of untapped creative potential,' we all go, 'yes! That's incredibly insightful. How on Earth did you know?' Astrology in that sense is built on psychology. I don't think there's any way of looking up to the heavens or looking at where the stars were when you were born and actually predicting the future.

Chris - That's quite good. I wonder if Jesus knew that when he was born on the 25th of December and he knew it was going to be Christmas. What an amazing possibility.

38:08 - Nutritious Sprouts and how to keep them that way

Which way of cooking do you think will have the best outcome for the healthiness of your sprouts? We sent out Ben to find out.

Nutritious Sprouts and how to keep them that way
with Kate Guberg

Ben - Christmas is a time of many traditions and one of these is, of course, your Christmas dinner. Christmas dinner wouldn't be a true Christmas dinner without Brussels sprouts. Love them or hate them they're almost always there on your plate come Christmas and you have to eat one or two. If you are going to eat sprouts what's the best way to cook them and still keep all of their nutritional value? I went to the Medical Research Council's Human Nutrition Research labs in Cambridge and met up with Kate Guberg who set up an experiment to help us find out.

Kate - I divided the sprouts into five different groups: frozen sprouts, raw sprouts, oiled sprouts, microwaved sprouts and steamed sprouts. They were then homogenized in an acid to produce the vitamin C that was remaining.

Ben - So why are we looking for the amount of vitamin C in these sprouts?

Kate - Obviously cooking, anything you do to the Brussels sprout will actually affect the amount of vitamins in that vegetable. We want to see what's left after various ways of cooking.

Ben - Can you consider the same thing for other vitamins or will this only show us for vitamin C?

Kate - All the other water soluble vitamins will be affected in a similar way by the leaching of the water. When you cook them, they'll be lost into the water as well. It'll give us an idea perhaps of what's left of the other vitamins.

Ben - What's the next step now then?

Kate - I'm going to react it with various chemicals to give a fluorescent colour which we can measure to give an idea of the amount of vitamin C that's left in the vegetables themselves.

Ben - So you measure chemicals that will make vitamin C glow, effectively. By recording quite how bright the glow is, that shows you how much vitamin C is left.

Kate - That's right. We also have various amounts that we know of vitamin C and we can compare the amount of glowing that we get with the known amount. That will give us an absolute figure that we can use to calculate the vitamin C levels.

Ben - While we wait to find out how much vitamin C is in different types of sprouts I met up with Toni Steer who works here at the MRC HNR. Toni it's Christmas time, traditionally a time to be stuffing our faces with rich, fatty foods. What can people do to avoid poor nutrition at Christmas?

sproutsToni - The reality is Christmas day is a once-off. It happens once a year. Really, it's time to enjoy yourself and have a great day. I think the problem happens when Christmas day turns into a whole month. One of the big culprits here is the buffet.

Ben - Buffets are very popular at office Christmas parties and that sort of thing so what's the problem with the buffet?

Toni - If you imagine walking into a room with a buffet table and it has nothing but cheese sandwiches on, how many cheese sandwiches would you really eat? Probably not very many. Now you imagine the same room again. You go in and the buffet table is covered with a whole variety of foods: sausage rolls, mince pies, crisps, nuts, biscuits. Now imagine how much you would eat.

Ben - I think I'd fill my plate a couple of times with that sort of choice.

Toni - Absolutely. The more variety you have the more likely you are to eat too much. Remember, if you're going to a party it's a social situation. You're there to have a really good chat with your friends so make sure you do more talking than eating.

Ben - So now we have our sprout results back we can see what difference it makes with the different cooking mechanisms. What have we actually found?

Kate - There's no real surprises. We can see that cooking sprouts, no matter what method you use, does result in a loss of vitamin C. Boiling the sprouts actually lost up to 60% of the vitamin C. That's really gone into the water. The water you throw away down your sink contains the vitamin C that you could have had in your body. The steaming, we saw a loss of 40%. Microwaving, we have very similar results.

Ben - So any form of cooking Brussels sprouts seems to reduce the amount of vitamin C in there quite a lot. You said you also got some fresh ones and froze them. What difference does it make to freeze them?

Kate - Actually, I was quite surprised. The frozen Brussels sprouts showed a loss of 30% of vitamin C so obviously, if you then go on to cook those Brussels sprouts you're going to see even more of a loss. I think the message is that the best is fresh.

Ben - By the looks of it the best way to get lots of vitamin C is to eat raw sprouts. Maybe we should just give up on sprouts and eat oranges. They're rich in vitamin C, aren't they?

Kate - Actually, it's funny but Brussels sprouts are very rich in vitamin C, more so than oranges. They actually contain more vitamin C than oranges. Even with the loss of vitamin C in cooking a portion of Brussels sprouts is going a long way to fulfilling your daily requirement which is 40mg per day. I think the message is that no matter how you cook them, they are still worth eating. It's definitely worth trying to get your children to eat Brussels sprouts even if they only managed the odd one or two.

45:00 - Power of a Magnet?

Where do Magnets get the power to stick or repel?

Power of a Magnet?

Alastair Rae, University of Birmingham

At this time of year, many of us decorate our fridges by attaching magnets carrying pictures of Christmas puddings, holly, Father Christmas, snowmen and so on. One advantage of these magnets is that they are easily removed and replaced when Christmas is over. Brian Starkey asks, 'how can they stay on the fridges when there is no obvious power source?'

The first point to note is that we don't need any energy to stand still! A stationary car with its engine turned off doesn't use any petrol! Power is required only when the engine starts turning and the car starts moving. What we have in the case of a fridge magnet is a magnetic force pulling the magnet against the iron door; this then leads to a frictional force that stops the magnet sliding down under gravity, but once the magnet is in place, no energy or power is consumed keeping it there. It's not very different in principle to sticking the magnet onto the fridge using glue.

When Brian pushes the two like poles of a magnet together, he has to apply a force and use energy. If they are then allowed to move apart, this energy is released and converted into motion. However, if he holds them together without letting them move, no more power is needed. It's perhaps easier to understand this if we think of the magnets being supported by a rigid frame instead of by a person. Why then do Brian's arms grow tired if he is not doing any work? This is all to do with biology and the complex way our muscles work: chemical energy has to be burned to keep them stiff and able to exert pressure. But magnets are not like that: they exert a force pushing each other apart and do not consume any power as long as they don't move.

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