Dissecting Christmas Dinner

20 December 2009

In a festive mood, this week the Naked Scientists meet their meat and dissect Christmas Dinner, but not with a carving knife! We also hear how scientists are able to re-create the acoustics of long-gone churches and cathedrals to appreciate how ancient musical compositions and carols would have sounded to an assembled congregation. Plus we also come face to face with a submarine volcano, dip into the story of a planet formed exclusively from water and find out why the skull is impervious to the effects of osteoporosis...

In this episode

20:48 - 2009's Naked Science in retrospect

For the final show on 2009, and the decade, the team look back on some of the year's "Naked-Scientific" highlights...

2009's Naked Science in retrospect

Ben - This is the very last Naked Scientists show of 2009.  So we thought we'd look back on a few of your favourite bits.  It's been a great year.  We've had some very interesting guests, been to some incredible places, and done some fantastic experiments.  But first, Helen, what's been some of your favourite bits?

Helen - Oh, well there's so much to choose from.  But I think something that stood out for me was when we had Dr. David Aldridge in the studio from Cambridge University.  And he brought with him some creatures found in freshwaters around the world that really shouldn't be where we find them.  So this was all about the science of invasive species.  And he brought some critters for us to look at.

Ben - And we can have a listen to that now...

David - I've got a little menagerie of goodies here.  And I've got some zebra mussels. Zebra Mussels I've got a signal crayfish from North America.  And I've got a Chinese mitten crab.  They're beautiful.  But unlike our native freshwater mussels which just sit in the bottom of rivers with their foot being into the mud, zebra mussels have a beard, a bit of thread which is like the marine mussels that you eat.  So zebra mussels are able to sit on solid surfaces.  And they can attach to each other and sit in dense layers.  So they can foul pipelines and drinking water supplies, cooling systems to power plants, irrigation systems.  But also they sit on our native wildlife and one of the things they really threaten, such as a specimen I've got in front of me, are our native mussels which provide a really good substrate and they choke them and cause them to die.

Helen - That's a huge mussel you've got there.  And I can hardly see it.  It's been covered in smaller zebra mussels.  That's incredible.  And the Cray fish you got there, that looks quite tasty.  Can we eat those?

David - We can.  And that's the reason they were brought over here.  The American signal crayfish was brought over in the 1970s as a commercial aquaculture food.  The problem with these crayfish is that they can walk over land so they escaped out of these little ponds they were put in.  And they can move into the wider environment, so they are very good at changing the ecosystem through feeding on the bottom rooting plants, the macrophytes.  And they dig burrows, which can cause sort of destabilisation of the banks. But perhaps of greatest of immediate concern is that they carry a fungus, something called crayfish plague, which kills our native crayfish species, but these American ones are pretty resistant to it.  So we've had, for instance, in the Cam in 2000, an outbreak of plague which wiped out native crayfish from about 20 kilometres of river.

Helen - That was Dr. David Aldridge telling us about some of the creatures that get into freshwater bodies and cause trouble where they shouldn't be.  And we had a look at some of them in the studio.  And that was quite fun.  That was great.

Ben - It's very nice to have our own innovation of invasive species.  It's not often people bring things into the studio.

Helen - I think we should do that more often.  And that's what we should do in 2010, is bring creatures into the radio studio.  Is that alright with everyone else?

Ben - Well we do have a cooked chicken with us .  But I think that's a slightly different way of thinking about these.  Now, speaking of species that we don't want around, there was also a lovely new story from earlier in the year about the love song of the mosquito.  Now if you listen very carefully to this, you could almost hear Dr Kat squirming in her seat.

A mosquitoChris - Now have a listen to this...  That is a male mosquito buzzing its wings at something like 600 hertz, 600 times a second. 

Now have a listen to the female mosquito; these are Aedes aegypti mosquitoes.  Here we go...

Now I won't subject you to too much more because Dr Kat has got her fingers in her ears but that's at about 400 hertz. 

But if you do what two researchers at Cornell did, that's Lauren Cater and Ben Arthur, they put one of those mosquitoes tethered to a pin with a piece of superglue to keep it in one place.  Then they bring in a mosquito of the opposite sex and record what happens to the wings of the two.  Have a listen to this...

And what's actually happening is that the two mosquitoes are adapting the beating frequency of their wings so that they harmonise.

Ben - Isn't that lovely, mosquitoes singing in harmony?  And I've never seen such a visceral reaction as Kat squirming in her seat like that.  But fair enough it's a horrible sound, the sound of mosquitoes.  But  I thinking of something a bit more pleasant.  We've had loads of great experiments in Kitchen Science.

I remember at the start of the year, we made some jelly to show how fruit enzymes can cut up proteins and stop the jelly from setting.  Although I think it may have just been an excuse to make lots and lots of jelly.  But, Dave, what else have you really enjoyed this year?

Dave - There are all sorts of things this year.  Ranging from videoing popcorn popping, watching they way...  It's absolutely beautiful the way it unravels because it's a really strong pressure vessel, you get it really hot and the water inside boils.  The pressure builds up and it breaks.  And it opens itself up almost all the way.  So I got a few minor oil burns from that one - it's not something you really want to try at home. 

We did all sorts of lovely things which I keep bringing out at dinner parties as well. There's one which I found from a guy I met at the British Interactive Group.  You just have a nut on one end of a piece of string and a mug on the other end, hold it over a pencil and just let go of the nut.  Despite what you'd expect, every time as long as you don't mess-up too badly, the nut runs wraps itself around the pencil and it doesn't hit the ground.

I also had one which actually got a proposal of marriage from my housemate which my girlfriend wasn't entirely impressed with, which was getting an orange peel, an especially good juicy orange peel and squeezing it next to a candle.  You get these huge fireballs, maybe five or six inches across.  It's absolutely beautiful especially in slow motion as well.

Helen - That's very cool.  I like that one too, actually.  But another one that sticks on my mind especially was when you soaked me in the studio.  I thought that was rather mean.  But it was great fun.  And I think we've got a clip from that one coming up...

Dave - So if you spin that nice and quickly...

Helen - Do I let go of it or do I try to hold on to it?

Dave - Just keep holding it and spinning it nice and quickly.

Helen - In one direction?

Dave - In one direction.

Helen - Oh!  Oh I see.  I see.

chris - That was fantastic.

Helen - I'm covered in water.  And that's the last time I offer.  So what happened is the waters flew out of the open ends of the straw.  I'd have another go but I think I might get the microphone wet.

Dave - Yeah, we should be careful.

Chris - That was really good.

Helen - It was awfully but  rather a beautiful fountain for a moment there.

Ben - Well, clearly that tickled Dr Chris.  Dave, did you know that was going to happen?

Dave - I'm afraid that fairly simple physics made it pretty inevitable that that was going to happen.

Helen - Ooh, I'm shaking my fist.  Oh well, anything in the name of The Naked Scientists, that's fine.

Ben - Of course.  And we didn't get any microphones wet, not at all.  We do never do anything that could in any way harm any of the equipment in the studio.  We wouldn't dream of it.

Now I've really enjoyed meeting some of the people I've interviewed this year.  I spoke to science minister Lord Drayson about why science is so important.  But a bit more fun was talking to comedian Robin Ince about how science and comedy are very closely linked.

Robin - What is happening is there's a huge, an accidental rational movement basically.  I think after we put together the show Nine lessons and carols for Godless people where we, on the science side, you had Simon Singh, Ben Goldacre, Richard Dawkins, then various musicians people like Jarvis Cocker and Darren Hayman, and then comedians.  And all of them are doing something on the rational world.  And you have people like Dara O'Brien, Chris Addison, Stewart Lee and Josie Long, all of them are approaching things from a rational spectrum. Especially Dara who has a physics background.  He's very excited about talking about science.  And I think that perhaps, I don't know, but perhaps TV isn't really pandering very much to intellectual programming.  So I think there has been an accidental rational/scientific movement start in comedy.

Dave - And we've also been to some amazing places this  year.  Laura Soul climbed to Everest base camp and reported back on how her body reacted to the low levels of oxygen.  It clearly wore her out somewhat... Mount Everest

Laura - Yes.  It's good to sit down.  I have a bad headache and so do most people.  I felt a bit sick on the way but I'm OK now.  Some people feel very sick.  The view from here is absolutely amazing.  You can see the Khumbu ice fall which is really beautiful with these huge big jagged peaks of ice.  It's been a very hard route to get up here.  But I'd say that it was definitely worth the climb.

Helen - I think you can just about feel kind of just how exhausted she is. It's amazing.  Well, I was rather, well I was a little bit envious, I have to say, of Meera's trip to South Africa this year and when she got to meet some cheetahs.  How lovely...

John O'Brian - Somewhere very nearby here is a cheetah on a kudu kill...there we go...

Meera - Oh my God!  Yeah.  Uh-oh.  It spotted us.  Does that matter?

John O'Brian - Oh, no, no, no.  They're very relaxed.  They're feeding so it's got other things on its mind.  And cheetahs aren't, animals that are dangerous or anything to humans.

Cheetah (Acinonyx jubatus) with Impala (Aepyceros melampus) that it had recently killed, Masai Mara National Park, Kenya. Meera - So we've parked up alongside this tree.  And I can just see the cheetah's body and its head, and oh, its tails wagging now.  It is just quite literally having a feast down there, munching away.

Ben - You can hear how excited she is by that little gasp of breath. Really excited to hear that.  It's also quite nice to know that cheetahs are quite a bit like my cats at home and that once you gave them some food, they don't care about anything else whatsoever.

30:48 - Acoustic Archaeology

For hundreds of years composers have been creating beautiful and complex pieces of music, written to be sung by many voices in harmony. But if the buildings for which these movements were...

Acoustic Archaeology
with Prof. Malcolm Longair, Cavendish Laboratory, Cambridge

Ben -  Now, as it's Christmas, there'll be plenty of carol singing either through groups knocking on your door or going to carol services in church.  But why is it that some places make a choir sound good while others can make them sound flat and lifeless.  Now have a listen to this.

We are joined today by Malcolm Longair who isOspedaletto and Sopranos waiting to sing. taking Sir John's College Choir to Venice to explore the acoustics of architecture and even indulge in some acoustic archaeology.  So what are we listening to right now?

Listen to this sample...

Malcolm -   What you're listening to just now is the magnificent performance of the Jean Mouton Nesciens Mater, performed by the gentlemen of the St John's College choir, in a tiny little chapel, the Emiliani Chapel, in one of the churches we were dealing with in Venice.  I should explain that this whole project came out of my wife's work.  She is professor of architectural history.  And since she's been working on Venice for almost 40 years, she wanted to understand exactly how music worked in the great churches in Venice.

So she was very fortunate to get a very substantial grant to study this, to characterise acoustically exactly what the buildings are like, to take the St John's Choir out to Venice to try all the possible positions and the various combinations, and also get the audience responses to what they were hearing.  So my role in this was very much secondary.  I was the person responsible for doing the acoustic and the scientific analysis of the data which appears as an appendix for Deborah's book which only came out just last week.

Ben -   Well, I'm pleased to hear that.  I think I sort of talked by your wife a little while ago.  And it is fascinating stuff but what is the relationship between architecture and acoustics?

Malcolm -   Exactly.  That's what it was about.  Now the reason that this project was so intriguing is that the Renaissance period was the time when new music was being written which required a very detailed understanding of polyphony.  So the split choir is where you want to hear 8 voices or some of Gabrielli's 15 part motets.  You have to have an acoustic which enable those who paid the money for the music to actually hear the 15 parts or the eight parts.

So that's a great acoustic challenge.  The architects such as Palladio and Sansaviudo, they were attempting to taken into account these requirements in the churches that they were building at the same time.  Now what we've been doing following the whole project went extremely well but with a bit of problem, which is when we try to simulate what they sounded like.  We were getting far too long reverberation times.

So what I've been doing with Braxton Boron, an excellent student who has joined me from the United States, we're building virtual models of all the churches from which we acquired The Ospedaletto.acoustic data.  And we're trying to reproduce the acoustic volumes virtually.  And the idea is that once we've done that, then we can change the nature of the buildings.  We can put in different roofs.  We can put in different hangings, different audiences, different clothes, everything and see how it will get to the proper understanding of what it must have sounded like in the 16th century when this is being done.  So it's an absolutely wonderfully, great-fun project.

Ben -   You've brought some samples with you today actually.  Now this first one, this is the real acoustics.  This is what it generally sounds like...

Listen to this sample...

Ben -   Where is this?

Malcolm -   Yes.  This is the most wonderful place in Venice which if you go to Venice, you can go into the Ospedalettoo.   It's got the most wonderful acoustics.  This is the sopranos from the Sir John's Choir singing from the organ gallery of the Ospedalettoo and being recorded in the middle of the day.  It's quite a small volume but a very simple shoebox-like shape.

Ben -   So it certainly sounds lovely. But how do you go about analysing the actual acoustics in there?  How do you find out why it sounds so good?

Malcolm -   Well, this is great fun.  What we did was to characterise acoustically using the most modern equipment, sourced different microphone positions.  And we did many positions within each of the churches so that we've got all the acoustic parameters that we need, the wave forms coming from all of these.

Once we've got that, then Braxton has built a virtual model of the church.  And then we run it through the most recent program, which is a program called Odeon, developed in Denmark, which enables you then once you put all the materials on the wall was marble, lathe and plaster and so forth to get what the response looks like.

And so once we've got that, we can check that we got this now the calibrated data for this existing church.  And we can then try to get this sound all the acoustic characters.  Now that we've done that just for the last two weeks.  Once we've done that, then we can put an anechoic recording of the choir through our virtual church and see if we've got back to where we are.

Ben -   So we have an accurate recording of the choir here.  Now this is in the room that just keeps down all echoes in it.

Malcolm -   This is done in West Road in the Music and Science Centre that Ian cross runs there.  And we've got the choir in it.  They hated this.  This was really terrible.  They did not enjoy this experience at all.  But you will hear what an anechoic signal sounds like...

Listen to this sample...

Ben -   Oh they certainly sound very capable.  But it does sound very flat.

Malcolm -   It sounds very, very dry.  Right?

Ben -   Yes.

Malcolm -   So what we now do, we take that same signal.  And we put it through our Virtual model of the Ospedaletto.virtual model of the Ospedalettoo.  And you can see what it sounds like...

Listen to this sample... 

Ben -   So all that beautiful reverb are really bringing certain music to life.  It's all fake.  It's all simulated.

Malcolm -   Well, Ben, it depends on what is real, what is simulated? Let me explain why we're doing this.  The reason for doing this is this is the simplest example that we could get.  And we wanted to find out the rules we have to follow to be able to do accurate reconstructions of the huge churches in Venice, things like San Marco, the Redentore, the San Giorgio Maggiore, which we will now begin to do.

But there we know that the huge volumes were very, very bad for acoustics.  We've got 68 second reverberation time.  So how did the people actually hear the wonderful polyphony that was being written by the Gabriellis, Bach, Monteverdi, and people like that?  Well what we believe is that by the time you put in all the decoration, the hangings, the large audiences, we will be able to bring down the reverberation time so that everybody could appreciate the genius of the polyphony.

Ben -   Well, that's fantastic.  I'm afraid we're going to have to leave it there.  But that's Professor Malcolm Longair explaining how we can use acoustic modelling to recreate the sound of churches that have long since disappeared or changed their roofs or changed their dressings and find out really what the experience would have been like.

39:02 - Dissecting Christmas Dinner

Dr John Brackenbury gets out his scalpel to reveal what the inner anatomical workings of a cooked chicken...

Dissecting Christmas Dinner
with Dr John Brackenbury, Cambridge University Vet School

John -  Now, the result is a lovely tasting bird but the muscles are completely useless for flying.  It's just too big.  It's lost all its natural strength.  And it's only good for eating.  Now, the other one we mentioned, the deeper one, that's used for the up stroke.  So that does the opposite movement.  When a bird wants to beat its wings back up but after the down stroke, it uses that smaller one.

So these are two pectoral muscles.  Roast ChickenAnd they're used in flying.  Now the other thing that we've exposed by separating the meat along the midline, very easy to do, are several things.  First of all, right in the midline, and if your Christmas listeners are doing this, you'll see a ridge, a ridge of bone.  Actually in this chicken, it's a ridge of cartilage.  It should be bone.

Helen - Oh, right.

John -   But nearly all chickens are slaughtered so early in their lives, all of them.

Helen - So actually because it's young, it hasn't become bone yet.

John -   Exactly.  It's not yet trying to turn into bird.  

Helen - Right.

John -  So it's just gristle.  So that's one thing.

Helen - Almost up to where the muscles are attached to.  Is that why it's there?

John - That's where they're attached to.  And that's why it is so deep.  It's actually about two centimetres deep because this great big great muscle is attached into it.  But anyway, that's one of the things we could see in the midline.  Now if we move towards the front, towards the neck of the chicken, we see something else which everybody well know: that is the wishbone.

Helen - Right.  That V-shaped bone.

John -  That V-shaped bone right at the front.  In fact, technically, this is called the little fork or forcula.  I mean, it is a fork.  It's shaped like a fork.  Anyway, that's one of two sets of collarbones the birds have.

Helen -   Oh, so this is the bird's collarbone.

John -   That's right.

Helen -   Right.

John -   That's the little collarbone.  And actually, it doesn't do much.  But deep down under that second layer of muscle I mentioned earlier is a second set of collarbones.  These are much stronger.  And they're essential for flight.

Helen -   Is there two collarbones because there's two sets of muscles?

John -   There are two collarbones because the wishbone itself is a bit of an apology.  It won't really do the job, which any flying bird needs to, which is to stop its shoulders crunching towards its breast when it makes a powerful beat.  And the function of that deeper collarbone is to stop that happening.

Helen -   So would we get an even better wish if broke the inner collarbone?

John -   I knew we would.  You would be.  It takes a bit of getting to.  And I think by then, you'll be so tempted to eat this thing that I think you would have forgotten the functional aspect.

Helen -   Well we certainly  are getting into the grips of this chicken.  And if we were looking at a turkey, would it be very different, or would it have a structurally very similar once you get inside them, or goose, or a duck?

John -   Yeah.  There are differences, many on accounts of size.  Now the turkey's going to be very similar to the chicken whereas the goose is going to be quite different.

Helen -   Right.

John -   The turkey and the chicken have white meat.  It has a distinctive taste because it's full of something called glycogen.

Helen -   And that's what makes... So we have white and red meat.  Is that right?

John -   That's right.

Helen -   Yes.  Why are those different?


They're different as I say, the white meat has glycogen.  And they're tend to be used when a muscle beats very quickly but exhausts very quickly as well.

Helen -   So it's for a very, very fast moves.  Right.


Should it not be "feed a cold TO starve a fever"?

So thank you so much for that, Douglas. That's not something we'd heard of. It sounds highly plausible that it should be feed a cold TO starve a fever because, as we have pointed out previously, you need to eat properly to mount an effective immune response, without which you might well develop a more severe fever.

Why is unhealthy food so tasty?

Helen I have something to protest about this. Vegetables can be very tasty. I bet in fact made a very nice nut roast this weekend. So I disagree on that point but I'm afraid of nasty food and not everyone agrees with me.

Ben - I think you're right. I certainly agree with you. I think especially fresh vegetables, when they still got all of the lovely taste straight from the garden, are really tasty. But I think the deep fried, the fast food, the high-calorie stuff I think that's probably a bit of an evolutionary throw back. I think our body rewards us for taking in lots of calories. And so when we do this, as it used to be essential to find food, we get a molecular reward in our brain that says, "Well done! You've found some good rich food that will keep us going throughout the winter."

So we get that sort of pleasure sensation. Nowadays finding food isn't really a major pressure like that, but we still get this reward. So when we eat something that's full in calories, this brain mechanism still kicks off and we think that we've really enjoyed it. He also asked, and this is a very interesting one, "Is there any deep fried food that's better than others?" Now, Helen, I'm not sure how you serve your vegetables?

Helen - Tempura vegetables are quite nice, aren't they? And that's a form of deep frying. I mean, I'm sure a deep-fried piece of broccoli is slightly less good for you than that piece of nice, fresh, unfried, lightly-steamed broccoli. But you're still, if you haven't overcooked it, getting lots of the nutrients and the vitamins that are so important in vegetables if you do that kind of style of cooking. So that's not too bad, I should say.

Ben - That was exactly what I thought because, with the tempura food, the food is still very fresh. And it's fried only for a very short time. You're supposed to use ice-cold batter - apparently that's why it's so fluffy and tasty. Basically, the food isn't overcooked. And I suspect actually that boiling carrots for 10 minutes will probably get rid of more of the nutrients than deep frying them for one minute.

Helen - Yeah. I quite agree actually! Yes! If school dinners could be more "tempura vegetables" instead of carrots boiled to death, then that would be a good thing, I think!

Why are scientists celebrating Christmas?

Dave - I think this is very strange that we're promoting an ancient Roman holiday of Saturnalia, when everyone used to get drunk because it was the winter solstice. People used to eat lots because of all the animals were going to have to be slaughtered anyway because there wouldn't be enought to feed them in winter, especially in northern latitudes. Basically, it's the holiday which every religion, seems to use.

Helen - I actually think it's that strange, in fact. I think maybe it harks back to a really important part of human social evolution which is wanting to belong to a tribe. We want to belong. We want to feel we're part of a group, because that was beneficial and it meant we could do better things in a group compared to just on our own.

So I think that's maybe part of the reason we all join in to celebrate Christmas: we're celebrating the same thing, and you know, whether it came from a different religion or not. And why not?

Dave - And of course it's also depressing at this time of year in those high latitudes. They wanted something to cheer them up whatever religion, so Christmas was ideal!

So scientists are just following the crowd!

51:38 - Why is chocolate toxic for dogs?

This week we ask why chocolate is not a good Christmas present for a dog...

Why is chocolate toxic for dogs?

We put this question to Sorrel Langley-Hobbs from the Vet School at the University of Cambridge. Yes. Chocolate, unfortunately, is toxic to dogs. And the reason for that is because it contains a compound called theobromine. Theobromine and caffeine are both present in chocolate but theobromine is the problem. They're both methyl xanthines. In dogs, theobromine is very long lasting. So it's got a very long half-life of about 18 hours. Whereas in people, the half-life is only two or three hours. And people readily absorb the theobromine.I think it's just a fact that every species has a different metabolism. We see differences between dogs and cats. With certain drugs, say for example, you shouldn't give a cat paracetamol whereas dogs can tolerate paracetamol. So it's just a species difference; probably down to different enzymes that are present in the system.So how much theobromine is toxic, you might ask yourself. So if a dog eats a couple of M&Ms, that's not going to cause any problem. The toxic levels vary from 20 mg per kilogram of theobromine to about 150 mg per kilogram of theobromine. So what does that mean in reality?Well, putting into a typical scenario, if you got a labrador and that ate a 200 gram bar of dark chocolate, that, potentially, is enough to kill your dog. So it's actually not very much. And the big problem this time of year is someone gives you a box of chocolates, wrapped up, and you put it under the Christmas tree, and the dog eats the box of chocolates. If that happens you certainly should call your vet as soon as possible.

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