The 12 Scientific Days of Christmas

Chris Smith and Graihagh Jackson, joined by a host of festive luminaries including Hugh Hunt, Alan Calverd and Amy Thomas are exploring the scientific side of the festive period...

Graihagh - This week we’re celebrating each of the 12 days of Christmas with a science experiment.

Chris - And how’s your singing, Graihagh?

Graihagh - Let’s find out with day 1. A partridge in a pear tree. Ready everybody? I’ll lead us in.

Everyone sing: on the first day of Christmas my true love gave to me, a partridge in a pear tree

Graihagh - So we have a beautiful pear tree (sort of) here in the studio! Well actually it is a lavender with white flowering the odd pear hanging from it, but it will suffice! I thought we would start by making our own snowflake decorations for the tree. So in front of you you should have some paper and scissors. Let’s get cutting! It’s like being back at school and making paper chains... So Hugh, you’re a physicist, could you start off by telling us how snowflakes form?

Hugh - Snow is made of water, and water molecule H2O has an oxygen with two hydrogens, and the angle between the hydrogen atoms is about 120 degrees. But it’s only approximately 120 degrees, isn’t that right Alan

Alan - Yes, it’s actually about 110 degrees, which is possibly why no two snowflakes look exactly the same.

Graihagh - I was going to say, does that matter the angle? Is that what causes them to be like fingerprints and be completely individual?

Alan - I think the old idea was that it was the hydrogen bond angle that determined the hexagonal shape but because the hydrogen bond angle doesn’t make a hexagon, we’ve got to think of some other reason why the come out that shape.

Hugh - You can kind of think that this 120 degree angle, it’s like the angle you get in a boomerang. So you can imagine three boomerangs connecting together makes this kind of hexagon shape and that’s the kind of base building block of a water crystal. And if you imagine drawing a snowflake, you might start by drawing three dissecting lines like an asterisk, and then at the end of each line you might draw another asterisk, and then at the end of those little lines you can draw another asterisk. You keep on adding…

Graihagh - You just keep going for ever and every.

Hugh - And if you ask five different people to draw using those instructions, you’re going to get five different snowflakes because they’re going to draw their asterisks at randomly different places. So every snowflake's going to look different.

Graihagh - But why do they stop growing, is there a moment when they stop growing?

Hugh - Well the water is coming out of the atmosphere, and they’ll only grow when there’s water vapour in the atmosphere around the snowflake, and once the snowflake has formed and the air is just a little bit drier around. Snowflakes need very particular conditions to grow in and amongst those conditions don’t exist anymore they stop growing.

Graihagh - Yeah. I suppose it’s hoping for a white Christmas this year, what do you reckon?

Hugh - I think the weather forecast is a bit blustery for Christmas I think.

Graihagh - I haven’t actually looked… I don’t know. I always want a white Christmas because I always want to go outside sleighing. And I remember thinking we did this every year when I was a kid but, actually, that never seems to happen any more. I thought climate change was supposed to be happening. I mean, why isn’t there any snow?

Hugh - Well, you could do what you do in Australia at Christmas time because it doesn’t snow then. So it make snow out of mashed potato.

Graihagh - How much mashed potato do you need to…

Hugh - I was only kidding!

Graihagh - I was going to say that must be a colossal amount of potatoes.

Chris - Amy, tell us about the psychology behind all this -what makes an aesthetically pleasing snowflake because I want to win this competition? So I haven’t started cutting yet actually, so I might start now.

Amy - I think as we’ve heard about how they grow and crystallise and the hydrogen bonds are able to form sort of hexagonal shape. And hexagons are quite prevalent in nature and symmetrically, obviously, is something we’re quite in tune with as humans.

Graihagh - Why are we particularly fond of…?

Amy - I think it because there’s some mathematical reasoning behind hexagons. When they fit together you’re maximising your area but minimising your perimeter. So, if you have like a beehive and you’re making honeycomb, it’s more energetically favourable for the bees to make hexagonal shapes by reducing their perimeter but maximising their area.

Graihagh - Okay. So I want something as symmetrical as possible, basically?

Amy - that’s what you should go with.

Graihagh - And that’s how I’m going to be onto a winner.

Amy - Symmetrical and hexagons, I think that’s where you should start off from.

Chris - It’s a bit late for me now. I wish I’d known that five minutes ago.

Graihagh - And Alan - very briefly, I’ve heard that all snowflakes are different, just like a fingerprint. Is this true?

Alan - Probably. I think it must have been about a hundred years ago, a couple of Canadian scientists collected snowflakes and photographed them. And they published books containing thousands of snowflake photographs, no two of which are alike.

Graihagh - Wow! And they had to trawl through every single one of them to identify the fact that they’re not alike?

Alan - I remember this was an exam question in crystallography 101, which said “the average snowflake is less symmetrical than the average photograph of a snowflake” and I think there may be a lot of selection bias in what actually goes into the photograph of a snowflake.

Graihagh - Okay - mine’s not gone very well. I’ve only just barely cut a hexagon. Oh wow that’s amazing.

Chris - Some amazing results here!

Graihagh Jackson and Chris Smith are celebrating the 12 scientific days of Christmas, assisted by Hugh Hunt, Amy Thomas, James Bowers and Alan Calverd...

Graihagh - Moving swiftly on from bird calls to rings, it is of course time to celebrate the 5th day of Christmas...

   Everyone sings: on the fifth day of Christmas my true love gave to me five gold rings, four calling birds, three French hens, two turtle doves, and a partridge in a pear tree...

Chris - Alan Calverd, you’ve been looking into some famous gold rings in science history. What have you got for us?

Alan - I think possibly the best known gold rings in physics and medicine were the ones on the hand of Mrs Roentgen. Wilhelm Roentgen discovered X rays in 1895 and published X ray a photograph of his wife’s hand with, apparently, one very thick wedding ring on it. I’ve tried to get a reasonable copy of this photograph, and I’m rather baffled. I’ve now come across five different images, each of which claims to be Anna Bertha Roentgen’s hand with a wedding ring.

Chris - She must have a lot of hands!

Alan - Yeah. The one I think is most likely is actually of her right hand with what appears to be two quite thin rings on it. I’m still not entirely convinced. the photograph that most often appears in textbooks is of a left hand with a thick wedding ring on the ring finger. And it appears to be signed and has some sort of provenance. The problem is is that the German tradition is not to wear to rings, but to have one ring on engagement and on marriage it’s transferred from the left hand to the right hand. So now I’m prepared to believe that the likely photographs of Anna Bertha Roentgen’s hand are actually of her right hand. And I’ve now found one which is paired with a photograph of a slightly chubby woman with fairly small hands who seems to have a single thin ring on her right hand and, I believe, that’s probably the only actual photograph.

Chris - Do you not think that she was exposed to so many X rays that she just grew fifteen extra hands and that could account for the anomaly?

Alan - No, this was definitely the first X ray ever published.

Chris - I also like the way he experimented on his wife and didn’t do it on himself.

Alan - Yeah.

Chris - Interesting, obviously a brave physicist. Hugh…

Hugh - Can you actually tell that they’re right or left hands. The X ray could be flipped upside down on the photograph?

Alan - All the radiology textbooks say you always do it from the top downwards.

Hugh - Ah, so there’s some logic...

Graihagh - And James, what gives gold its special properties? Why do we like to wear it as jewellry?

James - Gold is interesting because it’s not interesting at all, really.

Graihagh - an oxymoron?

James - Yes. Because in terms of chemistry it’s actually really unreactive, which is why we can use it for so many things, and it’s actually quite easy to extract compared to other things we might use. But also that means it could last for a very long time so it’s a very good kind of measure of wealth, for example.

So, if I had a gold bar and I had it for a hundred years, it wouldn’t really change. Whereas if I had and iron bar, for example, it would probably get rust on it which is iron oxide because the the iron is reacting with the oxygens. Gold doesn’t really do that, and it’s just very malleable, it’s very easy to use, but it’s also just rare enough so that everybody can have some, but not too much.   

Chris - Amy - can you tell us about the psychology of gold though, because there’s no doubt about it, for generations people have found gold particularly valuable and attractive? So why do people a) like gold, and b) like jewellery full stop?

Amy - Oh, there’s a few  different theories about this. And I think one of the reasons why people like jewellry in general is because it can signify things which might be a little bit awkward to communicate with words. So, for example, a wedding ring perhaps; it’s there, it’s a symbol of marriage already, you don’t have to say it, it’s already there. So that’s already like a nice body que that you don't have to tell people.

Also, if you wear a necklace, you might want to draw attention to specific areas but not want to say it. so for that reason…

Chris - I’ve never thought about it like that but you’re absolutely right!

Amy - Yeah. It’s kind of like this underlying subtle signal thing, which is really cool. But then there’s more anthropological reasons to jewellery and gold is status, and monarchy, a sign of wealth. And also a sign of love and belonging if it’s something that’s bought for you by something that you love, and you wear it and you feel loved and that you belong to someone.

Chris - Wonderful! I wonder what I’m getting for Christmas...?

Seven swans went swimming, according to the song. And some people also enjoy a cold dip at Christmas. Caroline Steel went for a swim in the name of science, and Chris Smith heard from Eleanor Drinkwater how birds avoid getting cold feet...

Chris - So far we’ve covered 6 of the 12 days of Christmas… Now it’s time for the 7th...

Everyone sings: on the seventh day of Christmas my true love gave to me, seven swans a swimming, six geese a laying, five gold rings, four calling birds, three French hens, two turtle doves, and a partridge in a pear tree.

Chris - Even at this time of year when it’s freezing here in Cambridge, it’s common to see swans swimming down the River Cam. But there are also people who enjoy swimming outdoors at this time of year. So we sent producer Caroline Steel to the pool in Tooting, London, to break the ice - almost literally - and take a dip with cold water enthusiast Alex Harper...

Alex - You can imagine being in a spar and you go in a plunge pool and you get a rush from it.  Well this is exactly the same kind of rush. It’s definitely getting cold, and getting warm in the sauna and getting cold again. It’s a huge endorphin release, or certainly a high buzz.

Caroline - Given that I don't think I’ve actually swum in about six months, what do you think will happen to me - how am I going to feel?

Alex - Well, we’ll walk in. but it’s up to you, you can walk or jump. I suggest walking down the steps and you will feel cold. It’s cold water and there’s no getting away from your skin will cool down, and mildly painful, but, honestly, it is mental. Physically you'll be fine, it’s the mental anguish of feeling cold, feeling uncomfortable.

Caroline - Okay. So before you hear my reaction, I just want to emphasise that the water was less than four degrees celsius. Actually, it has frozen over just three days earlier. Okay, so excuses over it’s time to jump in…

Okay, so I’m as ready as I can possibly, physically be.

Alex - Excellent.

Caroline - Is your plan to go in first and…

Alex - Do you want to go in first? Do you want to go in? And we go… no hanging around. Okay, so just get in.

Caroline::. So obviously, it was pretty cold. My skin cooled down straight away and, as my blood vessels constricted, I went really pale. But by the second length my skin went numb and it became marginally bearable.

Alex - Excellent. How was it?

Caroline - I feel like I’m not completely with it. But I enjoyed…

Alex - You did it. You finished. Well done!

Caroline - I enjoyed the second leg.

Alex - You could have done two more, couldn’t you?

Caroline - Phew, phew. Oh my Gosh!!

I’m on a beach, it’s boiling, it’s so hot that I actually want to go in the sea. I need to put on more sunscreen, I’m burning. It’s boiling… it’s boiling.  Okay, so as much as I wanted to believe that, it didn't really help me warm up. So here’s cold water enthusiast and doctor, Martin Thimbar...

Martin - Well, the dodgy thing is you get a warm glow. You often get a feeling of a warm glow after you’ve been in there, which is deceptive because, actually, it’s going to mean you lose quite a lot the heat. And so the thing to do with anyone who's a bit cold and that is put layers on. People sometimes make the mistake when they’re really quite cold of going into a hot shower and standing up. That doesn’t warm your core quickly enough but what it does do is it encourages your blood vessels on the side to dilate, and you blood pressure can drop down. So when people faint, they can faint from being cold and then having a hot shower. The best thing to do is just sit quietly and put layers on.     

Chris - Good advice. Eleanor - How do swans manage to swim in 3 degrees C water?

Eleanor - They have an amazing system called the countercurrent exchange system in that their veins and arteries are very, very close together - those going down to the foot and those going away from the foot. So you have this amazing system where the warm blood from the body gets cooled by the blood going in the opposite direction, so when the blood gets to the foot it’s already cold so the bird doesn’t lose that much heat.

Chris - Neat. So by basically pumping hot blood out of the body and passing it very close to cold blood coming back, the cold blood grabs all the heat from the hot blood so by the time it gets to the foot it’s so cold it’s not got much heat to lose. So it stays as cold as the foot was without the bird actually losing any energy?

Eleanor - Yeah, that’s exactly right.

Psychologist Amy Thomas explains to Chris Smith why humans like to jive, and what constitutes a "good" dance with musical accompaniment from Hugh Hunt...

Everyone sings: on the ninth day of Christmas my true love gave to me nine ladies dancing, eight maids a milking, seven swans a swimming, six geese a laying, five gold rings, four calling birds, three French hens, two turtle doves, and a partridge in a pear tree.

Amy - There’s a few theories about this. One of the main ones is that dancing is a mate selection gesture. There’s been studies done on looking at the relationship between the symmetricality of one's body and their ability to dance. And what they found out was that people with symmetrical bodies are better dancers, quite substantially.

Chris - Why?

Amy - I think it’s because of the way you balance, and you can move, and you're more flexible, and it looks more aesthetically pleasing when your body is symmetrically. If your hands are exactly the same size and your legs are exactly the same size, it’s going to look better.

Chris - Are you going to show me what I need to do better then in order to impress this Christmas?

Amy - Yes. I’ve got a little experiment to do to show you how to improve your dance skills.

Chris - What have you got in mind?

Amy - I’m going to stand up and do one dance, which is a bad unattractive dance. And then I’m going to do one dance which is an attractive dance and you’re going to tell me which one’s which.

Chris - Now I happen to know that Hugh Hunt is a very good human beat box so we’re going to get him to do the musical accompaniment for you Amy. so if you’d like to take to the dance floor, which is this patch of carpet behind my chair. So we're not going to know what order these dances are coming in. They could be the unattractive or the attractive one so could we just cue the music please Hugh. If you could kick us off with a little rhythm..  A bit more invigorating than that.

Hugh - Bum bum bum, ber dum dum  dum ber dum.

Chris: - We’ve got a bit of hip swaying action happening. The arms are outstretched like a Jesus Christ posture with fingers extended and palms out. So I’m seeing palms being presented to me and she’s looking straight out surveying the vista. Okay, is that dance one?  We need a different tune for dance two.

Hugh - do do do dodo do do do.

Chris - Okay so this is a very vigorous dance. There’s a lot of shoulder action happening here and sort of twisting of hips and arms are moving around. It’s not symmetrical at all. Okay, thank you very much. Very hard for you at home to picture what Amy was doing in dance two. It was quite hard for me to picture was Amy was doing in dance two. Alan, what was your observation?

Alan - Well, Amy was wearing a full length chiffon lab coat, brilliantly decorated with forty thousand sequins sewn on by her mum.

Chris - Is this a nod to the good old days of sexist British television?! What did everyone think then? What did we think about the attractiveness of the two dances? Graihagh - what is your instinct telling you?

Graihagh - Well, the first one was definitely more controlled I would say, and the second one was a bit more sort of loose, wasn’t it. And you’re smiling much more in it which makes it kind of more attractive to me because you're laughing, you’re smiling.

Chris - So your money’s on number two?

Graihagh - I’m going for number two.

Chris - Hugh…

Hugh - Arms higher up above the shoulders as opposed to arms lower down. So the second one had more arms up than arms down.

Chris - James - your thoughts for the judging on that side of the…?

James - It’s weird because the first one was a lot more symmetrical but it just felt a lot more robotic. We were just saying that symmetry is kind of attractive but, at the same time, it didn’t feel like I was enjoying it as much as…

Chris - So Amy, put us out of our misery. Of the two dances, which one was ostensibly the attractive dance and what are the go to points for people to bear in mind on the dance floor this Christmas at the office party?

Amy - I can safely say that you guys were correct. The second one was supposed to be the attractive dance and I’m happy that that worked. And it’s interesting because they have actually pinpointed it to specific movements in the body.

There was an experiment done a few years ago looking at particular movements of the body and they rated the attractiveness of the dance, and these were variation around the central region of your body, so if you’re doing isolations to the rib cage, that kind of thing. Quicker foot pace as well. So you notice in the second one I was speeding my feet up.

Chris - You did have to compete with the music a bit, but…

Amy - Yeah, I know. It was hard.

Chris - You did well under the circumstances.

Right so you’ve got have movement around the ribcage, move your limbs, feet..

Amy - Feet quicker.

Chris - Hands?

Amy - Hands - what you want to do is get variation in your dance moves. So as James said about the first one being a bit symmetrical, a bit boring, that has been scientifically proven in that you have to have variation in your dancing otherwise it’s not attractive and it’s boring.

According to the song, by the twelfth day of Christmas, 11 pipers were piping and 12 drummers were drumming. Alan Calverd explains to Chris Smith the physics of the wind section of an orchestra...

Alan - You have to start off by making what’s called a ‘buzz.’ Basically you blow a raspberry in a funnel.

Chris - Go on!

Alan - Pthhhhhhhhh or Pfffffff depending on which level of brass instrument you’re playing. And then that contains a whole lot of tones and you select the resonant length of tubing by pressing the valves up and down.

Chris - Why do the valves actually change the notes though? Why should the length of the tube affect what comes out?

Alan - What you’re trying to do is produce a standing wave within the tube. Now the end of the tube being open means that there’s got to be an antinode at the bell and there’s going to be a node where your lips are because the air’s not moving at that point.

Chris - What’s an antinode?

Alan - Antinode is where the air is moving at it’s most rapid and the node is where the air is not moving. Essentially, if you imagine the tube is stretched out you have something like about 15 feet of tubing, you can draw lots of sine waves within that 15 feet.

Chris - Wiggly waves along it?

Alan - Wiggly waves along it. And provided they all start at zero and end at maximum, then you can have waves of various different frequencies all fit in the tube.

Chris - Would it have to be all curled up like the tuba is or could you get the same tune out of a long straight piece of pipe - it’s just that we coil it up for convenience because it would be hard to move otherwise?

Alan - It’s very difficult to march with a 15 foot drainpipe. Also, it upsets the other guys in the orchestra.

Chris - Fair enough. Why are these instruments made of brass - is there a reason why they go for brass or could you make it out of anything?

Alan - In principle you could. You can play a hosepipe if you’ve got a decent mouthpiece.

Chris - I’ve seen people do that with a funnel on the end. And by swinging the hosepipe almost like you were going to do a lasso, you get a range of different sounds out. Very interesting.

Alan - Yes, that’s quite interesting. You get quite a harsh tone out of a hosepipe - very similar to a trombone because it’s the same diameter all the way down.

Chris - What are you saying about trombonists. They won’t be very happy to hear that.

Alan - Trombonists are always happy because they always get to play the loud bits.

Chris - Fair enough!

Alan - It’s because the trombone is, essentially, the same diameter all the way down the tube. That means you can get a whole lot of harmonics and overtones and you get this good rasping sound if you really blow it hard.

Chris - But the reason for brass?

Alan - The reason for brass is it’s an easy material to work; it’s ductile, it’s malleable so you can beat the shape of the bell that you want and you can draw tubes of any size and length. You can solder it quite easily, it doesn't corrode, and most important of all from my point of view is it’s a biocide. There’s so much copper in brass that bugs don’t grow on it.

Chris - And that’s quite important because you don’t want to catch tuberculosis do you?

Alan - Urghhhhh.

Chris - Are you saying then that, actually, this is a useful aspect of the instrument because of the you’re blowing all that moisture and warm air in there and a whole bunch of bugs from your mouth, presumably instruments do end up riddled with bacteria?

Alan - The first thing they tell you when you join a brass band is... never breath in.

Chris - And what about the brass section and other parts of...say woodwind - is it pretty much the same physics or is there a difference there?

Alan - Slightly different physics. The real difference is in the way that the first edge tone is generated. Instead of blowing raspberries, woodwind either use a reed or an edge like a whistle, which is the recorder and the flute have an edge and everything else is a reed. But the question is whether the saxophone is brass or reed?

Chris - What do you think?

Alan - I think it’s interesting, it’s almost entirely in a class by itself because of all the instruments it’s the one that sounds most like the human voice.