The Science of Lasers, Light, Kung fu and Archimedes

02 October 2005
Presented by Chris Smith, Kat Arney


In this show Symon Cotton joins us to discuss how Raman Spectroscopy can be used non-invasively to diagnose malignant melanoma, Russell Cowburn describes how laser scatter effects can be used to genetically fingerprint a banknote, Sam Reay chops his way through a 3-inch block of concrete to highlight the physics of Kung fu, and Uwe Bergmann describes how synchrotronic x-rays are helping him to read the 1000 year old Archimedes Palimpsest.

In this episode

How Music Is Good For The Heart

We've all heard the saying "music soothes the savage breast", and now scientists in Oxford have been studying how different types of music can affect your breathing and circulation. The researchers tested twenty four young men and women with different types of tunes, including raga (Indian classical music), Beethoven's ninth symphony (slow classical), the Red Hot Chilli Peppers (rap), Vivaldi (fast classical), techno, and a piece by modern composer Anton Webern (slow "dodecaphonic" music). The team found that faster music speeded up the circulation and breathing, regardless of whether it was techno or Vivaldi. Also, Indian raga music had the opposite effect, providing the greatest amount of relaxation. Intriguingly, the researchers found that during gaps in the music, people became more relaxed than they were before listening to any music at all - especially if they were musicians. Music has also been found to have unusual benefits in the past, such as boosting milk production in cattle. But I'm not sure how good cows are at dancing.

An End To Being Browned Off By Burnt Toast

Cambridge-based company Magnetic Design have developed a device that, with the help of a little radiation, promises to deliver "perfect toast every time". By combining a smoke detector with a toaster their new kitchen must-have can tell automatically when it's time to pop up the perfect slice. It works by sucking in particles of caramelised bread, which are released as the toast cooks, and blowing them into a stream of radioactive particles similar to those found in a smoke detector. The toast particles mop up the radioactive particles, reducing the number picked up by an adjacent sensor. The more singed the toast becomes, the more particles it emits, and the greater the amount of radioactivity that gets mopped up before it can reach the sensor. By setting the toaster to switch off when the radioactivity drops to a certain level you can guarantee that your toast will always be cooked to perfection, no matter how brown you like it, and regardless of whether you start with warm, cold or even frozen bread.

Getting To The Bottom of The Quick Sand Question

What is quick sand, how does it work, and are you likely to sink into it without trace ? Moreover, what's the best way to escape if you do find yourself stuck? Writing in this week's edition of the journal Nature, these were the questions bothering Dutch researcher Daniel Bonn when he recently wandered around some Iranian quicksand pits which, local legend has it, have been known to swallow camels from time to time, and for that matter anyone who cared to disagree with the local regime. To solve the riddle he recreated some Iranian quicksand in his lab and used the resulting model to figure out how quicksand works, and that it's actually impossible to drown in it (as long as you don't do something stupid), indeed you should only sink to waist depth. But don't try to pull a stuck person out - because the force needed to extricate just a stuck foot is similar to that needed to move a medium sized car, so you might inadvertently pull the person apart ! Instead, the best way to escape is to turn the stuck body part in small circles to resuspend the sand particles in water, withdrawing gently as you do so.

Breast Cancer Awareness Month

It's Breast Cancer Awareness Month this October, but why is it so important to be aware of breast cancer? It's because there are 40 000 cases of breast cancer each year in the UK, which amounts to around 750 each week. Cancer Research UK are hoping to raise money for research into the causes of breast cancer and finding new ways to treat it. And to do this, they're hosting a range of events, including sponsored walks called 'All Walk Together', and Pink Parties where everyone wears pink. If you want to get involved, go to or you can phone the hotline on 08701 602040. Get involved, raise some money, and have a good pink time this October.

- The Physics of Kung Fu

The Naked Scientists spoke to Chris Smith interviews Sam Reay from the Institute of Physics, London

The Physics of Kung Fu
with Chris Smith interviews Sam Reay from the Institute of Physics, London

Sam - I'm going to attempt to break this huge block of concrete in front of me using my hand.

Chris - And this is an established kung fu move is it?

Sam - Yes, exactly.

Chris - It's quite intriguing to think that there's so much physics underlying kung fu.

Sam - Well I think there's quite a simple reason for that. Kung fu has been evolving for thousands of years, and the techniques have been improved upon by many generations of teachers. This means that people use their bodies in the most effective way to defend and attack. It's not surprising therefore that by learning kung fu you get an intuitive understanding of physics.

Chris - This piece of concrete is three inches thick, and you're going to break it with your bare hand. Why don't you talk us through the move you're going to do, and how physics is at work in breaking this bit of concrete.

Sam - The move that I'm going to use is very simple. I'm going to hit the concrete block with the bottom of the palm of my hand. Obviously if I just push down on the block, then there's no way that I'm going to break it, so I have to accelerate my hand before I hit it. I'm going to put kinetic energy into the block, and that's what's going to break it. Kinetic energy is proportional to speed squared, so if I can maximise my seed, I can maximise the amount of energy I give to the block. I need to hit the block when my hand is moving at the maximum speed. To do that, I need to aim beyond the block, because as my strike progresses, I slow down towards the end of my strike. I want to hit the block in the middle of my strike, so I aim at a point well beyond block, not at the surface itself. Another part of the technique is to put as much body mass as I can into the strike. I do this by twisting my body and lowering my torso along with my arm as I break through. So it's not just the mass of my hand and my arm that's going into the strike, it's the mass of my whole body. This is important because kinetic energy is also proportional to mass. If I can maximise the mass of the strike, then I can maximise the energy that I have to break the board. The third thing is that I have to make sure I have the maximum confidence possible. I need to believe that I'm going to break the concrete block.

Chris - So it really is all in the mind?

Sam - Well it's in the body as well, but the mind plays an important part. If I don't believe that I'm going to break this block, I will naturally slow down my hand because I'll be scared of getting hurt. Velocity is really important, so I have to believe I can do it.

Chris - Does it hurt?

Sam - It does smart quite a lot with concrete. If I break wood, it doesn't hurt that much at all.

Chris - Are you nervous?

Sam - Yeah, a little bit. It's a pretty hefty looking piece of concrete actually.

Chris - So let's see if this guy can do this, just using his hand.

(Sam breaks the block - rapturous applause)

- Diagnosing Skin Cancer With Light

The Naked Scientists spoke to Symon Cotton, Astron Clinica, Cambridge

Diagnosing Skin Cancer With Light
with Symon Cotton, Astron Clinica, Cambridge

Symon - We make and sell a piece of equipment that helps to diagnose skin cancer and other skin diseases. And it does this by helping to unobtrusively probe beneath the skin. It's better than existing technologies because it gives more information to doctors. More information means that they can make better decisions.

Chris - How can we use light to diagnose skin problems?

Symon - the skin is nice and easy to get at because it's on the outside of the body. This makes it a very good thing to look at with light. The research we've been doing is to look at how different types of light interact with cells. After we've seen that, we can start to measure things about the cells, such as how many there are and their pattern over the skin. Particularly with types of skin cancer, we can identify certain types of cell and work out where they are. For instance, in melanoma, certain cells called melanocytes should be in a certain layer of the skin. If they become cancerous, they can start to grow in the second layer of the skin, and that's the key bit of information that dermatologists would like to know, and in particular the pattern they form. They can use this information to diagnose this kind of disease. They have to make the decision whether to have the lesion removed.

Chris - Presumably shining a light on the skin is much quicker than a pathologist having to remove it and have a look under the microscope. How good is using light compared to the pathologist?

Symon - Well the pathologist looking down the microscope is still the gold standard for doing the diagnosis, but if the pathologist never gets to see the bit of tissue, it doesn't matter how good they are. People are faced with the very difficult decision about whether something should go to the pathologist or not. Currently, diagnosis rates are at about 80%, so about 20% of these are being missed or coming through later.

Chris - So people have had skin cancers and it's been overlooked?

Symon - It is sometimes overlooked, and often picked up at a later date when it's harder to treat. The whole emphasis with skin cancer is diagnosing early. If you can give more information on how skin cancers grow, if they're picked up early enough, the following treatment is much less aggressive.

Chris - So how does your piece of equipment actually work?

Symon - We use light to identify different types of cells. We can do that because different types of cells absorb light in different ways. Some of them will absorb different colours more than others. But the other thing we critically use is that when these cells move into different parts of the body, the light moves indifferent ways. In the top layers of the skin, there is very little scattering, so the light doesn't bounce around very much. But in lower layers of the skin, it's a highly scattering area. Because of the way light bounces around, the colour that the cells appear changes, and we use that to identify the type of cell and critically, where it is.

Chris - I think it's important to say that this is something that we should be worried about right now. I think the cited figure is that there has been a 100% increase in melanoma rates in the past ten years.

Symon - We should be very concerned about melanoma. Melanoma is a ver very dangerous disease, but if it's identified early, then the treatment can simply be to have the lesion removed. However, the point is to get that lesion identified and removed early. If it's removed early, the treatment is very effective. If it's removed late, then the treatment has to be very aggressive. The whole emphasis is early diagnosis. If you have a funny looking mole that's changing and itching, then go and see your doctor because early diagnosis is the key.

- Rediscovering Archimedes With X-rays

The Naked Scientists spoke to Dr Uwe Bergmann, Stanford Linear Accelerator Center, USA.

Rediscovering Archimedes With X-rays
with Dr Uwe Bergmann, Stanford Linear Accelerator Center, USA.

Chris - One thousand years old, and you're reading it for the first time. Tell us the story of the Archimedes Palimpsest.

Uwe - The palimpsest was first rediscovered in 1906 in Constantinople, and then disappeared again. It is text of Archimedes work copied in Ancient Greek. It contains some of the works that have been unknown to the scientists following him, in particular, a work called The Methods. The works were over-written by a monk. The problem with the palimpsest is that about 25% of it has still not been read.

Chris - And this is because somebody has defaced it by turning the original work of Archimedes into a prayer book.

Uwe - That is one of the reasons. There are other reasons, such as some of the pages have been over-painted by forgers in the 20th century, and a lot of the pages have suffered from mould and general decaying of the parchment.

Chris - So it's presently unreadable, but how are you solving the problem?

Uwe - We are using x-rays to go through the layers that obstruct the reading by regular light.

Chris - So how do x-rays make what's hidden, visible?

Uwe - If you take a regular chest or dental x-ray, you can do that by just shining x-rays through, and the different materials such as your bones absorb more, and you get a contrast like that. It doesn't work like that in the Archimedes Palimpsest because the quantity of ink remaining is so tiny that you wouldn't see a contrast. So we are using a slightly different method. As an analogy, you can say that you wouldn't look for stars in the sky during the day because there's so much background from the sunlight that you won't be able to see them. With this method we are using, we can basically remove all the unwanted scattering signal and we can only focus on the one quality in the ink that gives us a signal in our detector.

Chris - So what does it look like when you shine this highly focussed beam of x-rays at the parchment?

Uwe - You shine the very small beam, which is about the size of a human hair, and you scan it through like you do with a printer. Each time the x-rays strike even a minuscule particle of iron, it will give you a signal in your detector. You then use a computer to reconstruct the image, and what you see is an iron map of the palimpsest and has very little to do with you see with your eye. We then see the ancient writing.

Chris - So the ink actually contained a lot of iron in the old days?

Uwe - Exactly. The ink does contain a lot of iron, but it does contain other elements as well. We have started by looking at iron, but we are going to look at different elements as well.

Chris - How many pages have you got through so far?

Uwe - Basically we have just started with this x-ray method. So far we have read half a page of one of the forgery pages, and we have a lot more to go. We will be reading more over the next three years.

Chris - It must be very exciting to be reading something for the first time in a thousand years.

Uwe - Yeah, it's incredibly exciting. Of course, the difficulty is that you can't just get the text and read it. It takes a lot of effort to decipher. Often we have to do it character by character. It's the scholars who actually make sense of what is written.

- Fighting Fraud With Light

The Naked Scientists spoke to Professor Russell Cowburn, Imperial College London

Fighting Fraud With Light
with Professor Russell Cowburn, Imperial College London

Chris - So you think you've found a way to combat fraud?

Russell - Yes we think so. We're all familiar with the concept of people having individual fingerprints. What we've found is that every bank note, passport, every credit card and virtually every item in the world has it's own secret fingerprint. Now we don't have to put those fingerprints there because they are naturally occurring, but they can be used to identify virtually anything you like.

Chris - How do you do that?

Russell - Well that's the trick. These fingerprints were out there all this time but nobody knew they were there. In my lab one day, we had an accident. We were firing a laser beam at a microchip, nothing to do with security, and the chip fell off. There was a piece of paper where the chip was supposed to be, and we found that when the light bounced off the paper, instead of not carrying any information at all, the laser light was carrying lots and lots of information. Essentially, the laser was interacting with all of the tiny little defects that you get on any surface of paper, plastic or whatever. By looking at those, you can think of them as some kind of fingerprint for that particular item.

Chris - Now we know that a fingerprint is fairly specific to an individual. How likely is it that two bits of paper have the same fingerprint?

Russell - The chance that two bits of paper have the same fingerprint is one in a billion billion billion billion billion billion billion billion billion!

Chris - So a lot!

Russell - Yes, so you can look but I suspect you won't find one!

Chris - That's amazing. So it means that with bank notes, you don't need to put a figure on it any more. You can just scan them as soon as they roll off the presses, lock away its fingerprint and you'd know straight away if it was a forgery.

Russell - That's exactly right, and that's exactly what we're trying to do at the moment. We're talking with some central banks about doing that.

Chris - You must be a millionaire now!

Russell - Er, no. We're very excited because we stumbled across something that we weren't even looking for. We were doing science in a different area, in nanotechnology, and it was only because that chip fell off that we saw that something was unusual and we asked a question.

Chris - Is it just paper that this works on, or does it work on other surfaces like plastic credit cards?

Russell - It works on pretty much everything. The rule of thumb is that if you hold it up and you can see your face in it, then it won't work. Unless it's a perfect mirror or a completely transparent bit of glass, then it has a fingerprint. We can read that fingerprint just by shining a laser beam onto it.

Chris - If I knew the fingerprint that went with a piece of paper, how easy would it be to make another piece of paper with the same fingerprints?

Russell - We don't know how to do that, and we think that that's what makes the technology really secure. Most of the ways of securing things like putting on barcodes and holograms, people know how to do. It doesn't take very long for criminals to work out how to copy that. The beauty of our method is that nobody, not even ourselves, knows how to reproduce the fingerprints. This means that if I turn criminal, I am as unable as anyone else at cracking the system.

- Why does red mixed with green make yellow?

When mix two colours of paint together, say red and green, you get brown. But if you mix red and green light together, you get yellow. Wh...

Why does red mixed with green make yellow?

When you mix paint, it's a subtractive process. You start with white, and you're putting a layer of something on top of it, which allows a certain wavelength of light through but takes away everything else. So whatever you add, it always gets darker, and changes colour in a certain way. When you mix light, you're starting with black, and you're adding something. If you think a the way a TV works, it sends out red and green and blue and makes a coloured picture. But it's adding something all the time. Paint is always taking something away. It's a fundamentally different way of doing something. An interesting aside to that is that when you take a picture with your camera, it records red, green and blue. When you print it out, the printer has to convert it into something called CMYK, which is cyan, magenta and yellow. These are mixed to make the colours that you see. Printers use a different palette because when you add things subtractively, you end up with different colours. Interestingly, the K is black. In theory, if you mix the cyan, magenta and yellow together, you get black, although in practice you don't quite, so they have to add black to make everything work.

- Why does it get darker earlier in the winter than it does in the summer?

Why does it get darker earlier in the winter than it does in the summer?

Why does it get darker earlier in the winter than it does in the summer?

Although the earth might look flat, if you look at it from outer space, it's a big sphere. But it's not straight. It's actually a bit wonky, and the amount of tilt is actually about 23.5 degrees. This means that part of the earth is tilted towards the sun, and part of the earth is tilted away from the sun. On one part of the orbit, the top of the earth is tilted towards the sun, which is the warm summer. This is when you get longer days. Further round in its orbit, it'll be pointed away from the sun. This is our winter, and the days are a lot shorter. Therefore, the length of the day is actually all down to how angled our planet is in space.

How does a light bulb work?

A light bulb is an electrical filament. What you have is a long piece of wire, and when you connect this to a socket, it basically completes a circuit. As electricity passes through, the electrical current excites the metal and gets it hot. As you know, an electric fire glows orange because there's electricity moving through it and it creates heat. In a light bulb, it's set up in such a way that it doesn't just glow red, but it glows white. The key thing about a light bulb is that if you have something that is that hot with oxygen around, just like Dave and Derek's brillo pad, it'll burn. So what they do with a light bulb is that they suck out all of the oxygen and put argon in instead. This is what's called a Nobel gas: it's completely unreactive and inert. It helps the filament to stay the right temperature by getting hot and carrying heat away from the filament to the edge of the glass.

- How long does it take the sun's rays to reach Pluto?

How long does it take the sun's rays to reach Pluto?

How long does it take the sun's rays to reach Pluto?

Pluto is about 6 billion kilometres away from the sun and light travels at 300 000 kilometres every second. To put that in perspective, if you stood on the equator with a torch and switched it on, in one second the light would travel round the earth at least six times. In other words, it's travelling about a billion kilometres every hour. That means that to get to Pluto, light will take about five and a half to six hours to get from the sun.

- What is the basis of Red Sky at Night, Shepherds delight?

There's a rhyme that goes 'Red sky at night, shepherd's delight. Red sky at morning, shepherd's warning'. I don't understand it.

What is the basis of Red Sky at Night, Shepherds delight?

I think it's just a myth. Red sky at night, Hackney's burning!

It's a well established old proverb, but I'm not sure whether it has any validity scientifically. When you have a very very rich sunset, it's because there's a high quantity of particulate matter (or dust) in the atmosphere.

A lot of dust in the air is usually down to volcanoes, traffic, industry and the harvest. But I don't think that it has any linkage to making the weather better.

I suppose you could argue that dust might lead to global warming, and that that will warm the planet up, but I don't think the rhyme is all that true to be honest.




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