Naked Science Question and Answer

Dr Chris, Dave and Derek answer all your questions including: why paintings fade in sunlight, why hairs on different parts of the body grow at different rates, whether UV light...
06 August 2006


In our last show before the summer, Dr Chris, Dave and Derek answer all your questions on science, technology and medicine including: why paintings fade in sunlight, why hairs on different parts of the body grow at different rates, whether ultraviolet light poses a danger at the disco, how weightlessness can be experienced on Earth, and sticking with space, Steve Miller from University College London explains the origin of Jupiter's giant red spot and its smaller relative, red spot junior. We'll also be repeating a famous experiment to see if people can accurately estimate physical attributes from the sound of someone's voice, and in Kitchen Science, Derek and Dave dice with death as they calculate the drag on a flag at 70 miles per hour...

In this episode

Electrical Discovery Galvanises Wound Healing

Researchers at Aberdeen University have proved that Benjamin Franklin was right all those years ago to zap injured people with electricity, because a squirt of current can make wounds heal more rapidly. Writing in this week's edition of Nature, Min Zhao and his colleagues have shown that, in a wounded area, an electric current flows out of the wound and into the adjacent tissue. This sets up a guidance signal which surrounding skin cells can follow as they migrate into the wound to promote healing. Artificially reversing the current causes the opposite to occur and the wound opens up. The team have gone on to identify two genes which play key roles in the process, called PI3k-gamma and PTEN. Knocking out PI3k-gamma prevents cells from responding to electrical signals, whilst inactivating PTEN boosts cell sensitivity to the effect. These results suggest that drugs capable of manipulating the action of these genes, together with electrified wound dressings, might hold the key to speedier wound healing in future.

PCs Saving the World

f you have a computer at home or at work which is on for long periods of time then you could be helping to find new drugs for HIV/AIDS, contributing to a model of how malaria spreads across Africa, or even working out solutions to a game of chess. And the best part is - you don't have to concentrate on any of it. This is all part of something called volunteer computing. The idea is the following: there are some big problems in the world right now, and some of them need a lot of computer power to solve them. To do this, we can either run a small number of computers for a long time - but the time required might be a thousand years or more. Or, we can all chip in by using the processing power of computers which are usually on, and usually connected to the internet. Since most computers, even if they're in use, are only using a minority of their processing power, some of this power can be donated to a computer program running elsewhere in the world. Volunteer computing could make a huge difference. With HIV, the search for new drugs depends, in part, on modelling how small molecules might block the action of key HIV proteins. Running this model on a single computer would take an age. But if, say, a thousand computers from around the world donate processing power, the running time would be a fraction of what it was before. The most well-known volunteer computing program is SETI, the Search for Extraterrestrial Intelligence, which is run from Berkeley University. It's analysing radio transmissions which come from outer space, and which are picked up by a telescope in Puerto Rico. The program can spot unusual signals in a narrow radio bandwidth, which - scientists presume - must come from an extraterrestrial civilization. There are now 5 million computers running SETI around the world and, in total, the program has used over 1 million years of PC time. And... they've found nothing so far. But if you fancy trying to find ET, or indeed helping to solve a range of problems, check out volunteer computing. You can do this at and

Wanted People with Time on their Hands

The brains of bored volunteers could be the key to unlocking the secrets of distant star systems. Scientists working on the Stardust Mission, which returned from the tail of comet Wild 2 in January, are currently analysing dust particles that could reveal the chemical composition of the early solar system. But amongst the primordial dust hide an estimated 50 particles of interstellar dust from other stars. To find these elusive hitch-hikers, Andrew Westphal from UC Berkeley has enlisted the help of 115 000 volunteers trained in the art of recognising ordinary dust particles. If a particle doesn't fit the mould, the volunteers alert Westphal to take a closer look. What's more the volunteers can browse the universe from the comfort of their front rooms as they can download over 700 000 images of the particles from the internet. But why not get a computer to do it? Unfortunately no-one knows what an interstellar dust particle looks like, and so the search can't rely on computer muscle. Westphal hopes that a little competitive spirit should keep the volunteers looking and eventually find him the proverbial needle in a haystack.

Spices Curry Favour in Fight against Alzheimers

Alzheimer's disease is certainly a hot topic this month because researchers from Singapore have found evidence for a protective effect of eating curry. Tze-Pin Ng and colleagues, from the National University of Singapore, looked at the eating habits of over 1000 Asians aged 60-93. Using a "mini mental test" to assess cognitive function amongst the participants, the team found that occasional curry eaters (those that ate curry once or more in 6 months) and regular curry eaters (more than once a month) had better test scores than "never" or "rare" curry eaters. Indeed, previous studies have hinted at lower Alzheimer's rates in countries like India, where curry is a staple. The teams suspect that the key to their findings might lie with the popular curry herb turmeric, a component of which, curcumin, has antioxidant properties. At the same time another research group, from Johns Hopkins in the US, have found that the same chemical, curcumin, in combination with an antioxidant found in onions, called quercetin, can help to warn off bowel cancer. Writing in the August edition of the journal Clinical Gastroenterology and Hepatology, Francis Giardiello and his colleagues enrolled five patients with a genetic tendency towards bowel cancer on a daily regime of quercetin and curcumin. In these patients the number of polyps (pre-malignant lesions on the intestinal wall) dropped by about 60% and those that remained shrank by 50% after 6 months.

- Red Spots on Jupiter

The Naked Scientists spoke to Dr Steve Miller, University College London

Red Spots on Jupiter
with Dr Steve Miller, University College London

Chris - Most people will be aware that Jupiter, that giant planet in our solar system, has a giant red spot. We've known about this for 300 years or so. But what actually is it and why has another one, which has been named red spot junior, appeared more recently? Well I asked University College London's Steve Miller to tell me all about it.

Steve - Jupiter's a very large planet. It has a diameter of about 140 000 km compared with something like 13 000 km for the Earth. It also spins a great deal faster than the Earth does; roughly two and a half times as fast. Jupiter's day is less than 10 hours and our day, as we all know is 24 hours. So this is a huge rapidly spinning ball of gas something like five times as far away from the sun as we are. Now the great red spot is a very large storm system on Jupiter: you could fit the entire Earth into it. It's at a latitude of about 22 or 23 degrees south of the Jupiter equator. That has been known probably for 350 years and the storm is probably quite a bit older than that.

Chris - Steve, how do we know it's a storm though?

Steve - We can see that there are clouds at the northern and southern edges of it that are simply being swept round in a circle, and some winds go up to about 600 miles per hour, so you can tell that this thing must be spinning very rapidly.

Chris - Why is there just this one mega storm system? Is it because it's so powerful that it draws everything else into it?

Steve - Well that's indeed how it might have formed. It's very likely that it's formed up from a lot of smaller storms merging and then forming this enormous structure. We do know that it's changing. It's now something like 17 000 km in the west-east direction and 12 500 km north-south. When it was really catalogued in the 1880s, it was something like 39 000 km east-west, so we can see that in the past 125 years the storm has shrunk in size. It's changing. But it's almost certain that it formed from the merger of a lot of smaller storms.

Chris - We've got some evidence that this may be happening on Jupiter in the wake of the giant red spot junior, which has crept up in more recent years.

Steve - Yes, that's right. That's a storm that's a bit to the south of the great red spot and this is a storm that has resulted from the merger about five years ago of three smaller storms that basically caught each other up and then merged into one. It's really quite big; about 40% of the volume of the great red spot. So red spot junior may be junior may be junior but it's still pretty massive.

Chris - Do you know why it's red though?

Steve - Difficult question. The most likely theory is that when the three storms that formed red spot junior merged together, they became much more violent as one combined storm. This has had the effect of bringing material up from Jupiter's lower atmosphere higher up into the atmosphere. Now it's probable that this Jupiter air has quite high concentrations, or relatively high concentrations of phosphorus compounds or sulphur compounds or something like that, and bringing it up higher into the atmosphere has allowed sunlight to cause chemical reactions to occur that have turned the colour red. It's giving us an insight but we still have no idea what the actual chemical compound is that gives the great red spot and now red spot junior it's red colour. We just don't know what that is.

Chris - Steve, I have an email from Richard Wood in Columbus in Ohio and he'd like to ask a couple of questions about Jupiter. First of all, he says why do storms like Jupiter's great red spot not have eyes like hurricanes on the Earth do?

Steve - I think it's just a question of how big they are. The funnel of the great red spot and red spot junior are so much huger in size so that they don't give you the impression of an eye in the same way that a hurricane does. But then if you distance yourself a bit from them, you can actually imagine that you are looking at an eye. So there is sort of an eye but it's so much greater than anything that we see on Earth.

Chris - Richard goes on to ask, why is it that these Jovian storms don't migrate towards the poles, ie: away from the equator, like hurricanes on Earth seem to do?

Steve - Well this is something we call the coriolis force, and the coriolis force will tend to keep things rotating in the same latitude. We have coriolis forces on Earth but because the Earth is much smaller and rotating much slower than Jupiter is, they're not so effective so you do get winds that move north and south on the Earth. It's very difficult to get winds to move north or south on Jupiter simply because the coriolis force will always tend to bend anything moving north or south, it will tend to move it again in an east-west direction. That's why Jupiter has these very stable light coloured zones, these dark coloured belts on the Jupiter atmosphere. They remain very stable because they're held in place by these coriolis forces.

Guessing Physical Attributes from Someone's Voice
with Derek Thorne

This week we're going to be replicating a famous experiment (Krauss et al., Journal of Experimental Social Psychology (2002) 38: 618 - 625) that examines people's ability to judge someone's height and age by listening to their voice. We've got our Kitchen Science guru Derek here in the studio, and we want you to let us know how old and how tall he is. We'll reveal the answer at the end of the show....

Chris - We've had quite a few guesses tonight about what you look like and how tall you are. It's ranged from age 45, 48, 32, 35 and people estimating between 5 foot 11 inches and 5 foot 6 inches.

Derek - Well I've been quite nervous to hear it all, but I can now reveal the details of my height and my age. I am in fact younger than all of those and younger, I think, than anyone guessed. I'm actually 27, I'm a fresh-faced young lad and I'm 5 foot 10, and I think someone did actually get very close to that.

Chris - Yes, Helen in Norwich thought that you were 28 and put your height at 5 foot 10.

Derek - Yes, so basically you're one year out. That's fantastic. So what I'm wondering is, do you know me, because everyone else was miles out.

Chris - Well now that we've done that, we've found that people can get it right but on average there was a bit of a skew in our study. When the scientists did this experiment, did they find largely this result or did it work?

Derek - It did actually work. The thing is that I work in radio and my voice is chosen because it's maybe deeper than other people's voices. Maybe that's affected people's thinking about how old I am. But when the scientists did this down at Columbia University in New York, they found that if they showed someone a picture or played someone a voice of the same person, if people made a judgement about age and height from the voice, it was practically as good as them using the picture. So using a visual cue was just about the same as using the speech cue.

Chris - So what this suggests is that when someone makes threatening phone calls or says that there's going to be a bomb somewhere, instead of hiring very expensive experts to come and analyse voices, you could do it cheaper by asking the radio listeners what they think of the voice.

Derek - Absolutely. Of course if I choose to do something like that then they're never going to guess who I am, which is perfect.

Chris - Yes, so if you ever need a new career Derek, you can be a threatening phone call maker or something.

Derek - Not something I'd really call a career but a one off maybe.

Darwin's finches or Galapagos finches. Darwin, 1845. Journal of researches into the natural history and geology of the countries visited during the voyage of H.M.S. Beagle round the world, under the Command of Capt. Fitz Roy, R.N. 2d edition.

- Darwin's Finches and Morning Sickness - Science Update

Evolution in Darwin's finches, and why pregnant women get morning sickness...

Darwin's Finches and Morning Sickness - Science Update
with Bob Hirshon and Chelsea Wald, Science Update

Chris - Now we're going to take our final trip to the States before the summer, where Bob Hirshon and Chelsea Wald will be looking at evolution in Darwin's finches and also why pregnant women get morning sickness.

Bob - This week for the Naked Scientists, the staff here at Science Update go out on a limb here in the States by throwing our support behind the controversial theory that life on Earth evolved by means of natural selection - a theory first proposed by foreign biologist Charles Darwin. In this episode, we'll learn about brand new insights into evolution from the finches Darwin studied. But first, scientists have long wondered why pregnant women get morning sickness. After all, they need all the sustenance they can get, so losing their breakfast doesn't seem to be the best course of action. But Chelsea tells us that there could be a good evolutionary reason for it. Chelsea - When morning sickness strikes, pregnant women often ask, Why me? Well, they'll be happy to know that scientists at the University of Liverpool are working on an answer. By comparing 56 studies from 21 countries, they found that pregnancy sickness is more common in places with diets high in sugars, stimulants, vegetables, meat, milk, and eggs. Evolutionary psychologist Gillian Pepper says this may be the body's way of protecting the foetus from harm.

Gillian - These were the foods that perhaps when man was evolving, were more likely to contain pathogens, because if you don't have refrigeration, meat, milk, eggs could very quickly could become infected or go bad.

Chelsea - Women fared better in places with diets low in these foods and high in cereals and pulses such as beans, but Pepper doesn't recommend that pregnant women change their diets. Much more research is needed on whether doing so would reduce sickness or even be healthy.

Bob - Thanks, Chelsea. Scientists have now reported seeing evolution in action in none other than Darwin's finches. Two decades ago, large ground finches moved to a Galapagos island where medium ground finches lived. The problem was, the large finches ate the same seeds as the medium finches, and they did it faster with their bigger beaks. So scientists predicted that the medium finches' beaks would evolve to take advantage of smaller seeds. Princeton University evolutionary biologist Peter Grant says that happened during a drought two years ago.

Peter - The recent immigrant species had almost eaten the supply of food for themselves, so they almost went extinct. The resident species, a species that was there before the new species arrives, underwent this large shift towards small size in beaks.

Bob - He says this adds to the evidence that competition between species can lead to evolutionary changes.

- Is a supernova explosion faster than light?

If you have a star which is approximately 860,000 miles across and it explodes like a supernova, would the matter coming from it travel f...

Is a supernova explosion faster than light?

Just to reassure everyone at home, the sun is probably too small to become a supernova; it's more likely to become a red giant, which will kill us all anyway but slightly less violently. But fundamentally no. Nothing can go faster than the speed of light. In a supernova things would get very very close and be very energetic, but according to Einstein you just can't get faster than the speed of light. Things can give the impression of going faster than the speed of light, however. A lovely analogy is that if you were to shine a torch beam at the wall and then move your hand across at the speed of light, the end of the beam would sweep out at a distance greater than the speed of light would have travelled if it were just travelling from A to B. This is because it's on the end of a long beam of light. So you can fool someone into thinking something is going faster than the speed of light, but as far as we know, there's no way we can go faster. As for gamma ray bursts, gamma rays are just a form of light. It's electromagnetic radiation. Light that we can see is just one collection of frequencies or wavelengths of light. Gamma rays are another very short wavelength of radiation. X-rays are a little bit longer than that and then you go through ultraviolet and then visible light and then infrared, microwaves and radiowaves and so on.

- Why do hairs grow at different rates?

Why do hairs grow at different rates?

Why do hairs grow at different rates?

The reason is that it is genetically programmed into us while we are developing inside our parents. As little babies your body develops as a series of segments and each of those segments inherits its own genetic programme. In some areas the length or growth phase of the hair follicle is longer than in other areas. In your eyebrows for example, a hair grows for about a month and on the top of your head a hair follicle is active for anything up to three years. Hair follicles have three phases to their life cycle: they have a growth phase, and this is called the anagen and can last up to three years for a head hair, 21 days for an eyelash and 3 weeks for a pubic hair. If you go through the growth phase, the next phase is what's called a catagen phase, which is when the hair falls out, and then you have a resting or telogen phase, and then the cycle resets itself. The length of hair depends on the length of the growth phase.

- Why do pictures fade in paintings and books? Is it a chemical reaction?

Why do pictures fade in paintings and books? Is it a chemical reaction?

Why do pictures fade in paintings and books? Is it a chemical reaction?

The colours in pictures are made out of chemicals. They tend to be chemicals that interact with light quite well because they have a colour, meaning that they absorb some colours and reflect others. If they are exposed to too much light, especially ultraviolet light from the sun, they break, become damaged and stop being coloured. It depends what dyes you're using. Inorganic dyes that include metals tend to survive a lot better in sunlight than organic ones, but basically the chemicals get damaged and bleached. If the molecule is broken by absorbing lots of UV light, then its absorbency changes. The same thing happens with human hair in summer. You can make the process happen a little bit quicker if you put some lemon juice on. On a similar point, the reason why bleaches work is that dye molecules are sensitive and quite easily damaged. A bleach is something which oxidises something, and goes round and damages things at random. The things that get damaged first tend to be the colour molecules and so things tend to go white.

- Does eating chillies help with neuralgia?

Does eating chillies help with neuralgia?

Does eating chillies help with neuralgia?

It's not the actual eating of the chillies. The thing that makes chillies hot is called capsaicin. Not only does it make things taste hot but can also be used as a topical ointment on the skin if you have various pain syndromes. One of those is shingles. If you've had chickenpox in the past then you have chickenpox living in your nerve fibres in your body for the rest of your life. Periodically it can come back out and cause a patch of chickenpox vesicles or blisters on one patch of skin. After they go away, it can be tremendously painful. However researchers have found that if you apply this capsaicin to the painful area, it can actually help to relieve the pain. This could possibly be because pain is mediated in the nervous system by a class of tiny nerve fibres referred to as C-fibres. Capsaicin activated those nerve fibres and in some cases activates them to death. This turns them off and indirectly makes them less sensitive, which is why the pain goes away.

What's the difference between hydration and water retention?

Your body is about 60% or more water and that's because we're made of cells and cells are literally bags of water. Cells have an oily membrane that encloses water and also on the outside of that membrane washing around our tissues and cells is water.

So the average 70kg person has at least 40kg of water. That water exists in an equilibrium between how much is in the blood vessels, how much is surrounding our cells and how much is in the cells.

Your body knows how much water it's got on board because it measures things like how much salt it's got in the blood stream.

Your kidneys work out whether you have too much or too little water and then secrete various hormones to regulate how much water is lost.

When you get water retention, something encourages your kidneys to keep more water back when you would normally put it into the urine and this increases the total amount of water in the body.

When you get a little bit too much water in the body, it spreads among the tissues and starts to surround the cells in your legs in what's called dependent oedema. It goes to the lowest point in your body under gravity, and that's why people get puffy legs.

Water retention can be caused by kidney problems and heart problems, but just in normal hot weather people who take on a lot of water to rehydrate and it sections out into various parts of the body.



- If it's ultraviolet light that causes skin cancer and there are UV lights in discos, are they dangerous? If not, why?

If it's ultraviolet light that causes skin cancer and there are UV lights in discos, are they dangerous? If not, why?

If it's ultraviolet light that causes skin cancer and there are UV lights in discos, are they dangerous? If not, why?

How dangerous UV light is depends on the kind of UV light. If it's got a very long wavelength quite close to visible light then it's not much worse than blue light. Once it starts getting beyond that it's getting more dangerous and closer to x-rays. The stuff in bakers and discos is called UVA and is closer to blue light and probably isn't that bad for you.

- Why don't canned fizzy drinks from vending machines explode when opened?

I want to know why a drink can doesn't get shaken up when it falls from a drink dispenser. It falls very hard but doesn't overflow when y...

Why don't canned fizzy drinks from vending machines explode when opened?

The reason for this is that when it drops, it tends to fall on its side. When the liquid hits the bottom it swirls and doesn't create much turbulence. This stops there being too many bubbles in the liquid and it doesn't fizz over.

- Why does my car air-conditioning increase fuel consumption?

In my car, if you keep the air conditioning on rather than having the windows open, it makes quite a difference to the fuel consumption. ...

Why does my car air-conditioning increase fuel consumption?

Then you have completely proved exactly what physicists say. At high speeds, such as 70 miles per hour, you're much better to use the air con and keep the windows closed. But at 40 miles per hour it's more efficient to keep the air con off and have the windows open. You get more air resistance the faster you go. The way the air conditioning works is that it's like a having a big fridge on your car. You take energy from the engine to drive this fridge, it you like, and it draws air over the fridge element and passes it into the car. So you're not getting something for nothing. It is taking energy from the engine. So if you want to be the most efficient you possibly can then you'll just sweat it out, although you won't necessarily be in the best possible state when you arrive at your destination.

- How does the vomit comet aircraft produce weightlessness?

I was always fascinated with the state of weightlessness and how it works. A month ago I saw a report on artificial simulations of the ph...

How does the vomit comet aircraft produce weightlessness?

Weightlessness doesn't mean that there isn't any gravity. All it means is that everything around you is falling at the same speed as you. So if you were in a lift that was accelerating at g towards the ground, it would feel like you were weightless. So in the case of a satellite, it's falling all the time but misses every time it goes around the Earth. The way they do it in planes is that they make it fly on a parabola upwards and then make it accelerate towards the ground at the same rate as you would falling. So the plane is falling at the same speed as you so you feel like you're weightless. So it's all a question of relative falling.


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