What Colour is a Dead Chameleon?

Are candles environmentally unfriendly? Why does tinfoil touching a filling set my teeth on edge? What colour does a dead chameleon go? Does antiperspirant deodorant make you...
18 December 2011


Are candles environmentally unfriendly? Why does tinfoil touching a filling set my teeth on edge? What colour does a dead chameleon go? Does antiperspirant deodorant make you sweat more elsewhere? Could we tether the moon on a string to stop it escaping? And why is the fine spray in the shower so cold? To find out, join Chris, Dave, Dominic and Helen for this festive Christmas edition of the Naked Scientists, which also sees the team connecting an oven shelf to their heads and a musical Higgs Boson-inspired interlude from Professor Karmadillo...

In this episode

Are candles bad for the environment?

Chris - If you wind the clock back a few hundred years when people made candles out of pig fat - tallow, the candles would've been made from an animal product and the animals would've eaten plant matter in order to make the fat that went into their body and then became the candle. And that's actually why rats used to love candles. Historically, if you read old John Mansfield books and things like that, you'll see that the rats gnawing on candles because they like the fact they're made of fat.

And because the pigs that they were made from would've eaten plant matter, the carbon in the candle wax would've come originally from the atmosphere. Trees would've turned it into sugars and turned it into starches, and cellulose and things that the animals would've eaten and then incorporated into their own body.

So, burning those candles isn't bad for the environment because, basically, it's carbon neutral in that regard, although I suspect there's a few partially burned hydrocarbons and I suspect Dave might have a comment on that.

Modern day candles though are made from paraffin wax. These are fairly long chains of hydrocarbons. They're oil based, burning those, you're burning a fossil fuel, so they're not so good for the environment.

Luke - Also, what sort of implications are they to a light bulb say, how many candles and how long do you have to burn those for to equate this with light bulbs?

Chris - Dave, do you know the relative comparison between a candle and light bulb?

Dave - I'm not entirely sure. I do know that candles are very, very inefficient compared to a light bulb. They are running very cold, they're not completely burning, you get quite a lot of soot out on top of them. Really 95%, 99% of their energy is going into producing heat radiation and heating things up rather than actually producing a light which you actually want.

Helen - And also, going back to the tallow point, pigs aren't necessarily carbon neutral. Certainly not greenhouse gas neutral, as they do produce a lot of methane and that's a very powerful greenhouse gas. I think you might have to take that into account as well.

Chris - True, but I guess historically, there wouldn't have been that many of them so we probably wouldn't have to worry too much, would we?

Dave - The other big environmental thing which was a really major issue with candles, especially best quality ones, is that they were made from spermaceti from sperm whales. They have a big waxy, oily area in their heads which they used to focus sound waves for their sonar. And really, quite a lot of the best quality candles are made from those and did hideous things to whale stocks.

Chris - I think you've got something ridiculous like 10 tonnes of oil coming from a single sperm whale weighing between - is it 30 tons, Helen, the sperm whale?

Helen - Absolutely, and I can't agree more that making candles out of whales is really bad idea!

Why does the wick of a burning candle shorten after you've blown it out?

Dave - The way a candle works is as follows: You've got a bath of molten wax. This is pulled up the wick by surface tension and then that evaporates. When a candle is burning normally, it's this vaporised wax which is combining with oxygen and burning away. The wick will stay there pretty much on its own and sit there. If you blow the candle out, you'll get a load of smoke and that's actually the wax vapour recondensing into little droplets of solid wax in the air. But the end of the wick can still carry on burning. It's still quite warm, and that will continue burning with oxygen. It's not actually the wick itself burning but the string inside the wick, and that will smoulder away for a bit like any bit of wood might. It smoulders for a while and eventually goes out, but it's not hot enough to re-ignite the wax.

What's the healthiest way to extinguish a Christmas candle?

Dominic - I guess that if you cover it then it becomes smothered in carbon dioxide and that means it's going to go out very quickly. Chris - What about the pinch technique? I suppose that's slightly unhealthy if you burn yourself in the process. Dominic - You want to be quite careful doing that, yes. Dave - But probably quite healthy in terms of what's been given out by the candle. The bad thing for you is if you have partially burned things, you get carbon monoxides and nasty hydrocarbons and things. And so, if you can get it going from burning cleanly to being out as soon as possible, that's probably the most healthy. But, unless you're doing it every day, all the time, I don't think it's going to kill you.

07:20 - Not finding Nemo

Not finding nemo is in fact more likely scenario, since it’s been revealed that one in six species featured in the movie Finding Nemo are at risk of disappearing from the oceans, due mainly...

Not finding Nemo

Not finding nemo is in fact more likely scenario, since it's been revealed that one in six species featured in the movie Finding Nemo are at risk of disappearing from the oceans, due mainly to overfishing.

Orange clownfish, Amphiprion perculaA research team from Simon Fraser University in Canada and the World Conservation Union (IUCN), examined the extinction risk facing over 1,500 marine species, including all the species the 16 families of marine animals that feature in Finding Nemo.  They include hammerhead sharks, sea turtles, pelicans, pufferfish, eagle rays, and seahorses.

Information came from the IUCN's Redlist Assessments, which rank extinction risk ranging from Critically Endangered, through Endangered, Vulnerable, and Near Threatened. These categories are all based on a detailed set of standards against which the size of populations and changes they've undergone are gauged. If there's not enough information on those factors, then the Data Deficient label is assigned.

12-35% of the species examined are considered to be threatened with extinction (including Critically Endangered, Endangered, and Vulnerable rankings).

The point of this study isn't to see if Hollywood has anything to say about extinction in the sea, but to assess how well famous, charismatic species are getting on both in terms of their current status and our efforts to protect them. Because if we can't figure out conservation for glamorous animals like sharks, turtles, and lovely coral reef fish, what hope is there for lesser-known species that don't make it onto the silver screen and few people have heard of?The research team also looked at how well these endangered movie star species are being protected by international agreements and found a general lack of conservation measures in place. An exception are the seahorses, which are some of the few bony fish whose international trade is strictly controlled and monitored by the Convention on International Trade in Endangered Species (CITES).

The study also highlights the lack of science focused on these marine species with still far more attention given to habitats and species on land compared to beneath the sea.

It's not all doom and gloom. Public awareness doesn't always come hand in hand with conservation - after Finding Nemo was released, there was a surge in sales of clown fish for aquariums, and in kids flushing their nemos down the toilet. But we are seeing increased interest in both research and protection for marine species - good examples are the recent bans on shark finning and shark fin trade in various countries and cities around the world.

Figure 1: The Andromeda Galaxy

12:14 - The Naked Scientists Dream Gadgets

The team discuss what they would most like to get under their tree this Christmas...

The Naked Scientists Dream Gadgets
with Dominic Ford, Helen Scales, Dave Ansell

Chris -  One of the things we're asking our crew to do this week is to come up with the piece of tech that they would most like to see under their Christmas tree on Christmas day.  Dominic, you're up first.  So what's your ideal dream tech Christmas present?

Dominic -   This makes it a bit like a cliché but I think for any astronomer to The Andromeda Galaxyhave a time machine...

Chris -   I thought you'd say your own black hole.

Dominic -   Well black hole might be quite fun as well.  I think a time machine to be able to sit at a telescope and to see how objects change over the course of millions of years would be really incredible because a problem that astronomers have, they get to study these absolutely huge awe-inspiring objects that are often incredibly violent in ways which are quite hard to comprehend; forming stars and supernovae explosions and so on. 

But because these objects, galaxies, are so large, it might take light 10,000 years to travel from one side of a galaxy to another and that galaxy isn't going to significantly change shape or evolve before your eyes in a human lifetime.  So, I think to be able to sit at your telescope and fast forward a million years and actually see these things colliding and forming stars, and doing all these processes that we theorise they undergo, it would be really quite awe-inspiring.

Chris - Dave, what's yours?

Dave -   What I'd really like is an incredibly strong piece of string.  I would really like to go to space but I think space rockets sound a bit dodgy.  You are essentially sitting on a huge great piece of explosive and they're also incredibly energy intensive because in order to get the force upwards, I'm going to get it by throwing fuel down and the further up you go, the more fuel you get carry, and the more fuel you're carrying up, the more fuel you need so that it get to be immense and incredibly inefficient. 

So, what you could do is build something called a space elevator.  You get a geostationary satellite, a big heavy lump just outside your stationary orbit, you just put a piece of string up to it and then that string is in tension because the Earth is actually pulling that satellite around all the time and you got a great big long wire which you can climb up.  The problem is, there is no material that we can produce at the moment which could possibly be strong enough.  If you made it out of steel, it would have to be bigger than the Earth at the top to be able to support itself all the way down at the bottom.  And so, a piece of string, strong enough to build a space elevator would be wonderful.

Chris -   Thanks very much, Dave.  So Helen, carrying on with the theme of your dream tech or gadget to find under your Christmas tree on Christmas day, what's yours?

Helen -   I would like to have a Babel fish that works underwater.  So by that I mean the invention of the little tiny creature that you stick in your ear and it will translate any language for you and my particular desire will be to have one that will let me know what the fish are thinking or if they're not thinking...

Chris -   So the aquatic equivalent of the Dr. Doolittle really.

Helen -   Well yes, I guess I do want to basically talk to the fish or I just really want to listen in.  I don't necessarily want to tell them anything.  I would just want to know what they're thinking because I think we could probably learn quite a lot if we understood more about how they perceive the world, what's going on around them, what's going on in there basically.  So a Babel fish that works underwater for all of the marine creatures, please.  That would be lovely, thank you!

Why does a spray of hot water from the shower feel cold on my skin?

Chris - I think what's probably happening in your shower is that although the water leaves the tap, or at least the showerhead, nice and hot, the fine spray is caused by two things happening. One, some of the droplets will break up as they pass through the air at high speed and two, a lot of the spray is there because the droplets hit something like the wall or the sides of the shower and then they split up into lots of smaller droplets and fly onto you. But they've had contact with something which was a cold surface and so, they've lost a lot of their energy to the cold surface. They've also, as they've gone through the air, lost more energy to the air, because they have a high surface area to volume ratio, so they tend to feel cooler. I think that's probably the most likely reason why the fine misty spray feels cooler than the big droplets which have got more energy in them because there, because they've got a bigger volume relative to their surface are. So they're losing less of their energy less quickly. Would you agree, Dave? Dave - Yes and I think the other really big thing is just evaporation. Water evaporates, and actually, if you have a bowl of water sitting at room temperature, because all the hot water molecules evaporate off the top, what's left actually gets cooler than room temperature. These tiny particles have got a huge area to evaporate from. So even just from the spray head down to your body, they've got enough time to cool down below your body temperature. Dominic - I think the other thing that will be going on is that when you're standing in the bath and the air is mostly still, you have a warm layer of air next to your skin. But when you turn the shower on it will start stirring the air around and blowing that warm layer of air off your skin, allowing cold air to come in instead.

Cape Chameleon

What colour is a dead chameleon?

Helen Scales and Chris Smith discussed this colourful question about the pigmentation of chameleons after they die...

Helen - Chameleons are fantastic. If you've ever seen a chameleon, especially in the wild, they are fabulous things. I've seen the biggest chameleon in the world and one of the smallest chameleons in the world when I was in Madagascar. The biggest ones are a good foot long and called Parson's chameleon - huge great big green things usually - and Pygmy chameleons which are so small, they'd sit quite happily on your little finger, they do a great job of just making themselves look like leaves.

But actually, an interesting point about chameleons and their colours is that, although we use the word "chameleon" to mean camouflage and to mean hiding away, this is a bit of a myth. In fact, recently scientists and researchers figured out that chameleons really use colour to show off and to talk to each other.

Males will fight each other, and they will use bright colours to communicate. Females and males will interact using colour. Hiding away and camouflaging themselves against their background actually isn't the main reason that chameleons have colour.

They can make themselves look very bright by having different pigments in their skin and different layers of reds, and yellows, blues, whites, and there's a neural signal that will cause those cells to essentially expand and contract, and reveal different combinations of colours and then that's how they get these colouration.

I haven't seen a dead one myself, and I asked my friends who've worked in Madagascar, which is where there are lots of chameleons, and they haven't seen a dead one either. I can only assume, that - given its a neural control, a nerve control, that gives these bright colours - that once those nerves stop, I would've thought they would relax back to the unexcited state. They're a browny, quite drab colouration that would generally just blend them in and not shout out, "Hey, look at me. I'm a fantastic male."

Chris - Helen MacClennan got in touch and she said, "Thought I'd let you know the colour of a dead chameleon. Unfortunately, my nosy be panther chameleon died earlier in the year. He was usually a bright-coloured chameleon - blue, white, green, and yellow - but, when he passed away, he went to very dark black or brown colour and, from my understanding, this is the normal colour of dead chameleon."

Why does metal cause pain when touching a metal tooth filling?

Dave - One of the things that could certainly be happening when you touch two metals together in your mouth, where there's a load of electrolytes, is you've essentially made a battery. If you have two metals of different reactivities, the most reactive one will tend to form ions. So if you've got aluminium foil, that's quite a reactive metal. That will form Al3+ ions that will dissolve in your saliva, which acts as the electrolyte. In the process, the less reactive metal will have a load of extra electrons given to it and it will have to somehow get rid of those electrons. So, if there are any dissolved things nearby, salt metals for example, they will deposit on the surface. Alternatively, there could be some other electrochemistry going on. My guess as to what's going on in your filling is that some of that electrochemistry is happening near the nerve in your tooth and it's annoying the nerve and causing you some pain. Chris - [The pain could result from] passing some of the electrons that result from the battery you've made in your tooth filling into the nerve and directly stimulating it, or perhaps it's making some gas locally by reducing some hydrogen ions in the solution. That would make some hydrogen gas which increases the pressure inside the tooth, and that could put pressure on the nerve and make you feel like you've got toothache, which is caused by pressure inside the tooth because of the activity of bacteria irritating in there. Dave - Or even just producing something slightly poisonous, which directly chemically annoys the nerve.

Artist's illustration of one model of the bright gamma-ray burst GRB 080319B. The explosion is highly beamed into two bipolar jets, with a narrow inner jet surrounded by a wider outer jet.

19:43 - All I Want for Christmas is a Gamma Ray Burst

A Gamma Ray Burst recorded on Christmas day 2010 was a special gift to astronomers...

All I Want for Christmas is a Gamma Ray Burst

This is something of a Christmas firework leftover from last year.  A gamma-ray burst was observed at about dinner time in the UK on Christmas day last year.  A gamma-ray burst is a burst of radiation similar to what you would find in a nuclear reactor, but thankfully very much weaker, coming out of the night sky.  These are normally very short events.  Many of them last less than a couple of seconds so they're very difficult to observe, but even longer lasting events are typically over within over a couple of minutes.  This one, however, was really quite a surprise because the gamma-ray particles carried on coming for about half an hour and some could even be seen after about 45 minutes!

' alt='Artists illustration of a gamma ray burst' >It's quite a challenge to explain what this could've been; an event so energetic it produced these high energy gamma-rays for such a long prolonged period.  We have various ideas about what causes most conventional gamma-ray bursts.  We think the short ones are probably caused by neutron stars colliding with one another, and the tremendous release of gravitational energy as those two stars combine and form a black hole.  That energy is released as gamma-rays over a period of about 2 seconds as neutron stars are so dense they can combine very quickly.  We think the longer bursts are caused by the supernovae at the end of the lives of very massive stars.  But even they will only last for a couple of minutes.  So how could they possibly prolong this process to last for half an hour?

Publishing in the journal Nature earlier this month, there were two papers presenting two very different theories as to what this could have been.  One of the theories is that this was a neutron star colliding with a massive star, just as it was about to go supernova, quite a realistic scenario because as a star is about to go supernova, it will expand;  If there is a neutron star in a close orbit around it, it will attract and engulf that neutron star.  This could lead to the two types of gamma-ray burst happening back to back, possibly leading to a prolonged emission of gamma-rays.

The other model is a complete contrast to that.  It suggests this was quite a small event, relatively nearby in our own galaxy.  Perhaps a rocky asteroid came to close to the neutron star it orbited, and became broken up by the tidal gravitational forces around the neutron star.  These pieces could then fall in, one by one, over the period of about half an hour, leading to lots of very weak gamma-ray bursts.  On Earth, we may see this as a continuous spread of gamma-rays.  

Both of these theories actually fit the observations pretty well, but this illustrates that there's probably not any one mechanism which is responsible for all gamma-ray bursts.  These interesting events are probably caused by a huge range of phenomena, and just happen to look quite similar when we observe them.


23:21 - Trillion frames per second

A camera capable of taking a trillion frames per second has been constructed.

Trillion frames per second

You may have tried slowing down a film you made of a mobile phone, eventually the playback become jerkey, because the camera only records about 15 or 30 images or frames a second, and there is no information about what is going on between the frames. Better cameras can takes more frames per second, Kitchen Science has various videos taken with a camera that can take up to 1000 frames per second, and others can take hundreds of thousands of frames per second. But Professor Ramesh Raskar at the media lab have created a camera that can produce a film at a trillion frames per second!

They have done it using a streak camera, which only looks at one line of the image at a time, which is projected onto a screen. This converts the light signal into a signal of free electrons. These are accelerated along a vacuum tube towards a detector at the other end of the tube. The beam of electrons is scanned across the detector very quickly, so as time passes they hit different parts of the sensor, and you end up with a 2D image which consists of how theline changes with time.

The camera isn't quite true 1 trillion frames per second as to build a proper video, you have to repeat the process for each line in the image, which limits its use, to things which exactly repeat again and again. Despite this the results are still increadable. They have illuminated various scenes using an extremely short pulse of light, and in their videos you can actually see the pulse of light moving at 300 000 km/s moving across a scene about 300mm across.

This is very pretty, but they have some more useful applications in mind, if they shine a very short pulse of light a scene where you can see an object and its reflection you see the reflection slightly after you see the object itself, which suddenly becomes very useful if you wanted to understand a scene which includes reflections of reflections, like you would see in you looked into a translucent object like many engineering devices or human flesh. So it maybe possible to reconstruct what is happening deep within your body using normal visible light.

african lungfish

27:40 - Walking on the Seabed, Miniature Steam engines and Cool Mosquitoes

We explore how African lungfish are providing insight into the evolution of walking, the design of the world's smallest steam engine, how birds tweet at a higher pitch to be heard in...

Walking on the Seabed, Miniature Steam engines and Cool Mosquitoes
with Heather King, University of Chicago; Clemens Bechinger, University of Stuttgart; Emily Mockford, University of Aberystwyth; Claudio Lazzari, University of Tours

Walking Lungfish

The African lungfish uses its fins to walk rather than swim underwater.  Publishing in the journal PNAS, Heather King from the University of Chicago monitored the movements of lungfish in tanks of water and found them using their pelvic fins as hind legs to walk along the bottom of the tankafrican lungfish.  The finding suggests that walking may have evolved underwater rather than on land.

Heather -   This is evidence to support the idea that perhaps walking evolved before feet evolved or digits or terrestriality in this lineage, lobed-fin fishes to which tetrapods belong, and of course, we are tetrapods, every land animal with a backbone and forelimbs is a tetrapod.  So that's why lungfish are important to look at because they're one of the last closest relatives of the tetrapods that still alive.

The World's Smallest Steam Engine

The smallest steam engine in the world has been developed by scientists at the University of Stuttgart.  Using a single colloidal particle called melamine, thousandths of millimetre in size, submerged in an equally small chamber of water, Clemens Bechinger used a laser to trap the particle and varied the laser's intensity to either restrict or free the particle, resembling the compression and expansion seen in a large scale steam engine.  A second laser was used to heat and cool the water bath.

Clemens -   If we change the intensity of the heating and compression expansion laser beams in the right way, we can then make this engine to work and a surprising result is that if you tune the parameters correctly, then the efficiency of such a small steam engine, although it stutters, and it doesn't run as smoothly as its microscopic counterpart, can be as large as that of a macroscope steam engine.

Urban Birds Tweeting High

Birds living in cities produce higher pitch sounds that those living in more rural environments.  It's long been known that urban birds produce a different song to those in the countryside but the reasons why had been Great titsubject to speculation.  But now, recording and monitoring the songs of great tits in and around the city of Sheffield, Emily Mockford from the University of Aberystwyth found that birds within the city produce sounds of a much higher pitch, enabling the sounds to travel further and echo less off surrounding buildings.

Emily -   The architecture of a city is in fact changing, the way that sound travels to the environment and it will affect how birdsong travels through the environment as well.  We need to think about the way we build our cities and the way that wildlife has to adapt around us.  It's not actually the noise that we're making, but it's actually the physical sound scapes that we're creating as well that they have to adapt around.  It is the larger cities that will have this problem because it's the massive reflective surfaces and urban canyons and open spaces that are changing the way that sound travels.

Cool Mosquitoes

Mosquitoes release droplets of fluid to keep themselves cool whilst feeding.   Scientists have often wondered how cold blooded insects such as mosquitoes prevent themselves overheating when consuming hot blood from a human.  Using thermal cameras to monitor mosquitoes during a meal, Claudio Lazarri's team from the University of Tours in France noticed that as they feed, the insects exude droplets of fluid to cool their bodies down to ambient temperatures.

Claudio -   We have seen that at the beginning, the mosquito warms up and very soon during the feeding process, they start emitting a droplet of fluid that they keep attached to their body and at that moment, the temperature of the mosquitoes' body start to decrease because of the evaporation of this fluid.  So, the evaporation produces a loss of heat in the mosquitoes' body.

The work could be used to control mosquito populations in the future and is published this week in the journal Current Biology.

Why does the rainbow sometimes seem to end?

When you see a rainbow, every raindrop, when sunlight shines onto it, actually produces a cone of rainbow. When you actually look at it projected, you see a cone projected from each individual raindrop. What that means is if you look at each raindrop from different angles, it can look a range of different colours. So if you're looking over to your right, low down, some of them will look red at one angle. If you see them see them at a different angle, they look green or blue or different colours. And because it's a cone of light, you get the same effects up above you and over to the left. So the whole rainbow ends up as this arch.

How close does it look? Well essentially that will be to do with how dense those raindrops are. If you're in a light rain, then the amount of light reflected back to you per meter is quite small. It will look like the rainbow is a long way away because there would be hardly any coloured light coming to you from the nearest 100 meters. This means you have to add up several hundred meters, maybe a kilometre, just for you to see the colour. So it appears to be a long way away. For an incredibly heavy rainstorm, which I expect which is probably what you saw, then there might be so much light being reflected off the rain close to you that most of that light is coming from just 100 meters away. This makes the rainbow appear in front of the building or the tree which is hanging behind it, even though the light comes from both in front of, and behind the object.

Tissue Section from the Brain of an Alzheimer's Patient

Could wrapping food in aluminium foil lead to Alzheimers?

Although there is a link between Alzheimer's and aluminium; if you look in the brains of people who have Alzheimer's disease, you find these build ups of protein called Alzheimer plaques or beta amyloid plaques, and if you look inside those, you can find aluminium ions there.

It's not clear whether the aluminium goes there because the plaque is there and therefore the brain is already abnormal, or whether the aluminium helps to start the process off in the first place.

What we know is that when you cook things in aluminium foil or aluminium pans, because aluminium is a very reactive metal, the surface of the metal is covered in a very thin layer of an oxide - aluminium oxide - and this actually protects the metal from the atmosphere. That's why aluminium doesn't rust like iron does: it's fairly well protected by that oxide layer. This protective layer also means that the aluminium can't actually get into the food in any appreciable amount. The exception to this is if you cook very, very acidic foods in your aluminium pot, and a good example of this Rhubarb.

Rhubarb is extremely acidic and if you make a rhubarb crumble in an aluminium cooking pan, you will find that it needs virtually no cleaning afterwards because the acid attacks the oxide layer and can liberate a small amount of aluminium from the pan and this can get into the food.

Whether that will then produce Alzheimer's disease subsequently is a bone of contention.

People say that you're advised not to cook very acidic foods in aluminium-rich cooking materials and utensils because there is a small risk that you might get aluminium in the food and it could therefore have health consequences.

Some of the interpretation is based on what happened to people in - I think it was Castleford - in Devon, England, where they accidentally dumped a whole lot of aluminium in a drinking water settling tank.

Aluminium is used in swimming pools and at sewage works as a flocculent. It causes small particles to clump together. They accidentally put some aluminium in a tank that people were going to drink from, rather than the tank they wanted to settle out.

So some people were receiving very high doses of aluminium and there were some alleged connections with Alzheimer-type changes in people subsequently, but we don't know if those people were just going to get Alzheimer's anyway.

So it's a good question. It's open to debate. But don't cook acidic things in those sorts of pans. That would be my advice...

How strong a cable could be used to stop the moon moving away from Earth?

Dominic - One problem that you would have is the fact that the Moon goes around the Earth every 29 days and so, you'd need some quite good bearings on this string to carry it around the Moon's orbit over the Earth. That will be made especially difficult because the Moon doesn't trace out the same path over the Earth each time it orbits. So you'd need some kind of travelling system to hold on to the end of this piece of string. Certainly, people have done the calculation for geosynchronous satellites to make space elevators and people have worked out that even spider's thread which is this strongest string that we know of, is not strong enough to support its own weight to travel up to a geosynchronous satellite. To go out to the moon, you'd need something considerably stronger than that. Chris - Because the moon is actually going further away by a couple of centimetres every year and in the process, we're giving the moon energy from the Earth's spin. So the moon is speeding up which is why it's departing. The moon slightly lags the Earth in terms of the Earth's turn which is why we're giving energy to the Moon as it heaps up water on the Earth's surface. Dominic - That's right. The Moon is triggering the tides on the Earth and in the process of triggering those tides, because the Earth is spinning, it's putting a force back on the moon which is spinning up the Moon's orbit and will eventually mean that the moon might leave the Earth's orbit altogether.

Fossilised Parargarnis - an insectivorous bird

42:03 - Fossil Feathers in Colour - Planet Earth Online

An international team led by Roy Wogelius from the University of Manchester has developed a new technique that reveals the colour, and even chemistry, of fossil birds – birds that are more...

Fossil Feathers in Colour - Planet Earth Online
with Roy Wogelius, University of Manchester

Chris -   A remarkable paper was published in the journal Science recently. An international team led by Roy Wogelius from the University of Manchester has developed a new technique that reveals the colour, and even chemistry, of fossil birds - birds that are more than 100 million years old.

The team used high-powered X-rays to detect trace metals in the fossils and related these to melanin pigments in modern birds. Unlike other methods, the process doesn't involve damaging the fossils. Planet Earth Podcast presenter, Richard Hollingham, went to meet Roy and see the fossils for himself...

Roy -   This is a 50 million year old fossil feather.

Richard -   And it's almost perfect. They're very fine, wispy strands.

Roy -   This is the kind of thing that we call exceptional preservation. You can see the central shaft and we can see the barbs that fan out from either side. The preservation is absolutely splendid.

Fossil of Parargarnis - an insectivorous bird that was similar to present day hummingbirdsRichard -   So this is 50 million years old and you can tell from a fossil with your technique the chemistry and from that perhaps the colour of it?

Roy -   That's exactly right. We know that the pigments in our hair and skin bind up with certain metals: Iron, calcium, zinc and copper. Copper is part of the enzyme that actually makes the pigment in our hair and skin and in bird feathers. So we thought that maybe by mapping the trace metals we could see if there's some kind of information about colouration, indeed maybe the colour that you're seeing, this preserved colour maybe that-

Richard -   That's real?

Roy -   Yeah, maybe that's real. And indeed what we found is at the base of this feather there are higher concentrations of copper than anywhere else in this sample, much higher than in the sedimentary rock and much higher than in the top portion of the feather. The other thing we're able to do using x-rays is, not just map the copper but also look and get the details of how the copper is chemically bound, what elements surround it. In other words does it look like an organic compound or is it a purely inorganic compound? And the thing that we found absolutely blew me away; the copper chemistry in the base of this feather is nearly identical to the copper chemistry in melanin sampled from existing organisms.  And so maybe we should go to the other specimen which is perhaps a bit more exciting.

Richard -   It's very well wrapped, in bubble wrap and then tissue paper - let's pull back the tissue paper.  Now that is incredible.  I suppose it's the size of a large crow that's been flattened.

Roy -   Welcome to our 120 million year old road kill. What's amazing about it is that this is the first documented bird with a beak.

Richard -   Oh yes! And again on here you've got colour. You've got much darker wings than the bones in here which are almost a bone colour, even though this is a fossil. But, again, how do you know these colours are real?

Roy -   What you can see here is that in the neck region and around the body there's this very, very dark colouration-

Richard -   Almost black.

Roy -   Yeah, that's right, almost like carbon black. And if you look at the flight feathers which are splayed around to either side of the body, the top has this relatively dark black colouration and then as we move away in the flight feathers and go further and further away from the body they get lighter and lighter in colour.  And what we find is that in the neck region and body region there's very, very high concentrations of copper.  We've also done infrared analyses on these regions and infrared spectra look exactly the same as modern day melanin.  We've done structural work and all this information sits together to tell us that the downy body feathers on this bird were very, very rich in this dark black umelanin pigment.

Richard -   So this was some sort of black bird?

Roy -   That's right, that's exactly right. It's unambiguously non-destructively and over the whole organism we can pull out patterns without having to destroy anything.

Richard -   Now this is fascinating - is this useful?

Roy -   There are aspects of behaviour and evolution and ecology that were inaccessible to palaeontologists until they could start to see colour patterning.  That tells us an awful lot about camouflage, sexual display, a whole different range of behaviours which you really can't get any kind of clue from just bone material, so it's the soft tissue.  So for the palaeontologists it's one of the reasons why they're so interested in this.  This really might be able to tell them something about behaviour.  These trace metals contribute to biochemical pathways, they're still present, we know we can map them and I think this gives us hope that things besides pigmentation actually become available to us as we study ancient life.

Why can't a snuffed candle be re-ignited?

Essentially, the wick just isn't hot enough to re-ignite that wax. You actually need to get the wax hotter than the wick needs to be in order to smoulder. So after it's been smothered, it just isn't hot enough to re-ignite the wax vapour.

Do antiperspirants make you sweat elsewhere?

Chris - The way that antiperspirant deodorants work, most of them are spray-ons, some roll-ons, they tend to contain lots of zirconium, aluminium zirconium salts and pro-hydrate salts.

The way they work is that you rub them on your skin and they form a layer on the surface of the skin, and wherever they come into contact with water from your own body, in other words, where there's a pore linked to a sweat gland under the skin, they soak up the water and then they form a little plug of gel-like substance inside the sweat gland, stopping any more water coming out.

If you, therefore, stop the water coming out, the skin surface becomes drier. And the reason that we want to make the skin surface drier is that if you have dead skin and water together in a warm wet place, you've got the perfect bacterial banquet. It's these bacteria eating your dead skin, flourishing and thriving in this warm, damp environment that makes the whiff that we want to avoid.

So, we tend to apply the deodorants where we sweat the most and you tend to sweat in those places for various reasons. One of them can be thermal. You do sweat to cool down because when you sweat, you put a thin layer of water on the skin surface. The water is exploiting an effect called the latent heat of vaporisation. In order for the water to go from a liquid into a gas, it has to rob extra energy from the skin surface to break the molecules apart. They're all sticking together as a liquid and to separate out as a gas it needs extra energy to do that and so, when you've got the water on the skin surface, it's taking the extra energy away and that cools you down very efficiently, and that's why we sweat.

Sweating is also under the control of something called the sympathetic nervous system, which means that it's under the control of a part of your nervous system that you activate when you're worried about things. So people can also break into a sweat when they're panic stricken, anticipating having to run away very fast, and things like that. As a result of that, you can also sweat everywhere on your body for a variety of non-thermal reasons. So, just putting on antiperspirant deodorant won't necessarily affect the rate of sweating on other bits of the body because if you're doing a stressful job, you might just sweat elsewhere.

Dave - But, I guess, if you're sweating for thermal reasons then you're going to have less skin to lose the heat from [if you apply anti-perspirant deodourant], so the rest of you is going to be slightly hotter so you might sweat a bit more of the rest?

Chris - I take your point, but I would say, the skin area that you're applying antiperspirant to is such a tiny fraction compared with the whole of the rest of your body that it probably is going to make almost zero difference.

Could we engineer Rudolph the Green-nosed Reindeer?

Helen - You would want to basically take the glowing gene from a jellyfish of some sort, and I'm sure there are some out there that grow redor are coloured red. Red is a bit rare in the deep sea but there are some fish in fact that produce red light. [You could] take the gene that produces that light in those species in the deep and stick it in a reindeer's nose. We've done it with mice. We've made glowing green mice. I don't see why we shouldn't be able to make a glowing red reindeer then.

Chris - There is green fluorescent protein which is found in jellyfish, and then there's a tweak that scientists made to make red fluorescent protein, so the green equivalent in red. So it could be expressed. I think there probably are gene sequences that could direct the gene to only turn on in the nose, so you probably could end up with Rudolph. Helen - I'm not saying we should direct our research money to such a frivolous event but it might be quite fun!

White Cliffs of Dover

60:07 - Why do my feet look farther away when lying down?

When I lay down, my feet appear farther away from me compared to when I am standing up. I wear contacts during the day and glasses during the evening. Could this be a product of my...

Why do my feet look farther away when lying down?

We posed this question to Dr Rebecca Lawson from the University of Liverpool...

It seems unlikely that any effects of glasses or lenses would differ depending on whether you are standing or lying down. We do seem to overestimate vertical distances particularly if we're on top of a cliff looking down it. We overestimate and think that the height of the cliff is greater than if we were at the base of the same cliff looking upwards and in fact, agoraphobics seem particularly prone to this overestimation. However, this effect goes in the opposite direction. So really, I don't have a good account of why Chris's feet seem further away when he is lying down than standing, but I think that his question really nicely shows of the complexity of human distance estimation. Perhaps surprisingly, we still don't fully understand how we judge the size and distance of objects.

A Danish Christmas tree illuminated with burning candles, adorned with homemade Christmas decorations such as red hearts, white paper snowflakes, a golden star at the top, and gifts stacked underneath.

63:15 - A Festive Treat from Professor Karmadillo!

We were joined by Professor Karmadillo, with a festive musical take on the recent news from CERN that they have seen tantalising hints of the existence of the Higg's Boson...

A Festive Treat from Professor Karmadillo!
with Professor Karmadillo

To the tune of "It's beginning to look a lot like Christmas"...

Its beginning to look a lot like a Higgs BosonAbove 115 GeVThat the two experiments gaveResults that say the sameWas greeted with a sigh of relief

It's beginning to look a lot like Higgs Boson / Below 130 GeVThey looked at the decay and with three sigma confidence sayIts here or its just a dream They cannot deny a sigma of five is what they most desireBut it's Christmas time so I hope they get to relax beside a fireA Christmas treeI'll take you back to the seminar on December 13thThe whole world was waiting on the edges of their seatTuned to the CERN website to catch the video stream Jaws dropped agape at what they could see

It's beginning to look a lot like Comic SansOn the presenters screenFabiola you may have fab results from your labBut your font lacks credulity

Its beginning to look a lot like a Vicar particleA Higgs Boson described accuratelyFor instead of looking inside aLarge Hadron ColliderMany find mass in church on Christmas eve

Its beginning to look a lot like a Higgs BosonThe particle that gives us mass It's hiding away in the mince pies and the cakeYou'll eat on Christmas Day!


Find more Professor Karmadillo music here!


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