Peruvian Mummies, Ancient Environments and the Sahara

17 September 2006
Presented by Dave Ansell, Kat Arney


Explaining how science can help us dig up the past is Lawrence Owens, who uses teeth and bones to uncover the life and sometimes gruesome death of mummies in Peru and Bolivia, and Harriet Allen describes how the pollen record and layers of lake sedimentation can reveal what the environment was like 10 000 years ago. Also on the show, Nick Brooks talks about how climate change in the Sahara may have given rise to complex human societies, and taking us back even further in human evolution is Clive Finlayson, who discusses how a new fossil discovery shows that Neanderthals were alive and kicking in Gibraltar well after the arrival of modern humans. Leaving the past behind them in Kitchen Science, Derek and Dave make their very own futuristic forcefield.

In this episode

Tree Code Cracked

Researchers at Ghent University in Belgium have managed to crack the genetic code of the humble poplar tree, working out the sequence of all the "letters" within the tree's DNA. Around six years ago, researchers worked out the genetic code of a type of cress called Arabidopsis but this is the first tree to have its DNA sequenced. Trees are very different from other plants - for example, they produce wood and can adapt to changing environmental conditions. We also rely on trees to remove carbon dioxide from the atmosphere, and increasingly for raw materials for paper, furniture and bio-fuels. The scientists found that the Poplar has about 45,000 genes (compared to 30,000 for humans). And around a tenth of these genes are unique to the tree, meaning there is no similar gene in cress. So this group of genes could represent the key differences between trees and other plants. Now we know the sequences of all the poplar genes, scientists can start looking at their functions. In the future, this could lead to ways to genetically manipulate trees. For example, this might allow them to survive challenging environmental condition, produce more accessible biofuels or remove more carbon dioxide from the air.

Get Off your Butt To Beat Bowel Cancer

Researchers at the Fred Hutchinson Cancer Research Centre in the US have found that regular exercie may help to prevent bowel cancer. The researchers recruited 200 healthy men and women, put them on a range of exercise programmes, then studied the cells in their bowels to see how much the cells were growing. If cells in the bowel grow too quickly, then this can be a precursor of bowel cancer. They found that for men who carried out exercise for an hour per day, six days per week, had less cell growth in their bowels than those who did fewer exercise sessions. And even men who just managed four hours per week had some protection. Unfortunately, there appeared to be no protective effect for women who exercised, although other research has shown that regular exercise can reduce the risk of breast cancer. Exercise also helps you to maintain a healthy body weight - after smoking, obesity is the leading preventable cause of cancer in the UK. So as well as helping you fit into your genes, getting moving could also reduce your risk of cancer. More about exercise and cancer here:

How to make a forcefield

This week Derek and Dave are venturing bravely into the future to make their very own forcefield. Providing the man power to do it are Matthew and Robbie from Campers Playscheme, which is held at Hunsbury Park Primary School...

To do this experiment, you will need:

Empty coke can Piece of polystyrene A full head of hair

How to do the experiment: 1 - Take the polystyrene and rub it on your hair for about one minute. 2 - Wave the polystyrene near the fizzy drink can and see what happens.

So what's going on?

When the polystyrene is placed near to the can, the can moves towards you. Why is this?

All materials contain electrons; tiny particles that are part of an atom. Electrons from one material can be passed to another material when they come into contact. It's a little bit like headlice: if one person has headlice (with the lice representing electrons) and their lice-free friend brushes past, then headlice can be passed from one to the other. If they keep their heads together long enough, then there's a chance that the rogue headlice will crawl back again. However if they quickly pull their heads apart, then the headlice have no way of returning to their original owner. This results in an overall headlice gain for the previously lice-free friend.

The same principle can be applied when thinking about the transfer of electrons: when two materials are brought together, electrons can move from one side to the other (and potentially back again). Whether electrons have enough time to get back again will determine whether a material ends up with more or less electrons than it started with.

Now it's all very well and good that materials swap a few electrons, but some materials will on average take a lot more electrons from other materials than they give back. These electron-loving materials can take an especially large amount of electrons if they only come into contact with the other material for a short amount of time - they take lots of electrons but the connection is broken before they can return to their rightful owner. An example of a material that behaves in this way is polystyrene (although polystyrene likes gaining electrons, whereas using the first example, no - one likes to get headlice!)

The perfect partner for an electron-loving material is one that wants to get rid of electrons. An example of this is hair. Each strand of hair donates some electrons as it comes into direct contact with the polystyrene. As soon as the polystyrene is rubbed on another part of your head, the contact with the original strand of hair is lost and the electrons can't jump back again.

The overall effect is a slow accumulation of electrons on the polystyrene, and this gives the polystyrene a negative charge. The charge is negative because electrons are negatively charged particles.

Once you've stopped rubbing your head, what you're left with is a negatively charged piece of polystyrene full of electrons that have been 'stolen' from your hair. But why does this attract coke cans?

Playing with magnets demonstrates that like-charges repel - ie: negative repels negative and positive repels positive. When the negatively charged polystyrene is placed near the coke can, it forces all the electrons in the metal as far away as possible (to the far side of the can). As the electrons in the metals move away, it makes the side of the can nearest to the polystyrene relatively positive. Positive and negative charges attract, which is why the coke can is pulled towards the polystyrene.

It is important to note that polystyrene is an insulator and coke cans are made of metal. Electrons in insulating materials can't move around very well, which is why they are bad conductors of heat an electricity. In contrast, electrons can move around very easily in metal, making it perfect for electrical wiring and saucepans.

When the coke can and the polystyrene are brought together, the electrons in the polystyrene pretty much stay where they are (because they find it difficult to move) while the electrons in the metal can whizz round to the other side. If the electrons didn't move to the other side, the can wouldn't polarise (have a positive and a negative side). If there is no polarisation, then the can won't be attracted to the polystyrene.

If you put the polystyrene near to another insulator, such as a plastic bottle, the bottle would not be attracted. This is because the electrons in the plastic cannot move easily, the material cannot polarise and thus the bottle stays where it is.

- Science Update - Aquatic Noise Pollution

The Naked Scientists spoke to Chelsea Wald and Bob Hirshon from AAAS, the science society

Science Update - Aquatic Noise Pollution
with Chelsea Wald and Bob Hirshon from AAAS, the science society

Bob - This week on Science Update, noise pollution is now a problem in seas as well as cities. But first, Chelsea has a much more pleasant noise to play for us-and you'll probably be surprised by its origin.

Chelsea - If a volcano could play piano, this is what it would sound like. Physicist Domenico Vicinanza of CERN in Switzerland created the music by converting a seismogram from Mount Etna into a score.

Domenico - If the volcano is quiet, the melody of the piano is confined in the middle part of the piano. As soon as the volcano is becoming louder and louder, the melody on the piano starts to scatter up and down, reaching higher and lower notes.

Chelsea - So how will this help? Vicinanza says people are often better at picking out patterns by ear than by eye, so this technique could help scientists find patterns in seismic activity across many volcanoes.

Domenico - Our aim is to use all the recorded data, to transform them into music, and try to understand what happens when the volcano starts to become louder and erupts, and so we can say which is the signature tune, the signature melody which can be taken as a signal of an imminent eruption or imminent earthquake.

Chelsea - He adds that this technique could prove useful in analyzing data in other fields, from stock-market numbers to patterns in language. He also hopes it will be welcomed by musicians as a new way to create nature-inspired tunes.

Bob - Thanks, Chelsea. Well, here's another tune of sorts, but one that's not so welcome.

Bob - It's the sound of a ship-underwater. Scientists think it might interfere with how whales and other sea mammals communicate and find food. Now a team has discovered that ambient underwater noise has increased ten times since the 1960s-at least in the Pacific. But it's not just that the number of ships has gone up. John Hildebrand of Scripps Oceanography says traffic has only doubled since that time.

John - So a very significant part of the increase comes from the fact that the ships themselves must be generating more noise-the ships are bigger, they travel faster, they have greater total tonnage that they're carrying.

Bob - Hildebrand and his colleagues were able to do this analysis because they found declassified Navy reports from the 60s on the ambient noise in the Pacific-part of the Navy's Cold War defense. They were then able to make recordings in the same spot and compare them. Although it's not hard to prove that noise has gone up, he says what is hard to prove is that it's having an effect on the mammals.

John - The insidious thing about this is that the ambient noise has been increasing at probably a fairly steady pace, so there wouldn't be some dramatic event where all of a sudden the marine mammals would be doing something differently. So it's tricky to figure out where the impact has been.

Bob - But he says it may not be as hard as it might seem to convince the shipping industry that noise is a problem-quieter ships would be better for the crew and should be more energy-efficient. He adds that in looking for a solution, scientists may turn again to the Navy, who are, after all, experts in being quiet underwater.

Chelsea - Thanks, Bob. That's all for this week. Next week we'll talk about some ants that do some amazing acrobatics. Until then, I'm Chelsea Wald.

Bob - And I'm Bob Hirshon, for AAAS, The Science Society. Back to you, Naked Scientists.

- Mummies of Peru And Bolivia

The Naked Scientists spoke to Dr Lawrence Owens, Birkbeck College, University of London

Mummies of Peru And Bolivia
with Dr Lawrence Owens, Birkbeck College, University of London

Kat - Now you've been to some really exotic places, Peru and Bolivia. I'm of the opinion that scientists work in these places because they want a nice holiday, but I understand that you've been doing some work. What have you been up to?

Lawrence - I have been doing some work. I was very lucky to go to Peru a few years ago to analyse some mummies they've discovered near Lima. I've been going there for the last few summers now to analyse all the remains of the something like 80 000 burials in this huge site that we have.

Kat - So are these mummies like Egyptian mummies? Wrapped in bandages and stuck in a tomb?

Lawrence - They're a bit slack at doing mummies in Peru. In Egypt they did all kinds of things: they sucked the brain out through the nose and all manner of horrible things. But in Peru they just buried them in a rather slack sort of way. But being in Peru, it's very dry and they preserved very nicely.

Kat - So what can we find out about ancient Peruvians? How old are we talking?

Lawrence - Well these ones vary from the Incas which are fairly recent at around 1400 AD, back to about the second century AD. But of course mummies in Peru go back much further than that, but in my site they just cover that period. Anyone you can learn by talking to someone you can learn from a mummy because your body, your bones and your teeth betray you completely. Nothing is sacred.

Kat - So what sorts of things have you found out and how do you do it?

Lawrence - You can tell, for example, exactly where somebody is from. You can tell it from their teeth, the shape of their teeth and their skull, and you can look at things like the isotopes in their teeth. You can look at the content of their bones and collagen to see the part of the world they came from. You can look at their health and their life and how sick they were when they were children. You can also see the kind of diet they had and, of course, what led to their demise. There's virtually nothing you couldn't find out from someone.

Kat - Could you find out what they did, such as occupation?

Lawrence - Yeah we've found these massive guys who are obviously into construction and so on. They had huge and brawny arms. Arnold Schwarzenegger would have paled in significance. These guys were massive.

Kat - So Peruvian builders basically.

Lawrence - Yes they were massive. Pyramid builders in Egypt show the same kind of thing. People who did sewing an ceramics had unusually strong hands. We know that they did this because they were buried with the tools of their trade, so everything is buried with them. You can also work out some very tragic stories, such as finding people that have died in childbirth. We know how old they were and can work out the sixteen years old was a very common time to have children. So there's virtually nothing that you can't find out.

Kat - How do you find differences between the different cultures in Peru? Are there distinctive cultures?

Lawrence - That's the thing about cultures: what's a culture really mean? It's very hard to define. These groups lived in a very defined area and very often their habits evolved in a single direction. For instance the Nazca, you must have seen the Nazca lines, had a very hard time of it because it was so desiccated. They used these things as a ritual and magical way of getting it to rain. The Incas were massive empire builders and they built roads across the nation. There are dozens of other tribes and groups in the Amazon living their different ways, so they were very distinct and we're talking over very large periods of time.

- Recreating Ancient Environments

The Naked Scientists spoke to Dr Harriet Allen, University of Cambridge

Recreating Ancient Environments
with Dr Harriet Allen, University of Cambridge

Kat - I understand that you're studying the environment of Portugal.

Harriet - Yes, I'm interested in the way ecosystems change over time, and that could be thousands of years or it could be over even shorter periods of time.

Kat - So what's the environment like now in Portugal, and how was it ten thousand years ago?

Harriet - In common with many other Mediterranean landscapes today, the vegetation is very much dominated by shrub land communities, which are extremely well suited to the hot, dry summers and the cool and relatively wet winters. About ten thousand years ago, you would have had a more deciduous type of vegetation with many more trees in the landscape than we would see today.

Kat - So big leafy trees?

Harriet - Yes, deciduous but not so much chestnut because many of those have been imported from the eastern end of the Mediterranean to the western end, but there would have been many more deciduous oaks and other taxa.

Kat - How do you know that this change has taken place? We only see the trees we've got now.

Harriet - There are certain types of environments such as wetlands where we can extract material the dates back over thousands of years. We can use sediment cores and go down a metre at a time where we can retrieve material. We then take it back to the laboratory and analyse small quantities of it and see which pollen has been preserved within the sediment. By looking at the pollen we can identify the different species or more commonly the genera or the families from which the pollen has come. From that we can reconstruct what the vegetation was like.

Dave - Are you just looking at the pollen grains and you can recognise all the different types of pollen grain?

Harriet - Yes. Pollen grains have different types of ornament depending on the species. Some of them look a little bit like mediaeval instruments of torture because they've got large spines sticking off them. These are large in the context of being microscopic of course. They may come from some of the more weedy species such as you might find in the daisy family. By complete contrast, if you look at something like pine pollen, it has air sacs. If you imagine Mickey Mouse's face just for a moment, the face is the basic part of the pollen grain and Mickey's two ears are the air sacs that help to make this particular grain very buoyant and well-dispersed. So different types of pollen have different ornaments that can be relatively easily identified under the microscope and allow you then to identify the grain either to the species or usually to the genus and sometimes only as far as the family level.

Kat - But how do you know how old these things are? Are they fossils?

Harriet - Technically for the last ten thousand years they're not fossils. We might refer to them as sub-fossils, but they are the intact grain that has been preserved in the environment. So they've been washed in or blown in, incorporated in the water column, and then settle out through the water column to be incorporated into the sediment that accumulates at the bottom of the lake.

Kat - But how do you know how old pollen is? It's just incorporated into the mud.

Harriet - Well it is just in the mud and in a sense you can't just date the pollen. What you're dating is the material in which the pollen is found.

Kat - So you're dating the mud.

Harriet - Yes or it could be a peat bog or it might be in a riverine environment where you've got more silty or sometimes gravel conditions. To some extent it depends on how much organic material there is available. If there's a lot of organic material then you can use radio carbon dating and that will then give you some dates.

Dave - Do you see big major events in the pollen record too, such as volcanoes and things?

Harriet - Well you don't tend to see that in the pollen record but you do see it in the sediments. I've got some colleagues who work in Greek lakes and they find layers of ash that have come from some of the Italian volcanoes. If you know what the chemical signature of the ash is, you can then identify which volcano it has come from and by extrapolation from other sources you can work out when it was deposited in the lake.

Kat - So to go back a little bit, you've said that over the past ten thousand years we've seen quite a dramatic change in even just a country like Portugal. What kind of thing has caused that change in climate and are we still seeing the climate changing now?

Harriet - It's a bit of a tricky question to answer because no two people will necessarily give you the same answer with respect to Portugal or other Mediterranean countries. It rather polarises between those who think that the vegetation has changed because people have changed the landscape, and those people who regard it as evidence of climate change. Somewhere about 5-6 thousand years ago there are suggestions that the climate became a bit more arid, and at that time you moved from the deciduous taxa to the more evergreen taxa. But other people argue that that was probably a result of people clearing the landscape for agriculture. The soils degraded and so when there was recovery of any vegetation, it was less likely to be the deciduous taxa that came back in than evergreen taxa. There's some suggestion that there was a slow spread between the eastern Mediterranean towards the western Mediterranean, which might have matched agriculture arriving in the eastern Mediterranean and towards the west and north west to the UK.

Kat - And to extrapolate a little bit to the UK, we know that the climate is changing and it looks like things are getting warmer. Do you think we'll see the sort of trees we have in the UK changing? We have our big oak trees and chestnuts, but could they be doomed?

Harriet - I'm not sure about doomed. There are some suggestions that gardeners ought to be changing the species that they're growing in their gardens. On the radio this morning there was some suggestion that people should start to grow olives and that maybe in a few years time olives will be a crop that you'll find within the UK. I think that it's being grown on an experimental basis down in Devon at the moment. I think it's very likely that the vegetation will change in response to the climate changes that we're seeing.

- Societies in The Sahara

The Naked Scientists spoke to Dr Nick Brooks, University of East Anglia

Societies in The Sahara
with Dr Nick Brooks, University of East Anglia

Kat - I understand that you work in the desert. What can you tell us about that?

Nick - Whenever I get the opportunity I pursue my own field research which is at the moment focussed on the western Sahara. Prior to that I've done quite a lot of work in Libya as part of a much wider project called the Fezzan project, examining the interaction between past climate and environmental change and ancient civilisations.

Kat - So when we think about the desert, you think of something that must have been desert for absolutely thousands of years. But this isn't always the case with the Sahara, is it?

Nick - That's true. The Sahara has been through a number of humid and arid phases that pretty much fall in step with the glacial cycles. The last humid phase in the Sahara lasted from about ten thousand to five thousand years ago. During this period the desert that we know today was more like a savannah environment with open woodland, lakes and rivers.

Kat - So what sort of different cultures and animals and things would we have found there compared to what we have now?

Nick - Well we actually have some very good records that the prehistoric inhabitants of the Sahara very kindly left us if we want to see what they were up to and what the environment was like. Archaeological studies tell us that the region was re-inhabited as it became more humid about ten thousand years ago by hunter-gatherer groups. But later we find the emergence of cattle herding societies and then later still we find sedentary societies such as the Garamantian civilisation in south west Libya. The environment, as I mentioned, was like a savannah much like the environments you'd find in southern Africa today. We also have literally millions of rock paintings and engravings that depict the large humid climate African fauna that we find in the more humid regions now.

Kat - So the civilisations that we find there, we've already heard from Lawrence today who's told us about cultures that were killing each other with a fight for resources. They wanted to keep their stuff for themselves. Do you see similar things as the environment is changing in the Sahara?

Nick - The Sahara is not the same as parts of, say, Egypt, for it's large ancient civilisations, it is a very good place to study these sorts of processes. It's essentially a laboratory of adaptations which has had very very extreme changes of environment and climate and people obviously respond to those. We know that the places in the Sahara that are now uninhabitable were densely inhabited, relatively speaking, in the past. There was archaeological material literally scattered across the desert surface. So yes, we can actually see how people responded to these changes. One of the things that seems to be happening as the climate becomes more arid is that people are becoming more territorial and it appears that we have an increase in social stratification. This is evident largely through burial monuments.

Kat - So do you think that in the same way as in Peru they might have become more blood thirsty or more competitive?

Nick - Obviously there would have been competition. You're talking about a landscape that has been widely inhabited and then desiccated, leading to the formation of very few environmental refugia where there was still water and pasture available. People would have naturally migrated out of the Sahara and there is evidence that people went south with the retreating monsoon. But we also know that people started to congregate around diminishing lakes and oasis regions, and so obviously the population density in these regions increased and there would have been more competition for resources. Whether this would have expressed itself in a particularly violent way, we don't really know. That's not apparent from the archaeological record. No doubt there would have been some conflict but we also know that people adapted their livelihood strategies of their social systems in order to survive in these smaller regions where different resources and techniques were required.

Kat - So do you think that it may have brought civilisations together to form bigger societies?

Nick - I do think that certainly in the Sahara that this did emerge through a process of adaptation to an increasingly arid environment. What you really have is the development of an irrigation-based largely urban society emerging in one of these environmental refuges and as far as we can tell, through a pretty clear process of response to environmental change. I do think that this is a model that seems to hold in other places. For example, it's not that controversial these days to say that the rise of Egyptian civilisation was largely due to the desiccation of the surrounding desert and the social changes that that engendered. So as for being more blood thirsty, we don't know. But we certainly saw the emergence of urban societies with organised armies and organised warfare as the societies developed.

Kat - So we've seen the Sahara getting much drier and as I talked about briefly with Harriet, our climate does appear to be changing. How do you think that societies are going to adapt to the changes that we're going to have in the future?

Nick - Well that's very difficult. Recently when I was away I was actually at the United Nations trying to do some work on adaptation. Obviously there's a big problem with how humans are going to adapt to future climate change. We have a lot of difficulty with this; it's not a trivial problem. We can certainly say that societies will change as a response to climate change, but it's interesting that when we look back in the past, most adaptations to climate change seem to involve things like population movement and migration. Now these are options that aren't really viable today so we're going to have to look for other means. I think that if we have very large changes in climate, as I think are probably going to occur by the end of this century, then there will be a problem.

- Neanderthal Remains in Gibraltar

The Naked Scientists spoke to Professor Clive Finlayson, Gibraltar Museum

Neanderthal Remains in Gibraltar
with Professor Clive Finlayson, Gibraltar Museum

Kat - So far this evening we've heard a number of different reasons why digging around and finding clues are great for reconstructing the past. Well now we're going to hear from Clive Finlayson at the Gibraltar Museum, about our ancient relatives, the Neanderthals. They were once widespread across Europe, and were thought to have disappeared about 30,000 years ago, but no one really knows why. Now, excavations in a seaside cave overlooking the Mediterranean suggests that they probably clung on to existence for much longer than we previously thought, but ultimately, perhaps the climate got the better of them.

Clive - What we found in a cave called Gorham's Cave, here in Gibraltar, facing the Mediterranean Sea is a series of levels of human occupation, and the Neanderthals that had been occupying this site since 100,000 years ago, continued to do so much more recently than people had expected. There are places where they were making their tools, left their tools, hearths, the food that they were eating, and we've been able to date this very accurately with radio carbon dating to at least 28,000 years ago, but very likely much more recently than that, perhaps as recently as 24,000 years ago.

Chris - How do you know that what you're looking at is definitely Neanderthal, in this region?

Clive - Well, Gibraltar, for a start, has almost a tradition for Neanderthals in the sense that a skull was found here in 1848, and eight years later, one was found, in 1856, in the Neander Valley in Germany, and named Neanderthal, hence the term. So it was, perhaps the first one was actually found in Gibraltar. Another skull was found in 1926, and in all we have eight caves with evidence of Neanderthal occupation, the tools that they made, which archaeologists call Mustherian, are very characteristic. I'm talking of tools made of flint and quartzite, in the shape of stone points to be hafted on to spears, cutting tools, for defleshing and so on. They made these very, very identifiable and very, very specifically characteristic tools. So here in Gibraltar we have evidence of those tools in these layers that we've found, but also close by we also have, from the 19th century, at least two fossils, in two caves, so we are very confident that we've had a long period of Neanderthal occupation, and one that meant their survival until much more recently than we had thought.

Chris - And is that the major implication, or are there others, on the basis of what you found?

Clive - Well, one of the things about the cave is the richness of the fossil material, as well as the archaeological material. The levels of occupation are rich in fossil mammals, birds, reptiles, there's also pollen that we've been able to extract, and of course charcoal from the fires, and that has allowed us to make a reconstruction of the landscape outside the cave. If you go to the cave today, and you look outside, there's a beach, and the Mediterranean Sea, but for much of the period when the Neanderthals were living there, the climate was significantly colder, globally, and the sea level was down by between 80 and 120 metres below the present level. This exposed a huge area of sandy plains, which I could probably best describe as a Mediterranean Serengeti. It was rich in herbivores, and the Neanderthals were eating them, and we know that because we find in the bones evidence of the cutter marks made by their tools. We suspect that their diet was probably quite diverse, there's a lot of bird species have been found there, so it's almost certain that they were eating ducks and partridges, but also marine material; mussels and marine molluscs, quite possibly also fish, and seals, and then the vegetation, which we can infer from the pollen. So this allows us to do a climatic and ecological reconstruction, and what seems to becoming through is that this was one of those, perhaps localised, privileged spots, because of the benign climate that perhaps contributed significantly to this late survival, so I think it goes beyond just the issue of late survival and possible overlap with modern humans; it also suggest reasons why it was that they survived.

Chris - So the cave gives you enormous clues about when these people were there, and up until how recently, but does it tell us anything about where they actually went, and why they may have disappeared?

Clive - Well, apart from the work that we're conducting at the moment, we've been collaborating with colleagues who are looking at deep-sea cores of the Mediterranean, and around 24, or just after 24,000 years ago, there seems to be a very sharp signal of a climatic deterioration. It seems to involve cold conditions, and particularly conditions are maybe arid. So it could be that these last surviving Neanderthals lived in very small populations, they were, after all, the last ones, and any slight environmental change, perhaps a famine over a period of years, caused by drought, may well have tilted them over the edge, never to recover again.

Kat - That was Clive Finlayson from the Gibraltar Museum talking last week to Dr Chris.

- Could cables in space generate electricity from Earth's magnetic field?

I've watched astronauts go to lots of trouble trying to install solar panels onto space stations. Why haven't they been clever and hung a...

Could cables in space generate electricity from Earth's magnetic field?

You can and they have tried it. They took a big long wire a couple of kilometres long and hung it from a shuttle. They tried to generate power by moving it through the Earth's magnetic field. The problem is that it's very difficult to manoeuvre a 2-kilometre wire through space. If you started a wave through it, there's no air to dampen down the vibrations. You also get some complex interactions between the magnetic field and the wire. The other problem is that it takes the energy out of the orbit, so the satellite will come out of orbit quicker. This is ok for a space station because it gets pushed regularly, but it's not ideal for a satellite that wants to stay up there for a long time. So actually it's a lot easier to use a solar panel.

- What are the basics of string theory?

Could you please explain to me the very basics of string theory? I failed lego at school and I'm not very technical.

What are the basics of string theory?

String theory is a way of looking at the world to try and work out what we're made of. You may have heard that we're all made of atoms, and atoms in turn are all made of other little bits such as electrons, neutrons and protons. If you break it down even further, things like neutrons and protons and stuff are made up of even tinier particles called quarks and leptons. All these different particles are what makes up stuff. There are different forces that can act on stuff to make things move and stick together. These are gravity, electromagnetic force and the weak and strong nuclear forces. Sounds a bit Jedi to me! These help to stick stuff together. We have a standard model for how you explain stuff, which is that quarks and things stick together and protons and neutrons stick together etc. But you can't really explain how gravity actually works using this kind of model. So some very clever maths bods have been trying to work out a way of explaining how gravity works using the bits that we have. They've come up with string theory, which says that all these tiny bits of stuff are actually like bits of string that wobble around in lots of different ways. It depends how you're seeing that particular waving string as to what you see. So if you see it waving in one sort of way you see a lepton, and if you see it in another way you see an electron. So everything is basically little bits of waving string and this can apparently explain gravity. You can find out more at However, no-one has found any evidence that this is the case. All the things it predicts happen at such high energies that no-one has been able to look at them yet.

- Why were ancient Peruvians so bloodthirsty?

I was in Peru a while ago and saw an saw an ancient ceramic pot from the Moche culture with a very gruesome decapitation scene on it. Wer...

Why were ancient Peruvians so bloodthirsty?

They did do it a fair amount. The Moche are actually one of the most epic examples of this sort of thing that you can find in the world ever. Some cultures did this to a certain extent and had sacrifices in a more modest way.

The Incas used to bury children on mountain tops for example. But the Moche were really really sanguineous. They had a little tiny area on the coast of Peru and they hacked it out of virtually nothing so it was very small with lots of canals and agriculture.

The society was very rigid and they would go out to fight other tribes and nick all their land and so on.

They would then ritually decapitate all of the captive men. They sometimes kept some of the women, but not very often.

They would cut off their arms and remove bones from their arms while they were still alive. They would smash bits of them off and then throw then off these cliffs into an enormous pit and leave them there for the vultures to eat.

They were pretty nasty! They even had a deity called the decapitator god, which had a giant eagle-like head and a nasty blade in his hand. He would go around decapitating all the captors.



- Did Atlantis actually exist?

Did Atlantis actually exist? Also, there's supposed to be a cave in France that seems to show planets and was drawn about 33 thousand yea...

Did Atlantis actually exist?

The myth or story of Atlantis is based upon a gigantic slip of land into the Atlantic or possibly Mediterranean, which contained a civilisation that was privy to lots of information that we no longer have. So yes, there is evidence of slip in the Iron Age in the Mediterranean and particularly around Turkey, but when it comes down to whether we've lost information which mankind would really benefit from today is a bit more difficult to demonstrate unfortunately.

As for the planets, people have interpreted it like that but most of the cave paintings are so bizarre that no-one really knows what they mean. They have animals, which is fair enough, and then they also have lots of demonic creatures. You then have people with duck's heads and so on. So the planet thing is one possibility but it's a rather slim one unfortunately.



- Did oil and coal deposits really come from primordial forests?

Did oil or natural petroleum deposits really come from primordial forests? With the thousands of barrels of oil taken out every day, ther...

Did oil and coal deposits really come from primordial forests?

Oil is the rotten remains of trees and other vegetation. If you go back to the time of the oil and certainly the coal-bearing strata we have in the British Isles, the British Isles wouldn't have looked like it did today. It was significantly further south towards the equator and therefore had a much more tropical climate. The nature of the vegetation would have been similar but not identical to perhaps modern tropical rainforests. As they died and fell down, they were buried over long periods of time, compressed and ultimately that forms oil. Quite a lot of oil is made from algae in the sea. Algae gets cooked when it's buried deeply. That gives off oil which floats up nearer to the surface.

- If we lose gravity, what will happen? Will everything fly up in the air?

If we lose gravity, what will happen? Will everything fly up in the air?

If we lose gravity, what will happen? Will everything fly up in the air?

If the Earth suddenly didn't have any gravity any more, I guess that the first thing to happen would be its effect on the atmosphere. At the moment, the atmosphere is being compressed by its own weight and squashed down onto the Earth. The first thing that would happen is that the atmosphere would expand very quickly and fly out everywhere. That might blow you up into space. If it wasn't for that, there would be any reason for you to be thrown away from the Earth. You'd just sit there and slowly get pushes around. So you'd have a huge explosion with all the atmosphere disappearing, and this could possibly blow you up into the air.

- Why would a pond on a hill never dry up?

I come from Dorset and there's a hill with a pond up there. The strange thing is that it never dries out. Why is this?

Why would a pond on a hill never dry up?

It's possibly a dew pond. These have been constructed through much of the South Downs and counties in the south of England. They're built on the top of hills so when the warm air rises, it condenses. The ponds are lined with clay and the clay cools down. This also helps when the air sinks to leave moisture behind. This forms a pond which farmers use to give water to their animals.


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