Digging in the Dirt and Looking at the Stars

15 August 2010
Presented by Ben Valsler, Diana O'Carroll.

This week, we've got a roundup of recent news and interviews from the Naked Astronomy and Naked Archaeology Podcasts. Digging into Archaeology, Diana O'Carroll will be looking into Bronze Age burial practices, meeting some of our oldest known walking ancestors and finding out how past human migrations are written in our genes. while Looking to the stars, Ben Valsler explores the challenges of building extremely large telescopes, finds out how rubic's cube size satellites can help test new technology and consults a team of experts to answer your questions on dark matter, planets and spacecraft propulsion.

In this episode

01:10 - Bones of the Bronze Age

A slightly grizzly start to this week as we’re looking at Bronze Age cremations. During the period which spans roughly from 2000 to 700 BC in the UK, there was a fashion for cremating the...

Bones of the Bronze Age
with Dr Jo Appleby, University of Cambridge

Diana -   A slightly grizzly start to this week as we're looking at Bronze Age cremations. During the period which spans roughly from 2000 to 700 BC in the UK, there was a fashion for cremating the dead.  Jo Appleby, a postdoctoral researcher in the University of Cambridge's Archaeology Department, has been studying these very early cremation burials, plus, some which appear even earlier -  and the information that can be drawn from them is quite surprising.  Listeners of a sensitive nature are warned that this interview does contain some graphic descriptions of what happens during the cremation process.

Jo -   I'm looking at the changing nature of burial practices from the mid-3rd millennium BC through to the end of the Bronze Age, and trying to figure out the changes in the ways that people approach death and burial over that time.  In particular I'm looking at the practice of cremation.

Diana -   And what kind of changes do you see happening?

Ancient cremated human remainsJo -   Well, during the beginning of the early Bronze Age, we see the first introduction of cremation as a burial ritual.  This is at first, quite sporadic and only occurs occasionally.  Then as the Bronze Age progresses, it becomes the most common form of burial.  Then eventually, towards the end of the Bronze Age, we find that formal burial rites almost disappear from the landscape, and we find occasional burials, but the majority of the human remains we find are as isolated deposits within settlements.  In fact, we're not very sure what was happening to the majority of dead individuals at all.

Diana -   And do you have any ideas as to why these changes were occurring?

Jo -   Well, that's the interesting thing, and is one of the things that my research is aiming to investigate, because burial is quite a good way of looking into people's minds in the past.  Death is a very stressful sort of time, and therefore, when it comes to funerary behaviour, you don't just do anything - You want to do something that shows your respect for the person that has just died and it has to fit in with your own cultural beliefs.  So obviously, bringing in a dramatic change like going from burying the body as an inhumation burial to setting fire to it, is something quite dramatic.  In the past, it's often being interpreted as a change of people, a new kind of people coming in, but actually it's quite difficult to interpret the beginning of cremation straightforwardly in this way because we don't have the evidence that that was occurring, so instead we see this as a change of belief.

Part of what I'm trying to do is to tease out precisely what's actually occurring within the cremation rituals, so not just saying were they burning the body or were they not burning the body, but looking at what they were doing when they weren't burning the body, and what they were actually doing when they were burning the body and trying to figure out what the similarities and differences that were occurring.

Diana -   So you've been working on a Bronze Age site.  Can you tell me a bit about that site?

Jo -   I've been working on a site from Erith out in the Fens, which was actually excavated by the Cambridge Archaeological Unit and I've been collaborating with Natasha Dodwell of the Archaeological Unit on this.  The site originally consisted of a ring ditch with a central inhumation - this was constructed in the early Bronze Age, and then this later became the focus for a middle Bronze Age cremation cemetery, where over 30 individuals were buried.

Diana -   And we've got a couple of examples here.  Let's look at this big tray -  it's full of quite a large collection of small bits of what look like quite burned bone.  What do we actually have here?

Jo -   We do indeed have a large trayful of quite small, burned bits of bone.  But what this can do is it can actually tell us a little bit about what was going on.  Despite the fact that these bones, to the untrained eye, look as though they could be pretty much anything, they are actually identifiable, if you know what you are talking about.  For example, I can pick out a piece here which is about 5 centimetres long and quite warped, and doesn't look like much of anything, but I can tell you that's probably part of a human tibia -  that's one of the lower leg bones.  As well as being able to identify that, I can tell you that the bones in this particular tray are of adult size, so we're dealing with an adult individual.  In fact, this individual has been identified as male.  But there are also some infant bones buried in with this individual. (I don't think in this particular tray, because the bones are sorted by size, and these are not smaller obviously).  So we can determine the age and the sex of individuals, and whether we're dealing with one person in the burial, or whether we're dealing with more than one person - and that actually occurs relatively frequently. 

In addition to that, I can tell you something about the temperature at which the bones were burned.  The majority of the bones in this tray are actually white.  You might think that the skeleton is naturally white, but in fact, it's generally speaking, more of a creamy, yellow colour when we excavate human skeletons.  This white colour tells me that the bones have been heated to more than 600 degrees.  That's a high temperature, and very efficient cremation practise that we're seeing.  In addition, the bones are quite warped and they're quite fractured, and that's to do with the effects that the heat has on the organic component of the bone.  So - bone is a matrix made out of organic proteins and an inorganic material that gives it great strength.  Obviously, when you cremate bone, then you lose the organic component, but you retain the inorganic component.  When the organic component is present, the burning up of that, causes the bone to warp and change shape.  So, from the fact that this bone is warped, I can tell that this individual was burned when bone was still fresh, as opposed to them having dug up some old bones from somewhere, and then set fire to them.

Diana -   Do you see the same sort of things happening across all the burials?

Jo -   This kind of practice,  I would say, was typical for a burial of this period.  In the middle Bronze Age cremation was typically quite efficient,  it was typically involving individuals soon after death and generally speaking, it was only one person being burned at a time.  In the earlier period, it was more variable, and in the later period, it was quite weird -  and we're not totally sure what was happening.

Diana -   Okay.  We've got another tray here of a collection of what looks like five bags of all sorts of different bits of bone.  So, what's going on here?  What's different with this one?

Jo -   Well these are just some pieces that I picked out to illustrate some of the things that we can see when we look at bone.  Here, I've got a bag with a piece of tooth in it and this is in fact a human molar.  When we look at it, we can see that we've got some sticky out bits at the bottom which were actually the roots, and there's not much left of the crown of the tooth, and this is because as the enamel heats up, it actually explodes.  So, what we tend to find, when we find teeth, is just the lower portion.  When we do find enamel, it's often because it's unerupted teeth from children which were still sitting inside the jaw - the presence of the bone of the jaw has actually protected the enamel and so that can be a clue as to the age of the individual that we're dealing with.

I also have a bag with a rather large bone in it which comes from the ankle of the individual, and when we look at this bone, we can see that the colouration on it is quite variable, so it goes from a sort of a dusty brown colour, through a bluish gray, to white in certain parts of it.  This is an indication that it has been subjected to varying degrees of heat.  So it's not totally burned out - there were still organic materials remaining in this bone, at the end of the cremation process.

Diana -   Do you find that that happens a lot to extremities like feet?

Jo -   Well, it's quite interesting because it happens according to the amount of tissue that is protecting the bone, and obviously, right within the ankle joint, which is where this bone has come from, then there's quite a lot surrounding it, with quite dense material that's protecting it.  But actually, we find that some parts of the body which we wouldn't expect to survive in that fashion do quite well, and that's because of the way that the body reacts to extreme heat.  So, when you cremate a body, the heat actually causes certain muscle groups to contract and that puts the body into a position that is known as the pugilistic posture, where the arms are drawn up, the hands contract into fists, and the legs go into what looks almost like a frog-like sort of posture.  And this means, for example, that the very ends of your finger bones (which you might expect to be burned very early in the process because there's not much flesh around them) when they're drawn into the fist, then they're very much protected.  And so they're one of the last bones that burn.  So here, I've actually got the very end finger-bone from somebody's hands that survived the burning process quite well.

Diana -   It's absolutely tiny.  It's incredible that something so small has survived.

Jo -   Of course sometimes what happens is that these smaller bones actually fall off and fall through the pyre and that can be another reason why they get protected and don't get burned up so much.

Diana -   And these bones are all several thousand years old.  How is it that they can survive even though they've been burned quite heavily and then presumably interred in the earth?

Jo -   Well, we have a slightly strange idea about what cremated bone ought to look like, because when our beloved relatives sadly die, and we take them down to the local crematorium, what we get back is an urn full of tiny unrecognizable ashes.  That's not actually what you get at the end of the cremation process.  What you get at the end of the cremation process is essentially a skeleton where some of the bones are a bit fragmented, but they come in very large pieces.  And because they've been burned, they're brittle, but they're still very recognizable.  In modern crematoria they actually have a special machine that breaks up the bones into a powder so that you cannot recognise any specific part of your relative, if you decide to scatter the ashes, because that would obviously be upsetting for you.  So, these individuals in pre-history would've gone into the ground in really very large pieces, and whilst they don't survive complete, they survive reasonably well.  And in fact, cremated bone actually in many conditions, survives better than uncremated bone.

Diana -   So, if you want someone to find you in a few thousand years and you're currently in the temperate climate, perhaps the best option is to get cremated the Bronze Age way.  That was Jo Appleby from the Department of Archaeology, at the University of Cambridge.

11:20 - Bigger, better telescopes

Douglas Adams found a very good way to describe how big space is. He said: “Space is big. You won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it’s...

Bigger, better telescopes
with Professor Colin Cunningham, UK Astronomy Technology Centre

Ben -   Douglas Adams found a very good way to describe how big space is.  He said:

"Space is big.  You won't believe how vastly, hugely, mind-bogglingly big it is.  I mean, you may think it's a long way down the road to the chemists, but that's just peanuts to space".

In order to see into the far corners of space and to make the invisible visible, we need bigger, better, stronger telescopes.  But building these presents a number of engineering challenges, as I found out from Professor Colin Cunningham from the UK Astronomy Technology Centre...

Gran Telescopio Canarias (GTC)

Colin -   We've been building telescopes for 400 years, and gradually, they've got bigger and bigger.  It has usually been driven by what technology is available.  So Galileo started off by using sort of spectacle lenses and a cardboard tube, and we've now gone to building 8 to 10-metre mirrors, which have given us fantastic new views of the universe. 

But what we found now is, because we've got the technology that has developed to allow segmented mirrors (so we take lots of hexagonal segments and join them together to make a bigger mirror) we're not stuck with the 8-metre size - we can go bigger and bigger.  In fact, we're only stuck by the amount of money we've got, basically.  So we can build a big telescope, and at one time, we were looking at building a 100-metre diameter one, but now, we've been more sensible.  We're talking about building a 42-metre telescope, which is very big.  And the big things it does; it gives you much more sensitivity, so it collects so much more light - more light than all the other research telescopes in the world put together.  And if you put that together with the fantastic spatial resolution, (in other words, the detail that you can see with this telescope)  you can really do very, very faint objects, like the early universe, like the early galaxies, and understand them, and to do astrophysics, and find out how they're rotating, and merging, and all the sort of thing.  And you can also look at nearby things, or relatively nearby things, like planets surrounding stars.  Because you can do that, you can actually understand much more about them, you can look at their orbits.  Potentially you can even look at the colours, and we might even find some that are similar to the Earth.  So that's why we want a bigger telescope, to do all these things that we can't do now.

Ben -   So what are the engineering challenges of building something this big?

Colin -   Well, it's very much bigger than we've done before, as I've just said.  The telescope itself is made up of 984 individual mirror segments - each of which is 1.4 metres across, so each of them is quite big, and you've got to keep them together in a nice, perfect shape as the telescope moves around the sky, and as gravity varies because of that.  And you've got to keep them aligned to something like 10 nanometres, which is very, very challenging. So you've got to have lots of instrumentation, lots of control systems to keep all that working properly, and that's got to work very reliably all through the night, and year after year. 

On top of that, we've also got to deal with the atmosphere.  In some ways, our life is quite difficult with ground-based telescopes.  We've not only got to deal with gravity varying, but we've also got to deal with the atmosphere varying.  If you build a space telescope, you don't have to deal with either of those things, but on the other hand, you do have to launch the thing, which is expensive and time consuming.  So, what we think we can do on the ground now is, by using something called adaptive optics, we can get over the limitations of the atmosphere.  The atmosphere moves around and blurs the images, but we can measure the amount of blurring by looking at a natural star, and measuring the wavefront from that star, or we can put an artificial star about 90 kilometres up in the sky by using a laser, and we can measure the wavefront from that.  If it's distorted, we measure that distortion, and then we apply the opposite of that, and then we've got effectively, a perfect image.  This means we can get fantastic image quality, which you couldn't do in space, because you couldn't ever launch a big enough telescope.

Ben -   We've had segmented mirrors, these hexagonal, individual mirrors, for a while. Can we just scale up the technology used there, or does the sheer size of this present a whole, unique set of challenges?

Colin -   It's pretty much the same technology - the big problem is just the scale of it really.  The current biggest telescopes in the world with segmented mirrors are the Kecks and the GTC in the Canary Islands.  They've got 36 segments, and making one of those segments, at the moment, takes about six months.  So it's actually the manufacturing process - if you multiply six months by 984, you'll realise that we are not going to be building this telescope in anybody's lifetime.  So we've got to make one of these mirrors, basically one a day.  So we need new technology to do that, and we've got new technology, actually in the UK.  There's a consortium of organizations working in North Wales, at the OpTIC Technium, that are making prototypes for this telescope now, and they've got some new technology that allows us to do it much quicker, so that the telescope is possible.

Ben -   Do we also have to find new materials to get over some of these challenges?  I assume that these mirrors aren't the sort of mirrors I have at home -  a sheet of glass with a very thin film of aluminium on the back?

Colin -   Well strangely enough, they are pretty much. It's better glass than you've got on your mirror in your bathroom - it's low expansion glass, it's quite tricky to manufacture, but it's the same thing that people have been using for about 150 years really.  It's a glass-ceramic with a coating of generally silver these days (as opposed to aluminium).  And we have looked at new technologies, new materials like silicon carbide compounds and composites, and even carbon fibre composites.  They do give you some advantages: They're usually a good deal lighter which means the rest of the structure becomes a lot lighter as well. But the general feeling is that they're not really there yet, and the conventional glass-ceramic, coated with aluminium or silver, held on a steel structure, is actually the best thing to do.

Ben -   Can we apply any of the lessons that we've learned through this, to more mundane things?

Colin -   We certainly can and we already are doing.  The adaptive optics technology that we use to correct the images from the sky, can also be used to correct images used for looking into your eyes.  So you can use adaptive optics to actually improve the quality of an image of the retina, and look at individual rods and cones, look at the individual blood vessels, and actually measure blood flow in those blood vessels.  That's the only way you can do that of course, without cutting somebody open.  That could be very important in terms of diagnoses of diseases like diabetic retinopathy.  If you go to the opposite extreme, the technology we're learning in order to make mirrors at a reasonable cost, and a reasonable speed, we can use for laser fusion in the future.  Already, people are building laser fusion systems in order to get green energy - You know, basically, we'll be reproducing what happens on the sun.  There's no radioactivity, there's no carbon emission, and you get almost an infinite supply of energy.  If this works, this could save the planet, and we can do this using the technology we're developing for astronomy.  So that's pretty good, if you ask me.

Ben -   Colin Cunningham, explaining how  technology developed for star-gazing may help to see inside your eyes, or provide ways to generate clean electricity,  as well of course, as seeing further into space.

Diana -   So, do astronomers get telescope envy?

Ben -   Well, I think that many of them would claim  that it's not how big it is, but it's where you put it that counts.  For example, there are only a few sites on earth which are good enough to detect much in the way of infrared radiation from space.  Our atmosphere absorbs too much, so you either have to get above much of the atmosphere, like in the Atacama Desert in Chile, or even out into orbit.  So where you put it is really is more important than size.

Diana -   Indeed.

18:53 - Sediba - a newly discovered ancestor?

Sediba - a newly discovered, 2 million year old possible ancestor, had a small brain, but probably walked a bit more upright than all the others. Professor Lee Berger, from the University...

Sediba - a newly discovered ancestor?
with Professor Lee Berger, University of the Witwatersrand, South Africa

Diana -   The 2 million-year-old Australopithecus sediba has been described.  This transitional species of early human could link the two-legged Australopithecines, of which the famous Lucy was a member, to the early Homo genus. 

Sediba had a small brain, but probably walked a bit less like John Wayne than all the others.  Professor Lee Berger, from the University of the Witwatersrand in South Africa, described the discovery to me...

Lee - Well it actually happened after an organised search for sites.  I had started a search back in early 2008, using Google Earth of all things, to look for new cave sites in the Cradle of Humankind area, just outside of Johannesburg.  At that time, we knew of about 130 cave sites and about 20 fossil sites. 

By July of that year, by both using Google Earth and then going out, and ground tripping with my dog and I, just walking in these very remote areas, I'd found almost 600 new cave sites, and over 30 new fossil sites.  By the end of July, I'd realised that an area very near to where I've been working for the last 20 years had a series of cave sites that I didn't know existed.  And on the first of August, I visited them, and found the Malapa site, a site that had never been seen before.  It was rich in fossils, but it had hardly been touched by miners.  (This area had been sort of searched over by lime miners in the late 19th and early 20th century). 

On August 15th, we went back to the site -  myself, my 9-year-old son Matthew, and my post doc, Job Kibii.  A minute and a half later, my 9-year-old son said: "Dad, I found a fossil".  And what he'd found was a collar bone, or clavicle, of an early hominid, and that started the whole thing.  And since then we've been in this remarkable period of discovery.  We've discovered, arguably the two most complete early hominids never discovered, as well as others, in what seems to be one of the richest paleoanthropological localities in the world.

Australopithecus sedibaDiana -   So, what did you do once you found these pieces?  Did you take them back to the lab and analyse them immediately?  Did they immediately seem different to you?

Lee -   Well, that's an interesting question.  Under South African law, I had to get a permit, but I called the South African Heritage Permit Resource Agency at that time, literally from the site, and got permission to take the first block out.  And we began preparing it here. 

These fossils - if you imagine, are encased in a very dense, concrete-like substance, and it was very soon that we realised we had a remarkable fossil, and that we had, what appeared to be, an associated skeleton that was in partial articulation.  And I think, even early on, I realised that it wasn't at least, typical of what we usually find here in South Africa.  (That is, one of the two species - Australopithecus africanus, the Taung Child or Mrs. Ples, or one of the robust Australopithecines, Paranthropus robustus which have those big saggital crests across the top of the head.  It clearly appeared to be different than that.  It would take us a while before we realised it wasn't something like Homo habilis, or Homo erectus, but an entirely new species.

Diana -   And how long did it take to come up with that conclusion, to compare all the species?

Lee -   That first discovery was a little over 18 months ago, and once we had the skull (and I discovered the skull in March of 2009) we had enough at that point, as we had two skeletons emerging from the rock, that we could compare it with everything that had been compared.  I think really, the turning point was when my team and I were in the Kenyan National Museum.  We just finished looking at all the Homo habilis material, all the material that had been attributed to some of these later Australopithecines, and we realised that what we were looking at was just not found in the range of anything that had been discovered.  And we also began to see how unusual it was, in its patterning, to other early hominids.

Diana -   So, tell me why is this important?  Where does it fit in the grand scheme of things?

Lee -   Well you know, firstly, these are probably the rarest sought-after objects on earth, and to have found literally hundreds of remains of them, representing a relatively small number of individuals - well that really gives us an unprecedented look into any period  in human evolution.

But of course, this occurs at a critical point in human evolution, right around 2 million years.  In fact, these are dated to between 1.78 and 1.95 million, in fact, closer to 1.95 million years, and that has been a great missing area in the fossil record.  Literally, there are only a few dozen fossils, most of them very, very fragmentary from that time period.  But it's a critical time period;  It's the period between where we have things like Lucy, or Little Foot, or Mrs. Ples. Australopithecines (with their relatively long arms and short legs, and not moving the way we do -  really almost apes that walk on two legs)  and then the emergence of what we call Homo erectus, that is something that is clearly very close to a direct ancestor, if not, a direct ancestor of ours, and it carries our body plan -  a relatively large brain, small dentition and an advanced face.  Well, sediba falls right in the middle there, and it interestingly carries combinations of both ends of that spectrum.  It has these long orang-utan-like arms, short powerful hands, however, and long legs and a very advanced pelvis - in fact, a pelvis very similar to a Homo sapiens' or Homo erectus'.  Its face is very advanced, its dentition is small, but it also has a very small brain, like an australopithecine.  So, it's a mix of characters that appear to be both descendant from those earlier hominids, and unique, and derive to things like Homo erectus.

Diana -   The thing that struck me was, I think it was 9 years ago, another fossil turned up in Georgia, which was supposed to be sort of similarly intermediate.  So, how do you think these two relate to each other, if at all. How can you even compare them?

Lee -   Well,  Dmanisi is an intriguing question, and has been.  Some people have said it's an early Homo erectus, some people have said it's an absolutely unique species, and I think that's exactly where we should be comparing Australopithecus sediba next,  because anyone who looks at them can see a lot of similarities in the face to Dmanisi.  Dmanisi does have a larger brain than ours.  It does seem to be derived a little more towards Homo erectus, or at least on its own pathway in that direction, but you know, I think sediba might make a very good candidate ancestor, because the big question was, where did Dmanisi come from?  It didn't look like a descendant necessarily of Homo habilis or Homo rudolfensis, or some of these other things.

Diana -   And kind of course it's 7,000 miles away as well.

Lee -   Well, but you know, one of the big issues had always been that one of the problems that people had with Dmanisi and even later things like Flores is, you didn't have an ancestor that appeared to be a facultative biped - something that it come down on to the ground.  The one thing with sediba's long legs and advanced pelvis, it's clear it's a very good walker, and it's the kind of thing that could be the type of hominid that expands throughout Africa, and potentially, will give rise to hominids that could leave Africa.

Diana -   And so, do you think there's anything else that might be in this area where you found sediba?  Do you think there's more possibility of similar finds?

Lee -   Well, I can answer that, that's not even a question.  In fact, we have at least two additional skeletons coming out and we haven't dug yet.  The site is remarkably rich.  It's a moment in time.  It's an extraordinary event and it continues to give us a really remarkable record of this species.

Diana -   It seems hard to imagine so many different species of early humans with vastly different brain sizes, different teeth, and even different walking styles ,all living on the same planet at once.  That was Lee Berger of the University of the Witwatersrand, where he's a Reader in Human Evolution.

Ben -   I had the good fortune to meet Lee Berger back in 2007, visiting him in his office in South Africa.  He's got the most amazing collection of fossils, telling the story of our evolution.

27:29 - Testing Technology in Orbit with CubeSats

The UK Space Agency has recently announced a pilot program, inviting companies and academics to device innovative ideas for payloads to be launched in a tiny cube shaped satellite, called a...

Testing Technology in Orbit with CubeSats
with Dr Chris Castelli, UK Space Agency

Ben -   The UK Space Agency has recently announced a pilot program, inviting companies and academics to device innovative ideas for payloads to be launched in a tiny cube shaped satellite called a CubeSat.  To find out more, I spoke to Dr. Chris Castelli, Head of Space Science Projects for the UK Space Agency.

Chris -   A CubeSat is, as the name implies, a very small satellite.  The basic CubeSat is cube shaped, so it has dimensions, 10x10x10 centimetres and it's a fully functional satellite.  The sort of CubeSats you can buy are made out of standardised parts.  So, this is perhaps one of the most important things to understand - the standardisation allows lots of suppliers worldwide to make the various components for the satellites.  And you could source these and build these into a standard structure which is the CubeSat.  So the basic building block, the 10x10x10 cube satellite is called a 1U.  You can make bigger CubeSats.  You can go to a 2U and I think probably, the largest size is a 3U, and as the name suggests, it's a sort of oblong shape satellite which is three units long.

Norwegian student satellite NCUBE2 Ben -   They're really tiny.  When reading about these, I was picturing something perhaps the size of a desktop computer or something around that size.

Chris -   Right.

Ben -   But these are really very small, aren't they?

Chris -   They are extremely small.  Basic one unit CubeSats could only weigh just a few kilograms.  And a lot of people have said, "Well what could you do with something so small?" and I think this is where innovation comes in to the equation.  If you look at the power, the computing power that is available in your average mobile phone these days, it gives you an idea of the sort of sophistication that you can pack into a small unit now.  What is happening worldwide is, people are realising that with very small satellites and advances that are made in microelectronics, putting those together forces people to think about clever ways of doing things, where you're limited in terms of mass and power and volume that you have.  But nevertheless, you can actually do some exciting sorts of things with them.  So, what we envisage is using a CubeSat as a vehicle, a platform for rapidly testing new technologies in space, for example, where you wouldn't have to go through the more classical route, which takes a very long time of ground base qualification, and testing, and more testing, before you get to really prove a technology is ready to go on a very expensive multi-million dollar satellite.  You can use a CubeSat as a way of getting an in-orbit demonstration very quickly, very cheaply, and very effectively.

Ben -   What sorts of technology can you demonstrate with a CubeSat?

Chris -   If we take the area of space science for example, future missions that are going to the planets, to Jupiter for example or other planets, want to use more sophisticated plasma and magnetospheric instrumentation, they're very sophisticated, they use new technologies.  A CubeSat, even though it's got small dimensions, could be used to test a new generation of plasma sensor, and get some in-orbit verification of how it survives the extremes of the space environment.  So, just putting a new technology into orbit would be one way of using a CubeSat platform.  It gets it into orbit in the environment of space, in the radiation, the cold, and the harshness of space, the vacuum of space, and you can get some real in-orbit understanding of how it has performed.  The other application of CubeSats is that you can fly many of these.  So what people are thinking about doing is, flying hundreds, or certainly 10s of CubeSats in a constellation of small satellites going around the Earth.  And you can actually, with the advances that are made in imaging sensors, you can get very powerful sensitive imaging sensors with optics, into say, a 3U CubeSat.  With constellation of these satellites whizzing around the Earth, you can pretty much get global coverage of any points from the Earth within 20 minutes, in a very cheap, and cost-effective way, which you can't do with any other system.  So people are talking about launching maybe 60 or 70 of these things in orbits that swing around the poles of the Earth, and with multiple CubeSats as a constellation, you can get live images - almost live images, every say, 15 to 20 minutes of anywhere on the globe.

Rubik's cubeBen -   How does launching a CubeSat or a constellation of CubeSats compare with launching a more traditional, larger payload?

Chris -   Again, it goes back to this idea of standardization.  One way I look at it is, if you remember the early PCs - as soon as PCs developed in a way that you could slot cards from various suppliers, so you could get a disk drive from different manufacturers, you can get mother boards, and memory cards.  You could assemble them altogether from standardisation, the cost really came down.  So obviously, the cost through standardisation is a key driver.  The fact that they are of this known mechanical interface means that low cost launchers provided by say, the Indian PSL rocket, they actually have standard attachments which are designed specifically for CubeSats to go on.  So, you have a big science or telecommunications satellite that is being launched and around it are attachments on the launcher interface for CubeSats to go up at the same time.  So essentially, the CubeSat is being piggy backed on the main payload which is paying for the launcher.  What you have to pay for of course is the necessary licensing and certification, to make sure that these things are safe, are worthy, or have a mechanical integrity to go on to the launcher, and they don't sort of fall apart during launch, and damage the main spacecrafts, which may cost hundreds and millions of dollars.

Ben -   The UK Space Agency is still, really, in its infancy...

Chris -   Yes.

Ben -   Why are CubeSats a priority for them?

Chris -   We're looking at this longer term.  What we hope to have is a longer term program, a rolling program of CubeSat developments built on the experience of this pilot program.  So the pilot program really is just a really cheap way of getting something off the ground, so to speak.  What we want to do is have a long term program of maybe one or two CubeSats every year to 18 months, then, therefore have a rolling call of ideas.  We could even have, for example, specific CubeSats which are just targeted at education - at schools, colleges and universities where students and teachers get together with help maybe from the industry, and from the CubeSat providers, to put little experiments onboard.  So they act as a vehicle for inspiring and also training young engineers of the future.  We want to sort of have a rolling program which then leverages opportunities for the UK in the future.

Ben -   That was Chris Castelli from UK Space Agency, explaining how  CubeSats devices, barely bigger than a Rubik's cube, can help us to test out new technology in orbit.

35:21 - Will Cubesats increase the Space Junk problem?

Will Cubesats increase the Space Junk problem?

Ben - Earth's orbit is becoming very crowded, but it's a great question. I asked Chris Castelli, who said that CubeSats will only be in low earth orbits, only 90 to 100 kilometres above the ground. And as there's still an atmosphere up there, that will exert a drag on the CubeSats, and they will quite naturally drop out of orbit, and harmlessly burn up in the atmosphere. So, existing satellites should be safe.

36:44 - DNA and the first Australian Settlers

It’s not only archaeology that can tell us about the first Australian settlers. DNA evidence has come up with some fascinating insights into the history of human migrations made thousands...

DNA and the first Australian Settlers
with Professor Toomas Kivisild, Leverhulme Centre for Human Evolutionary Studies at Cambridge University

Diana -   It's not only archaeology that can tell us about the first Australian settlers.  DNA evidence has come up with some fascinating insights into the history of human migrations made thousands of years ago.  Toomas Kivisild from the Leverhulme Centre for Human Evolutionary Studies at Cambridge University has been working specifically on the genetics of Australian populations.

Bathurst Island MenToomas -   Generally, the questions are about the relatedness of humans taken from different continents and trying to relate the similarities and genetic distances observed in DNA, with the known genetic evidence from the archaeology and anthropology.

Diana -   So we can look at Y-chromosomes which are handed down the male line and mitochondrial DNA which is handed down the female line, but once you've got this data from your samples, how do you go about processing it?  What are the methods that you use?

Toomas -   There are two types of methods that can be used - one is phylogenetic methods, which is basically building up a tree from the DNA data, and secondly, one can use statistical methods in which, basically, the DNA data set is converted into a summary statistic, and then the summary statistics for different populations are compared.

Diana -   And tell me what you found once you had all these data?  I mean, where does Australia fit into the story of human migration?

Toomas -   Firstly, I would have to note that there are a number of different hypotheses that would explain the origin of Australian Aborigines today, based on archaeological and skeletal evidence.  Some authors have suggested that there is a possible continuity of the archaic hominin species in Australia, because some of the skeletal sites show the presence of archaic features and secondly, some authors have argued that the Australian aborigines originated through a rather recent migration from the Indian subcontinent.  And while using mtDNA and Y-chromosome data, we tried to assess which of these theories would fit where the data.  Our results give the highest support to the theory which supports the origins of Australian and New Guinean populations as well as Indo-European and the East Asian populations to the out of Africa migration, which occurred approximately 60,000 years ago.

Diana -   And that date matches up with the data that you're getting from your DNA evidence?

Toomas -   Most approximately, so the DNA based tools are never as accurate as the archaeological dates are, and so, they also depend on the sample sizes, which are not unfortunately, as good as they would wish them to be.

Diana -   So tell me a little bit more about the India theory, the idea that modern Australian aborigines are more closely related to people in India or Southern India.  Where did this idea originate and why?

Toomas -   I think the idea is traced back officially to Thomas Huxley, but probably more generally to the age of colonisations, when people were looking at the physical similarities that were quite striking between the Australian and the Indian populations, and similarly, for example the Andamanese populations are physically quite similar to the African populations.  Nev,ertheless, they're genetically more similar to non-African than African populations.

Diana -   So the out of Africa model still holds, but do you have any evidence for the routes that they took to get to Australia?

Toomas -   This is all quite speculative because from the DNA evidence, we cannot really tell, but what is still currently one of the consensus views is that the route was the coastal rather than in land.  People talk about two potential hypothetical routes out of Africa.  One over the Arabian Peninsula, the so-called Southern route, and the other over the Sinai, the Northern route.  Hopefully, the evidence would be found at some point that would definitely be archaeological rather than genetic, because from the study of modern day populations, such questions cannot be solved in sufficient detail.

Diana -   You mentioned earlier that it was difficult getting hold of enough samples.  Why is that, and is there a plan in the future to increase the number of samples, and maybe bring this research a little bit further forward?

Toomas -   It depends on the willingness of the people themselves to give their DNA and unfortunately over the past 100 years, there has been a lot of misuse and abuse of not only DNA, but also other biological samples, and therefore, some populations of the world, native Americans and Australians in particular, are not very willing to cooperate with the scientists.  Unless this attitude, or the conflict between the scientists and the native populations would be solved, then it remains difficult to get DNA from them.

Diana -   Cambridge University's Toomas Kivisild, demonstrating how archaeology and DNA need each other.

Ben -   It's great to see how biological sciences can be used to support and enhance archaeology, but does this relationship work both ways?

Diana -   Yes.  So, as we discovered with the migrational DNA information that Toomas Kivisild has come up with, sometimes you need to tie that down to dates, so we can use archaeological evidence.  But it works the other way as well.  So, sometimes you'll have a bit of archaeology and you won't know who made it, who left it there, and this DNA evidence can give you some information as to who was there and how they got there.

42:31 - Does dark matter have structure?

Does dark matter have structure?

We put this question to Dr Andrew Pontzen:

Andrew - Well firstly, normal matter in the universe is really clumped together. It's not evenly spread out through the universe, it's clumped, for instance into galaxies. Galaxies are collections of around 100 billion stars, and they're relatively compact, and there's a lot of relatively empty space between each different galaxy. Now, dark matter certainly does clump together in that sense. We know that for sure, from observations of galaxies.

This was in fact the original evidence for dark matter, looking at the way that material like stars and gases moves around in galaxies, and inferring from that strength of the gravitational field in galaxies, and from that inferring how much stuff was there, and that's how we knew that there had to be dark matter.

In fact, because there's so much more dark matter than normal matter in the universe - there's around five times more dark matter than normal directly visible matter - its clumping is incredibly important in terms of determining the kind of structures that form in the visible universe, and the existence of galaxies effectively owes itself to dark matter. So in that sense, there are structures in the dark matter that are similar to the ones you see directly in the normal matter.

On another level though, we don't really know what dark matter is, and so, when we're talking about dark matter, we tend to be modelling it subject to some simple assumptions about what it's doing, and you get the best results for the evolution of the universe, matching what we see in the real universe, when you model the dark matter as completely non-interacting, except through gravity. So, other than the gravitational force which it exerts, and which it's also subject to, it's not subject to any other forces, for instance, the electromagnetic force which normal matter is subject to. In fact, the really interesting structures in normal matter arise through things like the electromagnetic force in all of chemistry for instance, and therefore, life really arises through forces like the electromagnetic force. And for that reason, the evidence at the moment would suggest that you can't have really complicated structures that will be required to create what you might describe as dark life forms. So, most likely, there's nothing quite that interesting going on in the dark sector, but until we really know what it is, we can't say for absolute definite.

45:45 - If the universe is expanding, are we getting further from the Sun?

If the universe is expanding, are we getting further from the Sun?

We put this question to Dr Carolin Crawford:

Carolin - Well this is about, not so much from the effects of dark matter on our solar system, but looking at more the effects of dark energy - so staying on the dark side. Space is expanding and it's carrying the galaxies along with it for the ride. They're all receding from us, and we think they're being pushed apart by a force that we call dark energy, and this is currently accelerating the expansion of the universe.

But the curious thing is, that this dark energy, whatever it is, is a property of space. So the larger the distance between bodies, the stronger they push to drive them apart. Conversely, gravity - which we're a bit more used to - is a property of matter, and it's a pulling force, so that opposes the expansion, and the gravitational pull is stronger the more mass that's there, and depends on how close you are to it.

So, whether the pull of gravity, or the push of dark energy dominates over a given region of the universe, depends on how much mass is there, and how widely separated it is. If they're far apart, the push of the dark energy wins, but if they're close together, gravity is going to dominate. You have to remember, in astronomical terms, our solar system is absolutely tiny. The planets and the sun, and all the constituents of our solar system, are very close together, and there's no question that gravity wins in that circumstance. Even on the scales of the galaxy, gravity is the dominating force. Even between groups or clusters of galaxies, gravity is gluing them together. You're only going to get this expansion of space on the very largest scales, where you have sufficient space that the dark energy can dominate.

47:40 - Will a laser work to propel a spacecraft?

Will a laser work to propel a spacecraft?

We put this question to Dr Dominic Ford:

Dominic - Well yes, in theory, you could. The way that any rocket works is that it ejects material backwards and there's a principle of physics - the conservation of momentum - which says that if the rocket exerts a backward force on that material to accelerate it backwards, there must be an equal and opposite push, pushing your rocket forwards, accelerating it to move faster. And what matters is how much momentum the ejected material has, and that affects how great the push is forwards on the rocket.

So, could you substitute the exhaust gases of a conventional rocket with a laser or light beam?

Well, yes you could, because light is made up of photons which - although they have no mass, do carry a very small amount of momentum. So for example, if you put your hand underneath a light, then the light is actually exerting a very tiny downward force on your hand. You don't notice it because the force is so small, but it is there.

So likewise, a light on the back of a rocket would push it forwards ever so slightly, but the problem is, this force is so incredibly small. I did a quick calculation this morning of what power of light source you would need to replace the thrusters on the Cassini Spacecraft in orbit around Saturn, which can produce a force of 440 Newtons, and the answer is you would need 130-Gigawatt light source. So that's equivalent to the output of several hundred power stations, all going into one light source. So, this isn't a terribly practical way of propelling the rocket.

Andrew Pontzen - But of course, there are actually ways you can use the pressure of light. For instance, in solar sail technology, and I think there's just recently been an announcement that the solar sail of the Icarus spacecraft is being unfurled.

Dominic - So this is a serious question because it's very inefficient to carry large volumes of rocket fuel around the solar system. So people will continually looking for new ways of controlling spacecraft and solar sails are one promising idea. How they work is you have a reflector which the sun exerts an outward force on, due to radiation pressure. Also, the solar wind exerts an outward force. What the Japanese Space Agency are doing at the moment, is trialing this experimental solar sail Icarus, which is 20 metres across. And they're going to try and to glide it down in the solar system towards Venus, using the solar radiation pressure to control their direction as they glide through the solar system. It will be fascinating to see how it goes.

51:03 - The Repatriation of Yagan

Duncan Howitt-Marshall and Diana O'Carroll discuss the repatriation and reburial of the head of Yagan, the Australian aboriginal warrior who was killed and beheaded by colonial...

The Repatriation of Yagan

Duncan -   The first news item is the repatriation and recent reburial of the head of an Australian aboriginal warrior who was killed and beheaded by colonial settlers in 1833.  In line with common practice at that time, his head was transported to England where it was put on display in a museum as an anthropological curiosity, and eventually buried in an unmarked plot in a cemetery in Liverpool.  His head is now being finally laid to rest in a traditional ceremony in a memorial park near the site where it is believed the warrior was killed 177 years ago in Western Australia.

Diana -   Who was he?

Portrait of Yagan by George CruikshankDuncan -   We know bits and pieces from the Noongar of Western Australia.  There are accounts from white settlers at that time.  His name was Yagan and he was the leader of the Noongar tribe at the time when British settlers were first moving into the area around modern day Perth.  Relations between the Noongar and newly arrived British were initially very good, but sadly this harmony didn't last and there were misunderstandings regarding land management practices where white settlers were essentially fencing off land for farming.  Now Yagan and the Noongar led something of an uprising against this and as a result, were implicated in the killing of several settlers.  They were declared outlaws and reward was offered for their capture.

Diana -   But what happened next?

Duncan -   But Yagan wasn't without sympathy from members of the settler community, but even so, on the 11th of July, 1833, Yagan was killed by two teenage brothers and his head was cut-off to claim the reward.  The head was transported to England and eventually put on display in Liverpool Museum.

Diana -   That sounds more medieval than 19th century, but what's happened since then?

Duncan -   Well the Noongar people have been campaigning for the return of Yagan's head since the early 1980s, entrusting tribal elder Ken Colbung with the task of locating the head in England.  Then he used the help of University of London Archaeologists, Peter Ucko and Cressida Fforde and successfully located the head in 1993.  But it took nearly six years for it to be repatriated to Western Australia, due to political wrangling and reported divisions within the Noongar community itself.  It's taken another 12 years for his remains to be reburied.  The delayed reburial of the head, which took place in the 10th of July, the last full day Yagan was alive 177 years ago, was due to disputes over the actual location of the site where he was killed.  Now the site is now the Yagan Memorial Park and the traditional ceremony was attended by around 300 people including Noongars and state representatives.

Diana -   That's quite a turnout, but do you think that this will prompt the repatriation and reburial of other remains of aboriginal people which are in museum collections all over the world?

Duncan -   That's absolutely right.  This certainly isn't a new phenomenon.  In fact, the repatriation of aboriginal remains has been going on for quite some time now.  I was attending the World Archaeological Congress in Dublin in 2008 where the issue of repatriation of human remains was very much on the agenda.  The overwhelming feeling among the archaeological community is to work side by side with the descendant communities to bring the remains of their ancestors back and rebury them according to their traditional beliefs.  I think we'll see much more of this in the future.

54:41 - Earliest Evidence of Pet Tortoises

Diana O'Carroll and Duncan Howitt Marshall discuss the discovery of tortoise bones at Stafford Castle - the earliest evidence of tortoises as pets...

Earliest Evidence of Pet Tortoises

Diana -   An archaeological discovery at Stafford Castle can tell us something of the early relationship we had with domestic pets in the 19th century.

Duncan -   So what have they found at Stafford Castle, Diana?

Indian Star TortoiseDiana -   Archaeologist Dr. Richard Thomas from the University of Leicester discovered a rather unusual leg bone amongst the skeletal remains of cats and dogs in the castle grounds, dating to the late 19th century.  The leg bone was identified as belonging to a tortoise - perhaps the earliest evidence of such an animal being kept as a family pet in Britain.  And these finds have been reported in the journal Post Medieval Archaeology.

Duncan -   How do we know the tortoise was being kept as a family pet?

Diana -   That's a good question.  The fact that it was discovered alongside the remains of cats and dogs is a good indicator that this tortoise was being kept as a pet by the caretaker family, and they were living in the castle at that time.  So, Dr. Thomas stated that whilst there is archaeological evidence in Britain for turtles and terrapins from the 17th century onwards, these were largely kept for food, and the discovery at Stafford Castle is the first evidence we have for a land tortoise.  Now the 19th century was also a turning point in the general attitude society had towards animals as domestic pets.

Duncan -   What do you mean?

Diana -   In medieval and early modern Britain, society was deeply religious and the morality of keeping animals as pets was highly suspect.  So exotic creatures, particularly those from outside Europe, generated a great deal of curiosity and fascination.  But to keep them as companions was socially unacceptable.  So, domesticated animals were kept for food, milk, cheese, butter, meat, wool, leather, and so on, and so on.  In the case of dogs, many were kept obviously for hunting and herding.  However, things began to change in the 17th century with the dog-loving Stuart Kings.

Duncan -   Yes, I love those 17th century portraits of members of the House of Stuart, sitting alongside their fluffy-eared King Charles Cavalier Spaniels.

Diana -   Exactly right and dogs especially were seen as wonderful companions to have around the house or in their case, the palace.  And so, certain animals were now seen in a different light and the famous 19th century Sculptor Joseph Scott, created a number of very sentimental sculptures of animals and in 1822, the British government passed the Richard Martin's Act which prevented cruelty to farm animals.  This paved the way for the Foundation of the Society for Prevention of Cruelty to Animals, in 1824, which was the first animal welfare charity to be established anywhere in the world and it was granted its Royal status in 1840 by Queen Victoria.

Duncan -   What an incredible achievement and something that I think we should all be very proud of.  I guess the founding of the RSPCA set into motion all kinds of wonderful movements around the world, dedicated to animal welfare issues that continue on to this day.  But what of our tortoise bone at Stafford Castle?

Diana -   Well tortoises were unusual, but it was this age-old fascination with the exotics that made them desirable as pets around this time, but suddenly their popularity in the 20th century meant that thousands of wild tortoises were transported from the Mediterranean and North Africa to the UK, but they suffered terrible conditions, only to end up as pets in households which couldn't look after them properly.  It was only with European legislation in 1988 that made the trade in wild tortoises illegal.

Duncan -   So there is a happy ending.

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