Nature Podcast

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Adam Rutherford: Coming up this week, we launch ourselves on a mission to the edge of the solar system with Voyager 2.

Edward C. Stone: It's really quite remarkable that this spacecraft which was launched when the space age itself was only 20 years old is now been operating for over 30 years on its journey to interstellar space.

Kerri Smith: And we're in for a few surprises on a musical mystery tour.

John Sloboda: What makes a performance special is if the performer does something which slightly but very appropriately tweaks a person's expectations. They didn't expect it to be like that.

Kerri Smith: This is the Nature Podcast, I'm Kerri Smith.

Adam Rutherford: And I'm Adam Rutherford. Interstellar space is our first destination this week, as we track the progress of Voyagers 1 and 2, their continuing missions to explore the boundaries between the solar system and the rest of the galaxy, to boldly go, well, you know the rest of it. Here's Edward Stone from the Jet Propulsion Lab, Caltech on the new data that these two explorers are sending back from the final frontier. Nature 454, 71–74 (3 July 2008)

Edward C. Stone: Nature has just published 6 papers about the giant bubbles the Sun creates around itself called the heliosphere and 5 of those papers depend on data from the Voyager 2 spacecraft. That spacecraft was launched in August of 1977 on a journey to the giant outer planets, Jupiter, Saturn, Uranus, and Neptune. Neptune, the outermost is 30 times as far from the Sun as the Earth, and today Voyager 2 is over 80 times as far from the Sun as the Earth, at the very outer reaches of this giant bubble and we are trying to reach outside of that bubble into interstellar space and both Voyager 1 and Voyager 2 are on their journey to be the first to reach interstellar space.

Adam Rutherford: That boundary is determined by the heliosphere, a bubble created as with all stars by the Sun itself. It is at the edges of that bubble that we can observe the interactions between our Sun and other stars. Thirty years after launch, its nuclear battery is still powered up; Voyager 2 has the hardware to tell us the shape of that bubble.

Edward C. Stone: Voyager 2 has 5 key instruments on it, to measure the environment and this huge bubble that surrounds the Sun. The key measurement has to do with the wind coming from the Sun. The solar atmosphere is evaporating and speeding away at a million miles per hour creating this giant bubble. And one of our instruments measures that wind; we measure it everyday, looking for an evidence that we have reached the outer edge of the supersonic solar wind.

Adam Rutherford: And the mission has now established that the heliosphere is not a spherical bubble, but it is in fact hugely lopsided. Voyager 2 made its crossing through the termination shock that's where the heliosphere meets interstellar space last year and revealed that the bubble is pushed in closer to the Sun by local interstellar magnetic field. It has also revealed more details about the termination shock and made crucial plasma wave and low energy Pascal observations. Voyager 2 is now the furthest manmade object from Earth, but still ticking over years past its official mission accomplished, when it cruised past Saturn in the 1980s.

Edward C. Stone: Well, I think all of us feel, we've been very fortunate to have been on a journey of discovery, even if it had stopped in 1989 with Neptune, we would have had an immensely valuable mission, but for it to continue now for decades and be the first to reach the interstellar space, I think it's just an incredible journey of discovery and we are all very fortunate to have been part of it.

Adam Rutherford: That was Voyager project Scientist Edward Stone from the Jet Propulsion Lab in Caltech. The six papers analysing the edge of the solar system are available on our web site and also on the home page is your chance to win an iPod by completing our short survey about the Nature Podcast. You've got to be in it to win it.

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Kerri Smith: As Voyager sails steadily further from us, back here on Earth, some species are making their exits too, through extinction. A new research suggests that the risk of extinction may have been wildly underestimated. Here's Geoff Brumfiel. Nature 454, 100–103 (3 July 2008)

Geoff Brumfiel: Extinction seems pretty deterministic; an asteroid hits Earth and its curtains for the dinosaurs. People start hunting dodos and before you know they are gone. But new research suggests there is also surprisingly random component to why some species die out and it could have big implications for conservation. I spoke to Alan Hastings at the University of California Davis to learn more about how sometimes extinction comes down to a roll of the dice.

Alan Hastings: So, one of the questions is how you get too few to reproduce and random events play a big role and understanding all the random events is the key.

Geoff Brumfiel: So when you say random events, what do you mean?

Alan Hastings: I mean chance things like variations in the weather, the fact that some individuals may have lots of offspring, some may have few and importantly some individuals may have a tendency to have more offspring than others.

Geoff Brumfiel: Can you give a specific example how weather or some other randomness could really lead to the extinction of a population with what we thought was quite a large amount of individuals in it.

Alan Hastings: Our findings were really focused on combining the weather events with the random births and deaths, but weather events play a big role all the time. Off the west coast of United States, the Salmon populations are way down and some of that may be attributed to one or more years where the usual upwelling, the bringing up of nutrients and organisms from the depths that then provide the growing organisms that provide the food eventually for the fish didn't happen, because the winds didn't blow and that's one example of an environmental fluctuation and in other words, be something like a hurricane coming through or a big storm that would knock down a population.

Geoff Brumfiel: What was the previous thinking about extinction?

Alan Hastings: So people had put random variables into looking at extinction, looking at the role of births and deaths occurring randomly and come up with estimates of population sizes above which populations would be relatively safe from this kind of random process and we have done a different analysis which comes up with a much higher number to be safe from the effects of these random processes.

Geoff Brumfiel: How much higher are we talking about in terms of individuals?

Alan Hastings: Perhaps 5 to 10 times higher.

Geoff Brumfiel: Really that sounds like it means there could be a lot more vulnerable species on the planet than we thought before. Is that right or?

Alan Hastings: That's right; our analysis at least suggests that people need to look much more carefully at estimates of likelihood of extinction for species with relatively small numbers.

Geoff Brumfiel: Your analysis is largely mathematical but I found one of the things interesting about your paper is that you put it to the test, right, you actually, you extinguish some test beetles.

Alan Hastings: That's right, yes, like much of scientific literature, the way you write is not necessarily the way you did it. We had the data first and then developed the model and then used the model to look at the data and as a matter of fact these data were really collected to explain some other work that's ongoing.

Geoff Brumfiel: And tell me a little about these beetles.

Alan Hastings: Well, flower beetles have been around for a long time and they've been associated as a pest of human grain products for a long-time, therefore they're great organisms to use as a model; to use as a way to understand population processes because they have been studied for so long and so we ran and just started with different numbers of individuals and then looked at the numbers of individuals that came out after one generation and tried to explain why the numbers we found after one generation was variable as they were and then the long-term consequences of this variability, you can get by just sort of running systems on a computer. So in the laboratory, we really didn't see extinction. We just found the variability that would eventually lead to extinction.

Kerri Smith: Alan Hastings at UC Davis with new and foreboding predictions on extinction. One creature that is both extinct and not extinct at the same time is Schrödinger's cat, but this beast and the quantum physical notion it represents are questions in a new story this week. News Editor Gaia Vince has joined us in the pod to tell us about it. Hi Gaia, welcome. Nature 454, 8–9 (2008)

Gaia Vince: Hello Kerri.

Kerri Smith: Now first of all you have to remind us of this quantum physical notion and the story of Schrödinger's famously endangered cat.

Gaia Vince: Well, it dates back to the 1920s when a group of scientists where hanging out in Copenhagen trying to understand quantum mechanics and trying to come up with a theory that explained what they were realising for the first time about subatomic particles, say particles that are too small to measure. And they came up with something that is now called the 'Copenhagen interpretation' which says that subatomic particles can exist in two states at the same time, but you don't know which state it is appearing in, because as soon as you try measure it, it flips to the other state.

Kerri Smith: And this has what exactly to do with cats?

Gaia Vince: Well, the cats are an analogy that was brought in to try and make this quantum mechanics sound a little bit more comprehensible. Basically, it is a thought experiment in which a cat is locked in a box with a vial of poisonous gas that would be broken if a quantum particle was in one state and remain intact if the particle was in another. While the box is closed, the particle exists in a superposition of both states simultaneously, so the poison must also simultaneously be both released and contained, in turn the cat must also be alive or dead, but you don't know because just by looking in the box, you immediately commit the cat to either death or an alive state.

Kerri Smith: The idea here is then that this cat is both alive and dead until you open the box, so at which point you discover it is one or the other and these particles the same thing is happening the instant they are observed, the fate of them is decided either way.

Gaia Vince: Exactly!

Kerri Smith: So, a new study then that you're featuring in this week's News section has turned that on its head rather, hasn't it?

Gaia Vince: Yes, well, what these researchers have done at the University of California is that they have pulled this quantum state back from the brink of collapse. They've effectively un-collapsed it. So, what they've done is they've peaked to the cat as it is about to die and dragged it back in to a living state.

Kerri Smith: Obviously there aren't any cats involved apart from the aptly named author who happens to be called Nadav Katz, but what have they actually done, sort of, in the quantum realm. How have they managed to experimentally manipulate this?

Gaia Vince: Well, obviously it would be unethical, don't try this at home to use a cat. What they had to do is something called a qubit. And a quantum qubit can be in one of two energy states, so a low energy or high energy state, but it can also be in both energy states at once and they use this quantum qubit in a supposition of both energy states at once and then what they did by adjusting the energy levels of their experimental system, they either nudged the qubit towards death, towards the low energy state or towards the high energy state. What they showed is that you can nudge the qubit towards the death state and then at the last minute pull it back into the alive state.

Kerri Smith: Wow! So this is quite a contradiction then of what quantum theories I suppose, thought was going on. How does the community feel about this result?

Gaia Vince: They are really excited and one of the things they are particularly excited about is how it might be helpful in quantum computing. One of the biggest problems for people who are trying to build large scale quantum computers is that qubits which is what they use to process the information are extremely fragile, even a slight interference from the outside world can knock a qubit out of whack, collapsing its quantum state and so losing any stored information, big problem if you've got a lot of programs going on your quantum computer. So, this work by Nadav Katz and his colleagues showing that it is possible to rescue a collapsing qubit, un-collapse it and return to its original quantum state could be used to rectify any errors, so if it's nudged out, you can rescue your stored information.

Kerri Smith: So qubits, quantum computing, Katz all quite heavy going, but what else is coming up in the News section this week?

Gaia Vince: Lots of treats, so this week the issue is looking mainly at Voyager. We are saying good-bye to Ulysses, a spacecraft that looked at the Sun's poles and we are previewing the new Solar probe which is going closer to the Sun than ever before and we've also got a preview of the G8 conference coming up in Hokkaido in Japan which it looks like will be dominated by fuel and food prices.

Kerri Smith: All Right, thanks Gaia. Coming up in just a moment, we'll be finding out what makes our minds so musical.

Adam Rutherford: But first Mike Hopkin reports on a new recipe for making stem-cells.

Michael Hopkin: More and more stem cell researchers are turning their attention to the latest hot property in the field Induced Pluripotent Stem cells or IPS cells for short made by genetically reprogramming adult cells, they have been hailed as an ethical alternative to stem cells collected from embryos, but one drawback is that the genetic reprogramming can often throw up damaging mutations. Now biologists have developed a simpler recipe for making IPS cells needing less genetic manipulation. I spoke to Hans Schöler of the Max Planck Institute for Molecular Biomedicine in Germany who led the research and asked him what sort of opportunities these new cells might offer. Published online (29 June 2008)

Hans R. Schöler: So, the amazing thing is that you can use now basically cells of your body and try to derive from these cells any cells that you're interested in. So far you needed to either do nuclear transfer using a nucleus and transfer it into an oocyte or to use embryonic stem cells derived from embryos and now you can basically take any cell that you wish to convert and convert it into a cell that can make then every cell and especially interesting at this stage is to derive cells from patients which have a genetic mutation that you would like to understand and to work on in this tissue.

Michael Hopkin: So this idea of making IPS cells is presumably there aren't so many ethical issues as there are say with cloning or using embryonic stem cells.

Hans R. Schöler: Yes, of course there are the ethical issues but there is a lot of basic research that you can do that you couldn't do before, because if you, especially if you think about human disease now you have a way to try to understand certain aspects of human disease because you can take a cell of a patient we know what kind of disease he is suffering and then try to see if you can get for example out of these pluripotent cells certain neurons and try to understand why are they having a problem.

Michael Hopkin: And what kind of diseases are we talking about when you are talking about this kind of research?

Hans R. Schöler: The first step is to look at monogenetic disease, so disease where one gene is responsible for certain disease, so those type of cells are the ones that you can I think better understand at this stage.

Michael Hopkin: Why is this recipe for making IPS cells better than the previous methods that people have had?

Hans R. Schöler: So far people have been using four different factors or three different factors and we are now down to two factors, and so that means that we need much less than in the previous other reports.

Michael Hopkin: And these factors, what sort of things do they do to the cells and what is involved in actually making IPS cells.

Hans R. Schöler: So, what you need is to use viruses that carry the different factors and the viruses infect the cells and in our case we have been using neural stem cells which only express a subset of the four, and they then transform the cells to pluripotent stem cells.

Michael Hopkin: And presumably doing away with these viral gene insertions as far as possible improves the safety because then you are never quite sure where these viruses are going to insert themselves that you can get damaging mutations sometimes.

Hans R. Schöler: Exactly, since you only have to use two different types of viruses not four, you would have less insertions, but nevertheless the final goal is to replace all viruses and so this is I think an important step towards that goal.

Michael Hopkin: Will your method also increase the supply of IPS cells, because I guess a lot of researchers are going to want to be able to use these sort of cells and they need to be made available?

Hans R. Schöler: Yes, that's certainly the case but now I think that even more than before people will be looking for other cell types in the human body and if you would find other cells which are even better accessible than neural stem cells, then you have even further development in methods.

Michael Hopkin: Here in Britain and in other countries we have been having a debate over whether embryonic stem cells, whether research should be allowed. Does your method mean that may be, we won't need to worry about having to use embryonic stem cells in the future.

Hans R. Schöler: No, I don't think so. I think also in the future you will have to rely on embryonic stem cells. First of all, you would want to understand what embryonic stem cells are because these are the pluripotent cells directly derived from the embryo, so these are like the gold standard, if you want to understand basic processes, but even if you would like to think about developing these alternative methods you would always need like the goal standard embryonic stem cells to compare these new methods with them because if you can't get things worked out with embryonic stem cells, I would rather doubt that you can get things worked out with the alternative.

Adam Rutherford: That was Hans Schöler talking to Mike, and that was Mike's final contribution to the Nature Podcast. He is leaving England for the sunnier shores of Australia. Good luck Mike.

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Kerri Smith: Finally for this week's show, music to your ears. What can science tell us about our affinity for music? For the past 9 weeks, Nature has been attempting to get at this question, running a series of essays by experts working at the boundaries of these two disciplines. Two of the contributors joined me in the studio to help unpick music's power and pervasiveness. Phil Ball Consultant Editor for Nature who penned the first essay of the batch and John Sloboda a music psychologist at Keele University in the UK, whose essay appears this week. I first asked Phil to take us through the main theories of how music evolved. Focus: Science and Music

Philip Ball: Well, Charles Darwin considered this question and he suggested that it may be something to do with sexual selection, basically music being a kind of sexual display, plus other people have other suggestions. The common one is that the music somehow promotes social cohesion; some people have suggested that actually the origins of music are linked with the origins of language and that in some sense music or some sort of music like speech patterns used to be a basic form of communication.

Kerri Smith: Now, I suppose a bunch of theories is all very well, but John turning to you how much can we really say about the why of music and why do we expect it even to be universal among humans?

John Sloboda: Well, I am a psychologist, so I take the position that in a sense we can only know what's in front of us, which is the human beings as inhabiting this planet now or we can find out from them and so lot of these evolutionary theories are pretty speculative and one has to ask the question, is there actually any data out there which would help us to confirm one theory or the other. Now the only anything I would put my money on is that the social hypothesis is probably a good hypothesis because we see musical behaviour from the very beginning of life in terms of mother-baby interactions and the building and the maintenance of that relationship that has very strong musical characteristics.

Kerri Smith: So, it's clear from all of this that it is pretty tricky scientific nuts to crack this music business, but nonetheless Phil, there is a long history of music being treated quite mathematically if not scientifically in the past, tell us a little bit about that.

Philip Ball: Well, in ancient Greece music was considered a science and it was studied as essentially as a form of mathematics, in legend at least Pythagoras is attributed with discovering the relationship between musical harmony and mathematics in terms of the divisions of the length of string and how dividing a plucked string into simple ratios of lengths, how that gives notes that seem to have a certain qualities and consonant quality and this idea was perceived certainly through the Middles Ages when music made up one of the, basically one of the four so called sciences that were studied at that time and people tended to study music in order to understand ideas about natural harmony which were quite distinct from the people who are actually performing music, they were never academics and in fact they were considered by academics who studied music to be rather lowly individuals, the business of actually going and performing it with something that, you know, as an academic you couldn't be bothered with.

Kerri Smith: Now this aspect of performance of music is something John, you have looked into, tell us a little bit about your research on that topic. What you are uncovering?

John Sloboda: Well, one of the things which is really interesting is that performance matters and I think we all knew that because if performance didn't matter you could just record one performance of a piece for all time and then pack up shop. But the fact is that each performance of a piece is very subtly different from each other performance of a piece in a way that can be extraordinarily, emotionally and aesthetically appealing. So that one performance can feel very flat and uninspired and another performance can feel, you know, life changing. And the question is can we actually analyse and explain those tiny differences of timing and time-breaks etc., which make a difference. And the good news is that science is beginning to give some answers to that. There is some rationality to this.

Kerri Smith: And so what does may be the effects of a particular performance tell us about how individuals react to music and what music does to us and why it might?

John Sloboda: Well, one of the strongest drivers of aesthetic reaction to any object be it music or something else, is this element of surprise and it sometimes a pleasurable surprise, one must wonder in admiration, 'Oh! You know I could never imagine it would be like that', so actually very often what makes a performance special is if the performer does something which slightly but very appropriately tweaks a person's expectations. They didn't expect it to be like that, so it might be a bit louder than they expected or bit slower or they delay a note a microsecond, it comes in a bit later than you expect it and it is those slight subtle playings with our expectations that creates that kind of emotional fizzle when we are listening.

Kerri Smith: Much that science can do for music then, how about what music can do for science, Phil?

Philip Ball: It seems to be possible that studying how the brain responds to music might give us some insight into how the brain functions more generally, it certainly seems clear that music uses an incredible amount of the brain if you like that in comparison to language say, they don't seem to be as far as we can tell so far highly specialised centres in the brain that are there for processing music. It seems to use all sorts of different parts of the brain and so in a sense it may be that music is a very nice stimulus to give the brain to start to explore some of the ways in which it integrates its activity.

John Sloboda: I would agree with everything that Phil said but I would also say that I think in some way music challenges science and that shows science some of its limits in terms of providing a complete understanding of a phenomenon like music. So I actually think science can't take us the full way with music, we need sociology, we need cultural history, we need philosophy, we need a range of subjects to capture the full richness of what this thing is and science has to sit alongside with others and get along with them.

Kerri Smith: And luckily for us, we don't need to fully understand music to be able to appreciate it. John Sloboda and Phil Ball thank you very much.

John Sloboda: Thank you.

Philip Ball: Thank you.

Adam Rutherford: There is an extended version of that interview available from or if you signed up to the podcast RSS feed it's winging its way to you right now. A snippet more music to finish this week this Sound of Science comes courtesy of two students of Middlesex University in the UK. Sebastian Heinz and Tracy Tsang have come up with the genetic algorithm that allows a piece of musical software to develop variations over time.

Kerri Smith: The variations it has to work with are short loops of music that are either melodies which represent female creatures or drum sequences which represent males. When they breed they create new musical children. Here's one example. I'm Kerri Smith.

Adam Rutherford: And I'm Adam Rutherford, thanks for listening.


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