Nature Podcast

This is a transcript of the 11th September edition of the weekly Nature Podcast. Audio files for the current show and archive episodes can be accessed from the Nature Podcast index page (, which also contains details on how to subscribe to the Nature Podcast for FREE, and has troubleshooting top-tips. Send us your feedback to


The Nature Podcast brought to you by Bio-Rad's 1000-Series Thermal Cycling Platform. When you re-think PCR you think about how easy it can be. See how at

End Advertisement

Kerri Smith: Coming up this week, we find out how and why scientists have constructed a fake tree in the lab.

Adam Rutherford: And the excitement mounts as the CERN crew prepare to switch on the Large Hadron Collider.

John Ellis: I sometimes compare it to climbing a mountain and I see it is a pretty big mountain and once we get to the top, we know we're going to have a fantastic view on the other side, don't know what is going to be but we know there is going to be fantastic view.

Adam Rutherford: This is the Nature podcast. I'm Adam Rutherford.

Kerri Smith: And I'm Kerri Smith.

Kerri Smith: Our first lesson of the day is double maths. You see there are two ways in which we think about numbers. One which other animals share based on guesswork, roughly how many people are on the bus or how many sheep in a field and the other on symbols and equations. Whilst it's obvious that people vary in their ability in taught maths it isn't clear whether the approximate number sense can also be better in some than others. Equally we don't know whether these two forms of maths correlate with each other. So, Justin Halberda and his colleagues from Johns Hopkins University in Maryland decided to find out. Nature advance online publication 7 September 2008

Justin Halberda: This approximate number system is activated, it is being activated when you're thinking about equations, thinking about addition, thinking about subtraction, but work of other researchers is also shown us that you've two kinds of systems. One is for doing very precise exact addition, not seems to rely on language centres, whereas your approximate quick addition like, you know what is 20 plus 30, oh it's somewhere around 50 of course. That might rely solely on the approximate number system. So it really looks like you have this quick fast approximate system and you have very very precise maths system, which relies on language.

Kerri Smith: And you wanted to know whether these two things were linked.

Justin Halberda: Right, so until now, until this paper we have coming out, it was unclear whether or not those two separate systems, the approximate one and the exact one is they informed one another or supported one another. We knew they were both active, but we didn't know did they affect one another. And what we found is different individuals have different accuracy with this intuitive sense of number and that difference and accuracy actually predicts how well people do in school mathematics, that was quite surprising.

Kerri Smith: And why is that surprising. Because naively, I mean, I am thinking to myself if both systems are concerned with mathematical skill in some way, isn't obvious that they would be correlated.

Justin Halberda: Absolutely, I mean, that's one of the reasons why we've looked at whether or not they would be correlated. There was certainly the possibility, because they are dealing with the same material but they are dealing with the material mathematics in two very different ways. One of them, the approximate number system is something that you know even a rat has and a rat certainly has never gone to second grade and learned mathematics. Individuals from cultures that have no mathematics at all, no formal mathematics, no formal schooling also have this approximate number system. Formal understanding of mathematics is something very different from what a rat does everyday when it's out looking for food.

Kerri Smith: But nonetheless though the two are correlated and one predicts the other.

Justin Halberda: Right, the fact that they end up being correlated shows that our formal fancy mathematics that we think of as a pinnacle achievement of mankind isn't in fact as distant from an intuitive sense of number that we all share.

Kerri Smith: Well that will give those of us who aren't very good at formal mathematics some comfort, I suppose. And could you tell us a little bit more about how did you actually go about finding out that there was this link?

Justin Halberda: So, we tested sixty four 14-year-old children and they basically played a simple video game of watching blue and yellow dots flash on a screen, so on a single trial, there might be, say 8 blue dots and 12 yellow dots, all spatially intermixed like confetti on a screen flashed very quickly. And then their task is to try and say were there more yellow dots or more blue dots. And then from your performance we can look at how accurate you were as a function of the numbers involved. Then we used the mathematical tools to model exactly how well each individual does and that gives us an estimate of the accuracy of their approximate number system, their intuitive number sense. And what we found is that that 10-minute video game, playing that 10-minute simple game of yellow and blue dots significantly predicts how well students did in mathematics all the way back to kindergarten in every single year tested.

Kerri Smith: Wow, it's a quite striking result. What could this mean for teaching kids, maths. I mean can we predict how well they will do in maths. Is there anything we can do to make them better if they don't look like they are going to be any good?

Justin Halberda: Let me take those two questions in turns. So, one is can we test early and predict how well people will do maths in the future and that's something that we're looking at right now. I think it will turn out to be able to predict how well somebody will do in the future, but it remains an open question that we need to actually test and we're testing 3-year-olds right now and then we will have to, you know, wait a couple of years to see how well does their approximate number system at age 3, predict how well they do in school maths once they get to school. The second question about how does it affect, how we think about learning mathematics, I think that's a very exciting opportunity here to see whether or not we can number one, train up the approximate number system, can somebody practice and get better at their approximate number system. There's some indication that that might be possible, you can practice and improve your approximate number system. What remains an open question is if you do improve your approximate number system, will you see some benefit and your performance in school mathematics and we are currently testing that as well.

Kerri Smith: That was Justin Halberda. Coming up, the second of our special podcast on science in the US election. This week Bio-medicine and health.

Adam Rutherford: But first, Charlotte Stoddart has some explosive news.

Charlotte Stoddart: We are all familiar with the devastation wraught on Pompeii when Mt. Vesuvius erupted nearly 2000 years ago. Today it's re-awakening would threaten the lives of the 700,000 people living in its shadow. Bruno Scaillet and colleagues at the National Center for Scientific Research in France have been investigating past eruptions of Vesuvius in an attempt to forecast its future. And Bruno told me how he and the team went about uncovering Vesuvius' in a history. Nature 455, 216–219 (11 September 2008)

Bruno Scaillet: What we have done it's we have selected four main eruptions those which are considered to be the most explosive and the most dangerous ones over the last 20,000 years and for each of these eruption, we have selected a representative rock and for each rock we designed experiments whose main goal is to define at which pressure, temperature, water content, the minerals that the rock contains are stable or crystalized.

Charlotte Stoddart: When you've worked out then the conditions under which each of your chosen rocks crystallized, what does that tell you about the eruption?

Bruno Scaillet: These tell me basically one important information. These tell me the condition at which this rock has been stored beneath the volcano. Basically, the main parameter we are looking at using this kind of approach is to define the pressure or if you want the depth at which the reservoir of the magma was located beneath the volcano.

Charlotte Stoddart: Was this the same then for each of your chosen four eruptions?

Bruno Scaillet: Yeah, what we did find out is that we didn't find one single pressure for all those eruptions, but instead we found out that the pressure of every eruption was different, was moving with time or changing with time.

Charlotte Stoddart: And how does it help us with predicting when the next eruption might be. How does it help us to know about the depth of the magma chamber, before these eruptions?

Bruno Scaillet: The main problem with Vesuvius is that our laboratory work has evidenced that the pressure was becoming shallower with time that is to say that during the Pompeii event, the reservoir was located at the 7-8 kilometre while for the most recent eruption the one which occurred in 1944, the depth was shallower than three kilometre, that is to say that the reservoir has migrated upward over the last 2000 years at least. So the problem is, what is the past eruption which can be used to forecast the next one. There is no, I must tell you that there is no answer to this important question. So the main implication of all results is that basically we don't know really now what is the next target.

Charlotte Stoddart: I see, so do you have any ideas how we can solve this problem. What will you be doing next?

Bruno Scaillet: The sole possibility we have now is to use geophysical surveys which can image the present day crust beneath Vesuvius so as to try and identify the level where there is melting magma material. So far those geophysical surveys, especially those based on seismic approach, this type of approach may be in the future used to infer at what depth there is partially molten material – magma - first thing, and the second thing important also is not only unique to image where it is located, the reservoir but also you need to know what is the sort of magma because the type of eruption is going to happen next will depend on the chemistry of the magma which will be able to detect and this currently is not possible.

Charlotte Stoddart: So you are saying that at the moment, we don't know very much about the depths and properties of the magma chamber in Vesuvius right now. And to get that information, we really need a lot more research and we need to refine our techniques.

Bruno Scaillet: Yeah, exactly. We currently miss that technique. We still need much work, much more surveys, geophysical surveys to try to answer this fundamental question of when and where will Vesuvius erupt again. That's still the open question in my opinion.

Adam Rutherford: Bruno Scaillet talking to Charlotte. We will be hearing from Geoff Brumfiel later in the show from the Large Hadron Collider. He is currently at CERN where he has been reporting and blogging about the big switch on today. First though, biomedical issues in the run up to the presidential election in the states, Kerri.

Kerri Smith: This week sees the second of our three special podcasts on the US presidential election. Nature columnist David Goldstein hosted the debates and he has joined me in the studio once more. Hi David.

David Goldstein: Good to see you Kerri.

Kerri Smith: You had your guests tell you what they thought the candidate should be focusing on in the area of biomedical and health issues this week, what did they come up with?

David Goldstein: There are a series of issues that they brought up, health research funding was certainly high on the agenda and particularly keeping it stable even more than the question of how high it should be. Concerns about workforce in the pipeline to get more researchers in, concerns about the drug approval process, and looking forward to either candidate if they become president lifting the ban on stem cell research.

Kerri Smith: The issue of stem cells obviously is something we've heard a lot about. What did the experts think the impact of lifting that ban might be?

David Goldstein: Well, there will certainly be an increase flow of funds into that area and increase interest among researchers. But two interesting things that came out was one, that we really don't know what the true potential of stem cell research is and so that one of our guests pointed out that this is the first thing will happen for the better sense of what can actually be promised and may be a more thoughtful debate on that.

Kerri Smith: On that was Tom Cech of the Howard Hughes Medical Institute, here's what he had to say.

Thomas Cech: We do not know how promising it is yet; we need to do more research and I am afraid that the polarization of the dialogue because it has become so politicized has encouraged some scientists to become very exuberant about the potential, whereas if it hadn't become so politicized I think they would be a bit more sceptical.

David Goldstein: And the other is that that there might actually be a whole series of additional bioethics questions that come up other than the use of embryos which has been the focus up till now.

Kerri Smith: Now aside from stem cells, the guests mentioned some other specific areas of research that they believe should be prioritized or at least thought about. Talk us through those.

David Goldstein: One of the areas that the guests felt was to some extent under research now and could be a big area for the future was antibiotic resistance and the ability, to increase our ability to stop especially hospital-acquired infections and other problems like extensively resistant tuberculosis and so forth. So that was one of the area that they thought could be an additional focus in the years ahead.

Kerri Smith: And here's Jonathan Moreno on that point.

Jonathan D. Moreno: I read a very good piece by Jerome Groopman in the New Yorker about antibiotic resistant organisms. It's a real concern. Anybody who doesn't believe in evolution can, you know, just look at these little bugs and see it's true. So one possibility is that some of the biodefence moneys that have been made available could and I think should be used to direct to this problem because it's one that the industry has kind of moved away from in recent years and I think it's time for us to refocus. This is a real problem for people who're hospitalized.

Kerri Smith: Are biomedical issues in general something we hear that candidates talk about a lot?

David Goldstein: Not particularly, there is a lot of discussion about health insurance issues and usually as an after thought the candidates say they support more funding for the National Institutes of Health, which both of them do, but the really nitty-gritty issue is on health research policy that the next president will face or don't tend to play a big role in the campaign, partly because they tend not be especially partisan issues and partly because there are technical issues that are really often left to the agencies.

Kerri Smith: All right, David Goldstein. Thanks for joining me.

David Goldstein: Thank you.

Kerri Smith: The full length discussion is available free at


Adam Rutherford: Now we come right out of the woods, transpiration is the passive process by which water moves from the wetness of the soil up a plant and into the air via the leaves. We've known about it for years and you probably haven't thought about it since school. The assumption is that transpiration works by a wick effect, where the negative pressure of the water in the leaves draws up water from the roots but until now it has been impossible to replicate this process in the lab. Abraham Stroock and Tobias Wheeler from Cornell University in New York have constructed a fake plastic tree which emulates the natural process. I spoke to Abraham Stroock and started by asking why synthetic transpiration has been such a tall order. Nature 455, 208–212 (11 September 2008)

Abraham D. Stroock: One fundamental challenge is that this process places the liquid at a reduced pressure and even a negative pressure. At this negative pressure, the liquid is being used like a rope and put under tension. This is actually a metastable state. The liquid in that case would prefer to be a vapour and so the liquid, it's a fragile state of the liquid and so that is one difficulty typically when we try to do this in the lab, the liquid breaks and vaporizes. Secondly, it's the question of material that generates this stress, generates this reduced pressure. There was lack of understanding of what the ideal material to perform that process was. The picture in the plant physiology was not incorrect but impractical and so finding the appropriate material was a major technical barrier to achieve this in the lab.

Adam Rutherford: Now just give me an indication of what the experimental set up actually looks like, I mean is it a series of tubes or is it like tree-like things. What is it look like in the lab?

Abraham D. Stroock: Well it's very much not tree-like in scale, it's formed by lithographic processes that on a silicon wafer originally that is only a 100 mm across and it is the series of capillaries of the scale of actual xylem in plants that is formed into a network in the root section coupled via a single capillary which we call the trunk to another network that is representing the leaf and all this is embedded within a slab of this hydrogel material like a very large oversized contact limb and so when we operate the system, we present the root section and the leaf section with water in different degrees of saturation, so for example the root would be presented pure liquid water and the leaf would be presented of vapour of water in air that's at relative humidity less than 100% and this then drives the flow through the synthetic tree.

Adam Rutherford: Okay so, where do you see the application of your fake plastic tree technology, what's the point of it?

Abraham D. Stroock: So, this ability to move liquids around use liquids as a rope effectively to pull themselves around allows you to use up the global difference in the amount of water present to passively drive water. So one example of an application is in heat transfer where you can use evaporation at the least to cool a heat source and capture that energy in the heat of vaporization, carry the vapour to a condenser and drop that heat and you can then recycle that working liquid back to the evaporator site even against very large pressure drops, gravity, viscous pressure drops back to the evaporator and use it again and this type of heat transfer strategy is already in use on very small scales in particular is embedded in almost all laptop computers and you know, can look towards using it on a scale of a building for example say to collect heat by solar means on the roof and carry the vapour all the way down through the building and pull the liquid back up to the roof to be used again and so that's how it completely changes the dimension of an existing very effective heat transfer system. Finally, we actually extract water for agriculture or for human use from soils that aren't completely saturated or in other words to be able to draw water out of soil without drilling a well all the way down to the water table, so there's water throughout all soils but most of it is inaccessible to human use at this time.

Adam Rutherford: Abraham Stroock there and his fake plastic trees. Clearly a Radiohead fan.

Kerri Smith: Finally this week, the big switch on at the Large Hadron Collider on the Swiss-French border. Has all the hype been justified. Will we glimpse the Higgs Boson, will the LHC really cause a black hole and end the world. Geoff Brumfiel was there watching the action unfold and having a quick coffee in the CERN cafeteria. Geoff, we've heard a lot about the LHC in the media already, what's the atmosphere like there.

Geoff Brumfiel: Well, I mean it's pretty crazy. There are a lot of people here, both physicists who are coming from around the world to sort of get started on the actual physics, the actual science and then of course there's a lot of press. Some of the parking lots are closed for their satellite trucks, I see a lot of film crews wandering around the campus looking sort of confused. So there's definitely a lot of energy here today.

Kerri Smith: And what is anyone hoping to actually see, because I gather that the collisions and things won't start for another few months.

Geoff Brumfiel: Well that's a question, I am sure a lot of the physicists are wondering themselves, you know, why are we bothering them right now. Because what's happening tomorrow is they are just going to circulate protons around the 27 km ring of the Large Hadron Collider and it's largely symbolic, the real physics won't start until there is actual collisions, but even now the detector groups are getting their detectors ready. There are doing a lot of tests and a lot of calibrations, they've been working on this project for about 15 years now and now finally they're going to be seeing something actually going around the ring.

Kerri Smith: So, what is it that they are actually hoping to see once the whole thing is up and running?

Geoff Brumfiel: They are hoping to see a couple of things. They're hoping to see the Higgs Boson which is a particle that they believe may endow all other particles with mass and they're hoping to see some new stuff as well and I really spoke to a theorist named John Ellis earlier today and here's what he had to say.

John Ellis: First off, the LHC is just going to be a much more powerful microscope to look inside matter than anything that we had seen before. It's going to be something like 10 times more powerful in terms of the distance scale that it explores than anything else ever been done before. I sometimes compare it to climbing a mountain and I see it is a pretty big mountain okay, and we are almost there and once we get to the top, we know we're going to have a fantastic view on the other side, don't know what is going to be but we know there is going to be fantastic view. Of course, we've got some ideas about what we expect to see, what me might see, what we hope to see on the other side of the mountain. Higgs Boson is almost the first thing that comes to peoples minds. I would regard the Higgs Boson as being more a sort of place holder for a mysterious part of the standard model that we know has to exist but we don't actually know what's in that and the LHC will be the first machine with a realistic chance of actually turning us.

Kerri Smith: CERN theorist John Ellis there, one of many scientists who is going to be delirious with excitement that this is actually being switched on. What does it mean to people like him to switch this on finally.

Geoff Brumfiel: It means quite a lot. High energy physics has been in a bit of doldrums since the 1990s or just hasn't been that much going on because really it's very expensive and so they have had to focus almost all their energy on building this accelerator here at CERN. So this is really their first opportunity to see some new and exciting physics beyond the standard model.

Kerri Smith: New and exciting physics, the other thing we've heard about is end of the world physics. What do you think and what did John Ellis think to the predictions that we're going to create a massive black hole with this piece of equipment.

Geoff Brumfiel: Well, there's a number actually if you want to get technical about it Kerri, there is a number of scenarios under which the world might end and a few frankly slightly mad people have taken this matter to court. This is the certain thing that really gets people like Ellis railed up, because it tends to get all the press, I mean, even my flat-mate before I left asked me if the world was going to end. He doesn't know a lot about physics but he managed to hear that about the LHC. I asked Ellis what he thought about these guys and here's what he had to say.

John Ellis: First off, the world is not going to end right, the LHC is absolutely safe. All that we are going to be doing is we producing under controlled conditions, experiments that nature has been doing on earth for billions of years. These ultrahigh-energy cosmic rays have been bombarding the earth and nature has already performed on earth something like a 100,000 complete LHC experimental programs. We calculated that throughout the universe, every second nature is reproducing the LHC experimental program 30 trillion times. So you know don't try to kid me that there's any problem with doing one more experiment, right. The people who bring this up quite frankly they're not physicists. The great majority are not scientists at all. I personally believe that they are after something completely different.

Kerri Smith: So as you've mentioned then, I mean, even people who aren't scientists have heard of the LHC being switched on have probably even heard of a Higgs Boson. I mean isn't that a good thing for physics.

Geoff Brumfiel: Well, I think in someways it is. Yeah, I mean I think you know there's an old adage that any press is good press and certainly the hype created by them to the world does definitely increase the visibility of CERN. I think it's now up to the physicists here to sort of keep that excitement going and actually explain to people what this accelerator will begin for.

Kerri Smith: All right, well we will leave you Geoff there to go and watch the big red button being pressed.

Geoff Brumfiel: Yeah, it should be pretty exciting, I can't wait.

Kerri Smith: And Geoff is also blogging and reporting from CERN. Check out for more from him. There is also an extended version of the interview with CERN theorist John Ellis available free at

Adam Rutherford: And that's it from us. Next week we bring you news of how your knashers evolved and the third of our special US election podcast this one on innovation. I'm Adam Rutherford.

Kerri Smith: And I am Kerri Smith. Now make like a tree and leave.


The Nature Podcast is sponsored by Bio-Rad, at the centre of scientific discovery for over 50 years. On the web at

End Advertisement