Inside the Atom: 100 Years On
100 years since Rutherford split the atom, we investigate the secrets of the building blocks of our Universe. How can we harness the energy locked inside these particles, how have scientists been engineering brand new elements, and are we all the children of starlight? Plus, news of an anti-aging protein, a dinosaur family tree shake up and a new technique which can create millions of stem cells.
In this episode
02:14 - Anti-ageing protein reverses senescence
Anti-ageing protein reverses senescence
with Peter de Keizer, Erasmus Medical Centre, Rotterdam
A drug that reverses the ageing process has been unveiled by scientists in the Netherlands. Administered to mice that were the rodent equivalent of human 80 year-olds, the agent triggered the animals to recover lost hair, move with renewed vigour and reversed age-related decline in their kidney function. The drug causes worn out “senescent” cells to kill themselves, preventing them from exerting harmful effects on surrounding healthy tissue. It works by prising a cell signal, called p53, away from the clutches of a protein called FOXO4, and this triggers the cell’s death programme. Chris Smith spoke with creator Peter de Keizer from Erasmus Medical Centre in Rotterdam...
Peter - Senescence is a state of hibernation. It can occur in cells that are irreparably damaged and cannot cope with the damage, and they basically stop dividing. That, in principle, is a good thing because you don’t want damaged cells going rogue. However, these cells secrete a whole range of factors that are unwanted. As we age we get more and more of these senescent cells and, therefore, we also get more and more of these unwanted factors in our environment of the body, and it’s actually shown that taking out these senescent cells from mice makes them live longer.
Chris - Why would the body elect to hang onto these cells which are, for want of a better word, sitting there poisoning the well? Why doesn’t it get rid of them?
Peter - It is thought that early in life these so-called senescent cells have the benefit over cell death. So, if a cell is irreparably damaged and chooses to die, if we have this too often in our bodies, then we would remain very tiny, and we would be outcompeted by nature back when we were still running around in bear skins. So early in life, it is beneficial to have these senescent cells over dying cells. However, we were never meant to become 80 years of age and, as we age, we get more and more of these senescent cells and that’s when they start becoming problematic.
Chris - What sorts of factors do they squirt out into the body, these senescent cells, which have a deleterious effect?
Peter - Over a hundred different kinds of proteins have been identified to be secreted. Some prominent ones are interleukins, which are proinflammatory factors. Also, proteases which break down the matrix of our tissues, for instance, and that’s undesirable. Also, there are plenty of growth factors which can actually promote tumour growth, for instance.
Chris - You think you may have a way to skew whether or not they choose to become senescent or to die off?
Peter - From a fundamental research point of view, we tried to figure out why is it some cell types die and others do not and they go into senescence? I tried to figure out what could be the molecular switch and we identified a protein and that’s the pivot between death and rest. And by making something to resemble this protein, I could fool the system and therefore we could eliminate these senescent cells.
Chris - Does that mean then, that if you were to administer that signal into an old animal that you could rid the animal’s tissues of these senescent cells which are contributing to the ageing process and therefore you could, at the very worst, potentially arrest ageing and maybe even wind the clock back a bit?
Peter - Yeah, you are spot on actually - that’s exactly the case. We started off in Petri-dishes with cells, and if we make those cells senescent, we could eliminate them by adding this compound. If we did this then in mice that were about two and a half years of age, which is roughly 80 years in terms of human years. They had, for instance, worse fitness; hair loss is a feature; they have worsened organ function, and we could normalise those levels with using this compound.
Chris - Right. So you can actually reverse some of those signs of ageing in these mice?
Peter - I think that’s the big novelty of this study. So far, much of the anti-ageing research has focused on delaying ageing, for instance, eating less and exercising more, but society actually shows the reverse. We exercise less and we eat more so this is a message that doesn’t really appeal to the general audience. We now show that it’s possible that when you are already aged, that we can actually reverse some of these effects and that’s a big novelty of this study.
Chris - What is this stuff and where can I get some, more importantly?
Peter - This chemical is actually part of a protein called FOXO4, and it’s physically associated with another protein which is called p53. What I designed is a small piece of protein that releases p53 and that leads to cell death.
Chris - So essentially what we’ve got is this FOXO4 sitting there and in a senescent cell, which is just stewing and being miserable, it grabs the p53 molecule and in that situation the cell just sits and stews? Your drug molecule gets between those two, stops the FOXO4 from grabbing the p53, and the p53 then triggers the cell instead to die?
Peter- That’s absolutely correct.
Chris - Now the critical question of course though is whether this stuff does harm because it sounds too good to be true? What happened to the mice that you administered this to, and what happens to a healthy mouse you give it to, do they have side effects?
Peter - This is a very important question we were having; that’s also why the study took us so long, and we showed that there was no toxicity. We’ve been treating healthy mice for over a year now. We started at one year of age, which is around 30/40 years in mouse years and we treated them for over a year, so another 30 or 40 years and they still do not show any negative symptoms. So there’s no accelerated cancer development, there’s no effects on the blood system so, as far as we can tell, this is perfectly safe to healthy mice.
08:17 - Will technology in cars make us safer?
Will technology in cars make us safer?
with Peter Cowley
Entrepreneur and angel investor Peter Cowley has car user-interfaces on his radar this week as he explains to Georgia Mills...
Peter - I noticed a couple of weeks ago that a company called Gestigon (a German company) which I met in Vienna some time ago have been sold to a French automotive company. So I started thinking about user interfaces on cars which started simply a long time ago with a Model T Ford, which had one on/off switch and one meter and, of course, it has got massively complicated since then. Slightly less complicated because we’ve got screens and touch screens, but if you go back to a car 20 years ago, it might have had 100/120 buttons on it.
Georgia - So this is the idea of people interacting with their cars?
Peter - Yes, with not just obviously the indicators and lights, but all the other things - the entertainment systems, the sat navs, the telephone, etc. So there are two elements to this, there is the output which is effectively what you need to see, which is the screen, maybe it’s some sort of voice generated information. Or maybe the head up display, which is the one that you get in some cars which sits in front of you projected onto the windscreen. And then the inputs.
The outputs aren’t really too much of a problem. You can get distracted by them but you’re more likely to get distracted by interacting with the device. If you're doing it with voice, which many cars have but, in my view, never seem to work that well. Otherwise it’s knobs and buttons. The ones on the wheel are OK or some sort of touch screen. What’s happening in recent times is that people are wanting more and more information which is similar to that on their mobile phones. There are a number of systems from Apple, from Google, etc which actually convert what’s happening on a phone onto the screen which means they don’t have to build in those complex technologies inside the car and you can have your address book, you can have your music, etc projected into the car.
Georgia - I suppose when you’re driving you do not want to be fiddling around with complex fiddly things, you want it to be a simple as possible. So how are these companies trying to make it easier for you to interact with your car?
Peter - The one extreme you’ve got is the Tessler which has got a 17 inch display in there which is a great big thing that replaces the central console which would be very tempting to browse the internet on. This would be fine if you had an autonomous vehicle but clearly not if you’re having to drive.
At the other end, this Gesticon company is actually monitoring the hands on the wheel and monitoring the fingers and it can detect where the fingers are in space effectively, so you can then either learn or teach it to recognise what volume up and volume down are, and changing the sat nav by selecting letters, etc.
Georgia - OK, and if I do jazz hands, turn the music up - that kind of thing?
Peter - Well, it could be as complicated as that but that means you have to take your hands off the steering wheel.
Georgia - Oh yeah, so don’t do that.
Peter - So don’t do that, exactly. The big issue, of course, is the fact that there’s too many people with phones in the cars and the real serious danger of using your phone while you’re driving. The figures are showing that in the UK the number of road deaths is creeping back up again, even though it’s been going down for many years. The suspicion is that people are texting and using the phone rather than the car.
Georgia - So with all this new technology there’s a danger that instead of helping us it will distract us more from what’s actually going on?
Peter - Absolutely, and it is doing that already. In the medium term, autonomous vehicles means that you can go to sleep in the car and you shouldn’t worry about this at all. But in the meantime, somehow, there’s got to be something in there that stops us. It’s mainly younger people, unfortunately, that are picking up the phone and doing things that they really, really mustn’t do.
Georgia - It’s too tempting to go on social media while they’re doing long journeys?
Peter - Yes, exactly.
Georgia - When will we see this across all cars do you think, this sort of brilliant interface where you can say “car take me here” or “car turn up the volume” or wave your hands?
Peter - Well, with your voice it’s basically there already but it never really worked for me. If you take in terms of the mobile devices, there are many of them. Not just the big electronic manufacturers like Apple, but there are many cars like BMW and Ford who have already got those built in.
12:59 - New cell synthesis technique makes millions in days
New cell synthesis technique makes millions in days
with Daniel Ortmann, University of Cambridge
Stem cells are the starting point for all of the cells in the human body and scientists can use to them to replace injured tissues, or to study how certain diseases affect different parts of the body. But it can take a very long time - up to twenty weeks - to turn a stem cell into a mature tissue. Now, scientists at the University of Cambridge and the Wellcome Trust Sanger Institute have reduced that to just a matter of days, thanks to a new technique that can make millions of identical cells at a time. To find out how, Chris Smith spoke to Cambridge University’s Daniel Ortmann...
Daniel - Essentially we focus on a process called “reprogramming cells” so, essentially, it’s turning one cell type directly into another. So rather than going down this fairly lengthy developmental process, we just convert them directly from, let’s say, a skin cell or, in our case, a stem cell.
Chris - In the old days we used to take a skin cell and turn it back into a stem cell, and then turn the stem cell back into what we wanted to turn it into. What you’re saying is we’re going to short circuit that equation and go from A to B directly, rather than via C?
Daniel - Yeah, exactly. Reprogramming processes are fairly direct because you don’t have to go through these cascades of normal development as it happens in the body.
Chris - Why didn’t scientists do that in the first place then? Why did they go all the way back to stem cells and then turn the stem cells into what they wanted? Why didn’t they do what you’ve now done?
Daniel - People have done similar things before. It’s just that what we have done in our study is rather than putting those genes that control the whole process, putting those randomly into a cell, what we did is we integrated this genetic information in specific locations into the genome - they are called “safe harbours.” In this way, we can ensure that all the cells have the same information, and we can also rapidly turn it on and then switch this programme that’s running into the cell.
Chris - Right. So you embed the reprogramming genetic information into the cell at the get-go, and then you can control what’s turned on, where, and when. So that cell passes all of that genetic information into its offspring so you get a whole clutch of cells that are the same or behave the same way and follow the same instructions?
Daniel - Yes, exactly. So, essentially, we are putting in the information and then it justs sits there until we decide to give it a chemical trigger to then activate those genes, and then the cells rapidly reprogramme and within five or six days they turn into an entirely different cell type.
Chris - When you say there’s a safe harbour, you put in the instructions. You know what the genetic instructions are that turn a skin cell into let’s say a heart cell or something, so you’d put those genes into a specific part of the genome where you know they’re not going to do any damage to the cell putting them in there?
Daniel - Yeah, exactly. There are some defined sites where people studied what are those locations doing? And also, at the same time, those locations are also protected from events like silencing. Usually when you put something…
Chris - What’s that?
Daniel - Something somewhere in the genome it’s very likely that the cell kind of shuts it down so it doesn’t want this strange information to be there and to be read, so it has mechanisms of shutting it off. Whereas when you put in the genomic safe harbours, it’s much less likely that that happens.
Chris - How do we know these cells are safe that you make with this if you wanted to use them therapeutically because, at the end of the day, having enough stem cells or mature tissue cells that can do something has always been a problem? How do you know they’re safe?
Daniel - So you’re talking about cell therapies now?
Chris - Yes.
Daniel - There are various ways to test whether the cells are safe. Obviously, we can make them in the lab first and then have them there and do all sorts of tests on proliferation and genomic stability to really ensure that the cells would be safe to put into a patient. But, for the more immediate applications, what we can do is we produce all sorts of cell types that are hard to come by from humans like brain cells, heart cells, all those types of cells to make them in a controlled way, in large quantities, so we can use them for drug discovery or screening process within the pharmaceutical industry for example.
Chris - When you say you turn a cell into a muscle cell, how do you know it really is a muscle cell? Because it might look like one but biochemically have you checked that that’s a muscle cell and also epigenetically? Have you looked at the genes which are being turned on and off - is that to all intents and purposes now a muscle cell that you’ve made?
Daniel - What we do is after we turn on those genes, we check other genes that are unrelated to the ones we activated and whether they come up or not, and that gives us an idea of is this programme of being a muscle cell actually activated in those cells?
Chris - It’s got the genetic fingerprint of the muscles and you can be confident in what you’ve got?
Daniel - Exactly. Then you can do also obviously do epigenetic tests, but what we also did was functional tests so we actually gave them the same kind of compounds that make muscle cells contract, for example, in the body. If we add those to the dish and the cells are contracting so, essentially, functionally also they are exactly what we would expect them to be.
18:14 - Dinosaur fossil shakeup
Dinosaur fossil shakeup
with Matt Baron, University of Cambridge
If your family tree is muddled up you could end up drawing some pretty incorrect conclusions about where you came from. Now, the entire dinosaur family tree has been called into question, which could mean we’ve been making mistakes when looking at how they evolved, and where they came from. Scientists have always classified dinosaurs very neatly into two simple groups: those with bird-like hips, and those with lizard-like hips. It's been the conventional wisdom for almost 130 years, but this week, a paper published in Nature suggests that we may need a shake down and reclassification of the entire dino family tree. Georgia Mills went to look at some fossils with lead author and PhD student at Cambridge University, Matthew Baron…
Matthew - We’re currently standing in the main gallery of the Sedgwick Museum in Cambridge which is the university’s earth science and palaeontology museum.
Georgia - We’ve got quite a few dinosaurs around us, which is very exciting. So could you tell me a bit about how dinosaurs are classified at the moment?
Matthew - The traditional model that’s been around since the late 1800s was proposed by a Cambridge scientist called Sealey, and his idea was all dinosaurs were either in this one category or they were in this other category. So, on the one hand, we had what were called Ornithischians - this is the bird-hipped dinosaurs, not the birds but the bird-hipped dinosaurs and examples include triceratops, stegosaurus, and this iguanodon that we’re stood in front of.
Georgia - Let's go look at iguanodon cause this thing is towering about us. It’s standing on two legs; it’s got a massive tail; it’s got a ribcage I could comfortably get in, and then there’s a giant head.
Matthew - These guys were sort of the very large cows of the Jurassic and Cretaceous. A large family of herbivores. So they are the ornithischians. Then, on the other hand, all the other dinosaurs were lumped into another group called Saurischia, which means lizard-hipped. Their hips look more like primitive reptiles than birds. Saurischia is made up of, in the old model, theropods, which are the meat eaters.
Georgia - Like T-Rex.
Matthew - Just like T-Rex and many earlier forms, and eventually birds. The other group are the sauropodomorphs, which some people shorten to sauropods, and they are the long-necked tree browsers like diplodocus (dippy at the Natural History Museum), brontosaurus, brachiosaurus.
Georgia - So those groups, in some ways they make quite a lot of sense. There’s the bird-hipped dinosaurs and the lizard-hipped dinosaurs. But then again, you have one group which is the veggies like triceratops, stegosaurus but then you have this other group which contains all the two-legged carnivores, but then these massive four-legged diplodocus-like creatures. So you’ve looked at these groups and you thought - no! So can you tell me what you’ve done and what you’ve found?
Matthew - We started looking at as many early dinosaurs as we could and we built a long list of specimens we thought were relevant and interesting in early dinosaur evolution. We cross-examined them for a very large list of anatomical features and we built the largest ever dataset of early dinosaurs and our computer software worked out for us various ways in which they could be related, which would be the most likely given certain circumstances. And what we found was that the old groupings that have always been thought to exist were just not recovered in our analysis, so were not supported by the anatomy, by the data. Our data suggest that the meat-eating theropods are more closely related to ornithischians like triceratops than either of those groups are to the long-necked tree browsers.
Georgia - So you looking at dinosaurs, you don’t have the luxury of just popping them all in a DNA analysis. So you have to look at all of their physical traits and then pump all that into a computer which can look at the similarities and the differences and work out the most likely scenario for the family tree?
Matthew - Yeah. Essentially, we are limited by the skeleton. All we have to work on is the skeleton and features of the skeleton, so we had to look at a lot of skeletons to see what features might be useful. We tried to be as objective as possible and then we built this very large dataset where each specimen was given a score for each feature that we thought was relevant. It was about 35,000 individual data points that we had to enter by hand - I had to enter by hand and, eventually, we were able to put together this huge dataset after three years and it produced drastically different results.
Georgia - So this is challenging over 100 years of the accepted theory. I remember learning about this in my text books and in museums and things like that. So this is quite a bold reshuffle you’re proposing?
Matthew - It is, yeah. And we’re expecting some degree of backlash but that’s just how science works. We have a hypothesis; we get new data; we look at old data in new ways and we present new hypotheses; we test them and test them again. But yes, the old scheme was the fundamental fact on dinosaurs in kids books, in museums and maybe they’re all going to need a rewrite.
Georgia - Do you suspect there’s going to be quite a big debate following this paper?
Matthew - I certainly hope so, yeah. I’m looking forward to the next big conference where I have to face all of the people that may disagree with me, but such is science. We’ve put that idea out there now and this flies in the face of 130 years of thinking. Completely disagrees with some very prominent people’s PhD theses and is drastically different to anything we’ve ever thought. So yes, there’s going to be some flack.
23:53 - How sea creatures become invisible
How sea creatures become invisible
with Kate Feller, University of Cambridge
The Cambridge Science Festival is one of the UK’s largest and most successful and this year’s edition is coming to a close. To celebrate the final day, we’ve invited the winner of this year’s Cambridge regional FameLab - that’s the competition where researchers have to give a three-minute science talk - to come along for a chat. Chris Smith spoke with Kate Feller...
Kate - I am a postdoctoral researcher in the Physiology, Development and Neuroscience Department here at Cambridge and I study the eyes of Mantis Shrimp. Historically my PhD training was studying the eyes of these remarkable crustaceans and their babies. What’s so amazing about them is the adults at least can see beyond the spectrum that we can see. They can see all the colours of the rainbow plus they can see different colours of ultraviolet light, and they can see the different types of polarised light, so they just have these remarkable eyes. And they’ve got one of the fastest animal movements on the planet where they can strike their prey or something that’s bugging them with these awesome raptorial appendages, and they can do it as fast as a bullet out of a gun.
Chris - I thought that was my daughter asking me for pocket money - that’s pretty fast as well. Now, why did you decide to go for FameLab and what's FameLab for people who are not initiated?
Kate - FameLab is a science communication contest to try and encourage us researchers to, I guess, be more effective science communicators and I kind of did it on a whim. I was in the middle of my fieldwork working in Spain and I got an email and I said hey, this sounds like fun.
Chris - You must be good at it. We’re going to find out I think, aren't we? We’re going to give you three minutes to strut your stuff and tell us in three minutes what you delivered as your talk for FameLab that won you the regional final…
Kate - Alright here we go.
Chris - Off you go Kate Feller.
Kate - There is a place on the Earth where animals can make themselves disappear. It’s called “the pelagic environment.” The pelagic environment is anywhere in the ocean where there is nothing but open water. There’s nowhere to hide; it’s just the same blue/green water in almost any direction.
And just like in Star Trek, many pelagic animals have cloaking devices that help them avoid being seen in open spaces. One cloaking device is to cover your body in mirrors. Have you ever noticed how silvery some fishes are? These silver mirrors reflect all of the colours of the visible spectrum equally and, since this light is the same in almost every direction, these angled mirrors on their sides reflect light that’s in front of them and it looks exactly like the light behind them totally hiding the fish underneath.
Though these mirrors are great, obviously the best way to disappear is Harry Potter’s invisibility cloak. But, since most pelagic animals are muggles, they have to accomplish basically the same thing by having totally transparent bodies. The larvae or babies of many crustaceans such as crabs, lobster, or mantis shrimp have bodies that are so clear they look like they’re made of glass. Even though you can’t see their bodies, there’s one thing that transparent animals can’t make despair, and that’s their eyes.
In order to work properly all eyes and we're talking all eyes, including humans, need to have dark, light absorbing pigments. These dark pigments surround the individual light sensing cells and isolate them from any stray light of their neighbours. If eyes didn’t have these dark screening pigments, it would be like drilling a bunch of holes into the body of a camera. The final image would be ruined!
So, transparent animals have a problem where they want to be totally invisible so they don’t get eaten, but they also need to be able to see so they can’t really have a transparent eye. But, as my research revealed, some crustacean larvae have the solution. Covering the dark part of a mantis shrimp larval eye is a blue/green eye shine that looks just like blue/green glitter on a chocolate cupcake.
Unlike the mirrors that we see in silvery fishes that reflect all of the wavelengths of the rainbow, this eye glitter only reflects the wavelengths of light that are behind them, which is blue/green as we covered earlier. So, the reflection that this eye glitter gives off is matched to the background which aids to disguise this opaque dark eye, and overall lend the animal the ability to disappear. And with that, I’m going to disappear.
29:22 - When Rutherford split the atom
When Rutherford split the atom
with Malcolm Longair, Cambridge Cavendish Laboratory
100 years ago when our idea of what atoms were was very different. Our understanding changed radically and rapidly, thanks to a Nobel prize-winning scientist called Ernest Rutherford. His feats were so impressive that element number 104 on the periodic table, Rutherfordium, was named after him. But what did Rutherford do? To find out Ricky Nathvani went to the Cavendish Laboratory in Cambridge where Rutherford first announced his landmark breakthrough...
Malcolm - I’m Malcolm Longair. I’m the Jacksonian Professor Emeritus of Natural Philosophy. I was Head of the Cavendish Laboratory for eight years and I’ve written a history of the whole of the laboratory from its founding in 1874 until the present day.
Ricky - And, of course, today we’re here to discuss the Head of the Cavendish from 98 years ago now.
Malcolm - Yes. Rutherford came to Cambridge from Manchester in 1919 following the retirement of J.J. Thompson. Rutherford was clearly the outstanding nuclear physicist of the time. He discovered the nucleus and carried on doing brilliant experiments with very simple apparatus to establish the properties in nature of the nucleus.
Ricky - In the early twentieth century, scientists had established the existence of atoms - the tiny building blocks of the world. At the time, scientists thought that atoms were a blob of positive electric charge with negatively charged electrons stuck in it, like chocolate chips in a ball of cookie dough. The electrons, these negatively charged chocolate chips were already known about, but nothing was known about the dough.
Now if you fire a bullet through cookie dough… you’d expect the bullet to go straight through and that’s essentially what Rutherford’s team did. Instead of bullets, they fired tiny objects called alpha particles from a radioactive source into a sheet of gold foil. They could then measure these particles (these bullets), as they went into the foil and collided with gold atoms - a process called scattering. But something remarkable happened: some of these alpha particles came flying straight back the way they came…
Malcolm - This is the famous statement by Rutherford says “it was the most remarkable event of his life. It’s as if you’ve fired a large, heavy shell at a piece of tissue paper and it came back and hit you.”
Ricky - So there must have been something very small and concentrated to repel these alpha particles. This wasn’t behaving like cookie dough at all. So Rutherford’s team investigated the scatterings and built up a new picture of the atom…
Malcolm - Rather than the positive charge in atoms being all distributed in the same sort of ball, there was an extremely tiny nucleus with the atoms, only about a hundredth of the size of the atom itself which had all the positive charge.
Ricky - So atoms are mostly empty. In our new picture, the electrons orbit around this tiny positively charged nucleus. If an atom was the size of a football pitch, the nucleus, where all the positive charge and most of the mass is concentrated, would be the size of a garden pea in the middle of the pitch. The electrons would be whizzing around the stands with nothing between them and the nucleus.
But what actually was inside this nucleus? To find out Rutherford’s team bombarded nitrogen atoms in the air with those same alpha particles to investigate further and this time they found something new being emitted...
Malcolm - Rutherford carried on doing these experiments, and by 1917 he had discovered that these particles really had to be very light, fast particles coming out of the nucleus and made a suggestion that these were fast protons and that was the nuclei of hydrogen atoms.
Ricky - In other words, what Rutherford found was that there was a small charged particle ejected from the nucleus of the nitrogen atom. This particle turned out to be a fundamental building block of all atoms, known as the proton.
Now we have negative electrons and positive protons, but our atom isn’t complete because protons alone couldn’t account for the mass of the nucleus. There had to be something more hiding in there. This mystery prompted another one of Rutherford’s brilliant insights…
Malcolm - Now, in 1920, in his pencurian lecture Rutherford proposed well maybe there is a new particle, which he called the neutron, inside the nucleus. So that the nucleus consists of protons, hydrogen nuclei, and neutrons, rather than be lots and lots of protons being neutralised by electrons. So that was the suggestion he made, and he and Chadwick carried out a very large number of experiments for the next ten years. Some of them extremely wild, trying to find evidence for this particle and it didn’t turn up.
It was only in 1932 that Chadwick carried out the crucial set of experiments in a matter of three weeks which absolutely identified there was a neutral particle with high energy coming out of the nucleus.
Ricky - And so the picture of the atom fell into place. This nucleus in the middle of atoms was made up of positively charged protons and the aptly named “neutral neutrons.” Add negatively charged electrons whizzing around the nucleus and “viola,” an atom. And by adding up different amounts of these building blocks of protons and neutrons to make up a nucleus, you could make up all the different elements of the periodic table that make up the world around us.
So, from the beginning of the twentieth century without a clue what atoms were, we arrived at the picture of the atoms we still use today. And it’s no understatement to say that it was Ernest Rutherford who got us there…
Malcolm - He really is one of the greatest experimentalists of all time - if not the greatest! And the thing about Rutherford is that he would leave no stone unturned.
35:32 - How does nuclear energy work?
How does nuclear energy work?
with Paddy Regan, University of Surrey (and National Physical Laboratory)
It wasn’t long after its discovery before scientists realised that atoms lock away enormous amounts of energy, which is what holds these particles together.This enormous power was demonstrated all too plainly during World War Two with the creation of the atom bomb. Today physicists more commonly use the energy of atoms in the nuclear energy sector, which generates one sixth of all the energy in the UK; in France, three quarters of the electricity generated is nuclear in origin. But what’s the principle behind it? Paddy Regan, is from the University of Surrey and the National Physical Laboratory, and he explained to Chris Smith how we can harness energy from atoms...
Paddy - The main thing to remember, I think it was mentioned in the previous section, is that the atomic nucleus is very, very, very small. And the reason it’s very small is because the fundamental force that holds together the particles that make up that nucleus - we call it the strong nuclear force - acts over a very, very short range, and that range is something like 100 million millionth of a centimetre. So what that means is that force is very, very strong and that extra binding or strong force, if you like, the sticking glue, between the protons and neutrons in the nucleus adds a little bit of extra energy to the system.
Listeners will be familiar with the only equation that sort of matters in physics which is the famous Einstein one e=mc2, and that idea is that energy and mass are sort of two interchangeable products - two sides of the same coin. And the idea is if you’ve got a very, very tightly bound stuck together nuclear system, some of the mass is converted into what we call “binding energy.” Not very much, only about probably less than one percent of the total mass of the nuclear system is binding energy but, if we can release that and that’s what happens in nuclear fission, we can release an enormous amount of energy that’s held together and compact in there. A little bit like bursting a balloon by pricking it with a needle.
Chris - And in this instance, what’s the nuclear prick that you use to burst that nuclear balloon then?
Paddy - Well, it’s the particle that was just mentioned earlier; it’s the neutron. And it’s a very interesting particle the neutron. So it wasn’t discovered as the previous gentleman said until 1932. That was almost 30 years after the discovery of the nucleus itself. The reason it’s hard to discover or to find it is because it has no charge.
There’s another interesting thing about the neutron in that if you have a neutron on its own, a sort of lone, standalone neutron, it only survives as a neutron for about ten minutes; it naturally radioactively decays. But when it’s bound inside an atomic nucleus, it can basically live forever. So the little magic bullet that tickles the specific chemical element that we use in most nuclear reactors to cause nuclear fission, which is uranium, is processing a very, very slow bullet of this neutron material. And it’s just captured by the uranium nucleus, and that tiny capture causes the nucleus to be unstable, to wobble a little bit, and split up into two smaller fragments releasing some of that binding energy. The amount of binding energy that’s released is about a million times more per energy release than you would have in a chemical reaction like coal burning, and that’s why nuclear power is so efficient.
Chris - So we have a nuclear reactor; it has something fissionable, something capable of doing this in it, in this case: uranium. Neutrons from that uranium hit the nuclei of other uranium atoms; they destabilise the nucleus; it falls apart and in the process releases some of this energy and want more neutrons so it can then do this again.
Paddy - That’s the idea of the chain reaction.
Chris -. So why doesn’t the power station meltdown or explode?
Paddy - There’s a very precise amount of neutrons that are produced in each nuclear fission. And what you need for a sustainable chain reaction is exactly one of those neutrons that’s released to produce fission in the next generation. In order to do that you basically control the amount of neutrons that are in the reactor and that’s done by materials called “control rods.” These are special elements, special lumps of material. They’re made of things like boron, or hafnium, or cadmium, and they’re material that basically drops into the reactor core and, for want of a better word, gobbles up neutrons. Takes the neutrons away from causing fission on uranium and the amount of control rods you put in will determine how many neutrons are still available to go on and cause fission. If you put in too much control rod, you basically don’t have any nuclear fission; that happens, they steal all the neutrons.
If you take all of the control rods out, then you would have an increased amount of fission. Most reactors wouldn’t be able to make a bomb just because of the nature of the uranium fuel that’s in there.
Chris - Why does the uranium respond in this feedback loop by fissioning and breaking apart and producing neutrons, but the other chemicals that you mentioned that are used to control the numbers of neutrons; they do not?
Paddy - There is something very special about the element uranium (element 92 in the periodic table), and that is it’s the heaviest element that occurs naturally on the planet. That means it’s got the most number of protons in it for a naturally occurring element. And what causes fission is that basically the repulsion between the protons in the atomic nucleus can be rearranged to give you a release of binding energy. So if you’ve got those 92 protons that form uranium, if you can split that uranium nucleus into two lighter elements, where those 92 protons are divided into two separate types of chemicals or different chemical species, you get a big release in binding energy. And the biggest release in binding energy you’ll get is from the heaviest occurring element, and that is uranium.
Chris - Where do we get all of the uranium that we’re using in our power stations from?
Paddy - Uranium is ubiquitous over the Earth. About one atom in a million in the Earth’s crust is uranium. It’s all over the UK; it’s in every bit of the ground here. There’s plenty of deposits of it in the west coast of Ireland, around Galway for example. But most of the mining is done in big countries like Australia, some bits of Russia, Kazakhstan, and South Africa, Canada. There are big geological deposits of concentrated types of mineral rich in uranium and that’s where most of the uranium comes from that would be used in nuclear power stations.
Chris - How do we get energy out of this to turn it into electricity?
Paddy - Well it’s a very simple idea. It’s the same way that all power stations work basically. It translates the energy that’s released off these atomic nuclei as they’re exploding, if you like, and it just turns that into heat, and it turns that into heat by interacting by slowing them down in so-called fuel rods. Heats up metal and that metal is then used to either heat up and boil water, or as in the earlier type British reactor, to heat up carbon dioxide and subsequently boil water. Boiling water turns to steam; steam turns turbines and you produce electricity in the way that any other power station would do.
Children of starlight
with Professor Marialuisa Aliotta, Edinburgh University.
Pushing atoms together and fusing them, is an ancient process that has gone on for billions of years. In fact, it’s what keeps stars, like our sun, burning. And this is where the atoms that we’re made of came from… Georgia Mills has been finding out how…
Georgia - There are plenty of elements that build our world. You and I are mainly hydrogen, oxygen and carbon. But where did these elements that make us, along with our entire world come from? And what makes an atom of silicon different from an atom of silver?
Marialuisa - A chemical element is defined by the number of protons it contains in its nucleus. So every time you increase the number of protons by one unit you are producing a new element.
Georgia - So hydrogen has one proton, helium has two, lithium has three, and so on. This is Marialuisa Aliotta; she’s an experimental nuclear astrophysicist from Edinburgh University and she’s here to explain how to build the universe…
Marialuisa - The first particles were created in the big bang so originally there were, essentially, protons, neutron, electrons, and there was a lot of gamma rays (high energy photons). Then, eventually, gravity starts kicking meaning that all of these particles and kinds of gas and dust starts contracting, and gradually you keep increasing the temperature of these gas clouds until, eventually, it is possible to reach temperatures that are so high that nuclear fusion can start. This is when we say that a star is born.
Georgia - Stars like our Sun are mostly made up of this basic atom hydrogen, which only has one proton. But stars can convert hydrogen into larger atoms through this process called nuclear fusion…
Marialuisa - These protons, which are nuclei of hydrogen, they kind of scatter off each other because you have to imagine this gas has a certain temperature and so all these particles are moving around, so they have thermal energy as we call it. And so they collide with one another and most of the time nothing really happens. This is like colliding billiard balls; they scatter off each other and nothing much happens. But, occasionally, some of these collisions may lead to the formation of a heavier particle and in doing so some energy is liberated. So this is the fusion process that occurs.
Georgia - So thinking about this snooker table analogy: if you’re playing snooker that balls are going to bounce off each other because of their tough outer shells. But, if for some misguided reason you were to play snooker in the core of the Sun, there is so much energy there that every now and then these turbo-charged snooker balls would smash into each other and stick together. This means you can make a heavier atom, like helium, from hydrogen…
Marialuisa - This is what powers our Sun. The sun has converted the hydrogen into helium for the last five billion years and will continue to do so for another five billion years.
Georgia - This process also releases energy which we eventually see as starlight or sunlight. But what happens next?
Marialuisa - After hydrogen has been converted into helium in the core of the star, the star has, eventually, no longer a source of energy that can sustain the gravity of the outer layers and so the star starts contracting. As it contracts it heats up and then eventually a new phase of nuclear burning can begin. That’s then the next stage which is called helium burning, when helium particles can fuse together to form, for example, carbon. Carbon can also interact with another helium nucleus and form oxygen and so this is how heavier elements are then produced.
Georgia - These heavier elements can only be fused in a much hotter star, as the more protons in an atom, the more energy you need smash through that tough snooker ball exterior and, after a certain point, nuclear fusion just can’t cut it anymore…
Marialuisa - Iron is the last element that can be created through fusion of charged particles. Once iron has been created it’s no longer possible to obtain energy by fusing together two hydrogen nuclei. And yet, elements heavier than iron we know they exist so the process that occurs then is a capture of neutrons on pre-existing heavy elements up to iron that then form heavier species. This is how elements heavier than iron have been created through processes of neutron captures.
Georgia - So imagine our snooker ball atoms. The biggest ones can’t stick with any more protons, they just bounce off their tough snooker ball shells but they can stick to something else - golf balls a.k.a. neutrons. And if they stick to enough neutrons they start to become unstable and then one of these neutrons actually turns into a proton, therefore building a heavier element. This process can happen during a star’s violent death throes, a supernova explosion, so all these different elements get thrown out across the universe and, eventually, find themselves in you and me…
Marialuisa - When I was a child there was a song by an Italian singer Alan Sorrenti, and the literal translation of the title of the song was “We are all children of stars.” I remember thinking this is so silly - what have we got to do with stars? But, in fact, I realise now how very accurate that picture was, Yes we are indeed, stardust!
49:54 - Building new, heavy elements
Building new, heavy elements
with Rodi Herzberg, University of Liverpool
As well as the naturally occurring elements, scientists can also make “artificial” atoms that wouldn’t exist normally. And this is how, last year, we were able to add a further four new elements, known as “super-heavy” elements, to the periodic table. They’re the biggest atoms known to exist. Chris Smith was joined by Rodi Herzberg, a Professor of Super-heavy Nuclei at the University of Liverpool to discuss how to make these atoms in the first place.
Rodi - What you do in order to get to these very heavy elements, the neutron capture mechanism that Marialuisa just described no longer works up to that heavy mass. So you start out by two lighter nuclei and you start to fuse them together. So you throw them together as often as you can and you hope that, eventually, two of them will manage to fuse together and form one of these superheavy elements.
Chris - So you basically give them a huge amount of energy and hope that they collide hard enough that it will squeeze the two different nuclei together and you get the sum total of the two nuclei - the cores of both those two individual atoms adding together?
Rodi - Indeed. Yet this is a very delicate process because, if you give it just a little bit too much energy, then they become so unstable that they will immediately split apart again, so it has to be very, very finely balanced.
Chris - How many atoms of these new elements have actually been made?
Rodi - Let me take one of them - element 113 (nihonium). Of that element three atoms have been made by the Japanese group. Don’t laugh! Not only that but it took them about nine years to produce the third one.
Chris - Goodness. How do you actually detect when you’ve made a new atom of nihonium, for example?
Rodi - It’s a bit gruesome because you detect them by watching them die. The alpha decay that has been discussed previously, is a very characteristic way for the nucleus to die to decay to a different one. If you measure those decays, then you can get a very characteristic sequence of alpha decays that you don’t know. And finally, the same nucleus ends up in a couple of alpha decays that you do know and those give you then an anchor point, each of a particle is two protons and two neutrons, so you can do the math and work back upwards to what you originally must have had.
Chris - So by watching really carefully you’re measuring these radioactive decays and you’re seeing the particles coming off. So you know something is decaying and if you add up all those things, and you work out what you end up with, you can add them all back together to work out what you must have started with, and then you know you’ve discovered a new element potentially?
Rodi - Indeed.
Chris - But if they're so unstable that they only hang around long enough to fall apart in a fraction of a second, and three atoms have been made in nine years, why are we bothering to make these things?
Rodi - Because just the fact that you can make them teaches us an awful lot about nuclei. There are many, many places where you cannot do experiments so you need to have a very good understanding of what the binding forces inside a nucleus, inside a very complicated system like a nucleus are, and the best way to test this is if you go to very extreme systems.
Just because three atoms of this configuration of protons and neutrons actually were living long enough that we could detect them and do some physics with them, that means that our theoretical models have to be able to get that right and that’s the big challenge. If they can do that right, then they can also understand how the elements are made in stars. How the nuclear waste that we may want to incinerate can proceed. All of that comes indirectly from these.
Chris - Could we also use them as stepping stones? Even though they may be individually short is it possible that you could leapfrog off one of them if you quickly add something else to it and make an even bigger element, you make something where the nucleus is stable and it won’t immediately fall apart, and then you’ve got some exciting new chemical you can do something really, really impressive with?
Rodi - I think you can already do some impressive chemistry with some of them. For example, thaumium or with einsteinium people had little microscopic vile of einsteinium in their hand that they could do experiments with. It’s a question of quantity and if you increase your capability to create more, better beams, better targets, then you can make more.
54:51 - What's the most efficient way to climb stairs?
What's the most efficient way to climb stairs?
Ricky Nathvani put his best foot forward to answer James' question, enlisting the help from Dr Dan Gordon, a physiologist and athlete himself from Anglia Ruskin University…
Dan - If we take a standard flight of stairs, they have a typical height of about 18 cms and the depth is also about 18 cms. Additionally, we have an additional cost associated with the lengthening and the shortening of the muscle. So, if we’re going to look at this, we’re going to have to make three assumptions:
The first one is that using every step would have a quicker step rate than taking two steps at a time.
The second assumption is that taking two steps at a time would be associated with a greater height and length displacement per step than one step at a time.
The third assumption is that the stepping rate does not change over time.
Ricky - That makes sense. Two at a time is slower, but it involves greater amounts of work to get up the extra height and length. So which one is more efficient? Throw some numbers at me, Dan…
Dan - We can estimate that for a standard flight of stairs that one step at a time would be associated with an oxygen cost per step of 0.1 mls per kilogramme per minute, compared to 1.1 mls per kilogramme per minute per step when taking two at a time.
So, taking two steps at a time would cost more energy and work your heart harder despite lower muscle actions. The reason being these actions have to be more forceful to overcome the increased height.
Ricky - So, two at a time wins for the workout unless, like me, you want to be as lazy as possible, in which case stick to one by one. But which method is better for James if he wants to build either muscle strength or cardiovascular fitness?
Dan - Well, this is a bit hard to answer. We’ve previously assumed that the stepping rate is constant. However this may not be the case because, as we know, the body temperature starts to rise, energy stores will start to deplete over time. Given that there is an energy cost using two steps at a time, we can right assume that this will induce fatigue sooner compared to one step at a time.
Also, given that when taking two a time you are stepping more slowly but using a greater force, and knowing that using high force at low speed is better for building strength, we could apportion two steps at a time being more strength orientated.
To develop cardiovascular fitness, however, we need to maintain the exercise for a prolonged period of time without getting too tired, which seems to fit the one step at a time approach.
Ricky - There you go, James. One at a time is better for cardio but two by two builds strength better. Thanks Dan for your help with that one.
Next time we’ll be sounding out this question from George:
When watching a film or documentary, a falling bomb or a missile always has a descending sound or a whistle. Why is this? Does it mean that if the missile fell down a bottomless hole the sound would go subsonic?