Dan Snow's History Hit - Atoms and X-rays: Experiments That Changed History

Episode Date: September 5, 2022

For millennia, people have obsessed over questions about the nature of matter in our universe. Then, by the turn of the twentieth century, we believed we had answered everything. Our understanding of matter was finally complete. But an unprecedented outburst of scientific discovery was about to change the course of history...Dr Suzie Sheehy is an accelerator physicist, academic and science communicator. Suzie joins Dan to introduce us to the people who staged ground-breaking experiments— from the serendipitous discovery of X-rays in a German lab to the race to split open the atomic nucleus, Suzie reminds us of the thrilling discoveries that have shaped our lives.This episode was produced by Hannah Ward, the audio editor was Dougal Patmore.If you'd like to learn more, we have hundreds of history documentaries, ad-free podcasts and audiobooks at History Hit - subscribe to History Hit today!To download the History Hit app please go to the Android or Apple store.

Hey everyone, welcome to Dan Snow's History. I'm talking physics today. I love a bit of physics. Dr Susie Sheehy is a physicist, she's an academic, she's a science communicator, she's a research fellow at Oxford University and she's also a senior lecturer at the University of Melbourne. What a lovely life, split between Australia and the UK. And she's written a book about 12 experiments that shaped our world. We're going to talk about x-rays, we're going to talk about atoms, we're going to talk about just, this is the world. We're living in the world that physicists built, folks.

It's probably worth finding out a little bit about those physicists, how they did what they did and what they were thinking. You'll have heard me talk about this before on the podcast, but the older I get and the more technology,

engineering, science kind of makes itself so obvious in our daily lives, the more I'm fascinated by the history of science. I think in 500 years time, we're going to be talking about Rutherford, we're going to be talking about Einstein, we're going to be talking about Bohr, we're going to be talking about Newton, probably more than about Hitler, Churchill and Lincoln. Maybe, we'll see. The good news is,

I won't be around for you to prove me wrong in 500 years time. So this is Susie and I chatting about some of the big breakthroughs in physics and why they matter. Enjoy. Susie, thank you very much for coming on the podcast. Thank you. Thanks for having me. I always get super excited when scientists write great history books because that's like a superhero mashup. It's terrifying. I love it. That's quite a compliment. I am a scientist, not a historian. Well, you've written a great book of history here. First of all, why? Why,

as a physicist, were you impelled to suddenly write this history? I mean, surely there's quite a lot of other stuff to be getting on with, isn't there? First of all, I've always been interested about the stories of people in my field. And I think I came to a realization a few years ago that I didn't know the actual human stories all that well. In my field in physics, we have these stories, we tell each other about how our amazing research into the fundamental nature of the universe has led to all this societal change. And I thought, well, who did that? How did they do it? How did it create that change? I sort of knew the end story.

I knew where we're at now. But I think I had this very simplified view of how that's actually happened over time. So on the bigger picture, who cares what Rutherford and Einstein were like? If E equals mc squared or momentum is mass time velocity, isn't that the point of physics that those exist? Or are you saying that by looking into how the present was created,

if these people have been different, would we be living in a different present? That's a really good question. That's really interesting. And I think a lot of people take the view that especially a subject like physics, where you're looking for sort of fundamental laws that underpin our universe, and that is a very hard thing to do and obviously it's very impressive when we come out with them and they work and they are predictive first of all that's a very difficult process but I think people perhaps mistakenly think that that's the entire point of the subject to me it's not and I think a lot of other physicists would agree with this that understanding the process of how we learn these things and the people and, you know, the approaches that we take, which nowadays require collaborations of thousands of people across many different countries, understanding the process of how we do that is almost as important as the end result.

end result. In some senses, because we are curious as people and because we want to understand how the world works on this fundamental level, and because we create the environments and the teams and the support networks through the process of doing science, I think we would be able to do this anyway, regardless of the individuals. And I think that's what makes it interesting to see the stories of the individuals and the teams, but also to put them in the context of their time that they were living in and what their daily lives were like and the struggles that they had and try and draw out of that a bigger picture story and some lessons for us, perhaps for the future, about, well, what is it that creates the right environment for people to make big breakthroughs? And then what is it that makes the right environment or the right impetus for those breakthroughs to be turned into life-saving technologies for example

i think those last two questions are so essential in physics in the history of physics but of course the history of kind of everything really and yeah you look at that generation i look at those pictures is it the solvay conferences when all the world's greatest physicists got together and it's it's electric I mean sorry pun in half intended like electrifying when you see these people all sitting around the table you think what happened in that generation like how did it go so bonkers how does that generation and that's we live in the world that they built right so let's go back actually to that sort of time 1900 1910 tell me what life was like when people alive today their parents would have been born at that time. Like what did the world look like? Around that time, there were no cars. Even at the

start of the 1920s, most homes didn't have electricity, probably only 20, 30%. Life was much simpler then. There was a lot more poverty. There was a lot less education. Rights for women were a lot less than they are now. life would have been much more of a daily struggle than it is now. The conveniences that we have, the fact that when we get sick, we can go to a hospital and there's high-tech equipment and gadgets and people with training to help us recover. The average life expectancy was something like 50 years, depending on which decade you take. So there's been a dramatic transformation in our daily lives between the start of this story and the end of it.

You identify key moments in the transformation of that world into this one where you and I think nothing of the fact that we're talking on supercomputers a couple of generations ago. We're talking on different paces in the world to each other with no lag. Just this is the most normal thing ever. This would have been miraculous to anyone who with no lag. This is the most normal thing ever. This would have been miraculous to anyone who's ever lived. Frankly, it would have been miraculous when I was growing up. So what are the big landmarks? What are the big mileposts? Is it going back to X-rays?

Or where do you want to start? So my story, the story of modern physics, effectively, begins really at that turn from the 19th into the 20th century in about 1896. at that turn from the 19th into the 20th century in about 1896. And really, at that point in time, people thought that physics as a subject was kind of done, right? We had this very deterministic view of the universe in the sense that everything was made of atoms. We'd sort of known that for a long time. And so there was this idea that if you took the different types of atoms and you pieced them together, you could create just about anything around you. So I'm looking in front of me, I'm like, okay, I've got a soft case of my charger, there's something soft, there's something hard, there's something light, something heavy, all of these materials could be created with different types of atoms. And then the other

piece to that, or what we understood from physics from things like the forces of gravity and electromagnetism, which had been teased out by then, was that if you knew the properties of these particles and you set them in motion, then you could predict their motion for all of time exactly. So pretty much, if you think the universe works that way, why would you be interested in learning more about it effectively? A lot of people are just like, okay, physics is done. Let's look at other things.

We understand the world in terms of physics now. That's the worst take in the history of the world right 1890 i think we i think we can close the book on physics i think we're done here guys yeah i love that it's a terrible take if you ever hear any scientists say that they're probably vastly more wrong even than you think they are yeah it's a terrible thing to say and so what happened at that point in time was that there was a number of phenomenon that couldn't be explained, obviously, by their existing theories. And by investigating these phenomena, one of which was called a cathode ray tube, this glass tube with an electrode in one end, and it would create these sort of glowing so-called rays called the cathode rays. And they were used sort of for scientific entertainment, as it were.

Nobody actually understood how they worked. And this experiment and a number of other experiments slowly but surely broke apart this idea that physics was this very predictable, done subject, and actually completely exploded our understanding of how the universe works and created a whole new type of physics, which we now call modern physics, which includes things like quantum mechanics and our understanding of the nucleus and the atom and radioactivity and all these things. So that was the other thing. They didn't even know about radioactivity. So they assumed that everything was static for all of time,

which is another mind-blowing concept to me, having grown up in my career always understanding that atoms can change. It's actually almost hard to put myself in the mentality of someone who thinks that atoms are stable for all of time. It's a very different way of thinking. So a few curious people were like, I'm going to get to the bottom of what this cathode ray tube thing is and how it works. And one of those people was William Röntgen, working in Germany in Würzburg. And in 1896, he had one of these cathode ray tubes, as did hundreds of other scientists around the world. And he decided to investigate it a little.

And he was using the tube when he noticed out of the corner of his eye, this screen that he'd had over the other side of the lab, glowing green. And it was a zinc sulfide screen, I think. At least it's one of the screens where if something hits it that has enough energy, it creates this sort of green glowing light. And he thought, oh, that's odd. He turned the cathode ray tube off and the glow went away. And then he turned it back on and it came back. And he could have ignored this, right? He could have just been like, oh, you know, it's just some reflection of the glowing light in the tube. or he might have ignored it, but he was curious enough to follow it up. So he embarked on a series of experiments for seven weeks, very intensive

experiments, where he didn't tell anyone what he was working on. His wife just sort of brought him food and he must have just sort of pushed her out the room again to get back to work. And he was working in this beautiful wood-panelled lab that you can actually go and visit in Würzburg. And so he tried, for example, putting things between the cathode ray tube and the screen. He sent it through the door to the second half of his lab and it got through the door. And then he started putting things like rubber and metal in the way of the rays. He started to realise that something was coming from the cathode ray tube that was fundamentally different from whatever was happening inside of it.

And eventually he realised that the rays didn't seem to pass through dense materials like they did light ones. So it wouldn't pass through lead, but it would pass through, say, wood. And so he, as all scientists are wont to do, he held his hand between the tube and the screen and he could see his bones inside his hand. Can you imagine? Nobody has ever seen that before, right?

Without cutting open the human body. And here he is, he's created these rays and he's put his hand in front of them and he can see on the screen the shadow of the bones inside his hand. So to make the point, he grabbed his wife, Bertha, her name was, he asked her to put her hand in front while he put a photographic plate behind.

And he exposed her hand to the X-rays and created the first X-ray image of her hand. And you can see her wedding ring, this big metal ring, as well as the bones inside her hand. Something I hadn't thought about before is where the name X-rays came from. And it's pretty simple, actually, because in science, in our equations, we tend to denote an unknown thing with the letter X. And so what Roentgen almost certainly did was just like, well, this is a new type of ray. It's not an alpha ray or a beta ray or a gamma ray. I'm going to call it an X-ray. It would have just been literally plucking it out of thin air because he had to give it a name. And X is the letter that we usually use. So he came up with this method of

using this new phenomenon to create these images. And then he had to make a decision what to do with it. And eventually he sort of opened it up to the medical community. He never patented it. He gave it away to them. He never made any money from his discovery. And that was the very beginning of using x-rays in our society. You know what I love about the history of physics is I'm such an idiot. I'm like, I just wish I'd lived back when like Anax Amanda was working in Miletus in ancient Greece or in Boyle or Newton, because I could have done that. I could have like put bits of rubber in it. That was low hanging fruit. And then you realize, of course, that's what future scientists will say about you and our work. And that's what's so joyful. Like, had I lived at the time, of course, I would not have been intelligent and brilliant enough to do that but it all seems

so wonderfully obvious when you look back on it now it does and it was actually pretty hard to put yourself in the mindset of someone doing that for the first time I'll bet yeah something that did teach me to appreciate actually some of the difficulty of doing it though was so for example if I build an experiment nowadays I I'm an experimental physicist, most of my experiments that involve things like vacuums and gases and whatever are in stainless steel vacuum containers. I work with engineers, we do 3D drawings, we have specialised machinery that mills and builds things and then you bolt it all together and we know it's going to work. But back in the early 1900s, to make an experiment like this, you actually had to blow it out of glass. You actually had to create the apparatus

yourself, usually out of glass. So most physicists back then also had to be sort of amateur glass blowers and they had to learn glass blowing as part of their training. And then if it got really tricky, then they'd have to get the specialist glass blower in their laboratory to make it. And it was an incredibly delicate process. And more often than not, something would break or you'd be midway through an experiment and a piece of it would fall off and you'd have to re-blow the glass to create it. Learning that, and actually I went to see a scientific glassblower in action and spoke to him about it. And that really gave me an appreciation for, oh, you know, there were

all these specialized skills that they would have had. You know, there were no calculators, there were no computers. Every calculation was done by hand. Even plotting the plots and communicating their work to others would have taken, you know, handwritten letters or sending it to some specialist just to communicate with others about what they were finding. So it's like what we're spending our time doing and the difficulties have changed but i think the fundamental idea of sitting there and planning out how to investigate the universe in a hands-on way i think that hasn't changed so much other than the scale on which we do that but you know the herschel siblings the big thing for them was getting those goddamn mirrors for their telescope was like unbelievably

grinding yeah it was like unbelievably... The grinding. Yeah, it was like insane. But good on them. You're listening to Darren Snow's History. We talk about the history of physics. Very clever stuff. More coming up. Aeroplanes, spacesuits, condoms, coffee, plastic surgery, warships.

Over on the patented podcast by History Hit, we bring you the fascinating stories of history's most impactful inventions and the people who claim these ideas as their own. We uncover exceptional stories behind everyday objects. We managed to put two men on the moon before we put wheels on suitcases. Unpack invention myths. So the prince's widow immediately becomes certain. Thomas Edison stole her husband's invention and her husband disappeared around the same time. Can only have been eliminated by Thomas Edison, who at the time is arguably the most famous person in the West.

And look backwards to understand technologies that are still in progress. You know, when people turn around to me and say, oh, why would you want to live forever? Life's rubbish. I just think that's a bit sad. I think it's a worthwhile thing to do. And the thing that really makes it worthwhile is the fact that you could make it go on forever. So subscribe to Patented from History Hit on Apple, Spotify,

or wherever you get your podcasts to catch new episodes every Wednesday and Sunday. research from the greatest millennium in human history. We're talking Vikings, Normans, Kings and Popes, who were rarely the best of friends, murder, rebellions, and crusades. Find out who we really were by subscribing to Gone Medieval from History Hit, wherever you get your podcasts. okay so let's go from x-rays i guess to atoms and then atomic weapons what we're talking 1920s and well 30s and 40s this is obviously a big one i guess right right so i'll separate those out a little actually but let's take it back a step before we get to these sort of things with really highly negative and emotional implications. Because prior to that, first of all, we didn't understand prior to Rutherford's experiments, what was inside the

atom and what the structure of it was, what we call the gold foil experiment, this classic experiment, where they pinged these alpha particles off to discover this very dense nucleus at the core. Now, of course, once you discover there's a tiny nucleus at the core of the atom and of all atoms, of course, then your curiosity leads you to say, well, what is that nucleus composed of? And there was a fundamental mystery about it because they knew it was positively electrically charged. But when things are positively electrically charged, they're going to push each other apart. So it wasn't clear how, if there was more than one proton in the nucleus, how it was held together. So it was immediately obvious that there must be some force in the center of the atom holding together the protons. And then even then,

when they studied it further, the masses didn't add up. They were like, well, there must be more particles in the nucleus than just the protons, but they don't appear to have an electric charge. So what are they? And they gave them the name neutrons. And it took until 1932, actually, for someone to find neutrons, even though they'd been predicted for many, many years. And that person was James Chadwick, who was working with Ernest Rutherford. who was working with Ernest Rutherford. So it was inevitable that people would learn to understand the nucleus of the atom. And that's a very, very good thing in terms of what came from that, both in our understanding, but also the incredible tools it's given us in society. So through the early 1900s, Ernest Rutherford and his team, including his first graduate student, who was a female physicist called Harriet Brooks, and a chemist named Frederick Soddy, who was originally from the UK and went out to Montreal. They were working together. And through that research came the discovery that atoms could decay, could transmute from one type to another, which of course had been a dream since the time

of the alchemists, as it were, to transmute one type of atom or one type of element into another and it turned out nature had been doing it for free all along so then understanding the different decay rates of different atoms and why they were stable or unstable and what the nucleus had to do with that was a whole series of questions and investigations which led to the field of nuclear physics. But out of that, one of the things that Rutherford actually developed quite early on in that process was this idea that if different atoms have different rates of decay, so different half-lives, if you took, say, a rock, you could compare the amount of one material, of one atom in it, to the amount of another atom or of one atom in it, to the amount of another

atom or element. And using those relative quantities, it would tell you, if you knew what the quantity had been when it was created or these elements were created equally in the rock, it would tell you how old the rock was by comparing the relative quantities at some point in time. So he was able, in his lab, to sort of go in and measure the properties of this and then start to take unknown objects like rocks. And a famous example with him is this rock called pitchblende. And he was able to tell for the first time, for example, that the earth must be far, far older than they'd previously supposed it. There's this famous anecdote that Rutherford came across the

geology professor, Frank Dawson Adams, on campus in Montreal at some point and he goes Adams what's the age of the earth and Adams says oh you know based on this method and that rock stratification and blah blah blah it's probably about a hundred million years old and Rutherford thrust his hand in his pocket and he brings out this black rock this piece of pitchblende and he shoves it in Adams's face and he says, I know beyond a doubt that this rock is more than 700 million years old. And he walks away, leaving the guy shocked. So exciting though. So exciting. It's so exciting. I mean, that's classic Rutherford though. He was very dramatic. But of course, then he had to convince the scientific community that this method provided a way of estimating the age of the Earth. And so radiometric dating now,

and just dating using methods from radioactive decay, including carbon dating, for example, they are absolute gold standard measurements that we use in lots of different fields of history, geology, archaeology, things like this, to give not just a relative dating, so from a stratification or from comparing objects in a local area, but you can compare the developments over time of geology, history, etc. anywhere on the planet. And in fact, if we could get objects from other planets, we could compare those too. And that is an incredibly powerful tool because these same laws apply everywhere. There's a joke somewhere here about how physics

has transformed dating from Rutherford to Tinder, but I'm not there. I'm workshopping it. What's the next big breakthrough you want to talk about after that? So we had the structure of the atom. All of those early experiments were really using natural radioactive sources, right? So radium, thorium, things like this, which you can basically dig up because they're in the earth, radioactivity is natural. And it really became really limiting in the scientists' experiments because they had very few particles coming from these radioactive sources with which to do anything systematic in the lab. And they realised that to really understand the structure of the nucleus and understand further the different forces in nature, that they would have to change the approach that they were making. And that's where they came up

with for the first time the type of technology that I work on, which is particle accelerators. So taking particles from inside the atom, subatomic particles, pushing them up to a really high speed as a projectile, and then using them to smash into something. And more or less the history of particle physics that's covered in the book after this point is almost synonymous with the history of developing techniques and technologies both to understand and control the behavior of tiny charged particles that we can't see. Even though I work on it and I design them every day, it is still phenomenal to me that we are able to understand electromagnetism and the physical creation of apparatus and the theory, of course, to such an extent that we can

control these things. And this isn't just sort of blue sky thinking. There's extremely practical applications that came out of all of this. One of the key ones is radiotherapy. That's a key form of cancer treatment used in about 40% of all successfully treated cancer cases. And that itself uses a little particle accelerator. What? Yeah. So it's about a metre long little electron particle accelerator. The electrons then hit a target and generate x-rays so coming back to x-rays again and then we use those x-rays in a

very well collimated and defined sense to deliver radiation dose inside the body to kill cancer cells without ever having to make a single incision to the skin i mean that's mind-blowing so when you are a historian or you love history, you walk around the streets and you look at things that have been shaped by our history. You look at place names or building styles or areas which have clearly seen Victorian industrialisation. And then it's like having a little secret key and it's fun. It's like putting little AR goggles on and you see things that maybe other people don't see. I'm sure the same is true for people who know about the natural world and bird life whatever is that what it's like physics do you just walk around the streets going there you go

everybody using your smartphone or that neon sign over there outside that hairdressers you're always monitoring your surroundings for that sometimes it strikes me like that I remember a distinct moment where I realized that I might think about the world a little bit differently from other people. I was sitting on a plane, on a flight, and you know how they give you wine in these little plastic cups sometimes? I'm familiar with that, yeah. I imagine. And I was sitting there watching the way that the light, which was streaming through the window, was bouncing around the wine in the bottom of my cup. And I'd just been to a conference where a colleague of mine

was talking about a particular mathematical thing called caustics. It doesn't matter so much what they are, but I looked at this cup and she'd been talking about this effect in beams of charged particles. And I'm watching the wine in my cup and I'm like, wait, that's what she was talking about. It's the same physical phenomenon happening here from the light from the window in my cup. And I'm just like sitting there looking at my cup and moving it around. I must have looked like such a weirdo, honestly. Yes, sometimes my physics brain does take over and I'm just fascinated at little things. But just seeing out in the world, you know, it's one of those things that I realized as humans, and it is one of our incredible skills is that we're incredibly

adaptable, right? We absorb new technologies, we absorb changes in our lives. The fact that now we do everything by Zoom, well, that wasn't normal a couple of years ago. Now it's absolutely normal to be able to do this. When I was at school, even, we didn't use email and I used the library. We didn't have Wikipedia. You know, we adapt so quickly to technological change, actually. But the flip side of that is that we forget where our technology comes from or where the basic ideas and knowledge and inventions happened. I think a lot of people probably walk around and they don't think, thank goodness for CERN, because otherwise we wouldn't have the World Wide Web.

People just don't think like that. They're just like, right, we've got the World Wide Web. Now what? We don't look back in time and go, oh, if we didn't have these people doing fundamental research into semiconductors and electronics, we wouldn't have the modern iPhone, something like that. But I think it's incredibly important that we can link those stories together and that we can see this parallel story, an interwoven story between things like our curiosity-driven research

into the fundamental nature of the universe and the technologies that have changed our lives in such dramatic ways. Because we're doing really difficult work at the edge of what is known, scientists and especially people working in sort of big scientific collaborations and really fundamental research, they just have a different way of thinking. And I truly believe, and I think the history tells us, that that does change the world. And we do need to value that more. Let the scientists do their thing. For God's sakes. Thank you very much, Susie. That was such a fascinating gallop through a century of physics and a century more. What's the book called?

So the book is called The Matter of Everything, 12 Experiments That Changed Our World. Thank you very much indeed. Good luck with it. Thank you. Thank you so much. I feel the hand of history upon our shoulders. All this tradition of ours, our school history, our songs,

this part of the history of our country, all were gone.