Do atoms never touch?

Jane: This is But Why: A Podcast for Curious Kids, from Vermont Public. I'm Jane Lindholm. On this show, we take questions from kids just like you and we find answers. Sometimes, you send us questions about really big things, like how big is the sky, or what's the largest animal that's ever lived? But today, we're going in the opposite direction with some questions you've sent us about things that are really, really small. Nope, even smaller than what you're probably thinking right now. Go even smaller. Even smaller! The things we're talking about today are too small to see, even with a microscope, but every living and non-living thing on earth is made up of them. We're going to learn about atoms, and the guest who's going to tell us about atoms is a guy named Ben Still. Ben Still: I am a teacher, a scientist and author. I teach high school physics, but I am still, at heart, a particle physicist, and I very much enjoy talking about physics and science in general to anyone that will listen to me. Jane: Ben is the author of a book called "Particle Physics Brick by Brick," and another one called "The Secret Life of the Periodic Table." His latest book, "How the Universe Works," will be released in September. Atoms are the building blocks of the universe. All matter is made of atoms. And while some of you might be hearing about atoms for the first time right now, we've actually already gotten a lot of questions about them. Noah: My name's Noah, and I'm five years old, and I'm from Louisville, Kentucky. Why is everything on earth made out of atoms? Ben Still: I'm gonna, first of all, go to the the word "why." And it's very difficult, when you're a physicist, to be able to answer "why" questions. Because as a physicist and a scientist, your job is to construct models, using the language of mathematics, to be able to describe the universe and the experiments that you see, and then make predictions about other aspects of the universe and then test whether those are actually the way in which nature behaves. So why everything is made of atoms isn't really a question that I would say science is able to answer, because, essentially, we just find ourselves in a universe with atoms, being made of atoms ourselves. And essentially, we are just seeking an understanding of nature. And through the understanding of nature, we build a model. And as part of that model, we have built the idea that there are these subdivisions of things in our universe and an atom is one of those subdivisions. So if you cut something apart, eventually, you'll get down to these atoms. And the atoms are kind of the individual units of molecules and materials that exist around us. Jane: Atoms are the individual units of all the things that make us people. And the things--or elements--that make a chair, a chair or a car, a car or a tree, a tree. When we think of what humans are made of, we think about things like skin and bones and hair and, yes, water. But if we get to the smallest fundamental elements of what makes us humans, we're made out of atoms of oxygen, carbon, hydrogen, nitrogen, calcium and phosphorus (and a few other trace elements). So if physicists don't ask why, we can still ask things like, "How do we know that?" Or, "What makes us think that everything is made out of atoms?" Or even, "How do atoms work?" Ben said, atoms are the building blocks of all the molecules and materials around us. But if everything is made up of atoms, how can all the objects and living things on Earth be so different? Ben Still: We can distinguish between different types of atom because they have different properties. But I think you're right, there's no way of distinguishing, say, one atom of carbon from another atom of carbon. And in fact, they're entirely interchangeable between the wood in the chair that I'm sitting on and the carbon in the molecules in my body. They're totally interchangeable. And and in a real sense, there's no way of identifying one as being a part of me and only a part of me. Because there's no way of kind of, if you like, stamping an identity on those atoms. That, I guess, is good in a way, because that means that obviously we can take in carbon atoms and we can use those to construct and build our bodies and grow. But also it means that there's no real kind of uniqueness to necessarily the atoms that make you up or me up, or the chair or the ground that we're sitting on, apart from the fact that there are different types of atom with different properties, and that leads to, in certain configurations, very special things like human body. Ari: My name is Ari. My age is six. I live in Seattle. My question is, why are atoms so small? Jane: Ari is asking another "why" question. But Ari wants to know, why are atoms so small? Maybe we just have to take the "why" off every question today. Ben Still: Yeah. I mean, yeah, atoms just are small. I guess it's always going to be the case that, you know, being such complex organisms as we are, it requires a lot of complexity to be built up from what is otherwise a rather simple building set, right? There's only 118 elements that we've discovered so far on the Periodic Table of Elements, and we're only made of a tiny subset of those particular types of elements and those particular types of atoms. And so with, with a limited kind of building set, if you want to create something complex, it's going to require each of those building blocks to be really small. I mean, if you think of... So, I'm a massive LEGO fan, and I've used LEGO in some of my books. And if you think of wanting to create a really complex LEGO model, then essentially you go to the small LEGO bricks, and you have to have lots and lots of them to build up a rather complex thing. And if you think about how complex life is and how complex humans are, it just means that those building blocks have to be so much smaller than we are for that level of complexity to exist. Jane: Ben mentioned the Periodic Table of Elements. When we talk about atoms, they fit into different types, depending on how many protons, neutrons and electrons they have inside them. Elements are specific and unique types of matter, and they can't be broken down into even smaller, unique parts by any natural processes or chemical reactions. So there are 118 elements that humans have identified, and we put them in a chart called the periodic table. So when we think about atoms, we're usually thinking about different kinds of atoms that are the different elements in the periodic table. Let's get to those things I mentioned that are inside of atoms. Luvina: My name is Luvina. I'm nine years old, and I live in Austin, Texas, and I want to know what atoms are made of. Hamish: My name is Hamish. I live in Christchurch, New Zealand, and I am eight years old. Are atoms made of anything? And if so, what are they? Ben Still: Well, for a long time, scientists, certainly in the Western world, thought that atoms were the smallest things that our universe was made from, and everything around us was made from these indivisible kind of small spheres, small balls. And actually, the word atom comes from the Greek "atmos," meaning uncuttable. But at the kind of turn of the 20th century, suddenly, it was discovered that there were things that were smaller than the smallest known atom, which was hydrogen. And these things were coming out of hot wires and they were called cathode rays. And it was discovered that these smaller things were about 2,000 times lighter than a hydrogen atom, and they were discovered to be actually something called an electron. And the electron is kind of what it says on the tin, is the particle of electricity. It's the thing that moves through wires and provides electric current. And so those electrons were discovered to exist, and they were thought to be boiling out of atoms. And later, it was discovered that there were other radiations coming out of atoms as well, and those radiations were actually, again, fragments of other parts of the atom. And they were used as probes to look inside and discover that not only were electrons inside, but there was also a central region inside of an atom called a nucleus, which contained most of the mass of the atom, but also particles called protons, which had an opposite electric charge to the electron. So the protons are what we say as positively electric charged, while the electrons are negatively electrically charged. But also inside the nucleus were other particles which didn't have an electric charge, called neutrons. So today we understand that atoms are made up of those three things: protons, neutrons in the very center of the atom in the nucleus, and then electrons, in kind of wispy clouds around the outside. Jane: There are even smaller things than protons, which are themselves made of smaller particles. Ben Still: The electron hasn't been seen to be made of anything smaller. When you smash them together, they create quite clean kind of crashes. But when you smash protons together, what you see is you see a mess, like smashing two grocery bags together. And from the splatter of all that mess, if it's done enough times, you start to see patterns. And those patterns showed particle physicists that essentially, protons are actually made of three smaller particles, which are called quarks. Now, it seems that quarks, like electrons, are kind of the smallest to which the universe goes, and so we call them elementary particles. But we only can say that they are the smallest things that exist considering the experiments that we've done, considering the kind of energies that we've got to and it might be that if we go to higher and higher energies, we suddenly discover that there is smaller detail to the universe. There are things that electrons and quarks are made from. There are lots of theories already out there which try to help us understand the universe in a deeper sense, that actually suggest and predict that there might be things that are smaller than the electron and the quarks as well. But right now, experiment has shown us that our current understanding ends with electrons and quarks. Charlie: Hi, my name is Charlie. I'm seven years old, and I live in Melbourne, Australia. How can an item be a liquid, solid and a gas? Yu An: Hello. My name is Yu An, and I'm six years old, and I come from Korea. You know that I have a question, and is liquid made of atoms? And I wonder, I was just watching a video about atoms, and it just said that everything in the universe is made of atoms. So I just start to wonder, is liquid also made of atoms? Ben Still: As we say, everything really, in the Earth and in our solar system is is made of atoms. And whether something is a liquid, a solid or a gas is not necessarily down directly to individual atoms, but the way in which atoms interact with one another. So it's to do with things like chemical bonds and the way in which these different atoms form molecules, but also how those atoms and those molecules, which are just basically atoms connected together by sharing electrons and things like that, how they interact with one another. Oliver: Hi. My name is Oliver, and I am six years old. I'm from Salt Lake City, Utah. My question is, how many atoms are there in the world? Jane: Yeah. And considering that, anything that we would use Ben Still: It's very difficult to estimate. But if we if we think about what the earth is made from, so predominantly to compare to, like 75 elephants or a million school buses, those elements like iron, silicon, oxygen and things like that, and are all made up of atoms. There's no there's no number we then we think of the mass of the Earth, we can make an estimate. And you get to something around 10 to the 50 atoms. That's one followed by 50 zeros. It's a huge, huge number, unimaginable, really. So yeah, it's... Yeah, again, my mind is blown when you start thinking of things in terms of atoms, because even a teaspoon full of material can have such an unimaginable number of atoms in it. could even conceive of, because whatever thing we try to compare it to is already made up of billions and billions and billions of atoms. Ben Still: Exactly, yeah. So when you're when you're going from the smallest structure in the universe, anything you choose is obviously going to be huge in comparison. Elizabeth: Hi, my name is Elizabeth. I'm a very young 70-year-old who wants to know what atoms and molecules look Ben Still: That's a great question. They're too small to like? be seen with visible light, because, as we mentioned, atoms Jane: Coming up: If we can't see atoms, how do we know they exist? are about 10 to the minus 10 meters in size. So that's extremely small, much smaller than the wavelength of light. So the way that we see things by the light scattering off and entering our eye won't work with an atom, because light won't scatter off of atoms directly. And so the way that we see atoms is not in the way that we see but we look at atoms through the interactions that they have with other particles and other atoms. So for instance, there is a machine known as a tunneling electron microscope, and a tunneling electron microscope has an extremely thin point on it that scans over a material, and that thin point exchanges electrons with the material it's imaging, and the amount of electrons that are exchanged tells you essentially how close you are to that material, and it allows you to actually image the shape of individual atoms. And so atoms, in terms of their shape, really embody, not anything outside of, really, the forces that they interact with the world. So a single atom would look very, very spherical and ball-like simply because it is made of a number of charges that are symmetrical, and so therefore will interact with the world in a symmetrical way. And so, like a sphere. And molecules will have certain other slightly different geometries dependent upon those chemical bonds and how those atoms have fit together, one to one. Because, again, those atoms in in those chemical bonds will sometimes pull electrons towards them and sometimes have electrons pulled away from them, which changes kind of the shape that those atoms fit together. So how we see them is not through the traditional sense, but instead, we see them through the forces that they exert on other atoms. I'm Jane Lindholm, and this is But Why. We're learning about atoms today with physicist Ben Still. He's the author of several books, and he's a high school teacher. Atoms are the building blocks of all the things that exist on Earth. In fact, all the things that exist in our entire universe. But how do we even know they exist if they're so small we can't see them? Dex: Hi, my name is Dex. I'm from Austin, Texas. I'm 10 years old. And my question is: how did scientists find atoms without being able to see them? Ben Still: Amazing question. Essentially, atoms were theoretical for a huge number of years. So the ancient Greeks, Democritus, thought that everything in the universe was made up of small units that were uncuttable. And then in the early 19th century, the idea was rediscovered and brought forward by John Dalton, who thought, again, that each of the chemical elements that were understood at the time were made of different-sized spheres. And again, the idea of atoms came about. But it was all theoretical, really, until 1905 and Einstein's "miracle year," and one of his three papers that he published was on something called Brownian motion. And Brownian motion was discovered many years before by a botanist, Robert Brown, who was commenting on the fact that little pollen grains seemed to bounce around in a liquid when he observed them underneath the microscope, and it seemed totally random. And Einstein was able to actually build a model, as we say, that physicists build models of the universe with mathematics, to explain this random motion. And his mathematical model assumed that the little pollen grains were being bounced about by the invisible atoms and molecules within the liquid hitting those pollen grains. And he was able to put a mathematical model to this. And so it was really Einstein's mathematical model that provided the basis that the experimentalist Jean Perrin could then go and confirm that that is how the universe indeed behaves. And that was kind of the way in which we got our first real, solid evidence that the universe that we live in is made up from atoms. Annabelle: My name is Annabelle, nine years old, from Palm Coast, Florida. How do scientists see how many protons are in atoms? Ben Still: The number of protons in an atom are always balanced by the number of electrons in an atom, and we know that because atoms are defined as being zero charge, that they're electrically neutral. And so every proton in the nucleus is joined by a negatively charged electron orbiting around that nucleus. And so it is through really the properties of the electrons that we can infer how many protons are in the nucleus, in most atoms. Roman: My name is Roman, and I live in Louisville, Kentucky. I'm seven years old. Why do two atoms technically never touch? Isabelle: Hi. My name is Isabelle. I'm nine years old, and I live in Queensland, Australia. And my question is: why do we feel our fingers when we have an atom-sized gap in between them? Levi: Hello. My name is Levi, and I'm nine years old. Right now, I live in Germany. I heard that atoms don't touch each other. If atoms don't touch, then how do we feel things? Ben Still: The way that we deal with atoms and particles and everything at that level is actually to say that they don't have any volume or space. They don't occupy any space at all. They're just points in space and time. And those points in space have certain properties like electric charge and mass and things like that, and it's those properties that we're actually interacting with. So atoms are points in space, but they're always going to repel one another through the force of electromagnetism. And so they're never going to kind of touch, so to speak, because they're never going to exist in the same space. But electromagnetism and the repulsion of electric charges and things like that is only one part of the story about keeping atoms apart. In fact, when you're sat on a chair and, again, you're feeling that force between you and the chair, yes, there is some of that repulsion because of electromagnetism. But there's also just properties of particles that also produce a force, and that is the simple fact that no two particles, fundamental or more complex, like atoms and molecules, can exist in the same space at the same time with the same energy. And that's that's a quantum mechanical process called the exclusion principle. And all particles, from electrons upwards, have that property built in, so that you can't essentially have these particles exist in the same space. And the way that nature acts to stop that is it has an additional repulsive force to keep them apart. So when you're trying to smush two atoms in towards each other, you've got two forms of repulsion from this exclusion principle, but also from the electric charges repelling them as well, which means that no two atoms can exist in the same space, and so we effectively say they can't really touch. So, it's the forces that keep them apart and the properties of particles that also push them apart from one another. Jane: So if I'm rubbing my fingers together, I'm not feeling different atoms rubbing together. I'm feeling the forces, essentially. Ellen: Hi, my name is Ellen. I'm 10 years old. I'm from Cambridge, Ontario, Canada, and my question is, how do atoms get color? Ben Still: That's great. So again, atoms are so small, they're smaller than the wavelength of visible light. So atoms, strictly, themselves, don't have a color, but they do emit colored light. They do emit visible light. So if we were thinking and seeing in the normal sense, the way that we see colors, atoms wouldn't have a color. They're far too small to have a color, because visible light wouldn't scatter off of them into our eyes, and that's how we see color around us. But what happens inside of the atom is that the electrons that are around the nucleus can exist at different energies, and what happens is you can excite those electrons by using electricity or heat, and those electrons will jump up to a higher energy, and then eventually, they will fall back down. And when those electrons fall back down, they do emit light, and that light is actually very unique to every single not only atom, but also every single kind of isotope as well. And so each element on the periodic table emits certain colors or wavelengths of light, and the exact colors of light that it emits is a unique kind of identifier for that particular element. And in fact, that's the way in which most of the elements on the periodic table have been discovered, not through the chemistry and the way that they interact with other atoms, but actually through the light that they emit in something called spectroscopy. So to summarize, atoms themselves don't have color, but they do have characteristic colors that they emit when excited. Luke: My name is Luke. I am eight years old, and I live in Perth, Australia, and my question is, how are atoms made? Jane: Maybe we shouldn't have saved this for last, Luke, because it's really the start of everything we've been talking about in this whole episode. But that's okay. Everything comes full circle in the end. The widely accepted current theory is that all the matter in the Universe, from our Earth to our sun to all the stars and planets and distant galaxies, can be traced back to something called the Big Bang. That's the moment 13.8 billion years ago, when energy was suddenly transformed into matter. But the Universe at that moment was so hot, hotter than anything on Earth could exist at today. It was 18 billion degrees Fahrenheit, or 10 billion degrees Celsius, hotter than we can even imagine. It took 380,000 years for the Universe to cool down enough for atoms to come together and form. Most of those early atoms were hydrogen and helium, and those two elements alone make up almost all the matter in our Universe today. Slowly, though, other atoms formed as well, and new atoms are still being made through the life and death of distant stars. Ben Still: As complex as everything seems in the Universe around us, at the heart of it, through thinking of splitting up nature into its smallest, indivisible parts, we've managed to create a model of our Universe that is actually quite elegantly simple. While the mathematics seems horrific initially, there's only a handful of things that make up pretty much everything in the Universe around us, and I think that that is quite, quite amazing. Jane: Ben still is the author of "Particle Physics Brick by Brick," which explains physics using LEGOs, and "The Secret Life of the Periodic Table." His new book, "How the Universe Works," will be released in September. I can't wait. Now, I find this stuff fascinating, but it's really hard to wrap my brain around it. In addition to Ben's books, we have some links to more articles about atoms and the origin of the Universe. You can find them in our show notes, and we'll put them in our newsletter as well. Your adults can sign up for our newsletter on our website, butwhykids.org. If you have a question you would like us to tackle in an episode, ask an adult to help you record it and then send it to us. Your adult can use a smartphone app like Voice Memos or Voice Recorder to capture you asking your question. You should make sure you tell us your first name, where you live and how old you are and what your question is, of course. And then your adult can email the file to questions at butwhykids.org. We love hearing your voices and learning about what's going on inside your brains. Our show is produced by Sarah Baik, Melody Bodette and me, Jane Lindholm. Our video series producer is Joey Palumbo. Our theme music is by Luke Reynolds. We make the show at Vermont Public, and we're distributed by PRX. We'll be back in two weeks with an all new episode. Until then, stay curious!
x
x