Instant Genius - The Fundamentals – Everything You Wanted to Know About…Physics, episode one

Episode Date: April 24, 2020

Prof Jim Al-Khalili breaks down the building blocks of the Universe and reveals what simplicity, beauty and elegance have to do with physics. Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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This is a new format for us where we source the most in-demand questions from Google, our listeners and readers, and a few from the team itself. And we put those questions to an expert to help you get to grips with the most important ideas in discoveries and science. To keep things off, we're starting with Professor Jim Alcalli. Jim presents the brilliant show The Life Scientific over on people. BBC Radio 4, which if you haven't listened to yet, you should definitely check out on BBC Sounds Now. Jim is a veteran science presenter author who, amongst many other accolades, won the inaugural Stephen Hawking Medal for his work in science communication. He also teaches physics at the University of Surrey and somehow finds time together with his team to still publish research

in the fields of nuclear physics and quantum biology. And if that's not enough work for one man to do, Jim has just published a fantastic book called The World According to Physics. So in today's episode, we're going to take a bird's eye view of the subject and delve a little into the building blocks, the particles that make the universe as we know it. So Jim, why did you decide to write this book? Well, it's an interesting format because the book is actually smaller than your typical popular science book covering all the areas of physics. there have been a number of really good popular science books have come out in the last few years. They tend to be like in a thousand page long, tome, discussing the whole history of physics going all the way back to Aristotle and so on.

I wanted to write something that was compact. I mean, the book has that pocket-size feel to it. So it's small, it's neat. But I also didn't want to write the full history of physics. What I wanted to do with, I guess, two things. one is to give people the state of the union type thing. Where are we at in our understanding of the laws of nature? What we know, what we don't know.

So I say if physics knowledge is like an island and around it are the great oceans of the unknown, this book isn't an exploration of the island. It's a stroll around the shoreline. So the very limits of what we know in fundamental physics, particle physics, all the way through to cosmology, and what the mysteries are that are still out there that we know, so wade out into the water a bit and figure out, you know, what do we still need to understand? The other reason for writing the book is that it's my own sort of love affair with the subject that I've spent most of my life thinking about. So I'm trying to get across my own personal sort of this is my ode to physics in the book, as it were. Yeah, it definitely came across that way to me and helped me to remember what I first loved about the subject.

Okay, so let's get started. First up, what's the most unbelievable thing about the study of physics that you can share with us? Well, I think broadly, for me, it's still the fact that I can scribble Greek symbols on a piece of paper solve abstract equations and end up with, say, a number that describes some property of the world. And then if I check that against, you know, if I do an experiment or by observing nature, I see that that number agrees with reality.

So it's this fact that the laws of nature are written in a language that we've cracked, and that language is maths. the fact that these abstract symbols on a piece of paper actually describe how the world works I will never cease to be amazed by that. So over the course of the next couple hours you're going to teach me a lot of physics. But before we do that,

tell me, why should a person want to know more about physics? You know, I'm sort of constantly amazed that not everyone is as in love with physics as I am. But hey, you know, eat to their own. But I think the reason why I think we should know more physics, it will, it'll be different reasons for different people. For some, it's just because they enjoy having their minds blown. You know, sort of, wow, that's incredible, amazing that time behaves in this way or so on. The universe is expanding.

You know, when they learn something, some fact about how the world works. for others I think it allows us to appreciate the beauty of the laws of nature. You know, just the aesthetic beauty, studying the world, understanding the world, the fact that we can understand the world is similar to an appreciation of a work of art or a piece of music. And it shouldn't just be the preserve of those who spent years in years studying physics. You know, what I've tried to do throughout most of my career is to try and bring that beauty, that enjoyment, that sense of wonder to a wide audience. And then on top of that, of course,

understanding physics benefits humanity. This, of course, applies to all of science, not just physics. But for physics, I'll just give one example. Those pioneer physicists who, back in the 1920s, were unlocking the mysteries of the atomic world, the rules of quantum mechanics, the theory they're very small. They weren't just crazy geniuses talking, you know, in some obscure technical language because they developed a theory, quantum mechanics, without which we wouldn't be doing this podcast. You know, most of the modern world relies on our understanding of quantum physics. Because without quantum physics, we wouldn't understand, we wouldn't have invented semiconductors, we wouldn't have had modern electronics, we wouldn't have had computers,

microchips, mobile phones, so an understanding of physics really has allowed us to develop the modern world. Without physics, we'd have no engineering, and without engineering, we'd have no civilization. So there you go. Well, there you go. I think that's a pretty good reason to keep listening.

So let's start with a question that caught my eye from Google. And it's something that you talk about in your book. Can physics be beautiful? Yes, and I'd like to think it's not just a beauty that can be appreciated by professional physicists. You know, I think it's something that everyone can appreciate. For me personally, I think it was one of the key moments when I was a student studying physics that really sent, literally sent a shiver down my spine. I remember it was in my second-year undergraduate lecture on electromagnet.

Now, that may not sound really sexy, but I remember the lecturer starting with a set of algebraic equations called Maxwell's field equations, describing electric fields and magnetic fields, just writing down these algebraic equations, and then working through this derivation on the blackboard and arriving at a new equation in which there's a constant number there, the symbol C, which turns out to be the speed of light. And you see, that's how James Clark Maxwell, the great Scottish physicist, realized that light is just electric and magnetic waves traveling through empty space.

Now, I knew that, but to look at the algebra and start from electric fields and magnetic fields and arrive at the speed of light, oh, my goodness. I remember turning to my mate sitting in the lectures next to me and just, you know, almost welling up. And I remember him thinking, he said, oh, Jim, you're such a geek. So, yeah, so in that sense of that transcendent, you know, sort of feeling that there's some beauty in the math, there's a beauty in our ability to describe the natural world.

I think that should not just be the preserve of physicists like me. I'd like to think that I can give a flavor of that beauty to almost anyone. And what about simplicity? I spend a lot of my time these days, scratch my head, trying to understand quantum physics, so I can communicate it clearly to our readers and listeners. And more than that, it just gives me a headache. Should physics be simple, or let me put it another way, does it need to be elegant? A number of very famous physicists have appealed to elegance and beauty and simplicity

as a way to uncovering the laws of nature. You know, if they come up with a theory, if it's clunky, if it's not, elegant if it's complicated to describe, then it's probably wrong. That's not always true. I mean, there are aspects of the physical universe that are just messy, that are just complicated. The idea of simplicity, I think we can sometimes push it too far. I certainly remember when I first started communicating science, over 25 years ago, I truly believe that there wasn't anything, I couldn't explain to a layperson if I, you know, as long as I could find the right language without, you know, getting rid of the technical jargon. And to some extent,

that's true. It depends on how much information you want to get across. But I think recently I'm, well, I'm reminded of a famous quote by the great Richard Feynman, American physicist. Apparently, when he won his Nobel Prize, a journalist asked him if he could encapsulate what he had won his Nobel Prize for in a soundbite for the journalist. And Feynman said, I don't know, I can't remember the exact words. Certainly, I don't know, I wasn't there at the time. But he said something along the lines of, if I could tell you what my Nobel Prize was for just in a few words, it wouldn't be worthy of a Nobel Prize.

You know, so, you know, some of this stuff is hard. You know, that's why we don't all win Nobel Prizes. So not all of physics is simple. You can simplify things, you can give a basic outline of an idea, but if you want to dig into really understanding it, it probably isn't that simple. Okay, now on to some detail. This came quite high up on the physics search ranking on Google.

The site uses AHRFs, by the way, if anyone wants to ever look at what people are asking out there on Google. What is the standard model of physics? Ah, okay. Well, this is something I talk about in my book. In fact, we should be careful that. If we're talking about standard model in physics, there are actually two standard models.

There's the standard model of particle physics, which is basically an umbrella term encapsulating everything we know about the building blocks, the tiniest building blocks of the universe, of matter and energy. And then there's the standard model of cosmology, which is the everything we know about the entire universe. So that's like the standard model of the very large, the standard model of particle physics is the standard model of the very small. The better known one, the one when we normally talk about the standard model,

what we tend to mean is the one of particle physics. And that really, it's not a theory. In fact, technically it's, a collection of everything we know about the building blocks of the universe. It's really two theories. Both of them rely in turn on quantum mechanics, which are the rules that govern the behavior of the microscopic world. But quantum mechanics was developed, you know, almost a century ago. And throughout the 20th century, it had advanced and developed and become ever more elaborate and actually ever more more accurate, to the point that by the time we reach the standard model of particle physics,

the latter half of the 20th century, latter stages of the 20th century, that standard model actually encapsulated two theories. One is called the electro-week theory, which describes two of the four forces of nature, electromagnicism and the weak nuclear force. And the other theory is called quantum chromodynamics, which describes the third of the four forces. of nature, the strong nuclear force. So three of the four forces of nature, electromagnetism, the weak force and the strong force are all described within this umbrella term, the standard model. The fourth one, the old one out is the force of gravity, which is described by relativity theory,

and that doesn't fit in. So the standard model of physics describes all the forces of nature, all phenomena, apart from gravity, which is quite a big missing chunk. Okay, so would I be accurate in saying that the model and those forces describe the way the building blocks that make everything up interact with each other? Exactly. Yeah, that's right. So the standard model gives a classification of the particles of matter and the forces between them. So how they fit together, how to make atoms, which then go to make molecules, which end up making all the stuff we see around us. So it's basically the building blocks at the most basic fundamental level and how those building blocks fit together. So you might think the building blocks of matter is that's chemistry. This is digging down far deeper than chemistry.

It's looking inside atoms of the particles that make up atoms. So given that there are a handful of these building blocks, these core components, how do you end up with so much complexity, so much richness in the, universe that we see and feel. Yeah, that that that is incredible. I mean, we think back to the ancient Greeks, they believe that in front of all ancient civilizations and scholars in antiquity believe that there were only four elements, earth, water, air, and fire, and everything derived from them. And then gradually, as, you know, chemistry evolves in the scientific revolution, and we discover all these different elements, how silly those Greeks were to think there's only four elements, you know, we've got, you know, now by the time we discovered, you know, the 92 natural elements of the famous periodic table, well, that's 92 different types of atoms and then they can fit together in almost an infinite number of ways to make all sorts of molecules the way they bond together. That's why, as you say, you look around and you see, you know, a solid table, soft, your skin, the paper, pages of a book, your concrete of the walls, all the different materials and stuff. And then the air that you breathe,

But chemistry explains to us how all those materials can be so varied. But of course, with the development of particle physics and digging down within those atoms of the different elements, we actually revert back to this basic simplicity. In the end, when you think about it, or when we physicists have thought about it and carried out to experiments, there were really everything that we see around this is only made of three, not four, but three types of particles. two types of quarks and electrons. So you've got the up quark, the down quark, not very imaginative names, but the up quark and the down quark, they make up the particles, the protons and neutrons, that make up the nucleus of an atom. So you've got up and down, ultimately up and down quarks are the matter particles that make up the nucleus, then buzzing around the nucleus are the electrons. Those three particles alone make up all atoms and its combinations, how many of them. of per atom and how they're arranged and how they fit together

that gives us ultimately the variety of the different atoms and the different chemical properties they have and ultimately the whole of the stuff that we see around us. So it's quite incredible from such a small number of ingredients we can get such infinite variety. And then I just want to touch on the way physics works, I suppose. How did we arrive at this model? I mean, I suppose that's a very big question, but let's just say focusing on the idea of the Higgs for a moment.

Scientists theorised its existence, you know, and then 30, 40 years later, we build particle accelerators that can search for it. And we end up with the crowning achievement of CERN, which was the confirmation of the existence of the Higgs boson. Can you tell me, or can we talk about how physicists move between that? You know, they move between theory and experimentation? Yes, I think the story of the Higgs boson, of course, it's well told now that Peter Higgs and others were developing the theory, the mathematics, the models, to predict the existence of this particle over half a century ago. You know, it took 50-odd years to confirm the existence of this particle in an experimental lab

at the Large Hadron Collider. That hasn't always been the way we have progressed in trying to understand the ingredients of matter. In fact, the reality is that theory and experiment have always worked in parallel. So to give you the opposite example, back at the beginning of the 20th century, Ernest Rutherford was trying to understand what atoms were made of and their structure. and so famously his two assistants, Geiger and Marsden, there's this famous experiment for,

if people remember from the school days, the firing alpha particles, you didn't actually do the experiments at schools, I'm pretty sure, firing, or maybe if we did, firing alpha particles at gold leaf. And there's the famous, this experiment's carried out in 1909 by Garga and Marsden.

So this gold leaf was very, very thin, so only was not that many atoms thick. and these alpha particles, sumatomic particles that fired from radioactive material, most of them would pass straight through the gold leaf without being deflected, but one in several thousand would bounce back again. So they were doing an experiment, which was essentially the precursor of the Large Hadron Collider, firing matter at matter and seeing what happens and seeing the result of that. There, the experiment was done first, and it took almost two.

years for Ernest Rutherford to develop the theory to figure out what that experimental result meant. And his theory was that what we now call the solar system model of the atom, the cartoon picture of the atom with a nucleus and electrons orbiting around it like a miniature solar system. We now know that isn't the correct picture of an atom because quantum mechanics tells us it's all fuzzy and cloudy and probabilities and whatnot. But essentially, there was a theory that had to be developed after the experiment was carried out in order to interpret and understand the results of the experiment. And throughout the 20th century, they have run in tandem. When people developed the first atom smashes, particle accelerators, they also were developing the theories to try and describe what they were seeing

or to predict what they would see if they did a particular experiment. And gradually these things were, and as they say, culminated in the Higgs boson, the large Hadron Collider. you know, was built not just to find the Higgs, but that's what it's discovered so far. And I think particle physicists are somewhat a little bit frustrated. They will never admit to it. But they're a little bit frustrated. They haven't found other new particles just as sexy as the Higgs. But, you know, who knows?

And then, you know, we heard about the Higgs, what was it, nearly, nearly, you know, five, ten years ago now. What's been happening at CERN since for anyone that hasn't been following the research coming out of the facility? Well, there were some recent results announced, but really they were discovering new, was it not exactly new particles, but sort of new high energy, sort of excited states of combinations of quarks. They were hoping that they would see evidence of new types of particles. For example, theoretical physicists are very keen on a mathematical idea called supersymmetry. which is very powerful, actually useful in developing new theories of everything, like string theory. The suggestion that everything isn't actually made of particles but made of tiny vibrating strings.

So this idea of supersymmetry may or may not be true. It's very mathematical. But if it is true, the prediction is that there should be new types of particles that are called super symmetric particles that the Large Hadron Collider would be able to create. out of the energy of collisions, of very high-energy collisions, but it hasn't found super-symmetric particles. It was hoping to find other hypothesized theoretical, theoretically postulated particles.

It hasn't seen anything new yet. So at the moment it's in downtime, but there's tons and tons and tons of data that still has to be analyzed. You know, you don't do the experiment and immediately you see something and you say, oh, we've just found a new particle. It takes months of analysis and number crunching with very powerful computers to work through the mess of all the stuff that is created in these collisions.

So it may be that in sifting through the data, we'll see something new. But as yet, you know, we're coming up to, there was eight years now since the Higgs. The Light Home Collider hasn't finished its work, that's for sure. But no one knows what new surprises it might throw up. up. You used the word there that I wanted to come to next, actually. Well, you said super symmetry. But on Google, a lot of people are trying to understand symmetry in physics, it seems. Can you explain to me, within physics, what is symmetry and why is it important to physicists? Yes, well, I mean, in more general language, when we say something is symmetrical, we mean it's, you know, it has a

balanced pattern, like you know, flip it left and right through a mirror. You know, if your face is symmetrical, it looks the same if you switch to the left and right around. We talk about geometric objects as being, you know, a square has symmetry because if you rotate it by 90 degrees, it doesn't change. It's still a square. If you chop it in half and swap the halves over, it doesn't change. So it has this a certain kind of symmetry. A circle has even more symmetry because you can rotate it by any angle and it doesn't change.

So in physics we mean something actually even deeper than that. we say it's not just the fact that certain shapes don't change if you flip them or rotate them. We mean a physical system, when we say a physical system has symmetry, it means that there's some property of that system that doesn't change, that stays the same, when something else is altered. So if you change something, by a system, I mean, you know, it could be a particle, it could be, you know, an equation, anything in physics. change one aspect of it and another aspect doesn't change, we say that's a symmetry of the system.

And it's a very, it's quite an abstract mathematical idea, but it's turned out to be extremely powerful in physics. Okay. And another concept that you talk about in your book, and it's one that's fairly well searched for on Google, is the idea of universality. Can you tell me what that is and why it's important? Well, physicists, when they talk about universality, some physicists actually mean something rather technical, so I won't go into that. But in general, what we mean by universality is that there are laws of physics that apply across a wide range of phenomena, phenomena

that we maybe didn't think were connected. And a really nice example of this is one of the earliest examples in our long journey of unifying the laws of physics. And that's Isaac Newton, discovering the law of gravity, you know, whether or not the apple actually fell from the apple tree when he was sitting on his mother's farm back in the 17th century. We don't know that's apocryphal. I think Newton himself tells that story. But essentially, what he realized was this profound universality of gravity, that this invisible force that pulls the atom to the ground is exactly the same force that keeps the moon in orbit around the earth and the earth in orbit around the sun. Now, that's not obvious. Why would that be obvious to anyone when you talk about

things that fall to the ground because they have a tendency to want to move towards the earth? And then you've got some other laws of the universe governing the heavenly bodies and the orbits of the planets and the moon, why should they be the same thing? Well, Newton realized it's this, the inverse square law, the force of gravity involving the masses of objects and square of the distance between them, which we learn at school, that law applies equally well to apples as it does to moons and planets. So there's a universality there of that particular law of nature. So for me, in a general sense, that's what physics does this, and incredible, Physics has these universal laws describing phenomena across a huge range of time and distance

that no other science can compete with in terms of scope. But I'm just, yeah, I'm biased towards physics. You're just bragging now. Yeah, exactly. Well, that brings me onto my final question for this episode. So from my perspective, and that's someone who didn't necessarily study physics at university, the laws of physics seem to operate two levels. You have the world of the big and the world of the very small,

which we call the quantum world. Now, is there a discrete point where the rules switch from one to the other? Is there a size at which we say, okay, now the laws that govern this world, they're the ones of the quantum world? Well, it's certainly true. thus far we haven't been able to use both at the same time. And that's the Holy Grail of physics to unify the description of the quantum world

with the description of the classical, the large, the macroscopic world, whether it's at the scale of us humans or whether it's the scale of galaxies and the whole universe. And you might think, well, why? You know, there are two very different domains. Why would you want one theory to describe two very different things? but of course there are examples or phenomena in the universe that you can only explain properly if you bring in quantum mechanics and the classical laws which we now would talk about in terms of Einstein's general theory of relativity.

But in terms of the boundary between what is our everyday world described by whether it's Einstein or whether it's just Newtonian mechanics, the classical physics, and the quantum world, the very small, which is a very different description, a very different reality, that boundary is something we are still exploring now. I mean, it's been a tremendously interesting area. What is the transition between the quantum and the classical? Where is that crossover? On the one hand, you could say, well, it's to do with something called the measurement problem that, You know, there's the famous Schrodinger's cat in the box. If you don't open the box, it's all behaving quantum mechanically.

Dead, the cat's dead and alive at the same time. As soon as you open and look, it's either dead or alive. And you can say, well, that's, you know, I've carried out a measurement. I've made it stop behaving quantum mechanically. And now it's behaving according to classical physics. But that's a very sort of rough and ready way of explaining it. Actually, the boundary between the two is a grey area. You know, in my research in nuclear physics very often to do the whole, and the atomic nucleus, everything's quantum mechanical there.

But to do a calculation in order just to be able to get a result, using quantum mechanics might be too difficult. So what you do is relax it a bit and say, well, what if it was half classical? What if I could use a simplifying idea and approximation and do what's called a semi-classical, calculation, you try and cheat it, but that's still a cheat because we still don't understand this transition between the quantum and classical. And it leads to a whole new era, which I'm interested in at the moment, called open quantum systems where your quantum weirdness, you know, the particles being in two places at once, that sort of thing, how it interacts with its surroundings and its surroundings are us, everyday objects. So what is that connection between the two?

It's still, it's still, I'm waffling on a lot to basically say it's still a mystery. that we're still working on. And that's actually what one of your research interests is in, isn't it? Quantum biology, which is how quantum effects might play out in our biology. Well, it's the fact that we're discovering potentially quantum effects happening inside living cells. So it's not the fact that quantum mechanics are suddenly now in the everyday world, but it governs the behavior of atoms and molecules. And if those atoms and molecules are inside living cells, there are certain things that seem to be going on in biological systems that require quantum mechanics.

So that has been my motivation for the last decade or more of my research. But essentially, what I'm really interested in is this idea of how does the quantum world interact with its classical surroundings? What, you know, things called, you know, very sort of esoteric things like quantum entanglement, quantum decoherence. I love it because it's very mathematical and it's like it's like puzzle solving for me so anything that that means because I don't write computer codes like I used to back in the day so I like scribbling equations on pieces of paper

or on my iPad these days because I've got a very flash iPad pro now with an eye pencil so I write my equations on a screen which is fun we're going to wrap it up there for today in the next episode which will be out tomorrow Jim and I are going to talk about the big stuff and by big I mean the really big concepts space and time

the universal speed limit the big bang and of course how it all ends so if you've enjoyed this episode I'll be tuning into the next one please do subscribe and if you can spare a minute leave a review and let us know

what subjects you want us to tackle next and of course if you want more primers on the big ideas in science from the science focus team head over to our website sciencefocus dot com or find us on Twitter, Facebook and Instagram. And if you want to dive deeper into any of the topics covered, then Professor Jim

Alcali's new book, The World According to Physics, published by Princeton University Press, is the perfect place to start. It's a concise introduction to the most important ideas in physics now, and Jim is a wonderfully clear writer who takes the grandest of ideas and makes them simple to understand. Thank you for listening to the Science Focus podcast from the BBC Science Focus magazine team. We're the UK's best-selling science and technology monthly, available in print and in several digital formats throughout the world. Find out more at sciencefocus.com or look out for us in your app store. This podcast has been created by the team behind BBC Science Focus magazine. If you've enjoyed listening, why not try out our magazine? In the next few issues, we've got a special report coming up on the progress

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