[Bugs Bunny: What’s up doc? What’s cookin?]
Elsa Silberstein: Hello hello hello, you’re listening to What’s up Doc, my name is Elsa and this is the podcast that gets you in the know in 15 minutes. We’re at UWA and there is just so much knowledge here and so little time. So, each episode we’ll be chatting to a pro at the university to help us debunk some academia. Today, my guest is a lecturer in physics, Dr. Darren Grasso, who, this year, published an article in the Journal of Nuclear Physics titled “Deriving all p-brane superalgebras via integrability.” Now, that to me sounds like someone that’s very unintelligent with a pea brain who’s trying to be a superhero? Am I like, on the mark there?
Darren Grasso: So the term p-brane, if you notice the spelling, its b-r-a-n-e, not as in a small brain. So p-brane refers to a structure in string theory in which “p” is arbitrarily dimensional and brane is short for membrane. So it’s sort of a p-dimensional membrane.
ES: Cool! Okay, let’s write into that later. First, we’re gonna do a bit of a warmup because we are in this elite sport of interviewing.
ES: So I’m gonna give you two options, you just say the first thing that comes into your head straight away, your preference. You ready?
ES: Jazz or Pop?
ES: Green or red?
DG: [pauses, then laughs] Red.
ES: Faster! Offense or defense?
DG: What was the question, sorry?
ES: Offense or defense?
ES: Bike or scooter?
ES: Peanut butter, crunchy or smooth?
DG: Uh, crunchy.
ES: Vegemite, fridge or pantry?
ES: Mac or Windows?
ES: Okay, you did well. [laughs] Let’s get started. So what’s up with string theory?
DG: Perhaps I should describe the current state of our art, what our current best theories tell us, what’s wrong with them, and why string theory purports to solve these problems.
ES: Yes please.
DG: So, basically, physicists have worked out that there are four forces of nature. So all the forces you see around you can be categorized into one of these four. For example, electromagnetism is one of the forces of nature. This holds electrons in orbit around protons, it holds your magnet to your fridge, powers your mobile phone, electricity and magnetism. That’s one of the forces of nature. Another force of nature is gravity. This holds you to the floor, the moon in orbit around the earth, the earth in orbit around the sun, and so on. Then there are two lesser known forces which are very short ranged forces, which don’t manifest at your usual scales. These are the nuclear forces. So there are four forces in nature, we have a good fundamental description of three of those forces, that is, the electromagnetic, the strong nuclear, and the weak nuclear, whereas the fourth force, gravity, we don’t have a fundamental description of that, its just got a classical description, which is known as general relativity.
ES: By description you mean maths?
DG: A mathematical model, yeah. So we have a good mathematical model which in one go, describes three of the forces, and then a completely different mathematical model which describes the fourth, gravity, and these mathematical models are at odds with one another. They don’t fit together, there’s sort of like, deep contradictions between them.
DG: It is hoped that the universe is just a single structure with one set of rules that we should be able to uncover, that’s the hope, and string theory is sort of the most prominent attempt to unify all of these forces into one single mathematical framework. What string theory does is postulate the existence of just a single fundamental object, rather than a whole zoo of fundamental particles. It[string theory] postulates that there is just a single thing: the string, a little loop, a sort of open-ended thing which moves through space and time.
ES: Is it a physical thing?
DG: In the same sense that the electron is a physical thing.
ES: Okay. Its just super small.
DG: Super tiny, yeah.
ES: So it’s a string in a c-shape?
DG: No, no, it can take on various shapes, but just imagine a single piece of string with two ends just wiggling through space.
DG: Or a closed loop of string wiggling through space.
ES: Should I ask how long is this piece of string?
DG: An obvious question, I can tell you its about ten to the negative thirty-three centimeters. So, super tiny.
ES: Right, okay.
DG: So we can’t see by looking, and there’s no hope to see that structure. Well, not in the near future.
ES: Okay, but we’ve got that. So they’re REALLY small pieces of string, they travel through time and space.
DG: Yes. And that’s the postulated single entity that’s supposed to replace all of the entire zoo that we see. So the idea is sort of unifying. We don’t have a whole bunch of different fundamental particles that are disconnected. We just have a single string. And the idea is that, um so, metaphor time.
ES: Metaphor tiiime! Pap parap pow! Metaphor! [laughs]
DG: So imagine you’ve got a guitar string and its pinned at both ends and you pluck it. And there are many different natural waves for the guitar string to vibrate. The entire length of the string can sort of vibrate in unison, or there can be different sorts of standing wave modes, or harmonics. The string can vibrate in different sorts of tones, right? The single pinned string.
DG: And so the strings in string theory are kind of similar. So we have a string and when we look at it through the quantum mechanical lens, it can vibrate in different natural ways, and the different modes of vibration that it has manifests to us at this sort of large scale because we can’t see the structure of the string directly but the different modes that it can actually vibrate at manifests themselves to us as different fundamental particles. So the string vibrates in this particular way, it looks like an electron. It [the string] vibrates again in a different way, it looks like a photon. So its supposed to be a unifying idea, it’s a single entity that describes everything in one go. That’s the basic idea.
ES: So, can I just add to this metaphor by saying that you’re suggesting that the universe is a huge guitar orchestra of music.
DG: [laughs] I’m pretty sure that’s exactly what I said.
DG: Well, it would make a radical shift in the way we think about the universe. But ‘what are the practical consequences’ maybe, is what you’re asking?
ES: Yeah, does it change anything?
DG: So, I’ll tell you a story about Michael Faraday. I think mid-1800’s he was demonstrating magnetic induction. Electricity and magnetism were only just starting to be rigorously investigated. And he was demonstrating magnetic induction or electricity or something to uh, the prime minister or some dignitary, and they looked at it and said, “what good is it?” and his response was “what good is a newborn baby?” which is to say, its immeasurable. You can’t know what’s going to happen. Take general relativity for example, when Einstein was studying general relativity, he didn’t know what the consequences were going to be of studying that. He was just interested in knowledge. I wanna know how the universe works, I want more knowledge, knowledge, knowledge, knowledge. So it’s just research for knowledge’s sake. But it has practical consequences. He[Einstein] would’ve been thinking at the time that, you know, there might not be any practical uses to this, its just ‘how does the universe operate?’ but nowadays GPS works on knowledge of general relativity. Without general relativity, GPS would not work. Quantum mechanics, another one, that’s the study of the, sort of microscopic if you like. Why are atoms the way they are? What’s the structure of an atom? Just studying that, what consequences does it have? All of the technology you see around you is a consequence of understanding quantum mechanics. And so there is no way of knowing what [the] practical consequences [of] understanding the universe at a fundamental level have. So you can’t predict where this will go.
ES: I think that’s a really nice um, way to sum up, I mean, this podcast is a UWA podcast in where we’re trying to exploit you academics for knowledge, and just knowledge for knowledge and you don’t know what’s going to happen.
ES: Let’s just touch on physics in general. Why is it important?
DG: Why is it important? Well um, do you value technology?
ES: Yeah sure.
DG: Okay, so there’s a satisfying answer I think. Why else is it important? Personally I’m just driven by a desire to know how the universe is, that’s why I find it important. I just wanna know about my universe, I wanna know how it works, what’s everything made from, what holds it all together, how does it tick. So that’s why I find it important.
ES: Have you always been curious in that way?
DG: Um, the first time I can recall being curious was around the age of fourteen. So prior to that I can’t recall ever being deeply curious about the way the universe worked. There was a moment I remember quite vividly, that sort of ignited my passion for this. My parents had a book on their shelves, it was something like ‘The Reader’s Digest Big Book of Facts’ or something, and it was quite a thick book and it just had a collection of scientific facts in it. You know, things from chemistry and geology and evolution and many different ideas, and I read bits and pieces, I skimmed it, and nothing really ignited my passion or caught my eye, but right at the back of the book, there was this throwaway sort of comment about the twins paradox. Have you ever heard of it?
ES: No. [laughs]
DG: Its about special relativity, I’ll come back to that. But reading that [twin paradox], I just thought, “wow, I need to understand how that can possibly be true in our universe” and I’ve sort of pursued physics ever since. So what’s the twins paradox? This is just a thought experiment to demonstrate how weird the universe is.
ES: Kay. Love thought experiments.
DG: Okay, so imagine a pair of twins are born on earth, and now they move through the universe in different ways for some time and then they reunite later on.
ES: Can we name them?
ES: Ben and Jerry. [laughs]
DG: Ben and Jerry. Okay, so suppose Ben stays on Earth and just lives on Earth, and Jerry gets into a rocketship and moves through the universe in a very different way. So Jerry’s flying in this rocketship really fast, very close to the speed of light. This is to exaggerate the effect.
DG: Right. He goes out for some time and reunites with his twin. When they reunite, they’re not the same age. The difference in their age depends precisely on relatively how they moved through the universe. So in this case, Jerry returns, and again, depending on how far he went, how fast he went, when he gets back to meet with his twin brother..
ES: The dropout brother that didn’t get into space school [laughs]
DG: Yeah [laughs]. Jerry is say, maybe he was put in the rocketship when he was an infant, and he gets back and he’s just 4 months old, okay? But Ben? He could be as much as 80 years old, or he could’ve been long dead centuries ago, right. And this isn’t just a story, this is actually what theoretical physicists believe is true about the universe. We’ve got very good experimental evidence to say, “if we actually did this, it would happen.” In fact, we’ve even done it with accurate clocks. We’ve got one clock, we’ve put it in a lab, we’ve got another clock, and we’ve flown it on domestic aircraft around the world. When the clocks come back together again, they don’t record the same amount of time as being lapsed.
ES: So time and space are connected?
DG: Very deeply, yes. And the notions of duration and distance between events, they’re relative concepts. And so, in this case, there are two events, the twins are together, they separate, and then the twins return [to each other], so the being together at the beginning and being together at the end, the two events, they disagree on how much time has elapsed between those two events. And when I read that, I needed to understand how that could possibly be true. How is it that I’ve misunderstood time so badly, [so] intuitively, that that’s (time dilation) true about our universe.
ES: Yeah because my general concept of time is, time is sort of linear.
DG: It’s not malleable or flexible in that way, which is just utterly wrong. Its because like I’ve said, we’ve got this small window into the universe, and our perceptions are based on a long evolutionary history where we weren’t moving around relative to one another at very high speed. This only manifests itself if you move at very high speed. So we don’t have an intuition for it. There’s no need for it, doesn’t help our survival.
ES: Wah! Look, let’s stop at there. That was incredible, my brain’s a little bit fried. Can we just go over what we’ve talked about?
DG: So we’ve talked about aspects of special relativity, which is the twins paradox. I’ve talked about aspects of general relativity, the starlight deflection by massive objects. So we’ve covered a lot of ground here and we’ve talked about, in various ways, the four forces of nature and how string theory hopes to unify them into a single, coherent mathematical framework. But that’s yet to happen.
ES: The full forces of nature, Dr. Darren Grasso! Thank you so much.
DG: It was my pleasure.
ES: If you have suggestions about academia you want deciphered, or a crazy cool professor who’s just waiting to be interviewed, email us: firstname.lastname@example.org, thanks for listening!
[Bugs Bunny: That’s all folks!]
[Looney Tunes credits outro]
As transcribed by Xander Camit