Why Erdős Was The Original Kevin Bacon

Some objects feel like they’re from another world. One of these might be the giant structure that makes up a quantum computer. Lifted straight from the TV series Devs, Professor Hannah Fry shows Michael Stevens a prop that was designed to look just like one…now it hangs from the ceiling in her house. In this episode of Field Notes, Hannah and Michael examine the extraordinary technology behind of quantum computing. They explore how qubits differ from classical bits and consider the ways this technology could reshape our world, from encryption to drug discovery. Answering your questions, they also look at the eccentric mathematician Paul Erdős and discover what Erdős and Kevin Bacon have in common. Welcome to The Rest Is Science: Field Notes. Every Thursday, Hannah and Michael rummage through their personal troves of scientific treasure, sharing discoveries that reveal the hidden forces shaping our universe, the objects that bend our brains, and a few things that are just plain incredible. They’ll also be tackling your questions, so email The Rest Is Science at [email protected]. ------------------- For more information about Cancer Research UK, their research, breakthroughs and how you can support them, visit ⁠⁠https://cancerresearchuk.org/restisscience⁠⁠ Cancer Research UK is a registered charity in England and Wales (1089464), Scotland (SC041666), the Isle of Man (1103) and Jersey (247). A company limited by guarantee. Registered company in England and Wales (4325234) and the Isle of Man (5713F). Registered address: 2 Redman Place, London, E20 1JQ. ------------------- Find The Rest Is Science all over the internet by ⁠clicking here.⁠ ------------------- Video Producer: Oli Oakley Video & Social: Bex Tyrrell Assistant Producer: Imee Marriott Producer: Becki Hills Senior Producer: Lauren Armstrong-Carter Head Of Digital: Samuel Oakley Learn more about your ad choices. Visit podcastchoices.com/adchoices

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Hannah Fry?

  This episode is brought to you by Cancer Research UK.

• 0:02Michael Stevens?

  Dinosaurs walked the Earth 180 million years ago. But you know, cancer was part of their story, too. Scientists have found tumors in ancient fossils.

• 0:13Hannah Fry?

  Well, that is a part of the reason why cancer is a big, big part of our story, right? It's the other side of evolution. It's the most complex disease that we face. There are more than 200 types of cancer in total, each with distinct characteristics, challenges and mysteries.

• 0:28Michael Stevens?

  And that complexity demands scale. Cancer Research UK is the world's largest charitable funder of cancer research, with more than 4,000 scientists, doctors and nurses working across more than 20 countries in the search for answers. And then sharing their discoveries beyond borders.

• 0:45Hannah Fry?

  And the impact of this collaboration is clear, because over the last 50 years, the charity's pioneering work has helped to double cancer survival in the UK. That is more people who are living longer, better lives.

• 0:57Michael Stevens?

  Fossils can show us the past, but research is shaping the future. And for more information about Cancer Research UK, their research, breakthroughs and how you can support them, visit cancerresearchuk.org/restiscience.

• 1:14Speaker 02

  Observe the North American dad. 50s, great polo collection. He enters his vehicle information on Carvana. An offer appears in minutes. Remarkable. He squints, reads it again, smiles and says, "Dang, that's a good offer." The highest form of approval. No haggling, no hassle. No one called him "boss." He's still on the couch. Astonishing. Sell your car today on carvana.com. Pickup fees may apply.

• 1:44Speaker 03

  This episode is brought to you by Indeed. You're ready to level up your business, but the pressure to find the right person to make that happen is intense. Indeed sponsored jobs can help carry the load. It boosts your job post to help it reach quality talent fast. Cut through the chaos with Indeed sponsored jobs. Get a $75 sponsored job credit at indeed.com/podcast. Terms and conditions apply. Hiring now? Then this is a job for Indeed sponsored jobs.

• 2:20Hannah Fry?

  Welcome to The Rest Is Science. This is Field Notes. It's a sort of a podcast expedition, if you will, where Michael and I are going to trade curious objects or things that have been occupying our minds.

• 2:31Michael Stevens?

  Yeah, that's right. Every week, we're going to bring something from our little, you know, the mystery bags of our lives to share with the other and with you.

• 2:39Hannah Fry?

  I mean, put it this way, Michael and I are massive nerds and always have been. So over the years, we've collected all manner of bonkers and bananas, objects and ideas. And that's, I mean, we've got, we've got at least seven to eight years' worth of stuff to go through, Michael, I reckon, in terms of episodes.

• 2:55Michael Stevens?

  Yeah, right. And there's even more than that, because we want things from you guys. So send in your questions and ideas to where, uh, well?

• 3:05Hannah Fry?

  I know. It's the rest is science at goalhanger.com.

• 3:08Michael Stevens?

  Oh, what a great email address.

• 3:10Hannah Fry?

  Yeah, it's, you would think that by now we would have remembered it, but, but no, it still remains a difficult task for us. Later on in this episode, I'm going to be showing you the ultimate nerd trophy. It's, uh, it's the most remarkable and weird thing that I own.

• 3:25Michael Stevens?

  Oh.

• 3:26Hannah Fry?

  That's coming up in our episode. But first, some questions from you.

• 3:29Michael Stevens?

  That's right, from you guys who are out there listening, not from me. I will read this one to you, though, Hannah. This is a question from Hayley, who asks, "Who is, or was, in your opinion, the scientist with the most peculiar personality?"

• 3:43Hannah Fry?

  Most peculiar personality? I mean, there's a lot of, there's a lot of people who could be in that category, right?

• 3:47Michael Stevens?

  It's like all of them. Like, you have to be peculiar to, uh, well, we're all peculiar in some way.

• 3:54Hannah Fry?

  Some of us more peculiar than others.

• 3:56Michael Stevens?

  Luckily.

• 3:57Hannah Fry?

  It definitely helps, doesn't it? I think if you're willing to completely dedicate your entire life to advancing human knowledge by just the smallest, smallest amount, no guarantee of success, then, then I think there's, usually does have to be something a little bit peculiar about you.

• 4:12Michael Stevens?

  Yeah.

• 4:13Hannah Fry?

  I mean, mathematicians, I think, are often...

• 4:17Hannah Fry?

  Right up there with the most peculiar of all. I mean, there's Cantor, who discovered that infinities can be different sizes. I mean, that in itself is a wild idea. But he, he at one point thought that he was causing the rain by stirring his own urine. So, I mean, there's a lot of.

• 4:34Michael Stevens?

  Wait, really?

• 4:34Hannah Fry?

  Yeah.

• 4:36Michael Stevens?

  Oh, that's incredible. See, I don't know anything about him outside of the mathematics that he worked on. I'm gonna write that down because I love examples of things like Isaac Newton believing that the world was going to end on a specific date and all the esoteric work that he did. D. H. Lawrence, the author, believed that the moon produced its own light.

• 4:54Hannah Fry?

  Oh.

• 4:55Michael Stevens?

  And it's just kind of surprising when you're like, oh, yeah. It was easier to, to believe that confidently back then.

• 5:02Hannah Fry?

  Yeah, absolutely was. I think number one, though, number one for me is gonna go to Ehrlich.

• 5:06Michael Stevens?

  Is that the six degrees of Kevin Bacon mathematician?

• 5:09Hannah Fry?

  It absolutely is the six degrees of Kevin Bacon mathematician.

• 5:11Michael Stevens?

  Okay, explain what that is to our listeners.

• 5:14Hannah Fry?

  Okay, so he did a lot of work on graph theory, which it's not about graphs as in X and Y axis. It's graphs as in networks. That's what mathematicians call them. But he also was a sort of lived example of this. He published an incredible number of papers, but in particular, he published with a lot of co-authors. And what he would do, actually, he, he didn't have a house, right? He didn't sort of, he didn't have a kind of traditional life. What he would do is he would rock up at different mathematicians' houses and then turn up and say, my brain is open, and, and sleep on their couch, where they would take on the responsibility for cleaning him, feeding him, laundering his, actually, he didn't do laundry, he chucked his clothes away once he'd worn them.

• 5:57Hannah Fry?

  Not because he was ostentatious and rich, just because he, he didn't care for such things. But while he was there, he would write papers with them. But what it then meant is that, um, over time, he had collaborated with such an unbelievable number of people that, uh, people came up with the idea of an Ehrlich number, which is how many steps away in a network you are from having collaborated directly with Ehrlich, the man himself.

• 6:23Michael Stevens?

  So not only a lot of collaborators, but it sounds like also a very diverse. Variety of types of papers in mathematics.

• 6:32Hannah Fry?

  Yeah, absolutely. And this, I think this is the one that is the most famous idea. So the Bacon number is analogous, but the idea is that Kevin Bacon has been in so many different films with so many different people that you can have a Bacon number too. So if you have a Bacon number of zero, you are Kevin Bacon himself. If you have a Bacon number of one, you have appeared on screen with Kevin Bacon. And a Bacon number of two, and you have appeared on screen with somebody who has appeared on screen with Kevin Bacon, and so on, and so on, and so on.

• 7:04Michael Stevens?

  If you have an Erdosh number of zero, you are Erdosh.

• 7:08Hannah Fry?

  Yeah.

• 7:09Michael Stevens?

  Which, by the way, until you said it, I thought it was Erdos.

• 7:12Hannah Fry?

  Oh.

• 7:13Michael Stevens?

  So that's, that's why it's helpful to do audio programs about mathematicians. Erdosh.

• 7:18Hannah Fry?

  I think I've got an Erdosh number of four, by the way. I think mine is four.

• 7:21Michael Stevens?

  That's, yours is, yours is four.

• 7:23Hannah Fry?

  I think so, yeah. Let me just double check.

• 7:25Michael Stevens?

  Now, we haven't published a paper together, which is like the rule, right? But if we did, I would have a number of five.

• 7:33Hannah Fry?

  Absolutely. But we have appeared on screen together. What's your Bacon number?

• 7:37Michael Stevens?

  I don't know. Is there a way to find out? I don't, I haven't really been in enough like IMDb type shows.

• 7:44Hannah Fry?

  Oh, it's five. My Erdosh number is five.

• 7:47Michael Stevens?

  Ah, okay.

• 7:48Hannah Fry?

  Oh, hold on. I've got a Bacon number of three.

• 7:51Michael Stevens?

  How?

• 7:52Hannah Fry?

  I've only done one thing ever where, which was drama. But I appeared on screen with Lenny Rush, who is this absolutely amazing actor. He has a Bacon number of two. So there we go. I've got an Erdosh Bacon number of 5'2". But that means you're 6'3" at the very least.

• 8:10Michael Stevens?

  You think? I have a Bacon of six?

• 8:12Hannah Fry?

  Erdosh of six. We have to publish something together, but after that.

• 8:16Michael Stevens?

  Well, should we come up with a name for the Bacon-Erdosh ratio?

• 8:20Hannah Fry?

  Yeah, go on.

• 8:22Michael Stevens?

  Oh, oh my gosh, there's an Erdos Bacon number. It measures the collaborative distance in authoring papers between that person and Erdos and their bacon number. Oh, no.

• 8:34Hannah Fry?

  Go on.

• 8:34Michael Stevens?

  It doesn't have a funny name, it's just called the Erdos Bacon Number. And the lowest is three. Mathematician Daniel Kleitman has an Erdos Bacon Number of three because he co-authored papers with Erdos and has a Bacon Number of two because he appeared as an extra in Goodwill Hunting with Minnie Driver, who appeared with Bacon in sleepers.

• 8:52Hannah Fry?

  Yeah, that is impressive. So what was his three? Mine's seven. Pathetic, pathetic. I need to hunt down Kevin Bacon immediately.

• 8:59Michael Stevens?

  Right, I mean, yeah, so, so, so you could probably collaborate with someone who worked with Erdos directly.

• 9:06Hannah Fry?

  Yeah, not, not, I mean, I haven't got long to go because this is, you know, he was around in sort of the, he was particularly big in the 1960s.

• 9:14Michael Stevens?

  Yeah, you gotta do it now, but you could achieve, what, at most today, a Erdos Number of two?

• 9:20Hannah Fry?

  Yeah.

• 9:20Michael Stevens?

  And then Bacon is still alive. That can become a one. So you could beat Daniel Kleitman.

• 9:26Hannah Fry?

  You could equal him, no? Two and one.

• 9:29Michael Stevens?

  Yeah, you add them together. So the best you could do would, would be to tie him.

• 9:35Hannah Fry?

  Records that can't be broken, Michael, one of your favorite subjects.

• 9:38Michael Stevens?

  Wow, okay, yet another tab I'm not going to be closing.

• 9:44Hannah Fry?

  How many are there out of interest?

• 9:46Michael Stevens?

  Uh, let's see if I can figure that out. Um, there's too many for me to easily navigate, but on this one window, I have, it's over a hundred.

• 9:56Hannah Fry?

  Can I tell you why I pick Erdos, right, as a, as the most peculiar person?

• 10:01Michael Stevens?

  Well, yeah.

• 10:02Hannah Fry?

  I mean, this is, the Erdos Bacon stuff is all very nice, but, but what makes Erdos peculiar, apart from the fact that he didn't have a house and just turned up at his friends' doors insisting that they take care of him. He also took a lot of amphetamines and some people were concerned that he was addicted to them. He was working like 19 hours a day. And so a friend of his, Ron Graham, bet him $500 that he could, he, he wasn't able to stop taking the drugs, right? He couldn't go cold turkey for 30 days. And so Erdos was like, fine, I'll do it. So he stopped, he immediately stopped. He took the $500 from, from Graham and, you know, didn't touch the drugs at all in that time. And then at the end, he said, look, see, you, what you've proved is you've proved that I'm not an addict, so well done you, but what you've done here is you've set mathematics back by a month.

• 10:48Michael Stevens?

  Because he needed the drugs to do math.

• 10:50Hannah Fry?

  And he needed the drugs to do the math, which I quite like. The other thing about him is that he, um, my, my favorite story about him is that he was totally incapable of feeding himself. Right. Just couldn't, didn't understand the most basic ideas of how to construct a sandwich, for instance. So there was one day where he was staying at a friend's house and he was hungry. He went into the kitchen, probably because of all of them amphetamines, went into the kitchen, um, opened the, the fridge and found a carton of tomato juice. Couldn't work out how to open it, so got a knife from the counter, stabbed it open. Tomato juice went everywhere, drank from the carton, left it on the side and then went off back to work.

• 11:31Hannah Fry?

  And his friend came down just to witness what looked like a murder scene in his kitchen. Just like, that's just Erdoche, that's just Erdoche. There he is.

• 11:42Michael Stevens?

  I mean, that sounds like something I might do in college. Not saying I'm Erdoche, but I get it. I get it.

• 11:50Hannah Fry?

  Yeah, fair. Um, yeah, what nice, I mean, what a great guy. He also, he thought that God was the supreme fascist. And he would, uh, he would regularly attribute every time he lost his glasses or, uh, you know, couldn't find a book that he wanted to read or whatever. He would be like, it was the supreme fascist that did that. But when he found a really beautiful mathematical proof that was, that couldn't be approved of, and that was essentially perfection. He said, look, that came from the book and the book was the supreme fascist's little handbook of perfect mathematical proofs. That could only even have been created by God.

• 12:27Michael Stevens?

  Oh, so it's like a bittersweet supreme fascist.

• 12:30Hannah Fry?

  A bittersweet, a bittersweet supreme fascist. That's a sentence I think that has not ever been spoken before and probably never will be again.

• 12:39Michael Stevens?

  Good.

• 12:40Hannah Fry?

  This is a great question. It's from Francisco from Lisbon. Would it be possible to explain to a humanoid alien, bilaterally symmetrical, via written or spoken message, no direct or visual contact, which side is left and which is right? The alien would have no access to anything on Earth or a human body as a reference, nor would they be really aware of north and south. Is there a fundamental, physical or cosmological real-world difference between left and right? And can that information be passed on? Great question, Francisco.

• 13:11Michael Stevens?

  Oh, my gosh. Yes, I love this because I got really obsessed with it years ago. I read Martin Gardner's Amidextrous Universe, which I recommend to everyone. It is a book all about mirror images, symmetries. He poses that same question and goes through all the ways we can't answer it. And so I read the whole book thinking, we still don't know the answer. And I'm like, I'm gonna make a video about this. It's such a deep mystery. And then at the end, he's like, oh, and then in 1956, we figured it out. So to kind of like, lay the scene, I think it's good to imagine communicating with aliens through, say, radio waves only, so we can't send images.

• 13:55Michael Stevens?

  And we're trying to tell them how to build something that is anatomorphic, like a coffee cup, a Father's Day Number One Dad coffee cup. All right, so you tell them, all right, this is easy. You make a cylinder. Fine. They know what a cylinder is, right? There are symmetries in our universe that make that something we can easily explain. We can talk about points and whatever. Now, we tell them, like, take off the top and empty the volume inside, but leave one side at the bottom. And now they've made a cup. And then you tell them, print Number One Dad, so that when you look at it, you see it. And they're like, yep, we're following, and they're doing this. And now, you tell them, you gotta put a handle on it. And you say, now, the handle should go, since, you know, here on Earth, most people are right-handed.

• 14:39Michael Stevens?

  We tend to put the handles on the right side. So when you hold it, you see the printing. And they go, which one's the right side?

• 14:49Michael Stevens?

  Think about it, this is much harder than you might imagine. Because remember, we cannot reference anything in the environment. You can't say, "Look at number one dad on the mug. Look at Earth and the Virgo superclusters to the right." You can't do that. If you're not allowed to do that, what do you tell them to differentiate left and right?

• 15:05Hannah Fry?

  Because you could say, "Okay, place the handle along the axis of the cylinder so that it's perpendicular to the base." That would be fine. And then you could say, "And now rotate it so that the handle, so it's no longer symmetrical about the central line." That would be fine. But distinguishing left from right, really hard.

• 15:27Michael Stevens?

  Yes, because we could tell them to, you know, looking at the handle, rotate the mug. But rotate which way? Which way is right and which is left? And how do we tell them with words alone and no references to any other models? Ever since at least Kant, people wrote about how, golly, it doesn't make any sense. Like, a right hand floating in a universe all on its own doesn't have a rightness or a leftness. So for decades, we thought maybe there wasn't an answer. Because of the four fundamental forces, three of them we knew made no difference when mirror reversed. Left and right didn't matter.

• 16:09Michael Stevens?

  So gravity, electromagnetism, and the strong nuclear force make no distinction. If you watch them do things in a mirror, it all looks fine, right? You look at a pendulum in a mirror, it's obeying all the normal physics and it fits all the normal formula and equations. So this was true for these three fundamental forces. But the weak force was hypothesized to not have that same symmetry. And an experiment was devised that essentially looked at the spin of electrons emitted by decaying Cobalt 60. This is called the WU experiment. So in the WU experiment, they use Cobalt 60 atoms that are decaying, and they put them

• 16:50Michael Stevens?

  into both, let's call it, regular spin orientations and mirror image spin orientations, and found that the electrons that decayed out came out in the same direction. It's not like, okay, you spin this way, the electrons come up, and you spin the other way and they come down. In which case, then you can't really know. You just reverse it and it's the same. Instead...

• 17:10Michael Stevens?

  They found it didn't matter. The electrons always came out in one direction. So that can be called, you know, your left or right, whichever it is. I don't know enough about cobalt. But that is a way to agree because you'll both see the same thing.

• 17:22Hannah Fry?

  So, okay, let me make sure I understand this then. Right, so you get the mug. You're like, you've got number one dad on it. And then the only way

• 17:33Hannah Fry?

  to distinguish left from right as innate properties of the universe, rather than just some sort of convention that we have decided on, is to get subatomic particles, perform these experiments where you are, looking at the spin, looking at the direction of the electrons. And then that's the way that they can print the handle on the right. I would say it doesn't matter if they print it on the left hand side. I think it'd probably be all right.

• 18:01Michael Stevens?

  I think if we want them to match, we have to do all of that rigmarole. And that is such a cool feature of our universe. Because it is otherwise so simple, left and right. Come on, you know, it's, it's, it's, it's, it's right there. And yet it isn't, except the weak force comes in clutch at the end and says, all right, guys, technically, if you're willing to do a lot of work, I can help.

• 18:25Hannah Fry?

  There is something really nice about this idea that there are directions. I mean, time is the other one, right? Time faces only in one direction. You know, you can't go backwards in time. There's something really nice about this idea, these fundamental rules of physics. Maybe this is, maybe I don't think about this deeply enough. But couldn't you just say, all right, you've got some electrons going through a wire. Those electrons are going in, say, one particular direction. And they will create a magnetic field that wraps around the wire. I mean, that's the right hand rule, right? Could you not say that it wraps around clockwise, anti-clockwise? Can you, I don't know. Is there not a way to get it that way?

• 19:08Michael Stevens?

  Yes, there is not a way to do it that way. And I unfortunately do not know why. I think it has something to do with you need to both agree on which is the north side of a magnet first.

• 19:17Hannah Fry?

  Oh.

• 19:20Michael Stevens?

  It's something like that. Now, we've since learned that you can use other things besides cobalt. You can use uranium-239. You know, that might help us if the aliens are like, "Ooh, we don't have any cobalt." But still, it's a lot of work.

• 19:34Hannah Fry?

  So then if you get the mug, to bring the mug in, you say, "All right, whichever way your electron goes off in, orient the mug so that the axis of, or the wording of the number one dad is in parallel to that, and then perpendicular, whatever." I mean, that's the way that you do it?

• 19:53Michael Stevens?

  That's the way you would have to do it, yeah.

• 19:56Hannah Fry?

  Wow. Extraordinary. Extraordinary.

• 19:59Michael Stevens?

  By the way, this is my dream Father's Day gift. I want my daughter to get me a number 2,587,312 dad.

• 20:09Hannah Fry?

  Why specifically that number?

• 20:10Michael Stevens?

  I just feel like that's probably where I am, you know? Like, I'm not the number one dad. There can't be more than one number one, but that's all they sell, number one dad mugs. I want to have a reasonable, I'm probably like, you know, top, top 30% maybe. Like, put me there. Make it act like I actually earned this. Anyway, that's the gift that I want. But after the break, Hannah, you've got a gift for me.

• 20:34Hannah Fry?

  It's a treat. Buckle up.

• 20:44Speaker 03

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• 22:19Hannah Fry?

  Welcome back from the break. I've been saving this one, Michael. This is by quite a long stretch the best thing I own. It's also the most ridiculous thing I own. So, you know, don't judge my entire character based on this. I will. I'm going to, okay. It's, as I described it earlier on, the ultimate nerd trophy. Okay, so there is a science fiction director called Alex Garland. He wrote The Beach, he directed Ex Machina, it's a really amazing film about the sort of future of humanity with artificial intelligence embedded in it. He also did this amazing HBO show called Devs, which was about a sentient quantum computer

• 22:59Hannah Fry?

  that was able to calculate the position of every atom in the entire universe, and thus all of the future and the past was available to it. Oh, like Laplace's demon? Exactly. Laplace's demon, this theoretical construct that was based on the idea that if the universe is deterministic, then every single thing should be predictable. The only problem is, is we don't know where all the atoms are, and that's, that's the thing that's stopping us knowing every single thing. Shucks, yeah. So this is, this is the, the central idea of this, of the show. Now, as part of the show, they made... A quantum computer, or at least a prop that looked like a quantum computer. And what they made was this very beautiful thing.

• 23:43Michael Stevens?

  Ooh, yeah.

• 23:45Hannah Fry?

  Very beautiful prop that was made for the show.

• 23:48Michael Stevens?

  Yes.

• 23:48Hannah Fry?

  This is designed to be an accurate representation of what you really see from quantum computers.

• 23:54Michael Stevens?

  So what we're looking at here is like the Tower of Babel, but upside down. Like an upside down tiered cake, but without the cake, just the tiers. A series of platforms like circular discs connected one below the other by thin rods with a big collection of very thin, very ultrafine wires coming out, but arranged very neatly. Like they've just been so precisely combed and gelled into this arrangement. It's almost like lit from inside as well, very gold and everywhere. Gold and silver are the big notes of color.

• 24:30Hannah Fry?

  It's very blingy, isn't it?

• 24:31Michael Stevens?

  It's very blingy, but very delicate, like a fish skeleton. These very thin bones arranged so purposefully.

• 24:40Hannah Fry?

  So they are indeed made with this incredible amount of gold. All of this wiring, this is all very accurate. I mean, it's sort of like slightly fancified for the purposes of production. If you've seen photographs of quantum computers, that is exactly what they look like. These great golden structures with wires all over the place. They're very beautiful. Would make, I think, a very nice chandelier. That's what I think about it.

• 25:04Michael Stevens?

  That's what it looks like.

• 25:05Hannah Fry?

  That is exactly what it looks like, very beautiful. Anyway, so they made this show and a little while after it was made, they still had this beautiful prop. The problem was that after they finished filming, they had this object in a storage unit and it was...

• 25:23Michael Stevens?

  How big was it? It's hard for me to get a sense of its scale.

• 25:26Hannah Fry?

  Big, we're talking sort of from top to bottom, maybe 10 feet.

• 25:30Michael Stevens?

  Oh, wow, okay.

• 25:32Hannah Fry?

  Right, giant, okay. So they have these giant crates, this big storage unit, and these storage units were costing an absolute fortune. So a couple of years after production ended, Alex Garland and his team were... They were like, "We don't want to throw it away. We spent an absolute fortune making this incredibly beautiful model of a quantum computer." So they were ringing around the different museums and places which might take it. And it just so happened that at the time I was doing up my house.

• 26:01Hannah Fry?

  I have in my house this um this big sort of hole that's cut in the floor, kind of a big void. And I was looking, I just so happened to be looking at that moment in time for something that I could hang in that void. Um, and so I basically rescued it out for skip.

• 26:16Michael Stevens?

  So it's hanging from the ceiling.

• 26:18Hannah Fry?

  It's hanging from the ceiling.

• 26:19Michael Stevens?

  Ah, like a big chandelier.

• 26:20Hannah Fry?

  Like a giant chandelier.

• 26:22Michael Stevens?

  Oh Hannah, that is incredible.

• 26:24Hannah Fry?

  No, isn't it? I mean, you can, Michael can see the picture of my house and he can confirm that my house is not massive. It basically takes up quite a lot of my house. Every time someone, I mean, the postman comes in, you can see it from inside the front door. Um, they wonder what it is because it sort of looks like a spaceship if I accidentally leave the curtains open.

• 26:42Michael Stevens?

  Yeah, I mean, it, it can pass as a chandelier, as an, as a piece of artwork. How is it lit up? Is that the way it was lit up in the movie? Or did you have to add the lighting, the bulbs?

• 26:52Hannah Fry?

  The light panels were in there from the movie. Real quantum computers, by the way, do not have.

• 26:57Michael Stevens?

  No, they wouldn't need them.

• 26:58Hannah Fry?

  Light panels. Um, this, you can see sort of like a, a scan of it in position. We replaced the LED so that they could be, um, they would last much longer. Also, what I did is I, I've made it so they're each individually controlled. So I have put a little computer in there, Bluetooth, uh, it's connected via Bluetooth. And one of my projects, uh, for a summer, when I have some time off, what I want to do is program it so that when I play music in the house, the, the quantum computer sort of twinkles in time.

• 27:25Michael Stevens?

  Visualizes the music.

• 27:27Hannah Fry?

  Exactly right. But what I really wanted to do, I wanted to show you this image because I sort of actually wanted to talk a little bit about, um, about the way that these things work.

• 27:36Michael Stevens?

  Okay, but first of all, I'm sorry, how did you, how did you get it? Did you reach out to them?

• 27:41Hannah Fry?

  No, so I have a, uh, my, my very good friend, Adam Rutherford, is, uh, was the scientific advisor on the series and is a very good friend of Alex Garland's. But I just so happened to be in the right room when they were like, we're gonna have to throw it away. We're gonna have to basically sell it for scrap because nobody wants it. The, the museums didn't want it because it wasn't a real quantum computer.

• 27:59Michael Stevens?

  Yeah.

• 28:00Hannah Fry?

  I mean, where else would you put it? You know? Who would be crazy enough to have one of these in the house?

• 28:04Michael Stevens?

  It's a very interesting thing because it's, it's beautiful. It's a piece of like science fiction history. It's a, it's a part of the history of human ambition.

• 28:15Hannah Fry?

  Exactly.

• 28:16Michael Stevens?

  And storytelling.

• 28:17Hannah Fry?

  And storytelling. That is something that is also this piece of art, this really stunning piece of art. So this is the real thing. Here's a picture of the real thing. This is IBM's quantum computer. This is a system two. This is, I mean, one of the most sophisticated objects in the entire world. The inside of these, the guts of them, they really are made of real gold, partly because it's such an incredible conductor. Also, these things need to be unbelievably cold. My favorite thing, by the way, about going to visit the proper one in Boston with IBM is that, I mean, you're standing there next to these machines that are worth quite literally hundreds of millions of dollars, right? The research project itself, probably billions. These are the most sophisticated machines in the entire world

• 29:02Hannah Fry?

  at the absolute cutting edge of technology. And then you go around the back of them and they're still using USB 2.0. They haven't upgraded to USB C yet.

• 29:12Michael Stevens?

  Oh, I love that.

• 29:15Hannah Fry?

  It's how you connect your computer to them. It's old school.

• 29:18Michael Stevens?

  Just USB. Yeah.

• 29:20Hannah Fry?

  Just USB.

• 29:20Michael Stevens?

  Doesn't work most of the time. Yeah.

• 29:22Hannah Fry?

  Like even the most amazing places in the world, once you peer under the surface, it's all still gaff tape and WD-40.

• 29:28Michael Stevens?

  Well, I love that it's like this progression of more and more sophisticated from the USB in the laptop all the way down to this like cradled chip.

• 29:38Hannah Fry?

  What you notice is that the physical design of this, I mean, basically what you're looking at here, the guts of quantum computer, it's just a fancy fridge.

• 29:48Michael Stevens?

  I actually know basically nothing about quantum computing. I have to attack the things I'm interested in one at a time. And so I literally don't know what a quantum computer is. How much of it is real? How much is sci-fi? How is a qubit different from and better than a bit? I mean, just give me like the for a kid version.

• 30:08Hannah Fry?

  Oh, yeah. Okay. So the thing is, is that. They're sometimes presented as though they're better, and I think that that's the wrong way to think about them. Okay. They're definitely different. It's a completely different paradigm. And the way to think about it is that bits, normal computers, are ones and zeros, right? It's like a switch, it's on or it's off. And what you can do with that is you can program things in a very deterministic way. There's no sort of extra probability that's thrown in there, there's no randomness. Everything ideally is like very controlled. You run the same program twice, you get exactly the same answer. That's sort of normal, traditional computing. The quantum computer is based on a qubit, which you can think of instead of it being

• 30:51Hannah Fry?

  like a one and a zero, like a yes or a no, it's much more like a distribution, it's much more like a, even like a dial, if you like. So instead of dealing with like absolute facts, yeses and nos, you're handling everything in probabilities. My favorite analogy to describe this, although, you know, all of the analogies eventually break down if you think about them too hard. Yep. But I think that this is a good illustrative example. If you wanted to solve a maze using a traditional computer, the only way that you can do that is you start at the beginning and you try one route and it fails and you go back to the beginning and you try again and it fails and so on. With a quantum computer, because you're handling probabilities, you're handling sort of numbers that take on more than one value, what you can do is you can chuck a bucket of water

• 31:35Hannah Fry?

  in at the top of the maze and what that will do is flow through all of the various possibilities simultaneously and give you a sort of probability distribution at the end of what happened across all of those different routes. And this is like both the incredible potential of these quantum computers, because it means that suddenly we are in a quantum world, right? We can handle probability and uncertainty and, and, and quantum effects, actually. You can now model things down at the level of atoms in a way that's really, really hard to do with a traditional computer that only deals in absolute certainties. Right. But it also simultaneously means that.

• 32:19Hannah Fry?

  All of our encryption, essentially, which is based on this idea that you have to do things one after the other, after the other, after the other, that it will take too long for you to try all possible routes. It means that that is now out the window. It means that the way that we send secrets online, the way that you keep your bank information to yourself, or the way that, I don't know, even like national security ideas transported around the world without being completely open to anyone who's listening, a lot of that falls apart because as soon as a quantum computer can check every possible variation, our traditional encryption methods are no longer secure.

• 32:55Michael Stevens?

  Are gone. Wow.

• 32:57Hannah Fry?

  There are ways around it, though, and maybe we'll talk about that in a different episode.

• 33:00Michael Stevens?

  Yeah, I would love to because I want to learn about this. It's unbelievable how little I know. So they, they aren't necessarily better at, you know, finding the square root of a three-digit number. A regular calculator can do that just fine, and Abacus can do that just fine, but these can tackle problems that were literally so hard for other types of computers that that's how we make things safe. And, and their paradigm is so different that it's a whole new world.

• 33:27Hannah Fry?

  It's a whole new world, exactly. And there will always be things that traditional computers can do that quantum computers are rubbish at. The key difference is that vice versa, things that have always been hard to do on traditional computers, like searching vast, vast, vast number of options, I mean, that in particular, or trying to model what happens in the deeply complex intermolecular forces of the sort of quantum realm. All of that stuff, which has been so hard to get computers to do, I mean, AI sort of manages to do a little bit of that, but all of that now is suddenly, suddenly open and available to us. So, so the real hope is that once you have quantum computers, things like drug

• 34:09Hannah Fry?

  discovery, you know, understanding how molecules interact with each other and proteins, you know, to the point where you can actually design something at the level of atoms, suddenly become way more available. Or, you know, battery design, right? Like, Imagine how different the world would be if we could design better batteries. This is another one on the list for quantum computers, once we get this sort of up and running. And I do think it is coming, you know. There's a sort of a joke about how far away it is. Quantum computing's always been 30 years away, a bit like fusion.

• 34:44Michael Stevens?

  Right, right.

• 34:45Hannah Fry?

  But I think that we're really starting to see genuine progress.

• 34:48Michael Stevens?

  You've got not a quantum computer, but our like hopes and dreams as shown in a show hanging in your home.

• 34:58Hannah Fry?

  I absolutely do. You can, next time you're in London, Michael, you can come and have a glass of champagne underneath my Laplace's demon. My imagined version of a future with scientific advances. Should just tell you, in the show itself, that quantum computer did not lead to good for humanity. So maybe be careful what you wish for, but nonetheless.

• 35:22Michael Stevens?

  Yeah, I can cheers to that.

• 35:24Hannah Fry?

  Yeah. As soon as I turn it on, I'm gonna, I'm gonna get it to calculate how to pay its own electricity bill. That's, that's what I'm gonna do.

• 35:30Michael Stevens?

  There you go.

• 35:31Hannah Fry?

  If you have any questions that you would like us to answer, or objects that you would like us to discuss, then you can send them in to [email protected].

• 35:39Michael Stevens?

  Yep, please do that. I cannot wait to hear from you. If you want to hear from us even more often, join our newsletter at therestis.com/science.

• 35:47Hannah Fry?

  We're gonna be back next Thursday with another edition of Field Notes and on Tuesday with our normal episode.

• 35:53Michael Stevens?

  Yep, see you then.

• 35:54Hannah Fry?

  Bye.

• 36:03Speaker 04

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