Luke Robert Mason: You’re lis­ten­ing to the Futures Podcast with me, Luke Robert Mason.

On this episode I speak to the­o­ret­i­cal physi­cist, Jim Al-Khalili.

But ulti­mate­ly, there’s a real­i­ty out there and for me, science—and physics in particular—is the best way of under­stand­ing the nature of that reality.
Jim Al-Khalili, excerpt from interview

Jim shared his thoughts on what the­o­ret­i­cal physics can teach us about the nature of real­i­ty and the mys­ter­ies of our uni­verse, the pos­si­bil­i­ty of a the­o­ry of every­thing, and how to make sci­en­tif­ic ideas acces­si­ble and captivating.

This episode is an edit­ed ver­sion of a recent live stream event. You can view the full, unedit­ed video of this con­ver­sa­tion at future​spod​cast​.net.

Now the­o­ret­i­cal physics has become our most use­ful tool in under­stand­ing the ori­gin of space and the mean­ing of time. It has been so effec­tive that the late pro­fes­sor, Stephen Hawking, claimed that physics might soon pro­vide us with a the­o­ry of every­thing. But new dis­cov­er­ies like quan­tum mechan­ics and dark ener­gy, com­bined with a chal­lenge of uni­fy­ing all of these con­cepts are forc­ing physi­cists to con­front cap­ti­vat­ing new unknowns. In his beau­ti­ful new book, The World According to Physics, Jim Al-Khalili explores just how far physics has gone in demys­ti­fy­ing the world, and then out­lines how far it still has to go in teach­ing us about the nature of real­i­ty and the weird­ness of our universe.

So, Jim, there is so much that I want to ask you, but from read­ing the book it is abun­dant­ly clear that you have a—perhaps an appropriate—love affair with physics. I guess I want to know what it is about the world of physics that makes it such a cap­ti­vat­ing way to under­stand our reality?

Jim Al-Khalili: Well, you know, I some­times am puz­zled why every­one isn’t com­plete­ly in love with physics because it deals with the deep­est ques­tions. I remem­ber when I was grow­ing up as a kid want­i­ng to know: Does space go on for­ev­er? What are stars made of? What do atoms look like? What is time? The big ques­tions of real­i­ty that we ask. At some point—I must have been about 12, 13 or 14—I realised that physics was the sub­ject that tries to answer those ques­tions, and that was it for me. So, okay, it helps that I’m good at maths. It helps that I like solv­ing puz­zles and solv­ing mys­ter­ies, but physics was real­ly, basi­cal­ly com­mon sense about how the world works. It gave me the tools to ask some of these real­ly deep ques­tions and that’s what I’ve done all my life, and I still keep ask­ing those same questions 

Mason: Now sci­ence and ratio­nal inquiry which under­lies physics: it’s done so much to demys­ti­fy our world. Do you think that’s nec­es­sar­i­ly a good thing or is some mys­tery actu­al­ly quite useful?

Al-Khalili: I think it would be a bor­ing world if we had all the answers. There’s no doubt about that. It’s a bit like the antic­i­pa­tion of open­ing your Christmas presents on Christmas morn­ing. There’s that excite­ment of not know­ing what you’ve got as a kid. I mean, maybe not so much for me now. I know it’s socks and after­shave. But once you’ve opened your presents, yes, you’ve got your new toys and what­ev­er is there, but the mys­tery is gone. Somehow the mag­ic has dis­ap­peared. I think it’s the same with try­ing to under­stand the uni­verse and our place in the uni­verse. The mys­tery about it is wonderful.

I think a lot of peo­ple have this mis­con­cep­tion that sci­ence is about—certainly demys­ti­fy­ing, because mys­ter­ies are there to be solved—but some­how we want for there not to be mys­ter­ies. We want just for the world to be ratio­nal­ly explained away with­out any puz­zles, with­out any mag­ic, with­out any won­der. That’s sim­ply not the case. There are still so many mys­ter­ies out there, so many things we have yet to under­stand. Yes, physics demys­ti­fies, but it also shows us new mys­ter­ies that we have to tack­le, and new challenges.

Mason: I mean, one thing that sci­ence and physics does real­ly well is show us a ver­sion of real­i­ty. In some cases—in the case of physics—it shows us a sin­gu­lar objec­tive real­i­ty that can be under­stood through sci­ence. Do you think there’s such a thing as a sin­gu­lar objec­tive real­i­ty? Do you think phys­i­cal the­o­ries could real­ly be able to be used to approx­i­mate the truth of phys­i­cal reality?

Al-Khalili: I do, yes, but that’s not to say that all physi­cists or philoso­phers of sci­ence agree with me on this. My view is that there’s a world out there, there’s a uni­verse, a real­i­ty out there. It’s been in exis­tence long before humans came about and start­ed ask­ing ques­tions about it. The role of sci­ence and the role of physics is, as you say, to approx­i­mate as close­ly as we can to that objec­tive real­i­ty; the truth of the way things are.

There aren’t dif­fer­ent real­i­ties or dif­fer­ent truths. It’s not that you arrive at a different…there are dif­fer­ent ways of explain­ing: dif­fer­ent ide­olo­gies, reli­gions, philoso­phies. But ulti­mate­ly, there’s a real­i­ty out there, and for me, science—and physics in particular—is the best way of under­stand­ing the nature of that reality. 

Mason: Where have we seen exam­ples of physics help­ing us to under­stand that phys­i­cal real­i­ty? Physics the­o­ries help­ing us under­stand that phys­i­cal reality?

Al-Khalili: The way physics has devel­oped for many, many cen­turies. An exam­ple I use in the book is: If I were to drop a ball from a height of five metres, physics tells me that it will hit the ground in one sec­ond. There’s a sim­ple for­mu­la, actu­al­ly devel­oped by Galileo—even before Isaac Newton—that tells you: Drop it from five metres on Earth, the pull of Earth’s grav­i­ty will mean it falls and hits the ground in one sec­ond. Not half a sec­ond, not two sec­onds. No ide­ol­o­gy, no amount of med­i­ta­tion or prayer, no phi­los­o­phy, noth­ing will tell you it’ll hit the ground in one sec­ond, oth­er than physics. The uni­verse, described math­e­mat­i­cal­ly, which we now explain using physics. That’s a fact, a truth about real­i­ty that physics tells us. It does­n’t mat­ter how far our the­o­ries devel­op. Einstein replaced Newton and some­one else will replace Einstein, but that will always remain true. 

Mason: When it comes to physics, it’s often this thing that’s done by, obvi­ous­ly, physi­cists. You say in the book that there are two types of physi­cist: Number one is the searchers and the dream­ers; num­ber two is those that play it safe by explor­ing the the­o­ries that can be attest­ed with exper­i­men­ta­tion. Jim, what kind of physi­cist are you?

Al-Khalili: Somewhere in between, he says, bor­ing­ly. Those two cat­e­gories, I guess they apply more to the­o­ret­i­cal physi­cists rather than exper­i­men­tal physi­cists. When you study physics at uni­ver­si­ty, if you want to go on aca­d­e­m­i­cal­ly to do physics research, you have to make this choice: you either become a the­o­rist or an exper­i­men­tal­ist. The the­o­rist does the maths, solves the equa­tions, writes the com­put­er code, devel­ops the mod­els and sim­u­la­tions. The exper­i­men­tal­ist, in the lab, car­ries out exper­i­ments to test the way the world real­ly is. But among the­o­rists, yeah, there are these two types.

The exam­ple I use in the book is: If you walk along a qui­et pave­ment late at night and you almost get home, but then you realise you’ve lost your keys through a hole in your pock­et. You go back and retrace your steps, to look for your keys. If you look in the pools of light under­neath the lamp­posts, that’s where you’re most like­ly to be able to see your keys, if they’re there. But of course, they’re more like­ly to be in the large areas of dark­ness, in between the lamp­posts. There’s two types of physi­cists. There’s the searchers in the dark who grope around in the dark. They don’t know what they might find. They’re less like­ly to find what they’re look­ing for, but the rewards are big­ger. Then, there are safer physi­cists who are in the pools of light. They’re more like­ly to make advances, but they’ll be incre­men­tal advances. They’re not like­ly to cre­ate a rev­o­lu­tion in physics. So yes, peo­ple work­ing on cos­mol­o­gy or string theory—these are the searchers in the dark. They’re the adven­tur­ers, but they could spend all their lives with­out com­ing up with a rev­o­lu­tion in physics. If they do, there’s your Nobel prize.

Mason: But which one is more fun? Is it the pre­dic­tion game or is it the proof game? Much of physics that was the­o­rised has now been proved, but the ones who did the pre­dict­ing are the ones, as you just said, who win the Nobel prize. Which one do you think is more fun? 

Al-Khalili: I think it depends on your per­son­al­i­ty as a sci­en­tist. There are physi­cists who are quite hap­py to spend their whole career devel­op­ing a very eso­teric, math­e­mat­i­cal mod­el of what hap­pens, say, before the Big Bang. They almost know there’s no way of test­ing that idea exper­i­men­tal­ly, but that’s fine. They will come up with their ele­gant math­e­mat­i­cal equa­tions and for them, that’s ful­fill­ing enough. Then, there are the oth­er physi­cists who don’t feel a sense of achieve­ment or ful­fil­ment unless they can test their the­o­ry against data; against obser­va­tion and experiments.

I’ve spent most of my research career actu­al­ly devel­op­ing the­o­ret­i­cal mod­els that can be test­ed against exper­i­ments and for me, that’s a suc­cess. If my mod­el pre­dic­tion match­es what peo­ple see in the lab, I say, Okay, well my equa­tion explains the way the world actu­al­ly works.”—and that’s very, very sat­is­fy­ing, but it may not be so exciting.

Mason: Well you do such a good job in this book of mak­ing physics excit­ing, regard­less of what sort of physics that it is. You do such a good job at sum­maris­ing many of the key the­o­ries in physics. Everything from space and time, ener­gy and mat­ter, quan­tum mechan­ics, ther­mo­dy­nam­ics. I want to take it one step back and ask you: What was the impact of the tele­scope and the micro­scope on human per­cep­tion? How were these two tools key to our under­stand­ing of the world, through some­thing like physics?

Al-Khalili: More than any oth­er instru­ment in human history—certainly in terms of under­stand­ing the world—the tele­scope and the micro­scope real­ly rev­o­lu­tionised our view. Until then, all we could under­stand about the world is the world that we could see with our sens­es; with our naked eyes. Once you have a tele­scope, that brings the very far close to you, so we could study the stars and under­stand the cos­mos. The micro­scope brings the very small, again, into view—and enlarges it—so we could delve into the micro­scop­ic world. Now of course, as you say, our two most impor­tant or pow­er­ful the­o­ries in the whole of physics are: General relativity—Einstein’s the­o­ry of describ­ing the very large, and quan­tum mechanics—describing the world of the very small. Without the tele­scope and the micro­scope, those worlds—the very far and the very small—wouldn’t have been avail­able to us. That hap­pened in the 17th cen­tu­ry, and sud­den­ly that real­ly kick­start­ed the sci­en­tif­ic revolution.

Mason: That hap­pened at that time, and also Galileo helped to math­e­mate­cise physics. Why was that so impor­tant to how we think about physics today?

Al-Khalili: It was­n’t obvi­ous that the uni­verse spoke in the lan­guage of math­e­mat­ics. Today we take it for grant­ed, that it does­n’t mat­ter what part of the world you are as a sci­en­tist or what lan­guage you speak. You know you can write down an equa­tion and it describes some aspect of the world which would be exact­ly the same equa­tion for any­one else in the world, for any cul­ture in any age. There’s a uni­ver­sal­i­ty about the math­e­mat­ics of the phys­i­cal uni­verse. Galileo was try­ing to under­stand how objects fall. They accel­er­ate in Earth’s grav­i­ty, but to give a sim­ple alge­bra­ic expres­sion which allows us to make pre­dic­tions and do cal­cu­la­tions real­ly meant that we could devel­op our the­o­ries because they could then math­e­mat­i­cal­ly make pre­dic­tions that you could go and test against an experiment—rather than just qual­i­ta­tive­ly say­ing, Well I sug­gest that the world looks like this. That the sun orbits the Earth.”—or what­ev­er the Ancient Greeks were think­ing about. They were very good at philosophis­ing but to pin the prop­er­ties of real­i­ty math­e­mat­i­cal­ly allowed us to devel­op our the­o­ries much more effec­tive­ly. Of course, there was no look­ing back after that. 

Mason: In many ways it feels like physics is this process of pick­ing the right mod­el and pick­ing the right math­e­mat­ics, apply­ing that to the right sys­tem. Is that a good way to sum­marise what physics actu­al­ly is?

Al-Khalili: By and large, yes. The sys­tem, the phe­nom­e­na that you want to study—you have to choose the right the­o­ry that applies there. It’s a mat­ter of scale, it’s a mat­ter of the sort of phe­nom­e­na that you want to under­stand. If you want to fix your wash­ing machine you don’t need to know the stan­dard mod­el of par­ti­cle physics, even though your wash­ing machine is ulti­mate­ly made of quarks and elec­trons. You don’t need that. You need to under­stand the mechan­ics and elec­tri­cal cir­cuit­ry. Yes—whatever phe­nom­e­non or sys­tem you want to under­stand in the uni­verse, you have to apply the appro­pri­ate the­o­ry that gives you the best way of learning.

Mason: Physics plays in two spaces, real­ly. It feels like it plays in the big of space and time and in the very, very small. But what is so reveal­ing about your book, as some­one who knows absolute­ly noth­ing about physics, is that there seems to be some sort of rela­tion­ship between the two. Could you explain that a lit­tle bit more?

Al-Khalili: Yeah. I mean these are the two most pow­er­ful the­o­ries in physics, cer­tain­ly 20th cen­tu­ry physics. Einstein devel­oped his two the­o­ries of rel­a­tiv­i­ty at the begin­ning of the 20th cen­tu­ry which we now know described space and time, and the cos­mos and the uni­verse at large. Essentially, how mat­ter and ener­gy have a grav­i­ta­tion­al field which shapes the struc­ture of the uni­verse. So that’s on the very large scale, and it’s a very beau­ti­ful, very accu­rate the­o­ry. But, it does­n’t apply when you zoom down to the tiny, micro­scop­ic scales. Down there at the lev­el of atoms, we need a com­plete­ly dif­fer­ent the­o­ry: quan­tum mechan­ics. Quantum mechan­ics, in its own domain, is also extreme­ly pow­er­ful. With quan­tum mechan­ics, even though it only describes things we can nev­er see with the naked eye—namely atoms and the par­ti­cles that make them up—without it, we would­n’t be hav­ing this con­ver­sa­tion. Without quan­tum mechan­ics, we would­n’t under­stand the nature of how mate­r­i­al con­ducts elec­tric­i­ty; how semi­con­duc­tors work. We would­n’t have devel­oped sil­i­con chips, microchips and com­put­ers. Essentially all of mod­ern elec­tron­ics relies on our under­stand­ing of the quan­tum world. It’s very pow­er­ful, but it does­n’t apply, as far as we can deduce at the moment, to the very large—in the same way that gen­er­al rel­a­tiv­i­ty, Einstein’s view of the cos­mos does­n’t apply down at the sub­atom­ic scale. That’s annoying.

You might think, well why? You’ve got the world out there, per­fect­ly described by a the­o­ry, and the world down there at the very small, per­fect­ly described by a very dif­fer­ent the­o­ry. To live with it, that’s the way it is. But there are instances and exam­ples where both the­o­ries should apply. They’re rather exot­ic exam­ples. The first exam­ple is the Big Bang itself, or the sin­gu­lar­i­ty at the cen­tre of a black hole. It seems that those two the­o­ries are very dif­fer­ent and don’t mesh togeth­er, and so the holy grail of physics—the ambi­tion that so many the­o­rists have—is to find a the­o­ry that some­how is an uber the­o­ry, from which emerge both quan­tum mechan­ics and gen­er­al rel­a­tiv­i­ty. This is what we call a the­o­ry of every­thing.

Mason: It uni­fies every­thing, and that’s real­ly key to this book—or at least it feels like it’s a key theme with­in this book: the idea that there will be a uni­fi­ca­tion of physics. What is uni­fi­ca­tion? What is this the­o­ry of every­thing? Why is it such a major aim for physics and physicists?

Al-Khalili: We’ve dis­cov­ered ever since mod­ern physics first devel­oped by peo­ple like Galileo and Newton that seem­ing­ly two dis­parate and quite inde­pen­dent phe­nom­e­na ulti­mate­ly seem to have a con­nec­tion between them. Newton start­ed it off. He realised that the rea­son an apple falls to the ground—whether or not one actu­al­ly fell on his head on his moth­er’s farm, we don’t know, he tells that story—but the rea­son the apple falls to the ground is due to the same force that keeps the moon in orbit around the Earth, and the Earth in orbit around the sun. The force of gravity—we learn about it at school now. Back in Newton’s time, it was­n’t obvi­ous that the forces con­trol­ling Earthly objects need not have any­thing to do with those forces con­trol­ling the heav­en­ly bod­ies. So there was that uni­fi­ca­tion of forces due to grav­i­ty. James Clerk Maxwell, a Scottish physi­cist in the 19th cen­tu­ry uni­fied elec­tric­i­ty and mag­net­ism, and showed that they are part of the elec­tro­mag­net­ic field, and light is a trav­el­ling elec­tro­mag­net­ic wave. Again, peo­ple did­n’t realise there was a connection.

Throughout the 20th cen­tu­ry we’ve seen this process of uni­fi­ca­tion actu­al­ly pick up pace. Quantum mechan­ics was devel­oped. That was com­bined with Einstein’s spe­cial the­o­ry of rel­a­tiv­i­ty. It was com­bined with Maxwell’s the­o­ry of elec­tro­mag­net­ism. The forces inside atom­ic nuclei were explained by quan­tum mechan­ics, and you get to a point where you have one all encom­pass­ing the­o­ry that describes all the forces down at the sub-atomic scale, and anoth­er all encom­pass­ing the­o­ry describ­ing the uni­verse at large. We sort of expect, or hope that there is that next step that brings these two the­o­ries togeth­er. We just haven’t fig­ured it out yet.

Mason: Why is there that hope, though? Why is it so nec­es­sary for physi­cists to find some­thing that uni­fies all of these the­o­ries? Does it just sat­is­fy some weird desire that physi­cists have for things to be math­e­mat­i­cal­ly per­fect, and they just like the­o­ries when they’re aes­thet­i­cal­ly pleas­ing? Or is there some­thing deep­er going on?

Al-Khalili: It’s just so that we can fit an equa­tion on our t‑shirts.

Mason: A hun­dred percent. 

Al-Khalili: No, it’s more than van­i­ty or just a sense of sat­is­fac­tion. In uni­fy­ing phe­nom­e­na and ideas, and forces, we devel­op a deep­er under­stand­ing. What we arrive at is a the­o­ry that gives us a bet­ter under­stand­ing of the uni­verse than the pre­vi­ous two the­o­ries that were not con­nect­ed. In uni­fy­ing, we’re not just sim­pli­fy­ing for con­ve­nience and just for neat­ness, but because it helps us reach a deep­er truth. That ulti­mate truth about the nature of real­i­ty that we spoke about at the begin­ning. We feel we’re get­ting clos­er to it. We don’t know how much fur­ther we have to go, of course. Almost some­times, it feels like peel­ing back lay­ers of the onion. Oh gosh, who ordered that? Dark mat­ter? Come on. But, we do feel we are mov­ing in the right direction.

One exam­ple of why as to why a the­o­ry of every­thing is there; why we want to uni­fy Einstein’s gen­er­al the­o­ry of rel­a­tiv­i­ty and the­o­ry of grav­i­ty with quan­tum mechan­ics is that in quan­tum mechan­ics, there’s this idea that a sub­atom­ic particle—say, an electron—can be in two places at once: what we call a super­po­si­tion. Or, that it can actu­al­ly have two ener­gies at the same time—two quite sep­a­rate ener­gies. Just say­ing the words means it’s absolute­ly mean­ing­less. Quantum mechan­ics is coun­ter­in­tu­itive. But, if an elec­tron is in two places at once, we also know from rel­a­tiv­i­ty that mat­ter caus­es space­time to curve around it. That’s a deep expla­na­tion of what the force of grav­i­ty is: the cur­va­ture of space­time. If an elec­tron is in two places at once, space­time cur­va­ture has also been split. Spacetime is also in a quan­tum super­po­si­tion. We know that ulti­mate­ly, our the­o­ry of spacetime—general relativity—must some­how be com­bined, log­i­cal­ly, with the the­o­ry of the quan­tum world. We know it’s there, we just don’t know whether we have to mod­i­fy quan­tum mechan­ics, mod­i­fy gen­er­al rel­a­tiv­i­ty, or some­how scrap both and start from scratch.

Mason: You intro­duce us to two pos­si­ble con­tenders for this the­o­ry of every­thing with­in the book. The first one is string the­o­ry and the sec­ond is loop quan­tum grav­i­ty, which sounds like some­thing out of sci­ence fic­tion. What is the dif­fer­ence between the two, and do you think either of these could poten­tial­ly become that the­o­ry of everything?

Al-Khalili: It’s pos­si­ble. They’ve both been going for some time now and they both have their pro­po­nents, their advo­cates and their cheer­lead­ers. Physicists who have spent their careers think­ing about them. They’re both high­ly spec­u­la­tive, math­e­mat­i­cal the­o­ries. String theory—developed first in the mid 80s and then under­went a sec­ond rev­o­lu­tion in the mid 90s—suggests that ulti­mate­ly, mat­ter is made of tiny vibrat­ing strings, not point par­ti­cles. These are strings vibrat­ing in high­er dimen­sions. It’s very eso­teric and very abstract, but it gives us a way of uni­fy­ing the force of grav­i­ty with the oth­er three forces which are already con­tained with­in our quan­tum theories.

Loop quan­tum grav­i­ty, on the oth­er hand, isn’t about uni­fy­ing the four forces—but rather: How do you quan­tise—this is the word you use when you make some­thing behave quan­tum mechan­i­cal­ly—how do you quan­tise space and time? Either of them could be right. I don’t work in the field. I’ve got good friends and col­leagues who work in both, and in fact I recent­ly inter­viewed Brian Greene, an American string the­o­rist who would argue that string the­o­ry is the the­o­ry of every­thing. We just haven’t fig­ured every­thing out about it yet, but it is the cor­rect the­o­ry. Then Carlo Rovelli, for example—an Italian physi­cist who has writ­ten some won­der­ful, best-selling pop­u­lar sci­ence books. He’s a fan of loop quan­tum grav­i­ty and again, he would say, Oh no, the string theorists—they’ve had their time. They’ve got­ten nowhere. They’ve been think­ing about this for decades. Loop quan­tum grav­i­ty is much more sen­si­ble.” It’s almost like dif­fer­ent ide­olo­gies, dif­fer­ent reli­gions. Which camp are you in?

In the book, I try…because I don’t work in either field, I can sort of step back and say, Well you know, they’ve got their good points and they’ve got their good points.” But what we need, of course, is to find a way of test­ing them. Ultimately, a sci­en­tif­ic the­o­ry stands or falls based on whether it cor­rect­ly describes the real, phys­i­cal universe—which means we need to find some way of test­ing; car­ry­ing out an exper­i­ment; car­ry­ing out an obser­va­tion that can tell us whether these the­o­ries are right or wrong. At the moment, we don’t know how to test them. 

You could almost ask whether they are prop­er sci­en­tif­ic the­o­ries. Are they just meta­physics? Are they just phi­los­o­phy with pret­ty maths? We don’t know how we can check whether or not they’re right.

Mason: Perhaps it’s a good thing that we can’t check if they’re right yet. If we did achieve that uni­fi­ca­tion, you talk about in the book achiev­ing some­thing else which is the end of physics. In oth­er words, you can pack up and retire because physics will have achieved what it want­ed: that uni­fied the­o­ry. What is the end of physics, and could physics actu­al­ly be in cri­sis in the 21st cen­tu­ry if we find this uni­fied theory?

Al-Khalili: I think many physi­cists would argue that if there is a cri­sis in physics, it’s because the end that we thought was in sight, isn’t. If you want more mys­ter­ies, if you’re think­ing about going to physics as a young bud­ding sci­en­tist then great, because I think the end is fur­ther away than we thought. At the end of the 19th cen­tu­ry, physi­cists thought that every­thing was done. We had Newtonian mechan­ics and his law of grav­i­ty; we had Maxwell’s elec­tro­mag­net­ism; we had ther­mo­dy­nam­ics; sta­tis­ti­cal mechanics—all branch­es of physics that are still good and prop­er today—but peo­ple thought that was all there was to know, and so the end was in sight. Then in the 1890s, we dis­cov­ered the elec­tron, we dis­cov­ered x‑rays—so called because x’ for the unknown; we don’t know what x‑rays were—and we dis­cov­ered radioac­tiv­i­ty. Then, in the turn of the 20th cen­tu­ry you have the quan­tum rev­o­lu­tion, Einstein comes along and you realise: Whoa, you thought it was the end of physics. We’re just starting.

We almost thought it was the same and we were get­ting to the end of physics at the end of the 20th cen­tu­ry. Stephen Hawking even wrote a famous paper around about 1980 say­ing: is the end in sight for the­o­ret­i­cal physics? We’re get­ting close to the the­o­ry of every­thing. It looks like we aren’t real­ly very close to it at all, and oth­er mys­ter­ies have popped up since then, any­way, that we have yet to try and understand.

Mason: Well if I can just be a cheer­leader for the 21st cen­tu­ry for a moment, we have actu­al­ly dis­cov­ered stuff in this cen­tu­ry. In 2012 and 2016. Could you tell us about some of those discoveries?

Al-Khalili: Yes, of course. What’s won­der­ful is that these are dis­cov­er­ies that have made it out into the wider world. It’s not just physi­cists who will know about it. Everyone heard about the Higgs boson, dis­cov­ered at the Large Hadron Collider in Geneva in 2012. Peter Higgs and others—the the­o­rists who had pre­dict­ed the exis­tence of the Higgs boson, this ele­men­tary par­ti­cle, this lump of energy—had pre­dict­ed it half a cen­tu­ry ago. Finally, the exper­i­ment con­firmed that it real­ly exist­ed and they got their Nobel prizes. 

Then of course in 2016, the dis­cov­ery of grav­i­ta­tion­al waves. These were absolute­ly remark­able lab­o­ra­to­ries in America called LIGO—they’re two twin lab­o­ra­to­ries on either side of the States, and they’ve picked up these very very tiny, del­i­cate rip­ples in space itself, com­ing to us—from the col­li­sion of two black holes. It’s like drop­ping a stone in a pond and then the rip­ples radi­al­ly mov­ing out­wards. If the pond’s very very large, you’ll just see a tiny rip­ple at the shore­line and that’s the evi­dence that a stone was dropped in the mid­dle of the pond. So 2016: grav­i­ta­tion­al waves. But again, they were pre­dict­ed by Einstein’s the­o­ry a hun­dred years ago. Yes, these were absolute­ly incred­i­ble exper­i­men­tal results and got the world of sci­ence and beyond all very excit­ed, but they were pre­dict­ed already. We would have been much more sur­prised if we had­n’t found the Higgs boson and if we had­n’t found grav­i­ta­tion­al waves. Having dis­cov­ered them, we’ve ticked the box. Good, yep okay, so Peter Higgs was right. Einstein was right. What now?

Al-Khalili: You almost reveal in the book—and you strug­gle to say it—but per­haps it would have been bet­ter for sci­ence if we had­n’t found the Higgs boson, because it would have chal­lenged the stan­dard mod­el of physics, and that could have actu­al­ly been quite a pos­i­tive thing.

Al-Khalili: I think had it been con­firmed not to exist, the stan­dard mod­el of par­ti­cle physics—as it’s known—would have had to have been…not ditched, but revised and rethought. It would have been back to the draw­ing boards. That’s what we want. We want to prove the­o­ries wrong and replace them with new ones, because there’s the excite­ment, there’s the mys­tery, there’s the Nobel prizes all around. You don’t want to con­firm that some guy a hun­dred years ago was right all along. Where’s the fun in that?

Mason: I mean the one prob­lem that that would have caused is the pub­lic per­cep­tion of sci­ence. Especially pub­licly fund­ing very expen­sive sci­ence would have been in real cri­sis if they’d turned the thing on and actu­al­ly found nothing.

Al-Khalili: Absolutely, and we do real­ly have to work hard—we’re see­ing this now dur­ing the coro­n­avirus pandemic—need to work hard at explain­ing to wider pub­lic and wider soci­ety, how sci­ence works. That it’s okay to make mis­takes, or to be wrong, or to make a wrong pre­dic­tion, because when you gath­er more evi­dence or car­ry out a new exper­i­ment, you learn some­thing new and you can revise your pic­ture of the world. To some extent, the Large Hadron Collider actu­al­ly has been suf­fer­ing from this point that you make about whether or not it was all worth­while. For a lot of peo­ple, once the Higgs boson was dis­cov­ered, they said, Right, okay, you’ve found it. So you’re just going to shut up shop now and go home?” and they say, Oh no no. The Large Hadron Collider…we want to dis­cov­er lots of oth­er things. We want to dis­cov­er if there is evi­dence of oth­er new types of par­ti­cles out there.”—but that was­n’t solved. The Higgs boson was the poster child of the Large Hadron Collider.

Of course what has hap­pened is that we haven’t dis­cov­ered any­thing since then. Since 2012, eight years lat­er, exper­i­ments have been run­ning and we’ve not dis­cov­ered any oth­er new par­ti­cles. There might be the accu­sa­tion that it’s a very, very expen­sive machine that has been built to con­firm some­thing that we thought prob­a­bly exist­ed all along. But then, you know, unless you’re curi­ous and unless you take the plunge and try to do what you can to unrav­el the secrets of the uni­verse, that defines our human­i­ty. It’s there, like Mount Everest, and you have to climb it.

Mason: In many ways it’s turned into just a very expen­sive cycle path. It looks fun when those peo­ple are cycling through that thing.

Al-Khalili: Maybe.

Mason: As I read the book and as I lis­ten to you now, it feels like physics is like your email inbox. When I’m try­ing to emp­ty my email inbox, the only way I can get to Inbox—0 is to reply to all my emails, but when I reply to all my emails, that leads to more inbound emails. In the same way, the more answers that you get from physics, the more ques­tions you seem to have. Why is that?

Al-Khalili: [laugh­ter] Why even both­er? You know, we think we’re approach­ing that ulti­mate real­i­ty. We did­n’t under­stand the nature of mat­ter. We dis­cov­ered that nor­mal mat­ter is made of atoms, then we look inside atoms and realise they’re made of atom­ic nuclei with elec­trons buzzing around the out­side. Then the nucle­us is made of pro­tons and neu­trons. Protons and neu­trons are made of quarks and glu­ons. Are the quarks and glu­ons real­ly vibrat­ing strings? In a sense, you think well, are we going to keep going for­ev­er? But at the same time, I think there’s good rea­son to believe that there should be an end in sight. We haven’t dis­cov­ered a fifth force, for exam­ple. We know there are four fun­da­men­tal forces in the uni­verse and we haven’t dis­cov­ered a fifth. There may be a fifth one, but we’re get­ting clos­er to tam­ing and under­stand­ing and uni­fy­ing four forces of nature, so it may be that physics will come to an end one day. It may be that we’ll get so close to under­stand­ing the ulti­mate nature of real­i­ty that there won’t be many more rev­o­lu­tions or par­a­digm shifts, or big changes in our world view. I think we’re a long way off from that, at the moment. 

Mason: I mean when look­ing at the entire his­to­ry of physics, what, per­son­al­ly, is more daz­zling to you? Is it the suc­cess of fun­da­men­tal physics to this day, or is it the ques­tions we still have yet to answer?

Al-Khalili: That’s an inter­est­ing ques­tion. I’m fas­ci­nat­ed by the his­to­ry of sci­ence and the his­to­ry of physics and I love read­ing the biogra­phies of some of the great heroes of mine—the big names. Niels Bohr, Richard Feynman, Einstein, Paul Dirac and so on. I get a tin­gle, a sense of fol­low­ing in their foot­steps and how they came to under­stand what they did. For me, there is a romance about the jour­ney that physics has tak­en thus far. In my day to day life, in my research, I’ve just spent sev­er­al hours this after­noon talk­ing to a cou­ple of my PhD stu­dents and my col­lab­o­ra­tor Andrea Rocco, at Surrey, try­ing to fig­ure out a way of solv­ing cer­tain equa­tions, or try­ing to fig­ure out a way of mod­el­ling a quan­tum phe­nom­e­non. We realise we just don’t know which direc­tions to go in. How do you solve that inte­gral? What sort of approx­i­ma­tion can we make there? There’s an excite­ment in not know­ing. Ultimately, that’s what keeps me awake at night. 

I swear, the oth­er night, I woke up to go to the bath­room, came back to bed, was lying in bed and I start­ed think­ing about this equa­tion that one of my stu­dents had sent me. I’m think­ing…okay. I’ve got Greek sym­bols float­ing around in my head and cal­cu­lus in my head, half asleep, and I fig­ured some­thing out! I did­n’t jump up and scrib­ble it down in my note­book because my wife would­n’t have been pleased about that—putting the bed­side light on—but the next morn­ing I thought, oh yeah, I can do that. So for me, that’s the won­der of what I do. It’s the thing that I want to fig­ure out lying in bed. It’s the last thing I think before I go to sleep, and it’s the first thing I think about in the morn­ing. Not every day—I’m not that sad—but that excite­ment of the mys­ter­ies that get to be solved.

Mason: Well it’s just as well you did­n’t solve a mys­tery in that moment, because it would have been a dis­cov­ery that you’d have to pub­licly tell every­body you dis­cov­ered just after tak­ing a real­ly good mid­night uri­na­tion. Ultimately, most peo­ple dis­cov­er things in the bath­room. We can say that you were in the bathroom…similar sort of thing. But ulti­mate­ly, where does that leave us? What do we know that we don’t know? How do you know that we might even­tu­al­ly know what might seem unknow­able? I don’t know if that made sense. 

Al-Khalili: The known knowns, the known unknowns, and the unknown…yeah. We know there are mys­ter­ies out there. There are phe­nom­e­na that we need to some­how explain prop­er­ly. The nature of dark matter—invisible stuff out there in the uni­verse that’s hold­ing galax­ies togeth­er. We know it’s out there, we know it has a grav­i­ta­tion­al pull, but we don’t know what it’s made of. We know the uni­verse is expand­ing ever­more rapid­ly, so we know some­thing called dark ener­gy, but we don’t quite under­stand its nature. We know that just after the Big Bang, mat­ter and anti­mat­ter would have been cre­at­ed in equal amounts, but we don’t know why there’s no anti­mat­ter around now. Most of the uni­verse, thank­ful­ly, is nor­mal mat­ter. We don’t under­stand how to uni­fy quan­tum mechan­ics and relativity.

There are oth­er exam­ples. We don’t under­stand, for exam­ple, what is the cor­rect expla­na­tion of quan­tum mechan­ics. How can a par­ti­cle be in two places at worse? How can Schroadinger’s cat be dead and alive at the same time inside the box? These are things we know that need to be resolved. Of course, we don’t know what sur­pris­es there might be around the cor­ner; new phe­nom­e­na to be dis­cov­ered. Dark ener­gy, when it was dis­cov­ered back in 1998, was an absolute shock­ing sur­prise that no one antic­i­pat­ed. We thought the uni­verse was expand­ing but the expan­sion rate was slow­ing down, that grav­i­ty was putting the brakes on. All the mat­ter and ener­gy in the uni­verse was stop­ping it from expand­ing so rapid­ly, slow­ing it down. We thought maybe one day, it’ll re-collapse in on itself in a Big Crunch. No one antic­i­pat­ed there was some­thing that was win­ning the bat­tle against grav­i­ty and mak­ing the uni­verse expand ever more quick­ly. That’s part of the excite­ment: that we real­ly don’t know how much we don’t know. 

Mason: Despite the fact that we don’t know some things, we can actu­al­ly apply what we do know to the cre­ation of new tech­nolo­gies. Our under­stand­ing of space and time, for example—that’s led to so many tech­no­log­i­cal inno­va­tions, has­n’t it?

Al-Khalili: Oh, absolute­ly. What I don’t want to give the impres­sion of is that some­how, we’re floun­der­ing and that we don’t under­stand any­thing about the nature of the world. We pret­ty much under­stand all the phe­nom­e­na and all the mech­a­nisms, all the stuff that goes on around us in our world. When I talk about what we don’t under­stand, that’s at the far edge of exis­tence, and does­n’t real­ly impact our dai­ly lives. Einstein’s the­o­ry of rel­a­tiv­i­ty that explained the nature of space and time tells us that grav­i­ty slows time down. Time itself runs slow­er, the stronger the force of grav­i­ty. Come on. Some guy with wild hair comes up with this thing. It’s great for sci-fi movies but not in the real world. But then, that’s how your smart­phone works and that’s how GPS works. GPS and your phone relies on sig­nals com­ing from satel­lites in orbit around the Earth, that tri­an­gu­late and pin­point your posi­tion. Because those satel­lites are orbit­ing the Earth, they’re feel­ing weak­er grav­i­ty than we are on the sur­face of the Earth. Their time lit­er­al­ly runs at a faster rate on a satel­lite than it does on Earth. We have to delib­er­ate­ly slow the clocks down on the com­put­ers on board the satel­lites, so that they match the rate of clocks tick­ing by on Earth in order to get GPS work­ing. There’s Einstein’s the­o­ry of rel­a­tiv­i­ty about time slow­ing down which leads to time trav­el and all sorts of won­der­ful expla­na­tions, but with­out it, tech­nol­o­gy that we take for grant­ed sim­ply would­n’t work. We’d be lost. 

Mason: We can go one step fur­ther now, because physics isn’t just being applied to tech­nolo­gies that are pure­ly based on physics the­o­ries. It’s being used in inter­dis­ci­pli­nary research. We’re start­ing to see physics inform­ing research in biol­o­gy and things like chem­istry. Could you give us some exam­ples of that?

Al-Khalili: Yes. It’s always been true that the bound­aries between…although we learn physics, chem­istry and biol­o­gy as sep­a­rate sub­jects at school, once you get into the cut­ting edge of research and devel­op­ing tech­nolo­gies, it’s always been true that you have this mul­ti­dis­ci­pli­nary approach. What we’re see­ing in the 21st cen­tu­ry is the most excit­ing areas and devel­op­ments in technology—whether it’s genet­ic engi­neer­ing, whether it’s robot­ics and arti­fi­cial intel­li­gence, whether it’s nanotechnology—they require input from lots of dif­fer­ent fields.

One area in par­tic­u­lar that I’m inter­est­ed in, in my research is the appli­ca­tion of quan­tum physics in mol­e­c­u­lar biol­o­gy. This is this new area called quan­tum biol­o­gy which is still spec­u­la­tive, and it’s built around the idea that there are cer­tain mech­a­nisms and phe­nom­e­na inside liv­ing cells which seem to only be explain­able by appeal­ing to the laws of quan­tum mechan­ics. In a very strange way that I think a lot of sci­en­tists still find…they’re very scep­ti­cal about it—and it is speculative—but for me, it’s won­der­ful­ly excit­ing to think that maybe the mech­a­nisms of life itself rely on these coun­ter­in­tu­itive ideas in the quan­tum world. Without quan­tum mechan­ics, life has had four bil­lion years and dur­ing that time, evo­lu­tion has reached down into the quan­tum world and plucked out some tricks that allow it to work more effi­cient­ly. That’s still ear­ly days yet, but a very excit­ing new field.

Mason: So it could even­tu­al­ly be pos­si­ble that quan­tum mechan­ics and quan­tum the­o­ries can explain the emer­gence of life itself?

Al-Khalili: It’s very easy to appeal to quan­tum mechanics—to say that all mys­ter­ies we don’t under­stand, Well that’s quan­tum mechan­ics.” Quantum mechan­ics explains con­scious­ness or explains, heav­en for­bid, non­sense things like home­opa­thy or what­ev­er. Because quan­tum mechan­ics has this mys­te­ri­ous appeal to it, it’s tempt­ing to use it to explain oth­er things we don’t under­stand. I would­n’t go so far as to say quan­tum mechan­ics might explore the ori­gin of life or the nature of life itself. But you know, who knows? It’s excit­ing to think that quan­tum mechan­ics might play a role in an area where we were least expect­ing it: inside liv­ing cells.

Mason: It’s so inter­est­ing what you say about that because peo­ple do get car­ried away by the idea of quan­tum. Suddenly, quan­tum can explain every­thing and we have things like quan­tum woo. If I think things then the uni­verse will align itself to give me what I so desire. There’s been such a mis­un­der­stand­ing in many ways of physics. You try and deal with some of that in the book by look­ing at this word, truth. In fact, the word truth fea­tures through­out the book and you real­ly look close­ly at how sci­ence deals with this tricky issue of: What is truth? What is con­sen­sus? What is dog­ma? Why do we have to be so care­ful when we talk about truth?

Al-Khalili: We’re see­ing the impor­tance of under­stand­ing how sci­ence works more than ever. When politi­cians say, We are fol­low­ing the sci­ence. We’re appeal­ing to the sci­en­tif­ic evi­dence. Science tells us this.”, peo­ple real­ly need to under­stand how sci­ence works: The idea of reach­ing con­sen­sus; the idea of com­ing up with a hypoth­e­sis that makes pre­dic­tions that are repeat­able, that can be test­ed exper­i­men­tal­ly. It real­ly is very wor­ry­ing when you see on social media the pro­lif­er­a­tion of con­spir­a­cy the­o­ries. People who pro­mote them seem to think they are behav­ing and think­ing sci­en­tif­i­cal­ly, but they’re not. In sci­ence, if you’re faced with evi­dence con­trary to your hypoth­e­sis or your the­o­ry, you have to revise your under­stand­ing in the light of that new evi­dence. In so many ways, when peo­ple appeal to sci­ence in a very loose way to devel­op what­ev­er the­o­ry, or dog­ma, or ide­ol­o­gy they want to pro­mote, they’re not fol­low­ing the sci­en­tif­ic method prop­er­ly. Yes, sci­en­tists have their own vest­ed inter­ests. I want to get my research grant. If I’m a string the­o­rist, I want to believe that string the­o­ry is the cor­rect the­o­ry of every­thing and I want peo­ple to give me research mon­ey and stu­dents so we can car­ry on doing that. But broad­ly, the sci­en­tif­ic process itself does evolve by con­sen­sus. If I come up with an idea or car­ry out a mea­sure­ment and dis­cov­er some­thing, some­one else has to con­firm it. It has to be reproduced.

There are lots of fail safes built into sci­ence but ulti­mate­ly, I still think there is that sin­gle objec­tive real­i­ty; that truth out there; the way the world actu­al­ly is. The sci­en­tif­ic method is the most reli­able way of get­ting as close as we pos­si­bly can to that truth. 

Mason: In this day and age, peo­ple seem to have their own truths about the way the world works, and you men­tion con­spir­a­cy the­o­ry there. How do we do bet­ter? How do we fil­ter what is real sci­ence and what is pseudoscience—especially in an age of things like Twitter? 

Al-Khalili: It is real­ly hard when there is so much being bom­bard­ed left, right and cen­tre by so many YouTube videos and views and opin­ions that go viral. There’s all this con­fir­ma­tion bias and we live in these fil­ter bub­bles where we are fed the stuff that we want to believe in, and there­fore we believe it. I’m not sure what the answer is. I could glibly say, Well, not only should we com­mu­ni­cate the sci­en­tif­ic ideas—we talk about the Big Bang and quan­tum mechanics—we should also explain how sci­ence works.”—but I think it’s true. I think teach­ing kids at school the sci­en­tif­ic method—what does it mean to have a the­o­ry? A sci­en­tif­ic the­o­ry is not the same as, I have a the­o­ry that aliens vis­it­ed me last night.” A sci­en­tif­ic the­o­ry has to sat­is­fy cer­tain cri­te­ria and strict rules and regulations.

I do think explain­ing to peo­ple how the sci­en­tif­ic process works and being open-minded. If you believe some­thing to be true, don’t believe it with cer­tain­ty. Use doubts and self-criticism and think about whether or not that could be wrong. Listen to evi­dence from an oppos­ing view and see if that makes sense. People think sci­en­tists are closed mind­ed. No, no—quite the oppo­site, in the hope that we would­n’t dis­cov­er the Higgs boson. We want to ham­mer and kill our the­o­ries. We want to replace them with bet­ter ones, if we can. We don’t want to main­tain the sta­tus quo. Be open mind­ed, but not so open mind­ed that your brain falls out—that’s the only wor­ry I have.

Mason: It was inter­est­ing to see in the book that you said that doubt, in not trust­ing your sens­es, and ignor­ing com­mon sense can some­times be the things that actu­al­ly make good physi­cists, good physi­cists. In many ways, those sorts of things are key to the pro­gres­sion of sci­ence. Is that right? 

Al-Khalili: Having doubts, yes. I said at the begin­ning, one of the rea­sons that I fell in love with physics was that I saw it as puz­zle solv­ing and com­mon sense. The way the world works seems to make sense. It’s explic­a­ble; it’s under­stand­able, and yet there’s a dan­ger in assum­ing that it’s just com­mon sense. Very often, if we don’t apply the sci­en­tif­ic method, we can be led to the wrong con­clu­sions and sci­ence stops us from using what we think is com­mon sense in com­ing to a con­clu­sion about some­thing, or the way some­thing works, or an expla­na­tion. Sometimes the sci­en­tif­ic method says, No, what you expect­ed to see, what you thought was log­i­cal, actu­al­ly isn’t the way the world is.” So hav­ing doubts and hav­ing the will­ing­ness to revise your world view in the light of new evi­dence is the only way we’ll make progress in sci­ence. We have to make mis­takes, oth­er­wise we’d nev­er change our minds. 

Mason: In a fun­ny sort of way, do you think that post-truth is actu­al­ly the key to the his­to­ry of sci­ence? In oth­er words, if it was­n’t for the seek­ers and the searchers invent­ing new ideas and sug­gest­ing new truths, then per­haps we would­n’t have some of the physics the­o­ries that we have today. For exam­ple, some claim the exis­tence of par­al­lel uni­vers­es just to make their sci­ence work today. It may be proven to be true and it may be proven to be not true, but we need peo­ple using the tools of post-truth to chal­lenge the sci­en­tif­ic dog­ma of today, for sci­ence to progress—don’t you think?

Al-Khalili: Yes, but sci­ence only pro­gress­es when those ideas can be test­ed. It’s true that pos­tu­lat­ing the exis­tence of a mul­ti­verse and an infi­nite num­ber of par­al­lel uni­vers­es is no dif­fer­ent from the­ol­o­gy or abstract phi­los­o­phy, because you could say any­thing if you can’t test it—I can come up with any idea. There’s a dif­fer­ence though between some of these high­ly abstract eso­teric ideas in fun­da­men­tal physics, like string the­o­ry, like mul­ti­verse the­o­ry. There’s a dif­fer­ence between them and oth­er post-truth ide­olo­gies or woo-woo, as I say. They are built on a foun­da­tion of try­ing to explain the world that we know. Parallel uni­vers­es do explain stuff. It will be great if it turns out that par­al­lel uni­vers­es real­ly do exist, because that would explain why our uni­verse is so spe­cial. How come all the dials for every­thing in our uni­verse were tweaked for just the right to allow us humans to exist and have this con­ver­sa­tion? Wanting some­thing to be true because it’s a neat idea isn’t sci­ence. Science is only when that neat idea gets test­ed and ver­i­fied and it makes pre­dic­tions that turn out to be bet­ter than any oth­er the­o­ry can predict. 

Mason: So in oth­er words, there’s real­ly a dif­fer­ence between sci­en­tif­ic the­o­ries and sci­en­tif­ic opinion?

Al-Khalili: Yes. I mean sci­en­tists are humans, so they will have opin­ions and ide­olo­gies and views and dog­mas like any­one else. But a sci­en­tif­ic the­o­ry that has been test­ed against exper­i­ments, against obser­va­tion, is some­thing that tran­scends human fal­li­bil­i­ty and opin­ion and views and ide­olo­gies, because it stands the test of the sci­en­tif­ic method.

Mason: Listening to you, Jim, it sounds like I’m lis­ten­ing to a physi­cist, obvi­ous­ly, by train­ing, but also there’s so much in what you say that makes me feel like you have a lit­tle bit of a philoso­pher in you. Do you think there’s a rela­tion­ship between physics and phi­los­o­phy? Do you think philoso­phers have added to the world of physics? Do you think philoso­phers and physi­cists can become uncom­fort­able bed­fel­lows? Or are some physi­cists actu­al­ly, deep down, secret philosophers?

Al-Khalili: Philosophy and physics, I think, have always been, actu­al­ly, not too uncom­fort­able bed­fel­lows. If you think back to some of those heroes of physics that I love read­ing about, cer­tain­ly as a student—Einstein and Bohr and Feynman and others—they were steeped in philo­soph­i­cal think­ing. They acknowl­edged the impor­tance of phi­los­o­phy in help­ing a sci­ence like physics move for­ward. I don’t think science—and physics in particular—can advance with­out the clar­i­ty that’s brought to new ideas from philoso­phers. People often talk about: Philosophy is there to help ask the right ques­tions and sci­ence then attempts to find the answers to those ques­tions.” I think that’s true, and it frus­trates me when col­leagues would say, Philosophy is dead. There’s no room for philoso­phers. We don’t need them any­more. Fundamental physics has tak­en over their role and we can do very well with­out them.” I think we’re get­ting to the point now where there are these mys­ter­ies about the uni­verse that we don’t under­stand. I think we do need the help of philoso­phers to sit down and talk to us and try and maybe give us a dif­fer­ent angle. A dif­fer­ent way of think­ing about solv­ing some of these problems.

Mason: Now we have one of our first ques­tions from YouTube, and it’s from Dave Weber who asks, Will trav­el­ling in per­son beyond this solar sys­tem ever be phys­i­cal­ly possible?” 

Al-Khalili: Since he’s put the word ever’ in, then absolute­ly. It won’t be in our life­time, but there’s absolute­ly no rea­son why we could­n’t imag­ine the tech­nol­o­gy. Nothing in the laws of physics would stop us doing it of course—it’s just the tech­nol­o­gy. Having this tech­nol­o­gy, the propul­sion sys­tem that’d allow us to trav­el that sys­tem is actu­al­ly pos­si­ble and sci­ence fiction—the very good sci­ence fiction—has real­ly shown how that might be pos­si­ble. You trav­el at a sig­nif­i­cant frac­tion of the speed of light and Einstein’s rel­a­tiv­i­ty says that your time will slow down rel­a­tive to the uni­verse out­side. What might, to us left on Earth, seem to be a jour­ney that takes many, many decades, on board a space­craft trav­el­ling at a frac­tion of the speed of light, it would be a lot short­er. You could actu­al­ly get one from one side of the uni­verse to the oth­er in half an hour, pro­vid­ing you nudged close to the speed of light. Just don’t both­er try­ing to come back again and tell your fam­i­ly all about it, because a lot more time will have gone by on Earth.

Mason: You might acci­den­tal­ly end up behind your daugh­ter’s book­case and that sort of thing might hap­pen. Do you actu­al­ly think that our phys­i­cal human bod­ies will be able to trav­el to out­er space or do you think it might just be our minds? In oth­er words, if we can get infor­ma­tion to trav­el at the speed of light, what we may do is send a robot in advance of us and sit here on plan­et Earth and con­trol that robot as an avatar ver­sion of our­selves on anoth­er plan­et or on anoth­er space­craft. Do you think it’s more like­ly that our minds will trav­el to space rather than our bodies? 

Al-Khalili: I think if we look into the far dis­tant future then that’s absolute­ly very like­ly, but of course the one thing we can’t do is break the laws of physics and send any infor­ma­tion faster than the speed of light. Even hav­ing that robot reach­ing Proxima Centauri—the clos­est star sys­tem to us, just four light years away—it takes four years for us to send our instruc­tions through to the robot there. Four years for it to come back again. Whatever tech­nol­o­gy we devel­op, we still aren’t, as far as we know, able to break that light speed bar­ri­er, despite that Star Trek might tell us.

Mason: Oh, if Star Trek was true. We have a ques­tion from Lisa on YouTube who asks, Will an under­stand­ing of dark mat­ter expand our under­stand­ing of gravity?” 

Al-Khalili: I’m not sure that it would. The fact is dark mat­ter behaves, grav­i­ta­tion­al­ly, like nor­mal mat­ter. It’s stuff. It just hap­pens to be made of par­ti­cles that don’t inter­act via the elec­tro­mag­net­ic force, so that’s why it seems invis­i­ble to us. The chal­lenge is real­ly not so much of under­stand­ing how dark mat­ter behaves grav­i­ta­tion­al­ly, but what it’s actu­al­ly made of. But then, you know, with this idea of hav­ing doubts and nev­er being cer­tain about things, we don’t know if dark mat­ter behaves in the same grav­i­ta­tion­al way that nor­mal mat­ter does exact­ly the same way. If so, does it mean we have to revise Einstein’s gen­er­al the­o­ry of rel­a­tiv­i­ty: the way that mat­ter curves space­time. Does dark mat­ter do some­thing dif­fer­ent? There are ideas that maybe dark mat­ter does­n’t even exist at all. That maybe we just have to revise our pic­ture of what grav­i­ty is to explain away what we see as dark mat­ter. The evi­dence for its real exis­tence is too over­whelm­ing at the moment. But yeah, who knows? It might revise our pic­ture of gravity.

Mason: We spoke a lit­tle bit about some of the appli­ca­tions of some of the new physics like quan­tum mechan­ics. Ben Greenaway asks, How far do you think we are from a home or per­son­al quan­tum com­put­er?” Of course, Google has achieved quan­tum supremacy—whatever that means. In terms of hav­ing one of these quan­tum com­put­ers in our homes, how far do you think we might be? 

Al-Khalili: Probably clos­er than we thought we would be ten, twen­ty years ago. Last year I pub­lished my first nov­el, sci­ence fic­tion thriller, Sunfall which is set twen­ty years from now, in 2041. In it, one of the pro­tag­o­nists, a young cyber­hack­er, uses a quan­tum com­put­er; a home quan­tum com­put­er, to hack into some high­ly encrypt­ed, secret infor­ma­tion which kick starts the whole adven­ture. I do think in maybe twen­ty years from now, we will have ful­ly work­ing quan­tum com­put­ers. As you say, com­pa­nies like Google and IBM and oth­ers are work­ing very rapid­ly. Quantum suprema­cy may not actu­al­ly mean we’ve built a prop­er quan­tum com­put­er, but it’s a big step along the way and we’re see­ing suc­cess hap­pen­ing quite reg­u­lar­ly now.

Mason: It seems like every­one wants you to make pre­dic­tions, but I guess this is the Futures pod­cast. We have anoth­er ques­tion from YouTube from Suzy, who asks, From your per­spec­tive on the cur­rent scene in physics, when do you think the next sci­en­tif­ic rev­o­lu­tion might arrive?”

Al-Khalili: My hunch…and what do I know? My hunch is that when we talk about want­i­ng the next Einstein or the next Hawking to come along, I think the prob­lem in real­ly rev­o­lu­tion­is­ing fun­da­men­tal physics is get­ting to be so com­pli­cat­ed that it may well be in AI—an AI algo­rithm that’s going to help us do that. A good friend of mine, a guy called Demis Hassabis, who is CEO of DeepMind, prob­a­bly the world’s lead­ing AI research company—I agree with him. He says that maybe we’ve come as far as we can with our crude mon­key brains, and we need an AI to real­ly solve these deep prob­lems. Finding the pat­terns in the math­e­mat­ics that are far too com­plex for humans to see. The next rev­o­lu­tion may well be 20, 30 years from now, but it may not be a human that actu­al­ly takes us forward.

Mason: What you’re doing here is such a won­der­ful exam­ple of the pub­lic com­mu­ni­ca­tion of sci­ence. Why do you think it’s so impor­tant that we make this sort of work acces­si­ble to as many peo­ple as pos­si­ble? Why is sci­ence com­mu­ni­ca­tion so impor­tant to you, Jim?

Al-Khalili: For a num­ber of rea­sons. One is that I’ve always, ever since I start­ed com­mu­ni­cat­ing sci­ence; talk­ing to the pub­lic; writ­ing arti­cles; talk­ing to journalists—I mean this goes back over twenty-five years ago now when I first ven­tured out of my ivory tow­er of acad­e­mia. I’d always felt that I want­ed sci­ence to be part of pop­u­lar cul­ture. That we would talk about black holes and dark mat­ter and quarks and what­ev­er, down the pub, in restau­rants, among friends in the same way that we talk about music, and sport, and pol­i­tics. So for it to be just part of the con­ver­sa­tion. I think to a large extent, that has hap­pened. People know about the Higgs boson. They know about the dis­cov­ery of exo­plan­ets and they know about grav­i­ta­tion­al waves and so on. In the same way that we appre­ci­ate art and music, there’s no rea­son why we could­n’t appreciate—even though we don’t have a deep math­e­mat­i­cal understanding—we can’t appre­ci­ate some of these con­cepts in sci­ence. That’s one reason.

Another, of course, is to inspire the next gen­er­a­tion. That’s always going to be true. We need more sci­en­tists and engi­neers in an increas­ing­ly tech­no­log­i­cal world. 

The third rea­son is one we’re now see­ing unfold today. People are faced and bom­bard­ed with con­flict­ing evi­dence about the coro­n­avirus: about how it’s spread­ing; whether we should wear face masks; whether we should social dis­tance. Do I go back to work? Is it com­ing down? Is there going to be anoth­er spike? There are so many ques­tions we want to know and every­one is told all the time that the deci­sions gov­ern­ments are mak­ing are based on sci­en­tif­ic evi­dence. It’s vital­ly impor­tant that peo­ple under­stand how sci­ence works. That it is not always about hav­ing all the answers to begin with. We have to be hon­est and trans­par­ent and say, Well, to the best of our under­stand­ing, this is what we think is hap­pen­ing. Maybe next week, we’ll find some more out, and we’ll realise that we weren’t quite right.” It’s not a fail­ure. It’s not like, Sack them all, sack all the sci­en­tists. What do they know? They were wrong. They said some­thing last week and they said some­thing dif­fer­ent this week. They know nothing.”—that’s why we have to com­mu­ni­cate sci­ence and how it works, and the sci­en­tif­ic method itself.

Mason: Sometimes, do you think there’s actu­al­ly a dan­ger that comes from increased pub­lic inter­est in sci­ence? For exam­ple, the Schrodinger cat exper­i­ment, orig­i­nal­ly, was sup­posed to make peo­ple think the whole thing could­n’t be cor­rect, but it entered the pub­lic con­scious­ness. With things like quan­tum, we now have quan­tum woo and, Our thoughts can affect the uni­verse.”, and all of these ideas that get mis­con­strued because the pub­lic thinks they under­stand some­thing about the sci­ence but in actu­al fact, it’s the way in which sci­ence is being com­mu­ni­cat­ed which is the issue, really.

Al-Khalili: There’s cer­tain­ly a dan­ger that peo­ple know a lit­tle bit of sci­ence and they assume that that means that they are experts. My view is as valid as yours. I’ve reg­u­lar­ly get very sweet emails and Tweets from peo­ple say­ing, I know noth­ing about sci­ence. I’m not edu­cat­ed in physics at all, how­ev­er I’ve fig­ured out what dark mat­ter and dark ener­gy are. It explains the Higgs boson and it explains this and that.“and you think: yes, but I’ve spent my whole life think­ing, work­ing hard try­ing to under­stand this stuff, and you just say, I’ve got no back­ground but I’ve just come up with this idea.” I think it is dan­ger­ous for peo­ple to know a lit­tle bit based on pop­u­lar accounts of sci­ence and then to just com­plete­ly get the wrong end of the stick. On the oth­er hand, it’s great that peo­ple are curi­ous. It’s great that peo­ple are think­ing about this stuff. When the LHC was first switched on, peo­ple were wor­ried that it was going to cre­ate a black hole that was going to swal­low up the whole Earth. Of course that was non­sense, but it got peo­ple talk­ing about par­ti­cle physics and quarks and so on. Part of the con­ver­sa­tion is fine, pro­vid­ing it does­n’t infect and cre­ate con­spir­a­cy the­o­ries and peo­ple going around burn­ing 5G masks and say­ing, 5G is cre­at­ing virus­es.” There is some dan­ger in peo­ple hav­ing a lit­tle bit of sci­en­tif­ic knowl­edge and extrap­o­lat­ing it into crazyville.

Mason: We have anoth­er ques­tion from YouTube, this time from Ingrid who asks, Are there par­al­lel or oth­er ways to explain phe­nom­e­na of real­i­ty besides math­e­mat­i­cal lan­guage?” for exam­ple, analo­gies or metaphors, or dia­grams or draw­ings. Could these actu­al­ly be clean­er and bet­ter than math­e­mat­i­cal lan­guage in many ways, or is maths always going to be the paragon through which we describe physics?

Al-Khalili: Ultimately, the uni­verse speaks the lan­guage of math­e­mat­ics, so ulti­mate­ly that is the way we have to under­stand real­i­ty. But in oth­er ways, I think she’s right. Metaphors and imagery can be very pow­er­ful. A love­ly exam­ple is the great American physi­cist, Richard Feynman, who devel­oped what are called Feynman dia­grams, which are ways of explain­ing how sub­atom­ic par­ti­cles inter­act and cre­ate new par­ti­cles, and e = mc squared. It was­n’t rig­or­ous math­e­mat­i­cal­ly, but it was a very pow­er­ful way that gave new insights. There are lots of ways that allow us to maybe under­stand the math­e­mat­ics bet­ter or give us a pic­ture of real­i­ty that allows us to move for­ward. All of those tools should be avail­able to us.

Mason: We have anoth­er ques­tion from Andre who asks, What do you think the con­fir­ma­tion of Bell’s the­o­rem through exper­i­ments tell us about the nature of the universe?”

Al-Khalili: John Bell was an Irish physi­cist who essen­tial­ly helped bring to a head a long run­ning debate in physics. Very often in pop­u­lar accounts, it boils down to an argu­ment between the two biggest names in physics—certainly in the first half of the 20th century—Albert Einstein and Niehls Bohr, the Danish father of quan­tum mechan­ics. Each of them had a dif­fer­ent view of what quan­tum mechan­ics meant, and what John Bell did was come up with a the­o­ry that said, You can’t both be right. If this con­di­tion is sat­is­fied, he’s right. If this con­di­tion is sat­is­fied, he’s right.” Bell’s the­o­ry, also known as Bell’s inequal­i­ty, was then test­ed exper­i­men­tal­ly. It gave us a way of real­ly prob­ing the mys­tery of the quan­tum world. It’s not the end of the sto­ry, through. It has­n’t resolved things yet. We still argue about whether Einstein was right or whether Bohr was right. What is the ulti­mate­ly cor­rect descrip­tion of quan­tum mechan­ics? We still don’t know. That’s one of the out­stand­ing mys­ter­ies. It’s prob­a­bly the thing that I will most want to have resolved in my life­time. John Bell is cer­tain­ly a big hero of mine—I’ve met him a cou­ple of times. If he says some­thing, I sit up and lis­ten because I think he’s one of the great, unsung genius­es of physics.

Mason: You men­tion, briefly, your work in sci­ence fic­tion. Science fic­tion is so impor­tant for how we per­ceive the world of sci­ence. I guess this is more of a per­son­al ques­tion that I have for you, but where have you seen physics prin­ci­ples best rep­re­sent­ed in sci­ence fic­tion? Also, where have you seen some of the worst case exam­ples of physics rep­re­sent­ed in sci­ence fiction? 

Al-Khalili: I give a reg­u­lar schools talk to teenagers on time trav­el and sep­a­rat­ing sci­ence fact from sci­ence fic­tion. When it comes to good sci­ence fic­tion with time trav­el, that’s a real­ly nice exam­ple. Probably the best movies on time trav­el are Interstellar—despite Matthew McConaughey float­ing behind the book­case in his daugh­ter’s bed­room bit towards the end, which gets a bit trip­py at the end of the film—but Interstellar, how­ev­er weird or wacky you think it is, is built on sol­id physics. There’s noth­ing in Interstellar that vio­lates the laws of physics, and that’s thanks to Kip Thorne, one of the Nobel prize-winning, American physi­cists who was one of the pro­duc­ers on the film. He made sure the sci­ence was right.

At the oth­er end of the scale, I don’t know. Hot Tub Time Machine? A pret­ty awful exam­ple of time trav­el. Yes. There’s a whole range. There’s sci­ence fic­tion that is real­ly well made in movies, or well told—particularly if sci­en­tists are involved. The bet­ter sci­ence fic­tion is prob­a­bly from peo­ple like Arthur C. Clarke or Isaac Asimov. Why? Because they were sci­en­tists them­selves. The worst sci­ence fic­tion is the fan­ta­sy which is not real­ly meant to fol­low the rigours of science—but that’s fun in its own way. I love watch­ing the Marvel movies. I don’t storm out of the cin­e­ma because Spiderman’s bro­ken the laws of physics. I just enjoy it.

Mason: Another part of that ques­tion is, what made you and inspired you to write sci­ence fic­tion? Why did you sud­den­ly realise: You know what? Instead of writ­ing these non-fiction tomes explain­ing sci­ence, per­haps the best way to do it is through the use of sci­ence fiction.

Al-Khalili: I’ll be hon­est with you, it was­n’t altru­is­tic in that sense at all. I’d just pub­lished a book and it was at the launch party—actually, a book on quan­tum biol­o­gy, this new area that I talked about earlier—the pub­lish­ers want­ed to know what my next book was. I said, Well, I’ve got every­thing off my chest that I want­ed to write about. I’ve writ­ten about rel­a­tiv­i­ty, quan­tum mechan­ics, and so on. Maybe I’ll write a nov­el.” I just said it as a joke and they said, Ooh, real­ly? What would it be about?”…“Probably sci­ence fic­tion. I enjoy sci-fi, Michael Crichton. It’ll prob­a­bly be a thriller because I love Stephen King books.” Before I knew it, they’d set me up with a sci­ence fic­tion com­mis­sion­ing edi­tor and I had to come up with an idea. Of course, once that seed was plant­ed in my head: Jim, maybe you should write a nov­el—that was it. That was what I was think­ing about last thing at night, and first thing in the morn­ing. It was a steep learn­ing curve, but an absolute­ly fan­tas­tic experience.

Mason: How does the process change from writ­ing some­thing like the book that we have here to some­thing that’s a sci­ence fic­tion book? Does it change the way you have to write? Does it change the way you have to think?

Al-Khalili: Very much so. It was very lib­er­at­ing in a way, but also I know how to write non-fiction. I know how to explain—that’s what I spend half my life doing: I explain. In fic­tion, I have to invent a whole uni­verse. I have to invent a world and invent peo­ple who did­n’t exist before my brain thought them up, and sud­den­ly they have to be peo­ple that you can believe in. They have to be three dimen­sion­al and have per­son­al­i­ties. I could­n’t come home from work or be in my office and think, Ah I’ve got an hour before my next meet­ing, I might get anoth­er chap­ter done. I had to shut myself away—actually in this study, here where I’m record­ing this evening. I’d block off days on end—I would­n’t stay in the study for days on end—but I’d block off days on end and I would­n’t check email, I would­n’t deal with any oth­er work. I’d just immerse myself in build­ing this imag­i­nary world. It was very, very dif­fer­ent from writ­ing non-fiction. Apart from all of the cre­ative writ­ing tech­niques that you have to learn: Show don’t tell; mind your point of view; all the stuff that had­n’t occurred to me.

I remem­ber start­ing one para­graph in my nov­el with nev­er­the­less,” and my edi­tor came back to me and she scratched it out and said, Don’t use the word nev­er­the­less’ in any nov­el you ever write. That word is barred from fic­tion.” Ah, okay. No one told me that.

Mason: I was sur­prised by so much in the book and you’re so mat­ter of fact about the way in which physics has evolved and changed through­out his­to­ry. I was per­son­al­ly sur­prised, but it made me won­der: Is there any­thing that still sur­pris­es Jim? It feels like he knows it all, so per­haps there’s no new sur­pris­es for you. Is there any­thing recent­ly that’s made you go, Oh wow! I did­n’t even think about that.”?

Al-Khalili: Yes, I think it hap­pens reg­u­lar­ly. That’s what makes physics research so excit­ing. I’m con­stant­ly appre­ci­at­ing how lit­tle I know. I think when you’re doing research—and par­tic­u­lar­ly when you move into a field, maybe, that you haven’t worked in before, as I’ve been doing for the last two or three years—an area called open quan­tum sys­tems—the nature of how a quan­tum object inter­acts with its sur­round­ings. Concepts that are bandied about now in pop­u­lar sci­ence: deco­her­ence, quan­tum entan­gle­ment. You realise there are peo­ple who have been work­ing in this field for years and years and years and they know so much more than you, that I’m con­stant­ly sur­prised when I learn some­thing new and think, ah, I real­ly have to remem­ber that. Of course, now I’m get­ting to the age where I don’t remem­ber stuff, so I read it again a month lat­er and I’m sur­prised all over again, because I’d for­got­ten it from the first time.

Mason: We have one last ques­tion, I guess, from YouTube, which is: Do you think that there’s a lim­i­ta­tion to what we can under­stand because of our human con­scious­ness?” In oth­er words, do you think there’s some fun­da­men­tal lim­it to what we can under­stand with math­e­mat­ics and metaphors, pure­ly because we have this wet­ware human brain?

Al-Khalili: It may be the case that our brains are not com­plex enough to unrav­el the deep­est lev­el of real­i­ty; the truth of objec­tive reality—which is why I said it’ll maybe take an AI to help us achieve that. You know, we’ve come this far and we haven’t reached any lim­it yet. Our brains are three dimen­sion­al, and yet we can imag­ine four, five, an infi­nite num­ber of dimensions—because we have tricks, and because we have math­e­mat­ics. Developing math­e­mat­i­cal tools allows us to go beyond the con­fines of the images that we can cre­ate in our brains. We haven’t reached that lim­it yet. That’s not to say that how­ev­er long the jour­ney is to uncov­er the deep­est secrets of the uni­verse, our brains are capa­ble of doing it. It may be that we will start to reach a stum­bling block where we think: No, that’s it. I can’t get my head around this any more, this is as far as we can under­stand. But, we haven’t got there yet, so I remain optimistic. 

Mason: I mean, you’ve teased it a cou­ple of times now but you say in the book, many times, that physics is wait­ing for the next Einstein to come along. Perhaps the next Einstein will be an arti­fi­cial intel­li­gence. Perhaps an AI-stein—if that makes sense. Suzy goes one step fur­ther and says, To under­stand that AI, will we have to actu­al­ly aug­ment not just our under­stand­ing of physics, but aug­ment our­selves?” How will we be able to realise if an AI made some rev­o­lu­tion­ary sci­en­tif­ic dis­cov­ery if again, we have this lim­i­ta­tion of our own con­scious­ness and our own understanding?

Al-Khalili: I think in that case, we’re going to have to rely on the AI to explain to us—as we would explain to a toddler—we are not going to be able to appre­ci­ate what the AI is doing or how the AI has come to the con­clu­sions it has. We’re already see­ing this. Famously, these AI algo­rithms devel­oped by DeepMind like AlphaGo and AlphaZero. These are algo­rithms that learn how to play chess or the Chinese game of Go, just by being giv­en the rules of the game. Then, they play against them­selves a thou­sand times and they can beat any human on the plan­et. How they do it is almost a mys­tery, because it’s gone beyond what we can fig­ure out. That’s the whole point of these ideas of machine learn­ing; that it’s learn­ing itself. We’re not pro­gram­ming the com­put­er and say­ing, Right, if this, do that. I’m giv­ing you the instruc­tions, there­fore I know, as the coder, how you’re going to behave.” True AI, when it comes, is going to be soar­ing off, solv­ing prob­lems with­out us ever under­stand­ing how it does it. It’s going to have to be quite gen­tle in explain­ing in sim­ple lan­guage to us mere mor­tals, exact­ly how it’s done what it does.

Mason: I love the idea that we have to to have to train our AI to become good sci­ence com­mu­ni­ca­tors before they’re good sci­en­tists. That thing about sci­en­tif­ic dis­cov­ery and curios­i­ty: on read­ing your work and lis­ten­ing to you, it feels like that is real­ly at the heart of what it means to be human. Do you think there’s a rela­tion­ship between our desire for dis­cov­ery and our desire to know these mas­sive ques­tions? Do you think that just goes back to the very heart of what it means to be human, our own humanity?

Al-Khalili: Absolutely. No, absolute­ly. I think that’s what defines our…we talk about what it is to be human, to know our place in the uni­verse. There are traits that we have to do with empa­thy and com­pas­sion and kind­ness, that I think are won­der­ful ways that we behave towards each oth­er, but also we’ve always had this curios­i­ty about the world. It’s built into our DNA. It was prob­a­bly even an evo­lu­tion­ary trait. You want to know what’s behind the next hill. You want to know if there’s a sabre-tooth tiger hid­ing behind that tree. Trying to under­stand the heav­ens and there­fore the sea­sons to make our lives more com­fort­able. We’ve always want­ed to know our place in the uni­verse so I think we’ll nev­er stop ask­ing those ques­tions. We are born curi­ous. All chil­dren are, by their nature, curi­ous. Why is this? Why is that? But why? But why? But why? Most peo­ple grow up and stop ask­ing, Why?” A sci­en­tist is just a child who’s nev­er grown up and has nev­er stopped being curious.

Mason: So on that note, Jim Al-Khalili, thank you for join­ing us today.

Al-Khalili: My plea­sure. It’s been fantastic.

Mason: Thank you to Jim for shar­ing his insights into the fas­ci­nat­ing field of the­o­ret­i­cal physics.

You can find out more by pur­chas­ing Jim’s new book, The World According to Physics’—available now.

Don’t for­get, you can watch the full, unedit­ed video of this con­ver­sa­tion at Futures Podcast dot net, where you can also find out about all of our upcom­ing live stream events. 

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Further Reference

Episode page, with intro­duc­to­ry and pro­duc­tion notes. Transcript orig­i­nal­ly by Beth Colquhoun, repub­lished with per­mis­sion (mod­i­fied).

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