Brian Greene is a Professor of Physics and Mathematics at Columbia University. His research has significantly contributed to the advancement of string theory, and he is widely regarded as one of the world’s leading science communicators. As a best-selling author, co-founder of the World Science Festival, and frequent guest on prominent television programs and films, Brian has a remarkable ability to make complex scientific concepts accessible to audiences across the globe. His latest book, Until the End of Time: Mind, Matter, and Our Search for Meaning in an Evolving Universe, is a fresh look at the cosmos. Brian joins the podcast to explore the fundamental nature of reality.

Transcripts of our episodes are made available as soon as possible. They are not fully edited for grammar or spelling.

Tom Burnett: Brian, welcome to the show

Brian Greene: Thank you.

Tom Burnett: When I initially contacted you about appearing on the Templeton Ideas podcast, I received a response from you while you were in Antarctica. I was curious and didn’t have a chance to ask, since I knew you were probably quite busy, but what were you doing there?

Brian Greene: Yeah. So, there was a ship that went down to Antarctica with William Shatner as its premier guest. William Shatner wanted some scientists to join him on this journey, which was primarily for research for the public.

So, I was a guest on this journey. As part of the voyage, I did some science conversations, but I took my family. We did the polar plunge, you know, jumped into the freezing water down there and insane, but it was completely memorable.

Tom Burnett: All right. Well, you got the full experience. So that’s great. I want to turn next. I want to take us way back in time because I love for our listeners to kind of here where our guests have come from. So, I was curious: given your long career as a physicist, when did you first start to fall in love with mathematics?

Brian Greene: Yeah. That was very familiar for many people who are in the field. I was about five years old when my dad taught me the basics of arithmetic, and I got so mesmerized by the algorithmic procedures that I would have my dad give me these Enormous, like multiplication problems—30 digits by 30 digits. I’d use big pieces of construction paper and spend days carefully getting the answer of this ridiculously large computation.

And that, to me, was sort of the beginning of a fascination with the algorithms and the operations and the deep truths of mathematics.

Tom Burnett: a lot of scientists have Family members or parents that have worked in a STEM field. Was that the case with you that you were able to kind of see them doing that? And follow in their footstep or not? Yeah.

Brian Greene: know, my, my dad was a singer, composer, vocal coach, dropped out of high school, went on the road when he would have been in 10th grade as a performer around the country.my mom, did finish high school, but she, didn’t finish college and

started a real estate business in New York and in that way, it was ultimately quite successful, but I like to think of it as my dad was about music and ideas. So, his head was sort of in the clouds. My mom was all about like real estate and things that you could.

Touch tactile surfaces. So, she was right here down on earth and it kind of put me in this spectrum between the two, which is I think where I’ve been ever

Tom Burnett: When did your fascination with physics begin to take shape?

Mm hmm. Mm

Brian Greene:  it was really in high school that I finally recognized that this structure of equations and numbers and symbols that I’d found so fascinating could do something. It wasn’t just a game.

If you did the right calculation, it would tell you something about the external world. And at that moment, math changed for me completely, and I recognized there was this kind of powerful, somewhat mystical, somewhat secret language that could be used to see more deeply into the nature of the world, the nature of reality.

And once that realization took hold, I knew what I wanted to do, because there’s a feeling that You can get when you feel more connected to the universe because you are You touching its fundamental levers, its fundamental dials, the fundamental things by which it operates.

And for me, those levers and dials were the fundamental equations of physics. And so that is an incomparable sensation when you

Tom Burnett: Kepler or Newton that said something along the lines of like, seeing God’s thoughts after him or something like that?

Brian Greene: Yeah, I mean, a lot of the great movie. Scientists, physicists of earlier days did draw a very clear association between the mathematical underpinnings that they were struggling to understand and the mind of God, because It feels like God must have been a fantastically astute mathematician to have been able to sort of set up the world to function according to these mathematical laws.

I have a somewhat different view of mathematics today than even I did. 30 years ago, I certainly held to a similar perspective, but I now see mathematics more as the.

Invention of the human mind as opposed to the discovery of the fundamental language of reality.

Tom Burnett: So, the language is a metaphor. Is it helpful? Describe mathematics as one human language among many or where the where does that metaphor work? And where does it fall short?

Brian Greene: Yeah, so it’s interesting that you refer to thinking of math as a language as a metaphorical way of using the terminology. I would press even further. Mathematics itself emerges from the human capacity. to function with metaphors. When you look at the history of ordinary spoken language, as, of course, many linguists have done over the centuries, it is astounding, if you’ve never seen it before, how widespread the use of metaphor is.

And I see mathematics as an extension of that natural growth of metaphorical thinking that our species went through.

Metaphor What is symbolism, and what is mathematics? It takes that to the next level where you articulate using symbols, things about the external world, but it’s our minds, in my view, that are conjuring up these useful symbolic representations of things that we experience. And so, what is math? We encounter the external world; we have this capacity to find patterns, which is how we survived; we encapsulate those patterns by inventing ideas, like the circle or the triangle, or the number pi, or a radius, or diameter, because these symbolic representations we find have utility.

In organizing our perceptions about the external world.

there are certainly clear distinctions between the language of mathematics and ordinary human language, most prominent being any given sentence in a language like English can be parsed typically in many ways.

If we’re talking about a word that has many meanings, it requires context to determine what that meaning might be, whereas mathematical sentences are, if they’re well formulated, they are parable in one way.

A good mathematical sentence, it is not open to interpretation. So, there are certain restrictions. on natural languages that come into play when we talk about things mathematically. But I think that’s just the natural evolution of language as opposed to some radically different beast that we should hold off on the side.

There are sentences in math. There is a grammar in math. There are fundamental symbols in math. It’s the same kind of structure. It’s just built for a different purpose.

And so, it’s got a slightly different grammar because of that.

But I consider them as a continuum. Now, I should quickly say that many mathematicians violently disagree with this perspective. And I have found that many mathematicians feel that the value and utility of what they’re doing Somehow rests upon math being in this platonic realm, this god-like realm beyond the dirty, messy realm of everyday experience.

And if that’s not the case, at least some mathematicians feel that somehow, you’ve undercut the value of what they’re doing. I see it quite the opposite.

How amazing that this human mind of ours. So spectacular that it can come up with this mathematical language that is so well suited to describe the world.

Tom Burnett:  I want to pivot from our discussion of mathematics to another area that’s adjacent to science and that’s a philosophy of trying to think the big thoughts, think about what is this world that we’re in, and I want to start with a concept. I most often hear it described as materialism, but I’ve also described it as physicalism.

where might we start? How would we like to describe it? And which term would you prefer to use?

Brian Greene: I tend to use the term physicalism, but maybe that’s because I’m a physicist, and it feels closer somehow to, uh, to how I identify how I engage with the world. But basically, regardless, what I view that word to mean is that reality. is made up of stuff, physical stuff, and by physical stuff, I mean, you know, the tables and chairs and the molecules and atoms, but also the photons and the gluons and the W bosons of the weak nuclear force, sort of all of the stuff that we have been able to understand in the mathematical language, say, of quantum field theory, of the general theory of relativity, all that stuff.

Stuff together with the laws governing how that stuff evolves from moment to moment, which at least in this epoch, we believe are the quantum mechanical laws interwoven with the laws of general relativity and all the other forces of nature, quantum electrodynamics and so forth. So, physicalism is the view that that is the be all and end all of reality.

Its stuff governed by fundamental laws.

Tom Burnett: Can you help me with understanding what these laws are? R, naming not specifically, but kind of the concept of something that’s governing all this stuff.

Brian Greene: Yeah, so I think it relates back to our previous conversations somewhat directly, because there are two ways to think about laws, and they’re not exclusive, they’re complementary.

One way of thinking about laws is to focus upon the laws as we have found them. And again, we don’t need to get into the details, but it is the laws of general relativity. And the laws of quantum mechanics broadly defined. And each of those do have a mathematical incarnation. Write down a mathematical equation for them.

I would view those as the human attempt to articulate the fundamental laws that are out there, I don’t consider those to be the fundamental laws. Number one, we all anticipate if you look back in history that the laws that we humans can put forward in a given epoch typically change when we go forward and we learn more, right?

So that’s number one. Number two, though, which is the more fundamental part of the question you ask is what we mean by laws of the universe, regardless

Tom Burnett: Right, regardless of how we spell it out, what is, yeah,

Brian Greene: Exactly. and that’s a somewhat hard question to answer, but I’ll give you my best take on it, which is simply this, we have noticed that there are these regularities you know, you throw a ball at the same angle with the same velocity in the same environmental circumstances, and it pretty much lands in the same place.

You go down to the quantum world and you take electrons and when you throw them, they don’t land in the same place every time, but they do have a probabilistic regularity to where they do land, which gives rise to the probabilistic way of thinking about the quantum laws and so on and so forth. And what this all boils down to is a

deep belief. That there is a regularity, a pattern to the way the universe changes from moment to moment to moment.

And whatever it is that describes that or governs those changes and those regular changes, that’s what we mean by the laws of the universe

Tom Burnett: To pivot to a 17th century philosopher who causes us all kinds of heartburn. And that’s Rene Descartes, who’s very famous for the doubts that he raised. And one of these doubts is whether there is an external world at all.

Eerything that I try to grasp, interact with, it’s, it’s within my consciousness.

So, I’m wondering, from your perspective, how have you come to relate to Descartes worry that neither you nor I can get outside of our consciousness? and everything we do, mathematics, telescopes, observatories, satellites, everything we’re doing is through our consciousness.

How could there be something more real than consciousness itself?

Brian Greene: So, my view is that Descartes dilemma could articulate the true reality. It could be that the entire scope of reality is what’s inside this thing called a head right now, you know, I think I’ve got a brain inside my head, but it could be just firings in that structure, making me think that we’re having this conversation, that there’s a real external world.

And I agree. It is virtually impossible to break free from that worry, that concern. And so, I’ve come to a place where I accept that. As a possibility, and I put it to the side solely because I don’t find it to be particularly useful to dwell upon it. It could be true, and I allow that as a possibility, and I say, I’m going to tell myself a different narrative.

There is this real external world that we can navigate through, that we can use our mathematical equations to try to describe and gain insight into whether it’s into black holes or the structure of the atom.

And at the end of the day, I do often come back to the other possibility, that’s all inside my head, and I feel thrilled by the possibility. I say, if that was all inside my head, what a wondrous imaginative capacity that consciousness has.

And so, it makes me even more thrilled to be a human being when I consider that story. However, from a daily working perspective, it can be debilitating, which is why I use this other approach on a daily basis narrative.Like, I’m really talking to you right now. That feels richer, and more to the point, and more of the moment, but the other story could be real, and it’s a perfectly exciting story if it is.

Tom Burnett: Yeah, the ultimate reality, like the biggest container in which everything is in. In a certain sense, we just must make an assumption and go with it. So, we could pick that our biggest container is fully material and everything that’s in it. It kind of builds up from that. But I was thinking, especially with some recent conversations, another way to think about the ultimate container could be like a big mind, whether it’s a solipsistic one, like my little mind having this rich reality, or a bigger mind that we’re all playing a part of.

And thinking more, I thought, aha, well, for theistic conception of reality is like the big capital M mind. is the ultimate container. I’m a big fan of George Barkley of the 17th century. To be is to be seen. There’s a big mind and that’s the big framework that we all fit in. But I’ve been thinking too about these conversations like in Silicon Valley that oh maybe we’re all in a simulation.

Some teenagers a million years from now in the basement has spun off a whole bunch of simulations and we’re like, I played Sim City 2000 when I was a kid, we’re a bunch of sims. I thought you know Both of those containers are in a sense. Equivalent from our vantage point, some big M mind, it’s the, you know, million years from now teenager, or, you know, capital G God thought this into being gave us these rules.

And through these rules and our intellectual capacities, we can explore the world. So, to me, it’s just, it’s, it can be paralyzing, but also very exciting to think I don’t know which container is the right one, but we can do science so long as we have rules and their stuff, we don’t have to resolve what the big container is.

Brian Greene: That’s right. And the one thing that’s worth pointing out with the analogy between imagining, that there’s a large capital M mind that you described in the deistic sense versus that kid in the futuristic garage.

The one thing that’s interesting when you compare those two is that if we are in a simulation. That kid, of course, is playing the role of a godlike figure, created our universe, wrote the computer program, or turned on the right switches for our simulation to start going.

But, usually, in the scientific frameworks that give rise to the possibility of a multiverse or universes beyond our own, which this is an example of that, that kid would still be subject to the regularities, the laws of physics. In that larger container,

often time when one moves toward the more theistic description, typically one wants to shed the laws of physics that only govern the physical universe. And this deistic structure is somehow beyond those physical laws. So, it’s interesting how godlike figure. In that simulation, but that godlike figure is subject to laws of physics at that level,

but you’re right, you know, describing the container within which the reality that you experienced takes place is extraordinarily difficult because you and extract yourself from the reality and look at that container from the outside, which is sort of typically how you try to articulate where its boundaries are.

You know, is it the boundary of the computer in which the simulation is taking place? Is it this larger reality that some godlike figure has created? Is it the multiverse with her many universes like ours, but somehow spread out through some even larger reality? It’s very difficult to answer these questions, of course, and what you find is as a working physicist, you don’t really have to.

just go forward Within the confines of the reality that you have access to and you can take excitement from or gratification from or inspiration from the fact that there are these many containers that are all compatible with the reality that we experience and so You know, again, some people, when you think about the simulation idea, they’d simply, uh, brush it off as silly now that you can’t really do that.

As you and I know, if you look closely, it’s hard to brush it off as silly. Others find it terrifying; I just find it exciting That there’s so many larger realities within which what we experience could naturally fit.

And so, I just allow myself to enjoy the range of possibilities that are out.

Tom Burnett: boxes within boxes within boxes. I guess would be very unexciting if somebody preferred to have certainty rather than uncertainty about like what the ultimate Reality is

But that’s a hugely important point, which is how comfortable is a given individual with. uncertainty. How much does a given individual need to anchor their sense of self and their sense of being in the world with definite answers to questions which unfortunately we fundamentally know are beyond our capacity to fully answer today.

Brian Greene: And so, for instance, with my students, I encourage them to celebrate Uncertainty to celebrate the fact that the human mind can hold even contradictory narratives, contradictory stories in mind and enjoy both, even though they’re mutually incompatible. And, you know, I’ve mentioned this before because it’s true when I do it, there absolutely are moments when I have conversations in my head with my deceased parents.

That is irrational by any physics standard. Nevertheless, it is completely understandable by human standards, and I’m a human scientist, so I take both, and that just enriches the way that I’m in the world. It doesn’t constrain how I’m in the

Tom Burnett: I want to pivot, I think that’s a very good segue here, to talking about the human condition. I think one of the things that people do worry about, in terms of like, the box that we’ve been talking about, a purely material box that we inhabit, is that it might lack any sort of inherent or objective meaning and purpose.

But as you and I know. People deeply, deeply long for meaning and purpose to their lives, like, you almost can’t live without it. And so,

There seems to be this strange friction or collision of what’s expected and what is.

Brian Greene: Yeah, well, the first thing I’d quickly say is I don’t think that That affliction of potential meaninglessness or purposelessness only is relevant for when you have a physicalist perspective and the universe, as you say, is sort of a box of stuff governed by laws. if you think deeply about it, you know, even if there’s a divine being, you must ask yourself, what about the existence of that divine being necessarily gives meaning or Purpose to my life, because I don’t think anybody fully knows what the mind of that God like being is.

And, you know, philosophers have a wonderful way of bringing these things down to earth. And I think it was Robert Nozick, the philosopher at Harvard, who was

Tom Burnett: Oh, how about that?

Brian Greene: back when I was an undergraduate. I believe him or Thomas Nagel or probably both of them asked a question like, well, what if God’s purpose for us human beings ultimately is to be sustenance, food for this other alien civilization that God is cultivating on some other planet, and ultimately we’re all going to be transported there, you know, to be their dinner, would that be a satisfying purpose? It’s God’s will. And we would be fulfilling God’s will by going there and being fried or baked or cooked, you know, but, but with that as an individual make you or I or other people feel like, ah, that’s my purpose. And I, that really is gratifying.

So, you can’t simply say just because there’s a divine being that necessarily the meaning or purpose that is associated with that will be satisfying or gratifying or fulfilling.

so, this is a question that emerges regardless of sort of what the, what the container is. But if we go back to the physical list container, let’s just take that for argument’s sake. When I say that I’m a physicalist, I always preface it by saying I’d be thrilled if that’s not how the world is, it would be exciting and interesting to learn that there is a God and then to try to interrogate what that really means and so forth, but I don’t know how to do that.

So, I focus on the physicalist perspective because the tools that I have at my disposal are well developed to make progress and understanding that reality and within that reality, you’re right, it’s tough. To see where there’s a fundamental meaning or purpose, because in that perspective, we are all just collections of particles that are in exquisite arrangements, allowing this brain of ours to think and feel and cogitate and imagine and communicate, but we’re just stuff governed by physical wall without any meaning. exterior rhyme or reason for how it is that we’re here or where it is that we’re going. It’s just the mechanical laws of physics that determine absolutely everything.

So, what do you do in a reality like that? And well, at first when you encounter it, you can find it distressing. And I have been in that place. I’ve been. Rest deeply by this perspective. But where I come out is versions of what we discussed before, because you see, it sort of infuses my perspective on everything.

I find ultimately that if this is the case, that we’re just these momentary agglomerations of matter that can Create beauty and illuminate mystery and explore the universe and do wondrous things like write the B Minor Mass or the Ode to Joy Ninth Symphony or construct the Great Wall or the Pyramids or figure out general relativity or quantum mechanics or go to the moon and Mars and beyond. If that’s all it is and yet we can do that as collections of particles. How thrilling.

And that I found makes me feel comfortable being in a universe that might Just be stuff governed by laws of physics.

Tom Burnett:  I’ve spent some time in the last week, thoroughly reading your book until the end of time, which for listeners who have not read it, you walk us through 11 chapters from the beginnings of the universe, from the big bang, I came up with a phrase I was thinking about halfway through from the big bang to big brain.

And then later in the book, you accelerate even further, perhaps even more billions of years. into the future So it’s this huge expanse of time. And so, as I, in my own imagination, kind of rode through this chronology as you narrate it, I was imagining this scenario.

in the, the earliest time, the first few billion years, there was matter and energy and motion, these regularities. And at some moment, whether it’s on this planet or many other places, life sprung into being.

And then Consciousness like mind springs into existence among some of these life forms and that we’re in that moment right now where consciousness was relatively recent, on this planet, as I then imagined forward, like billions of years forward.

might the universe reveal? a bigger container that we’re in, how do you see, like, these, you know, three extraordinary events, and whether there are more things to play out in the future?

Brian Greene: Yeah, well, you know, I’ve Absolutely thought about it But I am embarrassed to say that I have been unable to really make headway on what those other Singular moments would be but let me just say a couple of things so I do agree with you That the origin of the universe, the origin of life, the origin of mind, are sort of the big three moments that are as we know it. I suspect, and I think many scientists agree, that however singular they seem, There is a real continuum at work here, and I think that’s pretty important because if you think of them as singular changes, it’s very hard to understand how that could happen without some external input of something new to the system, injecting the life force, injecting the mind force.

But when you recognize that as matter begins to develop. Molecules can refine themselves over time and become ever more exquisite at carrying out intricate physical processes, which over enormous periods of time can gradually turn into the exquisite structures that we, humans, would label as living systems.

But it’s a continuum, no doubt, from the simplest of particles to these structures that fuse together and surge with the currents of life.

Similarly, for mind,  could there be other gradual continuums that yield radically different things in the future? Physics does suggest some odd and Striking possibilities

in string theory, for instance, several dimensions of space is not three. It’s a larger number. We believe we don’t see those other dimensions because they’re tightly curled up. Could they be gradually growing in time so that in the far future, we don’t live in a universe that has three large spatial dimensions but maybe has four. or five or six large spatial dimensions. That would be a radically different reality from the one that we experience here today on planet earth.

Could it be that the coupling constants, the numbers that govern the strengths of forces Could they be slowly changing over time, so that gravity gets much stronger or much weaker, or the electromagnetic force gets stronger or weaker, or even quantum processes grow in strength? space

these are the kinds of things that you begin to think about if you merge our current understanding of the laws of physics with the recognition of how these smooth changes in our past. led to moments that in retrospect, we now look at as singular changes.

Tom Burnett: there’s, I don’t know, once we open the possibility space, it really is fun to ponder. Like, we cannot imagine what could be beyond consciousness, but as you say, once there’s that next thing, looking back on it, you might see, oh, there’s a continuity. space

looking back over your life and as you did in the, in this book of yours, knowing like the mortality, the fragility of life, the fact that it’s so temporary, what are you most proud of in terms of kind of looking back over the decades?

Brian Greene: well, it may sound a little sappy, but I really do live my life putting family first. and so, to me, you know, having moments with my son, my daughter. My wife and I are just enjoying being together or helping each other through some difficult time or period or somehow just being ecstatic about being alive; if I have a deathbed, God willing, that’s how it ends.

Surrounded by family. Those are the things that I will be thinking of. And those are the things that will matter. and sure, when we live our lives, I think many of us want to make a difference broadly and have some impact so that our life mattered in some tangible way. And certainly, that’s important to me too.

I mean, the things that I’ve done in physics, you know, probably mirror symmetry is the thing that I did that had the most impact. I’m proud of that. not many people ever are going to study Chalabi Yau manifolds and understand how the Hodge diamond has a mirror reflection in another Chalabi Yau manifold, right?

It’s not going to matter to too many people’s lives. and so, you recognize that There are different ways in which you can have impact and, and, you know, look, if I’m at an event and this has happened where a kid comes up to me and says, you know, I read your book and I’m going into physics, that’s, that’s really exciting.

And so yes, those things feel good and do the matter they do, but none of them can reach, I think the place where one has impact in a deeply emotional way with people who are deeply connected to you.

And that’s why I ultimately come back to family.

Tom Burnett: There’s a lot more I could ask about Brian, but I feel like we’ve reached a good stopping point where we’ve really explored both your own story and mine. I think some really in depth, fun reflections on what mathematics is and how to think about it, the philosophical problems that keep us up at night;

these are things that we’re all going to struggle with, regardless of which big box that we that we think we may inhabit, we’re going to wrestle with it all. We have that all in common.

Brian Greene: Yeah, absolutely. So, thank you. It was a wonderful conversation. I enjoyed it very much.