“I feel altogether confident that the historian of the future will estimate the past thirty years as the most extraordinary in the history of the world up to the present.” These were the words of the Nobel Prize Winning Physicist, R. A. Millikan in 1926 as he reflected on an incredible period in physics, around the birth of modern quantum mechanics. “…there has been no period at all comparable with it unless it be the period about 300 years ago, which saw the development of Galilean and Newtonian mechanics. This was indeed of incalculable importance for the destinies of the race; the conceptions then introduced are not only the basis of modern material civilization, but they were the cause of a very complete change in man’s whole intellectual and spiritual outlook- in his philosophy, his religion, and his morals.” (Proceedings of the American Philosophical Society -Vol. 65, No. 2, 1926)
The philosophy of science has sought to introduce order into the chaos of existence by replacing supernatural and mystical with reason, logic and frameworks. Like most of our progress as a species- this isn’t a smooth curve, but unpredictable leaps forward in our knowledge that create platforms from which humanity can never go back. Quantum mechanics represents one of those fundamental leaps; a change in our understanding of everything that will have far reaching implications ranging from the future of technology, to the very understanding of who we are.
In these exclusive interviews I speak to Sean Carroll (Research Professor of Physics at Caltech and External Professor at the Santa Fe Institute), Jim Al-Khalili (University of Surrey Distinguished Chair, Professor of Physics and Public Engagement in Science), Brian Greene (Professor of Physics & Mathematics at Columbia University) and Carlo Rovelli (Director of the quantum gravity group of the Centre de Physique Théorique (CPT) of the Aix-Marseille University)
Q: What is quantum mechanics, and why is it so important?
[Professor Sean Carroll]: Quantum mechanics represents the second great revolution in the history of physics; it’s not a theory all by itself, but rather- it’s a framework through which you can write-down all kinds of theories. It’s a replacement for classical mechanics– which came down from Isaac Newton, who built on work by Galileo and others. In classical mechanics, you have objects- with locations in space- they have velocities, forces acting on them, and that’s the whole story. If you know the forces? You can use Newton’s second law of motion to figure out what the system is going to do, and what it did.
Quantum mechanics is a whole new way of thinking– it says that the world is all by itself as a wave function of the universe, but you can never observe that. You can never observe a wave function directly. There is a complex relationship between what the world is and what you see when you look at it, and that relationship involves the idea that you can never predict precisely what you will see, but you can simply say the probability of what you will see.
Historically, physics has always been set around these ideas of observation and measurement, but in quantum mechanics, we have to rethink the fundamentals of what it means to even measure something.
[Professor Brian Greene]: Quantum mechanics is the most radical break in our thinking of reality that we have ever encountered. There is an intuitive view of the world that Isaac Newton was able to make precise, but anyone who studies Newton’s math realises that he’s taking observations that we experience, and making systematic and rigorous descriptions of them. Quantum mechanics comes along and says that whole experience is misleading, and that the best you can ever do is to predict the probabilities of outcomes. Quantum mechanics says our world is nebulous, fuzzy, a haze of possibilities until it somehow snaps to attention upon an appropriate interaction, observation or measurement. That’s a very strange reality, and the fact that this theory is so demonstrably correct is radically important to our understanding.
[Professor Jim Al-Khalili]: The discovery of quantum mechanics was unexpected. At the beginning of the 20th century, no-one anticipated we were going to need a whole new theory of physics to describe our world, by the end of the 19th century, everyone assumed physics was actually coming to an end- and that we pretty-much knew everything we needed to know. It began with what we now call the old quantum theory, instigated by the work of Max Planck who realised that the only way to explain observations of the way hot bodies radiate heat was the idea that at the tiniest scale, things come in irreducible lumps (quanta). By the mid 1920s, quantum mechanics had developed into a new theory (replacing Newtonian mechanics when describing the microscopic world). The quantum universe is counter-intuitive, it’s fuzzy, probabilistic, and suggests things that we would regard as fantastical and magical if we saw them on the everyday scale- yet it’s the most powerful theory in science. Without quantum mechanics, we wouldn’t have the modern world… we wouldn’t have electronics… we wouldn’t have understood the semi-conductor, the computer chip…. All of our modern technology relies on this mathematical description of the world of the very small; albeit a world that is encased in this mystery that we’re still struggling with.
[Professor Carlo Rovelli] Quantum theory is the best theory is physics we have. It corrects Newton mechanics. It is almost one hundred years old and has been in every test since its discovery. We do not know any indication about its limits of validity. It is used routinely today by physicists, engignerings, biologists, chemists, astrophysicists, cosmologists, and many others. It is at the basis of the majority of the current technology like electronics, medical devices, nuclear energy, lasers. Its basis are in standard school programs of many countries.
Q: Why is quantum mechanics so challenging to understand?
[Professor Carlo Rovelli] Quantum theory is relatively easy to use. It works well, and is not particularly hard to study. All over the world is learned well by average students. However, it gives a picture of reality that is unclear. It shows that reality is not made by particles moving along trajectories in space, but is more complicated. The theory describes only the way objects interact with one another, without indicating what happens between one interaction and the next one.
Q: How does quantum mechanics spread across sciences?
[Professor Jim Al-Khalili]: The early pioneers of quantum mechanics realised that it underpinned so much of physics that it also explained chemistry (after all, what is chemistry? It’s how electrons arrange themselves in atoms, and how atoms fit together to make stuff). In the late 1920s and early 1930s, physicists arrogantly assumed that quantum mechanics would solve the mystery of life itself- that didn’t happen, and in fact, biology was tremendously successful, and we gained molecular biology and genetics without the need for quantum mechanics.
We’ve always known that quantum mechanics played this underpinning role in so many other sciences, but there has been a stray away from hard science into pseudoscience. In the 1960s and 70s, a lot of quantum physicists (probably high on LSD) thought that quantum mechanics could explain the nature of consciousness, and phenomena like ESP. To this day, you have the Deepak Chopras of the world who associate quantum mechanics with spiritualism and all manner of pseudo-science from homeopathy to teleportation.
There is a new area of research- quantum biology- which is seeing quantum mechanics being used in more novel ways, and also we are seeing the emergence of technologies such as quantum computing and quantum encryption which- in turn- are opening new areas such as quantum information theory. More recently, research suggests that quantum mechanics may be required to explain certain specific phenomena inside living cells, such as tunneling in DNA, or helping enzymes move particles around, or during photosynthesis in which it seems that captured photons from sunlight can travel in multiple directions at once within the cell in a leaf.
To a large extent, the mathematical framework of quantum mechanics was done and dusted by 1927 and practically all of our technology today relies on this understanding. Today however, we’re in what could be called the quantum 2.0 era, where we’re applying some of the more exotic, counterintuitive, non-trivial aspects of quantum mechanics to technology. Phenomena like quantum entanglements, tunneling and coherence. This will open new fields including quantum sensors, quantum encryption, quantum teleportation…. Technology will be transformed in ways that we perhaps can’t even comprehend right now.
Q: Does quantum mechanics describe a very different universe to classical mechanics?
[Professor Jim Al-Khalili]: Although quantum mechanics has a mathematical framework which has unrivalled predictive power, we still don’t have the correct interpretation. It’s not enough to have the maths, you need the narrative to tell you what the math means. Quantum mechanics is perhaps the only theory that has gained so much traction without a narrative. Let’s take Einstein’s special theory of relativity– the math had been done and dusted before 1905, but they had the wrong interpretation. People believed that there was a luminiferous ether that light travelled through. Einstein is credited with relativity because he gave the correct interpretation- that there is no ether and light travels at the same speed for all observers, and so on.
Interpretations are vital for scientific theories and in quantum mechanics these interpretations ask questions such as whether the universe is probabilistic? Whether there are parallel worlds? Whether the laws of physics are deterministic or indeterministic? Even if this has a bearing on whether we have free will? Until we have the correct interpretation of quantum mechanics, these questions will remain unanswered.
A lot of physicists think this is a matter of philosophical taste; maybe there are parallel worlds, maybe not, but it doesn’t make a difference to some extent because the math predicts the same results, with the same rules, regardless of whether I believe in the many-worlds interpretation or not.
But I still think it is vital that we find the correct interpretation, because that gives us the correct view of the physical world: what reality really is like.
Q: How has quantum mechanics shifted our understanding of space and time?
[Professor Carlo Rovelli] All the applications of quantum theory that we know do not modify our understanding of space of time. However, we also know that space and time themselves must be subjected to quantum theory and we are searching for the correct understanding of these quantum properties of space and time. We have tentative theories. The best current one is called Loop Quantum Gravity. This for the moment is a tentative theory, that has not yet been empirically confirmed. Once we take their quantum property into account, space and time changes dramatically. Space is granular, because one of the characteristics of quantum theory is to show that continuous things have often a granular structure, like light, which is a cloud of photons. Similarly, time cannot be anymore understood ad an external independently flowing entity. Time is just he counting of granular happenings in nature.
Q: Is there a single theory of quantum mechanics?
[Professor Brian Greene]: The physics community does not speak with a unified voice on what quantum mechanics really tells us about the deep nature of reality. We do speak with a unified voice when we are using the theory to make predictions of the world however, so anyone who understands quantum mechanics will make the same prediction for an electron’s magnetic moment, and will do so to the same degree of accuracy, up-to 10 decimal points. Whilst we all will make the same prediction, we will not agree what that tells us about how reality is constructed and what the mental image is that we should have when trying to interpret these laws. One day, I think we’ll speak with a unified voice- but we do not yet understand enough about quantum mechanics for that to be the case.
The history of the subject speaks of this resistance. Back in the 1920s and 1930s, Einstein himself famously resisted the world-view that was emerging from quantum mechanics. Most of us in this generation, and the next, grew up with quantum mechanics. We took quantum mechanics as part of our college course, so it’s part of our world view, and there’s very little resistance to it. The resistance is to the various interpretations of the theory.
Q: How close to the ‘truth’ is quantum physics?
[Sean Carroll]: Quantum mechanics is just physics, it’s not magic- but because we cannot observe in the way you would normally do so, people think that consciousness or human minds are somehow fundamental to quantum mechanics, or even more dramatically that we are somehow bringing reality into existence by our perception of it. There’s zero reason to believe any of those things are true; quantum mechanics are a set of equations that govern what the world does very physically, and there’s no need for words like mind or consciousness to be brought into the story.
When we think about truth, we have to think about the fact that in the 1600s, when Isaac Newton came up with classical mechanics- it seemed to be the truth at the time, but it turned out to be wrong. Classical mechanics always had some things we couldn’t understand- the structure of matter and things like that. Within quantum mechanics, we can explain almost everything we actually observe from the structure of the universe, down to atoms, molecules, chemistry… There are a couple of loopholes of course, gravity being the most obvious one- but we have zero experimental evidence that quantum mechanics is wrong or incomplete.
Q: Has quantum mechanics changed our fundamental view of the universe?
[Professor Sean Carroll]: Quantum mechanics has dramatically and profoundly changed the way we view the universe; sadly, I cannot tell you with complete confidence how as people disagree about the fundamentals of quantum mechanics. Our current method of teaching quantum mechanics- enshrined in text-books- represents a dramatic change from the Newtonian perspective because it puts the observer as having a fundamental role affecting reality in some way. The problem is that it doesn’t ever define what an observer is, what counts as an observer, and that’s why people who work professionally on the foundations of quantum mechanics are unhappy with the textbook perspective.
One of my favorites is the everettian version of quantum mechanics, also known as the many-worlds interpretation. This has a bad reputation in public spaces because the phrase many worlds seems extravagant. The idea fundamentally is that whenever a nucleus decays, or when you measure the span of a particle, the whole universe branches into multiple copies that look almost exactly the same except for a slightly different outcome of that particular quantum effect. That seems preposterously extravagant… all those universes being created all the time? It’s important to understand that Hugh Everett, who was a graduate student in the 1950s and who invented the theory never said, ‘let’s imagine there are a lot of universes…’ that was not the starting point. He started with the wave function, invented by Schrödinger, which is a complex equation that describes quantum systems. Absolutely every version of quantum mechanics has something equivalent to the wave function in it. Everett simply rationalised that if we don’t do anything other than imagine there is a wave function that obeys Schrödinger’s equation, that what will inevitably happen is that a single world will branch into multiple worlds. He didn’t create those worlds, they were already there. Every other version of quantum mechanics works very hard by changing the rules in order to get rid of other worlds- maybe you don’t like them, and that’s what you want to do- but other worlds don’t bother me, they’re leaving me alone, I can’t interact with them in any way.
Q: How is quantum physics helping us understand gravity?
[Professor Brian Greene]: Newton gave us a very intuitive picture of gravity in the late 1600s where one object pulled on another, with a force, that gave us an equation- the universal law of gravitation. Einstein revised that picture in a substantial way by describing gravity in terms of the geometry of space and time, and he showed how Newton’s theory fitted into this new description. Then quantum mechanics came along and said, ‘hey, you’ve got to include me in this picture too!’ and when you try to blend the equations of Einstein into quantum mechanics, those of gravity fall apart. For decades, we’ve been struggling to come up with theories that will blend the ideas of general relativity with Einstein’s theory of gravity and quantum mechanics in a way that makes the equations work- there are a handful of theories on the table that purport to do that, one being string theory, but the jury is still out.
[Professor Carlo Rovelli] We know that gravity and spacetime are the same entity. Loop Quantum Gravity is a theory of quantum gravity. It can be used to try to understand what happens in the regions where quantum property of gravity (of spacetime) become non negligible, for instance at the center of black holes and in the early universe. For instance in my research I am using Loop Quantum Gravity to understand at a black hole at the end of its evaporation. What may happen is a quantum transition to a white hole. We hope to connect this with astrophysical observations.
Q: Does quantum mechanics have philosophical implications?
[Sean Carroll]: The metaphysical implications of quantum theory are quite dramatic, but those implications are not a reason to not believe in the theory.
Another philosophical question is that if everything happens, what is the point in doing anything? If you take many-worlds seriously, you have to take the idea seriously that many things happen, not everything (electrical charges always conserve), but many things do happen- just not equally. There is a difference in the probability of seeing certain outcomes over others. There is a higher probability of a universe where I am sat in a slightly different position, than one where I am the MVP of an NBA team…
Q: How has quantum mechanics changed our understanding of space and time?
[Professor Sean Carroll]: Does quantum mechanics change how we treat space and time in the regime of our everyday lives? No. This is a crucially important feature of physics in the natural world; you do not need to capture the entirety of the information in the universe to be able to make enormously accurate predictions of what is happening at any given moment in the natural world.
The story of Laplace’s demon talks of this fast intelligence that would know the position and velocity of every particle in the universe, and so could predict everything. The general situation in physics is that you cannot predict anything unless you know that information. However, there are some very special situations where- without knowing the position and velocity of every particle- you can still make good predictions. I can predict when the sun will rise tomorrow by knowing the rotation of the earth- I don’t need to know the position and velocity of every atom; that’s actually amazing and remarkable. That is the higher-level emergent description of the universe that describes me, you, clocks, odometers, the things around us…. Quantum mechanics doesn’t really affect this higher order understanding much at all. However, what if we want to understand the fundamental nature of everything…. The fundamental nature of space and time…. We still don’t know those answers. For example; if you were to ask how quantum mechanics affects the big bang, the answer is a lot – but – the big bang in classical general relativity points to the big bang being a gravitational singularity, a point where equations break-down, and all the physical quantities are infinite. Quantum mechanics says none of that is possible, nothing can be infinitely big, and everything has to be smooth…. We don’t know the answers yet, but we know they will be profound.
[Professor Carlo Rovelli] Quantum theory shows that reality is radically different from what we thought. It changes very much in depth our picture of the world. It therefore affects all fundamental questions. The question “why there is anything at all”, which was raised by Leibniz, is a question that made sense for his rationalism, but I do not is a question that makes sense by itself. The simple answer is “why shouldn’t it be that there is something”? I see no reason for “nothing” to be better than “something”. Of course all the workings of the biochemistry of life depends on quantum mechanics, like all of chemistry. But there is nothing specific in quantum mechanics that helps resolving general open questions in biology. However, the general perspective of thinking reality as a net of relationships rather than a collection of entities gives a more general and more effective way of thinking, that is certainly more effective also in biology and in out efforts to understand ourselves.
Q: Will we ever be able to harness quantum mechanics?
[Sean Carroll]: There’s no question that the implication of some quantum technology will be profound. I am not convinced how ubiquitous these technologies will be- I don’t think you’ll have a quantum cellphone- but this does bring-up the really weird status of quantum mechanics in many ways.
When we first discovered quantum mechanics back in the 1920s, we needed it to describe atoms, maybe molecules at most- the differences between quantum mechanics and classical mechanics really only show up when you’re looking at one, two or three particles at a time. Once you have 10^28 particles, you don’t need quantum mechanics anymore. For a long time, this feature of quantum mechanics- that its effects disappeared when you have a large number of particles- held back our understanding of the theory. At that time [1920s], people knew that they were made of atoms, and those atoms obeyed the rules of quantum mechanics, but they didn’t want to believe it… because it didn’t seem to match their classical view. As our technology has improved, we’re now able to maintain the ‘quantum-ness’ – the entanglement of particles over larger and larger systems, and that means we’re able to build quantum technological devices.
Q: What are the biggest questions that quantum mechanics needs to answer?
[Professor Brian Greene]: Black holes provide a fruitful and highly investigated field of research. When you put gravity and quantum mechanics together, they tend to reveal strains and tensions when you study extreme objects- and black holes are the most extreme of all objects. Mass is crushed to an incredibly small size, and powerful gravitational fields are created, they are monstrous, extreme objects. When you try to blend quantum mechanics into the picture that Einstein’s theory gave us of black holes, many puzzles arise. If we solve this, it will fundamentally rewrite our understanding of space and time.
There was a time when quantum mechanics was seen as an esoteric subject, dealing with particles and atoms in a way that was pretty distant from anything relevant to day to day life, but the more we understand about quantum mechanics, the more we see its’ influence includes things that are closer to our everyday. There are quantum effects that are essential to photosynthesis, quantum effects that are needed for the syntheses that occur in stars, and also quantum processes that are necessary for the most basic functions of life. The threads of quantum insights do stitch all the way through the emergence of life and onto phenomenon that are essential to our existence.
Q: Does quantum physics change the nature of meaning?
[Professor Brian Greene]: It is important to have a conception of meaning and purpose that allows for conscious beings to emerge, that does not need the fundamental laws to have meaning written into their architecture. Our species has tended to look for value and meaning as being written in the stars- we have thought that somehow, in the wider cosmos, the answers are there if only we can decipher them. That’s a fundamentally misguided approach. There is no fundamental meaning or purpose written into quantum laws, or into particles of matter- and that’s actually wonderful, it gives us an opportunity to impose value and meaning on the reality that we perceive and if our value and meaning emerges from us, it’s organic, it’s internal, and even more gratifying.
And I think that’s a wonderful thing, because it gives us the opportunity to impose value and meaning on the reality that we perceive. And if our value and meaning come from us, it’s organic, it’s internal, it’s something that we come up with. And to me, that makes value and meaning all the more gratifying. This view gives us a different- more noble sense of meaning. If the universe came equipped with some overarching meaning and purpose, all we would do is absorb it. We would adhere to it and incorporate it into our lives, but that meaning would be external. If we find meaning and purpose because we come up with it, it’s a deeper reflection of who we are, and that to me is the more noble idea.
Q: How important is science communication in quantum mechanics?
[Professor Jim Al-Khalili]: There are a lot of us, physics communicators, who try to create analogies and metaphors to make quantum mechanics digestible, and that is important – but equally important is to be honest and say that we (scientists) still get headaches trying to figure out whether the world is made of waves or particles- whether a photon of light is a particle, a wave, or both…. How a photon of light can be both spread out and discrete, how it can have a particular energy or colour and yet still be a localised particle… or even whether at the tiniest level, elementary particles are vibrating strings….
Sometimes it’s better to be honest and say we as quantum physicists still don’t know the answers for sure, all we can do is give you an idea but part of the attraction, part of the joy of looking into this is that it’s still mysterious and we’re trying to figure it out. But it is complicated.
Q: What comes next after quantum physics?
[Professor Jim Al-Khalili]: Quantum mechanics isn’t wrong- as a theory it’s not going to be replaced by something else, but I certainly feel that it isn’t the last word on the matter. We are still looking for a quantum theory of gravity, a theory of everything, the one equation you can stick on your t-shirt that describes the physical phenomena of the universe. Twenty years ago, we thought we were close, but today? we’re not so sure.
We have quantum mechanics, but we also have Einstein’s general theory of relativity. There’s also a third pillar- thermodynamics- which gives yet another picture of reality. Let me give you an example. We still don’t know the nature of time itself. In relativity, time is a dimension- the fourth dimension, and one that can be stretched or squeezed. In quantum mechanics, time isn’t a dimension, it’s a parameter – a number you plug into Schrödinger’s equation ‘t=n’ which gives you the state of the quantum system at that time, and allows you to work out the state of the quantum system at a point in the future, and the past – the equations of quantum mechanics are reversible in time. Then, in thermodynamics, it says time is an arrow pointing definitively from the past to the future as entropy increases. So we have these three pillars which describe time in very different ways, and if we are to reach a unifying theory, we would reconcile which was the correct interpretation. As yet, we do not know how to do that.
Q: Have we reached the end of science?
[Professor Brian Greene]: The history of science certainly suggests that every time we think we’ve got it figured out, there’s some new surprise around the bend that will cause us to rethink and reframe our ideas. Quantum mechanics is not a specific theory, it’s a framework in which a series of theories and structures needs to fit.
It would be hubris to imagine we have everything figured out. Quantum mechanics is not a unified theory, but it does give us the framework in which we could fit a unified theory that is yet to be formulated. String theory is one approach- there’s no data to support it, no observation, no evidence from traditional sources, but as a mathematical articulation that does put together the laws of gravity and the laws of particles, electricity, magnetism and all the forces of nature? It works. Could that be the final, unifying theory? Maybe… only time will tell.
Q: How close are we to a unifying theory of everything?
[Professor Sean Carroll]: The end of understanding will eventually come, but I don’t think we’re anywhere close to it yet. Quantum mechanics is a framework not a theory- so even if it’s right, it doesn’t mean we’re done- it doesn’t say that we’re anywhere close to figuring out a theory of everything. We also don’t know whether that grand unifying theory will come tomorrow, or in a million years… and even if it did come tomorrow? We wouldn’t be sure if it was right.
Quantum mechanics seems robust, and none of our efforts so far have led to anything simpler, more elegant or which can explain our universe better. As it stands, quantum mechanics is the best theory we have- so that gives us two options. Firstly, we can say that yes- quantum mechanics is great- but maybe we can do better (we still have questions we can’t answer around the big bang, and gravity) – Secondly, we could realise that we don’t even understand quantum mechanics yet. It’s barely been a century since it was invented!
Sean Carroll (in his own words) “I’m a theoretical physicist at Caltech in sunny California. Most of my career has been spent doing research on cosmology, field theory, and gravitation, looking at topics such as dark matter and dark energy, modified gravity, topological defects, extra dimensions, and violations of fundamental symmetries. These days my focus has shifted to more foundational questions, both in quantum mechanics (origin of probability, emergence of space and time) and statistical mechanics (entropy and the arrow of time, emergence and causation, dynamics of complexity). See my research page or annotated publications for more details. I also wrote a personal narrative as part of applying for a Guggenheim fellowship. I’ve written a few books, both popular-level and textbook-level. My most recent is Something Deeply Hidden: Quantum Worlds and the Emergence of Spacetime. I’ve also done a few lecture courses for The Great Courses, and there is various video and audio evidence online of me talking about one thing or another. I started blogging back in 2004, and keep it up to this day. I’m relatively active on Twitter. My podcast, Mindscape, features me conversing with smart people about interesting ideas in science, philosophy, culture, and the arts. In addition to theoretical physics and book-writing, there are a bunch of other things I’m interested in, somewhat haphazardly collected on my activities page. I give talks, organize conferences, write in a number of modes, and do science consulting for film and television.”
Professor Jim Al-Khalili OBE FRS is a theoretical physicist, author and broadcaster. He is a University of Surrey Distinguished Chair where he has also held a personal chair in physics since 2005 alongside a university chair in the Public Engagement in Science. He is a living three-piece suite.
- Affiliation and membership:
- University of Surrey Distinguished Chair, Professor of Physics and Public Engagement in Science
- Fellow of the Royal Society (elected 2018)
- Honorary Fellow of the Institute of Physics (elected 2019)
- President of the British Science Association (2018–19)
- Trustee and Member of Council of Institute of Physics (2017–)
- Member of judging panel for Queen Elizabeth Prize for Engineering (2017–)
- Member of Board of Directors of CaSE (The Campaign for Science and Engineering) (2014 – )
- Patron and Vice President of HumanistsUK
- Member of Cheltenham Science Festival Advisory Committee (2007–)
Brian Greene is a professor of physics and mathematics at Columbia University.
Professor Greene is world-renowned for his groundbreaking discoveries in the field of superstring theory, including the co-discovery of mirror symmetry and the discovery of spatial topology change. He is the director of Columbia’s Center for Theoretical Physics.
Professor Greene is known to the public through his New York Times best selling books and numerous media appearances from the Late Show with Stephen Colbert to Charlie Rose. The Washington Post called him “the single best explainer of abstruse concepts in the world today.” Professor Greene has hosted two NOVA mini-series based on his books, receiving the George Foster Peabody award for “The Elegant Universe with Brian Greene.” Greene has had cameo roles in a number of Hollywood films including Frequency, Maze and The Last Mimzy and in 2008, with producer Tracy Day, co-founded the World Science Festival. He is the director of Columbia’s Center for Theoretical Physics.
Carlo Rovelli (born 3 May 1956) is an Italian theoretical physicist and writer who has worked in Italy, the United States and since 2000, in France. His work is mainly in the field of quantum gravity, where he is among the founders of the loop quantum gravity theory.
He has also worked in the history and philosophy of science. He collaborates with several Italian newspapers, in particular the cultural supplements of the Corriere della Sera, Il Sole 24 Ore and La Repubblica. His popular science book Seven Brief Lessons on Physics has been translated in 41 languages and has sold over a million copies worldwide.
In 2019 he has been included by the Foreign Policy magazine in the list of the 100 most influential global thinkers.