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Leonard Susskind: Quantum Mechanics, String Theory and Black Holes | Lex Fridman Podcast #41
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Introducing Leonard Susskind
In this segment, Lex Fridman introduces Leonard Susskind, a prominent theoretical physicist and a key figure in string theory. Susskind's background as a professor at Stanford University and his contributions to physics are highlighted, setting the stage for a deep discussion on complex topics like quantum mechanics and black holes.
"the following is a conversation with Leonard Susskind he's a professor of theoretical physics at Stanford University and founding director of Stanford Institute of theoretical physics he's widely rega..."
The Influence of Richard Feynman
Leonard Susskind reflects on his friendship with Richard Feynman, emphasizing Feynman's intuitive approach to physics. Susskind shares how Feynman's visualization techniques validated his own intuitive style of thinking about complex physical phenomena, influencing his work in quantum mechanics and string theory.
"you work two more friends with richard fineman house he influenced you changed you as a physicist and thinker what I saw I think what I saw was somebody who could do physics in this deeply intuitive w..."
Intuition in Physics
Susskind discusses the role of intuition and visualization in his understanding of physics. He explains how he prefers to visualize phenomena rather than focus on equations, highlighting the importance of intuitive thinking in grasping complex concepts like quantum mechanics and black holes.
"thinking about quantum mechanics or black holes or string theory using intuition as a first step or step throughout using visualization yeah very much so very much so I tend not to think about the equ..."
Rewiring Our Understanding of Quantum Mechanics
In this segment, Susskind addresses the unintuitive nature of quantum mechanics and modern physics. He explains how physicists develop new intuitions over time, allowing them to think more easily in quantum terms than classical ones, and discusses the challenges of visualizing higher dimensions.
"counterintuitive ideas so how that's true that's naive is something Connor into every their rewiring your brain in new ways yeah quantum mechanics is not intuitive very little of modern physics is int..."
The Limits of Human Visualization
Susskind explores the limitations of human neural wiring when it comes to visualizing dimensions beyond three. He discusses the challenges of conceptualizing higher-dimensional spaces and how physicists learn to think about these abstract concepts through mathematics and visualization techniques.
"is such that we understand rocks and stones and water and so I'm sort of evolved evolved for you do you think it's possible to create a wiring of neuron like state devices that more naturally understa..."
Ego and Humility in Science
Susskind shares his thoughts on the dual nature of ego in science, emphasizing the need for both arrogance and humility. He discusses how confidence in one's abilities is essential for tackling the complexities of nature, while also recognizing the likelihood of being wrong and the importance of remaining open to new ideas.
"think our neural wiring is just set up for that on the other hand we do learn ways to think about five six seven dimensions and we learn ways we learn mathematical ways and we learn ways to visualize ..."
Navigating Academia
Susskind reflects on his journey through academia, discussing feelings of discomfort and being an outsider due to his working-class background. He shares how he eventually found his place in the academic world and the transition from feeling like an outsider to becoming a central figure in theoretical physics.
"with nature it takes a special kind of person who can manage both of those I would say and I would say there's echoes of that in your own work a little bit of ego a little bit of outside of the box hu..."
Collaborative Idea Development
In this segment, Susskind discusses his approach to developing ideas in physics, emphasizing the importance of collaboration and brainstorming with peers. He contrasts his earlier solitary work style with his current practice of engaging with students and colleagues at Stanford.
"about whether I would succeed or not I never I never felt this insecurity am I ever gonna get a job that veteran never occurred to me that I wouldn't maybe you could speak a little bit to this sense o..."
The Promise of Quantum Computers
Susskind delves into the potential of quantum computers, explaining how they differ from classical computers in simulating quantum systems. He highlights the limitations of classical computing in handling quantum information and the revolutionary capabilities that true quantum systems can offer.
"at it what are your hopes for quantum computers so machines that are based on that have some elements of leverage quantum mechanical ideas yeah it's not just leveraging quantum mechanical ideas you ca..."
Simulating Quantum Systems
Susskind explains the practical applications of quantum computers in simulating complex quantum systems. He argues that quantum computers will be invaluable for understanding quantum phenomena that are too difficult to simulate classically. This segment underscores the significance of building quantum models to explore and manipulate quantum systems effectively.
"in the entire universe if it were packed so tightly that you couldn't pack anymore in right 400 cubits on the other hand if your quantum computer is composed of four hundred qubits it can do everythin..."
Quantum Systems vs. Classical Problems
In this segment, Susskind contrasts the capabilities of quantum computers with classical problems, particularly focusing on the unique advantages quantum systems offer in fields like chemistry and material science. He discusses the limitations of classical methods and the potential for quantum computing to unlock new insights into fundamental scientific questions.
"quantum measurements on it the advantages you can run it much slower you could say why bother why not just use the real system and why not just do experiments on the real system well real systems are ..."
Black Holes and Quantum Mechanics
Susskind draws parallels between black holes and quantum computers, highlighting their shared characteristics as large quantum systems. He discusses the fundamental nature of black holes and their significance in understanding quantum mechanics, suggesting that insights gained from studying black holes could inform our understanding of quantum computing.
"probably will run out of the ability to solve equations for these things you know solve equations by the standard methods of pencil and paper and solve the equations by the method of classical compute..."
The Brain and Quantum Mechanics
In this thought-provoking segment, Susskind reflects on the relationship between quantum mechanics and brain function. He expresses skepticism about the brain operating as a quantum system, suggesting that it likely functions classically. This discussion raises questions about consciousness and the potential for future discoveries in neuroscience through the lens of quantum mechanics.
"way right okay it is first of all unclear to me but of course it's unclear to me I another I'm not a a neuroscientist I have I don't even have very many friends who are neuroscientists I would like to..."
Simplicity in Complexity
Susskind concludes by discussing the quest for simplicity within complex systems, drawing on examples from physics. He emphasizes that while systems like superconductors may appear complicated, they can often be understood through fundamental principles. This segment highlights the ongoing pursuit of understanding complex phenomena in both physics and biology.
"and to analyze them you need the tools of quantum mechanics if we can go on to black holes mm-hmm and looking at the universe as a information processing system as a computer as a giant computer what'..."
Finding Simplicity in Complexity
Susskind reflects on the process of simplifying complex systems in physics, using superconductors as an example. He highlights the importance of not oversimplifying inherently complicated phenomena, suggesting that while physics often reveals simplicity, some systems, like the brain, may resist such reduction.
"interesting point you've in many cases if you look even at string theory when you first think about a system it seems really complicated like the human brain and through some basic reasoning then tryi..."
The Nature of Intelligence
In this segment, Susskind explores the challenges of defining human-level intelligence and the misconceptions physicists may have about it. He discusses the potential for creating superhuman intelligence through advancements in machine learning, while acknowledging the complexities that remain in understanding consciousness.
"them simple but what we don't want to do is take things which are intrinsically complicated and fool ourselves into thinking that we can make them simple we don't want to make I don't know who said th..."
Machine Learning Insights
Susskind shares his experiences consulting for Google X, where he advises machine learning physicists. He notes the gap in understanding why machine learning works so effectively and emphasizes the need for deeper theoretical insights into the mechanisms behind it, highlighting the intersection of physics and machine learning.
"easily exponentially so what do you think that way of thinking that comes from physicists is all about I wish I knew but there's a particular reason why I wish I knew I have a second job I consult for..."
Predicting the Future of Physics
Susskind reflects on the unpredictability of scientific discoveries, sharing anecdotes about how some concepts that seemed far off became understood much sooner than anticipated. He discusses the evolving understanding of quantum gravity and the surprising speed of progress in theoretical physics.
"difference between quantum construction of mathematics physically yes but in the structure the mathematics between a tension network designed to describe a quantum system on the one hand and the kind ..."
The Dream of String Theory
In this segment, Susskind articulates the overarching goal of string theory as part of theoretical physics: to achieve a unified theory of everything. He emphasizes the importance of string theory as a tool for understanding the relationship between gravity and quantum mechanics, rather than viewing it as a standalone subject.
"we jump around quantum gravity some basic ideas in physics what is the dream of string theory mathematically what is the hope where does it come from what problems are trying to solve I don't think th..."
Quantum Mechanics and Gravity
Susskind discusses the significant contributions of string theory to the understanding of quantum mechanics and gravity. He highlights how string theory has provided mathematical consistency between these two fundamental aspects of physics, which was once a contentious issue in the scientific community.
"that these particles call hydrants had could vibrate could rotate could do all the things that a little closed string can do and it was and is a valid and correct theory of these hydrants it's been ex..."
The Nature of Reality and Free Will
In this thought-provoking segment, Susskind delves into the philosophical implications of quantum mechanics on our understanding of reality and free will. He questions whether the probabilistic nature of quantum mechanics has any bearing on human perceptions of free will, inviting deeper contemplation on the nature of existence.
"other is there a possibility of something deeper more profound that still is consistent with string theory but is deeper that is to be found well you could ask the same theme of quantum mechanics is t..."
Understanding the Observer Effect
Susskind explains the concept of an observer in quantum mechanics, detailing how entanglement occurs when an observer interacts with a system. He discusses the technical aspects of observation and how it relates to our understanding of consciousness and entanglement in the physical world.
"if we look at the deepest nature of reality with whether it's deterministic or unobserved is probabilistic what does that mean for our human level of ideas of free will is there any connection whatsoe..."
The Nature of Time in Physics
This segment delves into the nature of time, with Susskind discussing whether time is emergent or fundamental. He highlights the role of entropy and the second law of thermodynamics in understanding time's arrow, emphasizing that time appears to be built into our physical equations.
"observation or measure now does that satisfy me personally as an observer hmm yes and no I find it very satisfying that we have a mathematical representation of what it means to observe a system you a..."
Reversing Time in Controlled Systems
Susskind discusses the possibility of reversing time in controlled laboratory settings, explaining how small systems can be manipulated to appear as if they are evolving backward. He contrasts this with larger systems, where the complexity and chaos make such reversals increasingly difficult.
"time always seems to be built into our equations as just what Newton pretty much were for Newton modified a little bit by Einstein would have called time and and mostly in our equations it is not emer..."
The Limits of Time Travel
In this segment, Susskind clarifies the distinction between reversing a system's trajectory and the concept of time travel. He explains that while reversing motion in small systems is theoretically possible, true time travel remains a complex and largely unattainable concept due to engineering challenges.
"mean like second law thermodynamics entropy and so on yeah the pack of cards and you're flinging it in the air and you look what happens to it yeah but what's random we understand it doesn't go from r..."
Simulating the Universe: A Quantum Perspective
Susskind explores the idea of simulating the universe using quantum computers. He discusses the differences between anti-de Sitter space and de Sitter space, emphasizing the challenges of replicating our universe's quantum mechanics and the potential for creating small-scale models of quantum phenomena.
"make it reverse its trajectory yeah how do we do what's the intuition there does it have is it just a fluke thing that we can do at a small scale in the lab that doesn't have what I'm saying is you ca..."
Understanding Cosmological Spaces
In this segment, Susskind contrasts anti-de Sitter space with de Sitter space, explaining their geometric properties and implications. He describes anti-de Sitter space as an isolated quantum system and highlights the exponential expansion of de Sitter space, which characterizes our universe. He expresses uncertainty about the mathematical understanding of dark energy and the universe's expansion.
"to our own you know we could ask oh we could we build in the laboratory a small version a quantum mechanical version the collection of quantum computers entangled and the couple together which would r..."
Eternal Inflation and the Universe's Origin
Susskind shares his thoughts on the theory of eternal inflation, suggesting that the universe may not have a definitive beginning. He discusses the philosophical implications of infinity in both directions and reflects on the nature of beginnings in the context of cosmological theories, emphasizing the complexity of understanding the universe's origin.
"would agree with me that I don't understand it what about their an understanding of the birth the origin no the bing bang so knows what normally theories there are theories my favorite is the one call..."
The Triumph of Black Hole Imaging
Susskind comments on the groundbreaking achievement of capturing the first image of a black hole. He reflects on the significance of this event in the context of general relativity and the evolution of our understanding of black holes, while expressing skepticism about the new insights it may provide regarding their nature and formation.
"you think about infinity Oh God so okay of course you can think about mathematically I just finished this I just finished this discussion with my friend Sergey Brin yes how do you think about infinity..."
Visualizing Black Holes
In this segment, Susskind discusses how the recent imaging of black holes aligns with his understanding of them. He emphasizes the importance of this confirmation for Einstein's theories and marvels at the technological advancements that made it possible, reflecting on the human capacity to achieve such scientific milestones.
"the sense that you go back a hundred years and it was a continuous development general relativity the discovery of black holes LIGO the incredible technology that went into LIGO it is something that I..."
The Future of Consciousness Research
Susskind addresses the question of whether science can eventually explain consciousness. He suggests that advancements in computer science and neuroscience may lead to breakthroughs in understanding consciousness, particularly through machine learning and the evolution of intelligent systems, hinting at the potential for machines to develop their own forms of intelligence.
"together right and took a picture of slightly advanced lemurs I think what kind of questions can science not currently answer but you hope might be able to soon well you you've already addressed them ..."
The Limits of Scientific Inquiry
In the concluding segment, Susskind reflects on the questions that science may never be able to answer, such as the existence of an underlying intelligence in the universe. He discusses the philosophical implications of such questions and the challenges they pose to our understanding of reality, emphasizing the complexity and mystery that still surrounds fundamental concepts in physics.
"is last question what kind of questions can science not currently answer and may never be able to answer yeah is there an intelligence out there that's underlies the whole thing you can call them with..."