Introduction

> "Black holes act like mirrors." When photons just miss falling into a black hole, they swing around it and can return to their source. This means you can see multiple images of yourself, an infinite number, as photons loop around the black hole multiple times before coming back.

> My work primarily focuses on "the unification of the fundamental laws of nature and the origin of the universe". This includes exploring the quantum structure of black holes and event horizons, delving into how these cosmic phenomena can help us understand deeper questions about the fabric of reality.

Black holes

> One of the key points I want to highlight is the intriguing explanation of why light can't escape from a black hole. Einstein's perspective on light carrying energy and being subject to a gravitational pull due to its energy content offers a unique insight into this phenomenon. The idea that sufficient mass in a compact region can prevent even light from escaping gives us a glimpse into the fascinating nature of black holes.

> Another important aspect to consider is the concept of escape velocity in relation to black holes. The analogy of comparing escape velocities on Earth and how they relate to the speed of light provides a tangible way to understand why even light can't break free from the immense gravitational pull of these enigmatic cosmic entities. Einstein's theory of relativity emphasizing the universal speed limit of light sheds light on the absolute nature of this phenomenon within these extremely massive regions of space-time.

Albert Einstein

> The process of discovery in physics is uniquely complex; often, "the best discoveries seem completely obvious in retrospect." It's fascinating how I and my collaborators can become deeply confused while grappling with a problem, and yet once we find the solution, everything feels clear, as if the confusion never existed at all.

> Einstein's struggle with concepts like black holes and gravitational waves is illustrative of how even the greatest minds can grapple with revolutionary ideas. He didn't believe in black holes despite predicting them, and this contradiction highlights how powerful intuition can be, even when it leads to erroneous conclusions.

> The singularities in Einstein's theory indicate a breakdown of framework and suggest that our understanding needs to evolve, emphasizing the idea that "everything is an approximation." Scientific theories are never perfect, and recognizing their limitations opens the door to deeper insights, particularly where quantum mechanics intertwines with gravity.

> We're living in an exhilarating time for physics because the "contradiction" between quantum mechanics and general relativity hints at profound truths waiting to be uncovered. The push to resolve this incompatibility fuels innovation and exploration, reminding us that it's often through tension and conflict that science makes its greatest strides.

Quantum gravity

> Unification in physics is an incredible journey that involves trying to reconcile the fundamental theories of the universe, like quantum mechanics and general relativity. It's amazing that the Standard Model describes all known electromagnetic, weak, and strong interactions with astonishing accuracy—up to 16 decimal places! This precision has resulted from unifying these interactions under a framework where even the enigmatic Higgs particle has been observed.

> One of the biggest mysteries continues to be quantum gravity. Unlike other forces which fit neatly into renormalizable Quantum Field Theory, gravity resists this categorization. We haven't managed to "tame" gravity in the same way, and this remains a tantalizing frontier, driving ongoing research efforts to find a coherent theory that unifies all fundamental forces, including gravity.

String theory

> String theory is a consistent reconciliation of quantum mechanics and general relativity, incorporating particles and forces we observe. While it hasn't been confirmed as the unified theory of nature, it remains a compelling framework. "String theory... is a consistent reconciliation of quantum mechanics and general relativity... it may not describe the physical world but it is able to incorporate particles and forces like the ones we see around us."

> The unique idea of replacing particles with strings in the early 70s resolved the infinities in quantum field theories. Despite initial skepticism, string theory was found to be able to encompass peculiar phenomena, like parity violation, observed in our universe. "If you replace particles by strings these Infinities go away and you get a consistent theory of gravity... in the mid-80s... you could construct a world involving strings that reconciled quantum mechanics and general relativity which looked more or less like the world that we live in."

> Viewing string theory as a stepping stone, similar to past theories like Yang-Mills theory or even early versions of general relativity, suggests it's a work in progress. The belief is that with each iteration, we get closer to a more accurate understanding of nature. "I would bet the farm that 100 years from now String Theory will be viewed as a stepping stone towards a greater understanding of nature."

Holographic principle

> Discovering the connections between string theory and black holes has truly transformed my understanding of physics; it's fascinating that "the universe is so weird," capturing how intricately information is encoded in black holes. The holographic principle reshapes our conception of reality, suggesting that "all the information that is in some volume of space-time can be stored on the boundary of that region," which has profound implications for how we view the cosmos and the fundamental laws governing it.

De Sitter space

> The concept of flat and curved space-times is fundamental but intricate. For centuries, we thought space-time was flat like a tabletop, but in reality, it can be curved like a basketball or even more complex configurations involving negative curvature. Einstein’s insight revealed that we live in a dynamic space-time continuum where space and time are intricately interconnected, making the visualization challenging but essential to understanding our universe.

> The mystery of dark energy and the cosmological constant is a humbling frontier. Astronomers have provided compelling evidence that a positive cosmological constant, synonymous with dark energy, is driving the accelerated expansion of the universe. Despite these precise measurements, we physicists are still grappling with why this dark energy exists in such small amounts and why it took so long to detect. It’s one of the many profound mysteries that make the pursuit of physics perpetually exhilarating.

Speed of light

> The speed of light is a funny one; you can always choose units to make it one, but the temporal reference frame of a human life is crucial for us to understand the world.

> Discovering the information in a black hole through string theory was a dramatic moment of truth. String theory correcting Einstein's description was essential; otherwise, it would have been inconsistent, leading to a major shift in our understanding, showcasing the beauty of alternate descriptions like the holographic plate idea.

Black hole information paradox

> The fundamental idea that has captivated my work is the revelation that "there are very subtle imprints left on the horizon of the black hole," allowing us to reclaim information that we once thought was irretrievably lost. This challenges the longstanding belief that "black holes destroy information," paving the way for a deeper understanding of the universe's mechanics.

> Moreover, my journey through theoretical physics underscores the importance of asking the right questions. It's a delicate balance; "the trick in being a theoretical physicist is finding the questions that you can answer." Instead of getting lost in the infinite complexities, I've focused on applying what we've learned from string theory to understand the real-world implications, enriching both our scientific inquiries and our comprehension of cosmic mysteries.

Soft particles

> The idea of soft gravitons and photons, particles with zero energy that spread across the entire universe, has profound implications for our understanding of the vacuum state and conservation laws. Zero energy particles aren’t trivial; they carry angular momentum and can store vast amounts of information. Ignoring them leads to inconsistencies, such as angular momentum non-conservation, which isn't physically viable.

> My work with Stephen Hawking was transformative. His passion for physics and unwavering dedication despite monumental personal challenges deeply inspired me. Hawking taught me the importance of perseverance and independent thinking in scientific research, as well as the value of filtering out external distractions to focus on what truly matters.

> Throughout my career, I've often chosen paths less traveled, like pursuing quantum gravity when it wasn't fashionable. This contrarian approach has been surprisingly fruitful, allowing me to stay grounded in my intellectual pursuits free from the shifting tides of popular opinion in the scientific community. Disagreements are intrinsic to our field, driving progress and innovation.

Physics vs mathematics

> The distinction between physics and mathematics blurs as physics is ultimately based on mathematics, reflecting a deep connection between the two: "I would like to think that there's no difference between physics and Mathematics... mathematics is realized in the physical world... they're really the same thing."

> The essence of physics lies in answering challenging questions with concrete solutions, focusing on understanding and making once confusing concepts clear: "I like questions that can be answered that it's not obvious what the answer is... having them seem obvious, that's wonderful."

> While experimental verification in string theory may be elusive, the potential for unexpected breakthroughs and lucky coincidences to provide evidence keeps the pursuit of understanding alive: "I don't know how we're gonna connect all these ideas... it could come together in an interesting way... the fact that we can't see the end isn't a reason not to do it."

Theory of everything

> The intersection of philosophy and physics is crucial; some philosophical questions can spark scientific exploration, especially in areas like consciousness, where ideas such as panpsychism can ignite new avenues of thought and discovery.

> The pursuit of a “final theory” in physics may be misguided; the more we uncover, the more questions emerge, suggesting that a complete understanding might always elude us. As Weinberg pointed out, the search is akin to the journey of explorers who never thought they’d find the end of the Nile.

> While predicting behaviors in the universe is important, true understanding is the ultimate goal for physicists. Even if artificial intelligence could perfectly predict phenomena, it wouldn’t provide the deeper insights into the underlying principles that govern our reality.

> The notion of a simple unifying theory may be appealing, but reaching it without addressing fundamental questions, such as the origin of the universe, would be unsatisfying. The challenge of understanding something arising from “nothing” remains one of the most profound puzzles in theoretical physics, one that I doubt will be solved within my lifetime.

Time

> Time being emergent rather than fundamental is a groundbreaking concept that redefines our understanding of reality. By seeing space as emergent through the holographic principle, we begin to appreciate that time can similarly be a kind of illusion, emerging from more fundamental constructs.

> The challenge of translating systems with temporal evolution into purely spatial systems is immense. While there are concrete ideas on this in the string theory community, they're not universally accepted. This keeps the field vibrant and dynamic, inviting bold explorations to see beyond the illusions of space and time, reshaping how we perceive the universe fundamentally.

Photon rings

> The collaboration on the paper "Photon rings around warped black holes" with Dan Coppets and Alex Lipska highlighted the importance of stepping out of one's comfort zone to discover new perspectives and insights, especially when analyzing images of black holes. Through conversations with experts from different fields, we were able to uncover the intricate self-similar structure of the photon ring, revealing new emergent symmetries related to black holes.

> By studying the behavior of light around a black hole, particularly focusing on the photon ring, we were able to propose a new idea suggesting that the holographic plate of a black hole may extend beyond its event horizon. This challenges the traditional belief that the plate is located solely at the horizon and opens up new possibilities for understanding the relationship between black holes and their holographic descriptions in space-time.

> While further experimental data may not directly confirm these ideas, the collaboration between theorists and observers remains crucial. The constant interaction between different disciplines like physics, philosophy, and mathematics is essential for pushing the boundaries of knowledge and exploring innovative ways to interpret complex phenomena like black holes and their intriguing properties.

Thought experiments

> The process of creating thought experiments is as vital to theoretical physics as mathematics itself; it's often in those precise moments of creative insight that I find the most rewarding challenges. There's a slope, a "knife edge," where problems shift from solvable to interesting, and that's precisely where profound discoveries can emerge.

> My passion for physics has always been driven by a desire to tackle some of the biggest questions in existence. Initially, I sought enlightenment and meaning, but over time, I realized that understanding the universe, with its intricate complexities—like black holes—was the most compelling pursuit. I felt I was "knocking my head against the wall", yet here I am, having not yet reached nirvana but still engaged, probing the depths of theoretical inquiry.

> I firmly believe that we're living in one of the most thrilling eras of theoretical physics, with opportunities for groundbreaking discoveries that could redefine our understanding of the universe. It's thrilling to recognize that what we achieve now could be legacy-forming, and I remain "easily excitable" about the potential truths we’ve yet to uncover.

Aliens

> Reflecting on the possibility of alien civilizations, I find it fascinating to imagine that the universe might be teeming with other intelligent beings, each with their own mathematicians and physicists striving to understand the world around them. The diversity of their perspectives and potential differences in intelligence or cognition could be far beyond our current comprehension. While our intelligence might be too narrow or our tools too primitive, the possibility that we are surrounded by beauty and phenomena we are yet to grasp is truly exciting, even if it can be a bit disheartening to realize how much we might be missing.

> The concept of math as a universal language intrigues me, yet the idea that alien civilizations might have developed their mathematical knowledge differently is equally compelling. Their approach to proofs and evidence might diverge significantly from our rigid methods. For instance, while we rely heavily on conclusive proofs, they might operate on a spectrum of certainty, much like how Ramanujan worked with a preponderance of evidence rather than strict proofs. Each alien civilization could redefine what it means to "know" something, offering us new ways to perceive and understand truths.

Nuclear weapons

> Point 1: "The power of ideas when manifested into systems is immense and carries a burden of responsibility. From nuclear weapons to artificial intelligence, the timing and ethics of implementing these ideas play a crucial role in shaping society."

> Point 2: "As a scientist, there is a responsibility to consider the impact of one's work on society. It's essential to recognize the potential influence one has and strive to contribute to making the world a better place, safeguarding the beauty and power of ideas for future generations."