#312 Sabrina Pasterski - Theoretical Physicist on the Hidden Code of the Universe

Childhood Shaped Her Learning and Problem-Solving Approach

Sabrina Pasterski Gonzalez grows up in a Chicago neighborhood with well-designed public schools and a strong community of public service workers. Both of her parents are lawyers—but not in the conventional sense. Her father works as a public defender for Cook County, while her mother helps regulate environmental compliance at the EPA. This background, combined with her mother’s family’s working-class roots in Cuba and her father’s hands-on approach to home repairs, instills in Sabrina a practical and resourceful problem-solving mindset.

From an early age, Sabrina’s parents encourage experiential learning over formal instruction. For example, when Sabrina realizes a classmate has a broader vocabulary, her parents buy joke cups in bulk so she can practice reading, and use incentives such as allowing car rides if she writes her request on the chalkboard. Her father’s trust in her technical skills—“If he says it’s fine, it’s fine”—encourages her independence, and their collaborative home projects nurture engineering instincts.

At nine, inspired by both her father’s example and the magical allure of "Harry Potter," Sabrina receives her first flight lesson instead of the flying broomstick she requests. Her father, who soon becomes a licensed pilot, supports her by identifying regulatory loopholes allowing earlier solo flights abroad and by taking her to air shows. Sabrina learns networking early, building mentorships in aviation by bringing donuts to the FAA and sharing photos of her flying experiences.

Between ages twelve and fourteen, Sabrina pours herself into constructing a single-engine Zenith CH601XL airplane by hand. This hands-on endeavor teaches her the value of “riveting things together” and shapes her ability to tackle abstract physics problems in a way textbooks cannot.

Selective Schools Provide Access to Elite Networks and Mentorship

Sabrina’s educational journey takes her to Edison Regional Gifted Center and then to the Illinois Math and Science Academy (IMSA), a state-funded math and science public boarding school. There, Nobel laureates frequently visit and engage directly with students, creating an atmosphere where high achievement and scientific ambition become normalized. Exposure to a faculty with numerous PhDs and opportunities to converse intimately with leading scientists expand her expectations and aspirations.

At IMSA, Sabrina strategizes persistently to access even greater opportunities. She leverages her history of networking—in this case, circulating at MIT with her airplane photo book and business cards. Her ability to connect with influential MIT faculty and friends who advocate for her candidacy becomes crucial. Although she is initially rejected by Harvard and waitlisted by MIT, Sabrina’s unique story and relationships help her secure admission to MIT off the waitlist.

From Aerospace to Physics: Seeking Deeper Understanding Beyond Engineering

Despite early encouragement to pursue aerospace, including internships at Boeing, Blue Origin, and NASA’s Kennedy Space Center, Sabrina becomes disillusioned with the field’s incremental progress. She finds engineering to be “a little too theoretical” and realizes that even groundbreaking companies can be mired in bureaucracy and research that stalls before meaningful results.

Her experiences convince her that the next leap in understanding lies not in designing better planes or drones, but in grappling with the fundamental laws of nature. Sabrina’s growing fascination with physics is fueled in part by MIT’s compelling physics courses and the example of mentors and aerospace luminaries who themselves revere physics. Her shift from aerospace to the “whole other extreme of purely theory” is both a rebellion against being pigeonholed and a pursuit of deeper, universal questions.

Harvard Grad Education Launched Career Despite Challenges

Sabrina chooses Harvard for her graduate studies in physics, reasoning that it offers greater flexibility than MIT, given her previous collaborations there. At Harvard, she focuses on string theory (eschewing what she sees as overhyped quantum computing) and rapidly makes significant contributions. Her research on gravitational waves attracts the attention of Stephen Hawking, w ...

Gravitational Memory: Scattering Events Imprint Spacetime

Gravitational Waves From Colliding Massive Objects

Sabrina Pasterski Gonzalez explains that the gravitational memory effect refers to how violent astrophysical events, such as the collision of massive bodies like black holes, emit ripples in spacetime known as gravitational waves. As these waves propagate outward, they imprint long-term effects on the fabric of spacetime itself.

Memory Effect Connects Conservation Laws To Spacetime Geometry Changes For Inferring Scattering From Boundary Measurements

When a gravitational wave passes two distant detectors, their relative distance changes. This permanent displacement, the gravitational memory effect, is a record of the energy and kinematics of the bodies involved in the original astrophysical event. Pasterski Gonzalez highlights that the memory effect can be framed as a generalization of conservation laws, where the conserved quantities in scattering—such as energy and momentum—are directly related to the measurable changes in spacetime. These changes allow, in principle, for the inference of the properties of scattering events by making measurements at the boundaries of spacetime, often very far from the actual collision.

Angular Momentum in Gravitational Memory Effect

Pasterski Gonzalez’s research introduced a variant connected to angular momentum, known as the spin memory effect. This effect relates to the loss of angular momentum and is observable through the motion of spinning or spinning particles after scattering events. The interplay between these imprints in spacetime and associated symmetries—especially when formulated in flat space—ties the motion of detectors at infinity to the fundamental symmetries of the system. Her work links these observational signatures to the underlying mathematical structure, drawing connections between soft theorems in quantum field theory and asymptotic symmetries in spacetime.

String and Gauge Theories Offer Languages For Understanding Quantum Gravity

String Theory Solves Quantum Field Theory's Inconsistencies With Gravity By Treating Particles As Strings

Pasterski Gonzalez discusses that string theory was particularly appealing for its potential to resolve the incompatibility between quantum mechanics and general relativity. While quantum field theory treats particles as excitations of fields, string theory replaces these point particles with one-dimensional strings. This approach smooths out problematic behavior at high energies (ultraviolet scales) and naturally predicts a graviton, the quantum of gravity, thus providing a platform to unify the spectrum of quantum fields and gravity.

Symmetries in Gauge Theories Extract Central Information Via Fields at Infinity, Inspiring Holographic Principle

Gauge theories such as electromagnetism and gravity exhibit special symmetries described mathematically by fields. These symmetries allow observers to infer properties of bulk systems by measuring fields at the boundary. For example, Gauss's law in electromagnetism enables the total electric charge in a region to be derived from measurements on the boundary. This boundary-centric perspective supports the notion that key information about the "bulk" can be mapped onto a lower-dimensional "boundary," inspiring the development of the holographic principle.

Speculative Frameworks: Unprobed Scales of Quantum Gravity

Pasterski Gonzalez notes that frameworks like string theory and semiclassical gravity (inspired by Hawking’s work) both arrive at the idea that to handle quantum gravity, it is often effective to find an equivalent, non-gravitational, boundary-based system. Both approaches point to untested realms of physics—such as extra dimensions or the true quantum nature of gravity—where these mathematical equivalences might reveal new insights about the universe.

Holographic Principle: Information in Space Encoded On Boundary

Holographic Principle and Math Equivalence in Anti-De Sitter Space

The holographic principle posits that all the information within a region of space can be represented as data on its boundary. In particular, the AdS/CFT correspondence establishes a mathematical equivalence between string theory in an anti-de Sitter (AdS) space and a conformal field theory (CFT) defined on its lower-dimensional boundary. This duality allows formidable calculations in one theory to be translated into simpler terms in its dual.

Research on Holographic Thinking in Flat Spacetime Scenarios

Pasterski Gonzalez is interested in extending holographic frameworks to flat spacetimes, which are more relevant for real-world scattering processes than AdS spaces. The goal is to reformulate the laws of gravity and quantum fields so that all observables and processes can be reorganized and computed efficiently using boundary variables, even in non-AdS geometries.

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The landscape of physics research is shaped by a complex interplay of institutional structures, career incentives, funding models, technological changes, and global competition. Sabrina Pasterski Gonzalez offers a candid examination of these dynamics, drawing on her experiences as a theoretical physicist and her observations from both academic and industry-adjacent perspectives.

Institutional Structures and Career Incentives Shape Research Questions

Universities, Funded By Teaching Revenue, Juggle Education and Research, Amid Citation and Grant-Driven Tensions

Universities operate as centers of both education and research, but these missions often collide. Undergraduates may perceive universities as purely educational institutions until graduate school reveals the priorities tilt toward research output, publication, and the acquisition of grants. This dual mission is funded significantly by teaching revenue, which supports a research infrastructure that privileges publications, citations, and successful grant proposals. The resulting dynamic is that while institutions benefit from a reputation of excellence in research, the incentives can also promote conservative choices in research topics, favoring established questions likely to yield publishable results.

Sociology of Physics Constraints: Outreach Researchers Face Skepticism On Theoretical Commitment; Unconventional Directions Risk Career Consequences Without Justification Within Established Frameworks

The community self-selects for individuals comfortable with existing academic structures; those who struggle to fit within these are often pushed to the margins or leave entirely. Outreach and popular science activities are respected by the public, but within the field, such efforts can distance researchers from the "real physicists," making collaborations harder and risking ostracization. Ambitious or unconventional research questions, or approaches that may not be immediately recognized as breakthroughs, are often dismissed. Career security depends on justifying work within established frameworks—venturing too far from prevailing norms can mean professional risk.

Perimeter Institute's Model: Research-Focused, No Teaching, Supports Outreach, Fosters Broad Thinking on Physics Organization

Institutes like the Perimeter Institute offer a contrasting model, with little or no teaching obligations and active encouragement of both research and outreach. Such setups allow for broader, less constrained exploration of physics organization, providing space to reconsider the conventions of university-driven research and to embrace more creative or interdisciplinary questions.

Funding Models Shape Experimentation and Support For Theories

U.S. Federal Funding For University Research

In the U.S., federal research funding flows primarily to universities, which act as both educational and research centers. This system, which can involve significant overhead and complex justifications for funding, is markedly different from models elsewhere, such as in Europe, where direct funding to institutions is more common. Debates persist regarding the role of public funds in supporting basic science versus more immediately applicable or profitable research. Sabrina argues that truly valuable research enterprises—like those supporting space exploration or fundamental physics—should be funded not simply for profit potential, but for their inherent scientific and societal value.

Centralized Funding in China Allows Diverse Strategies: Hiring Talented Physicists Who May Not Secure U.S. Positions Democratizes Access but Introduces Different Pressures

Unlike the U.S. model, China supports a more centralized approach to research funding, building large research centers and hiring talented scientists who may not find jobs in American academia. This democratizes access to research careers in some ways but can still be isolating due to differences in academic pipelines and sociological factors. Sabrina observes that many researchers in India and China struggle to break into the "club" of mainstream physics, which often remains centered in U.S. elite institutions.

Funding Challenges in Experimental Physics: Justifying Large Detector Costs in the U.S. and China

Large-scale experimental physics, such as work at CERN or on particle detectors, introduces practical challenges: massive expenditures are required to build, maintain, and upgrade detectors whose payoff in discoveries cannot be guaranteed. In both the U.S. and China, securing public money for experiments with uncertain outcomes is a difficult pitch—sometimes feeling less than honest to claim funding based on past success as opposed to clear practical benefit. However, Sabrina notes that the engineering side-effects (such as CERN’s role in the creation of the World Wide Web) may sometimes justify these investments beyond pure physics returns.

Ai & Machine Learning Reshape Physics Research

Language Models and Coding Democratize Computational Approaches, Accelerating Theoretical Work Once Needing Development Teams

Recent advances in AI and machine learning, especially large language models and code generation tools, are democratizing aspects of computational physics. Sabrina describes how tasks that previously required hiring a coding team can now be accomplished single-handedly in weeks using tools like Claude code. This opens new avenues for physicists—especially theorists with limited coding backgrounds—to build products, automate tasks, and experiment with research questions once deemed too resource-intensive.

Ai Tools: Opportunities in Physics Knowledge Compression and Risks of Bias in Discovery

AI tools also offer opportunities to compress and organize the accumulated knowledge of the field. Sabrina hopes to use language models to parse past papers and integrate new results with personal intuitions, which could help bridge gaps caused by narrow specialization. However, risks remain: AI companies may overpromise, and there is danger in placing undue faith in AI-generated discoveries without sufficient validati ...

In fundamental physics, researchers probe the deepest mysteries of reality, from black holes to the fabric of the universe, and seek to reconcile the two major pillars—quantum mechanics and general relativity—in a consistent framework. Sabrina Pasterski Gonzalez, through theoretical and empirical insights, discusses the open questions in black hole physics, cosmology, and the ongoing pursuit of quantum gravity.

Black Holes: Regions With Extreme Spacetime Curvature Changing Causal Structure

Black Holes Form When Matter or Energy Concentrates So Densely That Not Even Light Can Escape the Event Horizon

Black holes arise when enough matter or energy is packed densely in a region, producing intense gravity so that not even light can escape once it crosses the event horizon. Sabrina explains that black holes are a natural prediction from Einstein’s equations: if enough mass collapses into a small enough volume, a horizon forms, cutting off that region from anything outside. In terms of geometry, the Penrose diagram formalizes this, showing inaccessibility from infinity across the horizon—a direct consequence of spacetime curvature’s effect on causal structure.

Black Hole Geometry: Classical Is Clear, Quantum Creates Paradoxes Over Information Loss

The classical description of black holes is precise: solutions to Einstein’s equations describe their horizons, singularities, and symmetries. Non-rotating black holes are spherically symmetric; rapidly spinning black holes have asymmetry about their axis of rotation. However, precise understanding falters when quantum effects are involved. Placing quantum fields on classical backgrounds, theorists encounter paradoxes, especially regarding whether information that falls into black holes is lost or somehow preserved.

Sabrina points to puzzles such as Hawking radiation, where quantum pair production at the horizon implies one particle escapes and another is trapped, leading to questions about unitarity, entropy, and information loss. Some colleagues imagine new physics—“firewalls” or “fuzz balls”—beyond the classical paradigm, but these models remain speculative. The breakdown near the singularity, where curvature becomes infinite, demonstrates that our current frameworks, classical or quantum, remain incomplete.

Black Hole Interior Mystery due to Breakdown Near Singularity

In classical terms, the black hole’s center (the singularity) is where Einstein’s equations cease to make sense—the curvature blows up, indicating our approximations fail. Sabrina emphasizes that this is the limit where neither standard general relativity nor quantum field theory fully applies, and the “interior” remains one of physics’ greatest mysteries. Simulations visualize warped light paths and gravitational lensing, but what transpires inside the horizon remains unknown.

Universe's Expansion Questions Cosmological Constant and Spacetime Geometry

Distant Galaxies Accelerating Apart, Suggesting Dark Energy's Influence; Nature Remains Uncertain

On cosmological scales, the universe’s expansion is evidenced by distant galaxies drifting away from each other, as confirmed by redshifts in their spectral lines. Sabrina affirms these observations are not under doubt: galaxies and stars do move farther apart, indicating an expanding universe.

Sabrina Focuses On Flat Spacetime, Avoiding Cosmological Curvature and Expansion Issues, Concentrating On Scattering Processes and Asymptotic Symmetries

Despite the importance of curvature and cosmological-scale phenomena, Sabrina prefers to operate in the regime of flat spacetime, where quantum field theorists can compute particle collisions, scattering processes, and analyze asymptotic symmetries. She deliberately sets the cosmological constant to zero in her calculations—an approximation since potential changes in the cosmological constant could radically reshape our understanding of the universe.

Experimenting if the Cosmological Constant Changes Could Reshape Cosmology, but Implications Remain Uncertain Without Consensus

Recent experiments suggest the possibility that the cosmological constant might change over cosmological time, a scenario that excites string theorists pursuing the “swampland” program. Yet, according to Sabrina, cosmologists remain skeptical, and results are not universally accepted. If the cosmological constant does evolve, it would affect the ultimate fate and geometry of the universe, but theories and data have yet to converge on this possibility.

Quantum Mechanics and General Relativity Use Incompatible Math

Quantum Mechanics Governs Small-Scale Phenomena With Probabilistic Particles and Wave Functions, While General Relativity Describes Gravity As Curved Spacetime Without Inherent Randomness

At the heart of physics’ foundational tension, quantum mechanics governs the subatomic world through probabilities, wave functions, and fundamental randomness. General relativity, by contrast, describes gravity geometrically as the curvature of spacetime, with deterministic evolution and no built-in uncertainty.

Theories Suggest Incompleteness; Unified Framework Needed At Planck Scale

Sabrina re ...