Quantum mechanics at 100: David Tong on fields, history and textbooks

Summary

In the podcast, Cambridge physicist David Tong discusses the 100th anniversary of quantum mechanics and why a field-based view of the universe matters. He outlines his goal of writing a ten-volume set of textbooks to cover theoretical physics from basic mechanics to advanced topics like quantum field theory and general relativity. Tong reflects on the historical development of quantum theory, how quantum mechanics connects to classical physics, and the surprising links across disciplines from ocean waves to topological quantum materials. He also shares what makes Cambridge a unique hub for high energy physics and cosmology, and how experimentation continues to guide theoretical advances.

• Motivation for a large textbook project spanning the whole of theoretical physics
• Field picture of the universe and the dance of interacting fields
• The hundred-year arc of quantum mechanics and the early papers of Heisenberg and Schrödinger
• Connections between quantum mechanics, quantum field theory, and cosmology

Introduction and who is speaking

The podcast features David Tong, a professor of theoretical physics at Cambridge, speaking with the Voices of Mathematics hosts about a broad view of physics and Tong’s ambitious book project. Tong has taught in Cambridge for over two decades and has written many lecture notes that are publicly available. The discussion centers on quantum mechanics as a pivotal theory, its 100th birthday in 2025, and how it anchors Tong’s teaching and research in quantum field theory.

The textbooks project

Tong describes his plan to publish ten textbooks that together cover theoretical physics from the ground up. The initial volumes include classical mechanics, electromagnetism, quantum mechanics, and fluid mechanics, all published on the same day. He aims for a continuous voice and a framework that highlights connections between ideas across the subject, making complex topics accessible to first-year undergraduates while remaining valuable for PhD researchers. The audience is broad, spanning university students to experts who want a refreshed perspective on foundational physics.

Where quantum mechanics sits in the broader landscape

The conversation moves from historical narratives to the contemporary framework of quantum theory. Tong discusses the spectral lines that first pushed scientists to develop quantum ideas, the core notion of discreteness, and the role of uncertainty. He emphasizes that quantum mechanics is counterintuitive and deeply probabilistic, balancing precise measurements with intrinsic randomness. Tong also reflects on the differing historical formulations of quantum mechanics, including Heisenberg’s matrix mechanics and Schrödinger’s wave equation, and how both pictures illuminate the same physics from different mathematical angles.

Quantum field theory and the field picture

Tong explains that fields are fundamental in our description of the universe. Particles emerge as quanta of fields, such as electrons and photons, and multiple fields interact to produce the rich structure of matter and forces. This field-based viewpoint leads naturally into quantum field theory and the Standard Model, including the role of chirality and parity violation as essential features of modern physics. Tong argues that the field perspective reveals deep connections across phenomena and scales, from electromagnetism to particle physics to cosmology.

Historical perspective and the quantum revolution

A substantial portion of the talk dives into the genesis of quantum theory. Tong recounts Heisenberg’s pivotal insight on noncommuting observables and the birth of matrix mechanics, as well as Schrödinger’s quest for a simpler, more intuitive equation. The hosts discuss how these developments complemented each other and laid the groundwork for a robust and flexible understanding of quantum phenomena. The dialogue also touches on ongoing debates about how best to teach quantum mechanics and how to present equations without sacrificing accessibility.

Practical implications and current frontiers

The episode moves toward practical applications and current research frontiers. Tong highlights the usefulness of quantum field theory in understanding real materials, such as those involved in the quantum Hall effect, and he notes the broader relevance to cosmology and gravity. The conversation also covers the Nielsen Ninomiya theorem about placing chiral theories on a lattice and the implications for simulating physics on computers, a topic Tong finds both troubling and motivating as a challenge to revise assumptions and seek loopholes. The discussion closes with examples of experimental hints at new physics, including gravitational waves and cosmological observations, and Tong’s view that experiment remains indispensable to progress in theory.