How would you describe the core challenge in quantum gravity?

At the most fundamental level, our understanding of the universe is shaped by two predominant theories: quantum theory and general relativity. While general relativity addresses spacetime, quantum theory focuses on matter within that spacetime. The significant challenge arises from the fact that these two frameworks are not easily reconciled.

The crux of the issue lies in their differing perceptions of time. Quantum theory tends to disregard time, treating it merely as a measurement from a lab clock. In contrast, time plays a crucial role in general relativity, where its flow is influenced by the events occurring within the universe.

Efforts to unify these theories often expose their limitations. Quantum gravity must either ingeniously integrate them or surpass them entirely, with time being the central element. The question remains: how can we reconcile the responsive nature of time in general relativity with the static concept of time in quantum mechanics?

How have you approached the quantum gravity dilemma?

My method for tackling quantum gravity has been somewhat unconventional. Rather than confronting the issue of time—arguably the most critical aspect—I opted to focus on space. My goal has been to retain the notion of time as defined by quantum theory while redefining space. In the theories I've developed, space does not inherently exist; instead, it emerges as a consequence of other processes. There exists matter and time, and activities unfold in that time. By observing how matter behaves, one can deduce the characteristics of space. Essentially, space is a derived concept in my frameworks.

What draws you to quantum gravity?

Quantum gravity captivates me due to its position at the frontier of our knowledge, probing some of the most profound and challenging questions. Although these inquiries are incredibly difficult, they remain grounded in the realm of science, adhering to empirical rules. This adherence to verifiability and the boundaries of science makes exploring these deep questions both rewarding and challenging.

Why did you transition away from physics?

Pinpointing a single reason for my departure from physics is complex. A multitude of factors contributed to my decision. I have always had diverse interests, and although my previous immersion in quantum gravity was fulfilling, I felt an urge to explore other avenues. Balancing the abstract nature of quantum gravity with the tangible world of design has been crucial for my happiness. Creating and envisioning products is an inherently human endeavor, rooted in our desire to understand and improve our lives.

What projects are you currently pursuing?

My current focus is on Doppel, a wearable technology that helps users achieve calmness and focus or increased energy on demand. The concept originated from research conducted at the Royal College of Art and Imperial College, where we explored psychophysiology—the study of how our emotions influence our thoughts and behaviors.

Doppel essentially acts like music; just as upbeat tunes energize us while calming melodies soothe, our bodies respond viscerally to rhythm. Doppel translates this effect into a wearable format, providing a rhythmic sensation on the wrist that mimics a heartbeat. Setting it to your resting heart rate promotes calmness, while a faster pace can invigorate you.

Are there parallels between your previous work in physics and your current role in wearable technology?

While there may be some similarities between my past in physics and my present work, the connections can be subtle. One clear link is how Doppel influences our perception of time through rhythm. However, I find the more intriguing aspect lies in understanding a system from within it. In quantum gravity, we aim to comprehend the universe while being a part of it, complicating the typical observational approach in physics. Both psychophysiology and wearable technology involve investigating human perception while being inherently human ourselves. The idea of analyzing a system while also being a component of it fascinates me.

What questions do young women have about careers in science?

Previously, young girls often asked if there were women in science, a question that is now outdated. Today, they inquire whether women in science are content and relatable role models. During my public talks, I've encountered many high school girls who express admiration for our work in quantum gravity but also remark on my attire, noting it as a significant point. This highlights their curiosity about the stereotype of women in science, and I strive to convey that we are just ordinary women leading fulfilling lives.

What ignited your passion for physics?

Many of my colleagues in quantum gravity have poignant stories about how a book on Einstein inspired them to pursue the field. In contrast, I lack such a narrative. I never found Einstein particularly appealing, and my interests were diverse. I vividly recall being captivated by the starry ceilings of Greek churches, which evoked a sense of wonder in me. While the fundamental questions about the universe have always intrigued me, my journey to becoming a physicist was gradual and somewhat accidental.

Did you stumble into physics by chance?

If pressed to pinpoint a moment of decision, I have an almost amusing story about inadvertently entering the field. At 17, while wandering through Athens, I was uncertain about my future aspirations, torn between becoming an astronaut, an archaeologist, or pursuing various other interests. The Greek education system left much to be desired, so I sought evening classes to fill in the gaps. However, I mistakenly entered a building offering A-level courses aimed at preparing students for university in England—a path I had never considered. Yet, after a lengthy conversation, I found myself signed up for theoretical physics in England.

Is it feasible to resolve quantum gravity within our lifetime?

During my Ph.D., my supervisor, Chris Isham, asserted that it would take two centuries for any meaningful progress in quantum gravity. At the time, I thought he was mistaken, yet now I find myself uncertain. I occasionally ponder what it would feel like if someone were to solve it while I was still around—though I would find that somewhat disappointing. Still, I would love to witness the answer, leaving me with mixed feelings.

Sally Davies is a London-based writer, formerly an associate editor at Nautilus and technology correspondent for the Financial Times. She currently serves as a senior editor at Aeon.