The Naked Scientists: Time, Clocks, and the Brain’s Perception

The Naked Scientists delve into time as both a physical measure and a human experience. Starting with the history of timekeeping, Greenwich Mean Time, and the railway’s demand for a single standard, the episode moves to daylight saving and the dilemmas of keeping clocks in tune with the sun. It then shifts to how our brains perceive time, examining circadian rhythms, temporal order, and memory, and how emotions and attention can warp our sense of time. The show also covers biology’s clocks, the synchronization signals across tissues, and how timing affects medical treatments. Finally, the discussion looks to the future of timekeeping through atomic clocks and UTC, including the leap seconds debate and potential changes to global time standards.

Overview

The Naked Scientists tackle time as a scientific concept and a daily experience. The episode opens with a broad definition of time and then traces its cultural and scientific roots, explaining how standard time emerged from the needs of navigation and rail transport, and how Greenwich became the reference point for longitudes and time worldwide. The program then ventures into the psychology of time, biology, and medicine, and finally looks ahead to the frontier of atomic clocks and the evolving definition of the second.

Historically, timekeeping depended on Earth's rotation and the sun, with longitude serving as a key reference. Emily Ackermans, curator of time at Royal Museums Greenwich, explains how the 19th-century push for standardized maps and the 1884 conference in Washington cemented Greenwich as the prime meridian. She also describes how railways forced a harmonization of local times into a single railway time, later generalized as universal time. The conversation covers the practical challenges of matching local time with train schedules, and the eventual adoption of Greenwich time as Britain’s legal standard in the 1880s, followed by broader adoption in other countries. The development of daylight saving is traced to William Willett’s proposal in 1907, its wartime adoption, and parliamentary debates that echo today’s discussions about health, energy, and social preferences.

"Greenwich time becomes the legal standard time for Britain" - Satnam Shemar, National Physical Laboratory

Historical Timekeeping and Standardization

The episode then explains how time zones formed as countries centralized observatories and navigational data. The railways highlighted a clash between local time and railway timetables, a tension resolved by adopting a common time standard. Emily Ackermans further notes that the later question—whether a country’s eastern regions should observe different local times—was addressed by creating a uniform time standard, often tied to the capital’s observatory.

The discussion also delves into the practicalities of early time transfer, where individuals compared their clocks to observatory standards and physically transported timepieces to set remote locations. The segment concludes with daylight saving’s origins, its adoption during the First World War, and the ongoing debates about whether to keep seasonal time year-round or to standardize time continuously. A critical question emerges: will society revert to a fixed time, or keep shifting with seasons and technological advances?

"part of the reason that time passes very quickly when you're older is that you just don't have any of it" - Ruth Ogden, Liverpool John Moore's University

Time Perception and Biological Clocks

With time defined historically, the program then moves to perception. Ruth Ogden explains that human time experience is not as precise as physical clocks. Our perception depends on arousal, memory, attention, and the number of memories formed in a given interval. When we focus intently on an activity, time may seem to fly, whereas waiting or inactivity can drag time on. The concept of temporal order is explored, highlighting how we remember events more clearly in the recent past and how memory degrades over longer timescales, leading to telescoping effects that distort our sense of when things occurred.

In the segment on circadian biology, Eva Winniebeck from the University of Surrey discusses the body’s master clock and peripheral clocks across tissues. She explains that each cell contains a timekeeping mechanism that is synchronized by signals from the brain’s suprachiasmatic nucleus, but that this synchronization can drift under certain conditions such as jet lag or shift work. The discussion emphasizes the interactions between clock genes, hormones, body temperature, and behavioral patterns like sleep, mood, and metabolism. A key point is that a coherent, organism-wide time system supports health, whereas misalignment can contribute to adverse outcomes and disease processes.

"one gene turning off another and feeding back to turn off others" - Eva Winniebeck, University of Surrey

Time in Medicine and Chronobiology

The podcast considers how understanding clocks can improve medicine. Chronobiology explores how drug efficacy and side effects vary with time of day, an approach that could optimize therapies and reduce adverse events. The host notes that cancer therapies and immunotherapies may be most effective when timed with the body's rhythms, illustrating the practical biomedical value of time awareness. The discussion highlights shifting research into precision medicine, where treatment regimens consider the circadian phase of individual patients to maximize benefit and minimize harm.

"immunotherapy against cancer seems to often, in many instances, depend on the time you receive that first drug" - Eva Winniebeck, University of Surrey

Future of Timekeeping and Leap Seconds

The program turns to the future, explaining how atomic clocks underpin coordinated universal time (UTC) and GPS systems. The atomic second is defined by cesium-133 transitions, a definition that enabled synchronization across the globe, including navigation and telecommunications. Yet, Earth’s rotation now drifts relative to atomic time, leading to leap seconds inserted to keep UTC aligned with the Sun’s position. The episode presents NASA/physics laboratory perspectives on the leap-second debate and ongoing plans to remove leap seconds, seeking a continuous UTC that avoids disruptions in critical infrastructure. The discussion ends by contemplating a future where timekeeping may evolve beyond traditional concepts, potentially redefining how we measure and experience time in a rapidly changing world.

"there are plans in place or proposals in place to end leap seconds such that atomic time, universal coordinated time will not be disrupted" - Satnam Shemar, National Physical Laboratory