When Michel Siffre climbed out of a glacial cave in the French Alps on September 14, 1962, he was genuinely shocked. The French geologist had been underground for two months, alone in total darkness, living without clocks or sunlight. By his own careful reckoning, it should have been August 20. He had lost 25 days. Time, for Siffre, had collapsed into what he later described to Cabinet Magazine as “one long day.”
Cut off from sunlight, clocks, and social cues, Siffre let his body decide when to sleep and eat. Without external time-givers, his circadian rhythm free-ran at its own pace. He sometimes stayed awake about 36 hours, then slept around 12, and those long cycles felt like ordinary days rather than 48-hour blocks. Laboratory chronobiology has since confirmed the pattern. In a landmark 1999 paper in Science, Charles Czeisler and colleagues showed that the human circadian pacemaker, when stripped of time cues, drifts a little beyond 24 hours, averaging about 24.2 hours. That biological fact matters philosophically. It shows that the body carries a tempo not identical with the social 24-hour day. When the environment stops resetting us, lived time begins to follow the body’s pattern rather than the clock’s.
Siffre also discovered that his estimation of duration diverged from clock time. During simple counting tasks, what felt like two minutes to him lasted closer to five minutes on the surface team’s stopwatch. That does not prove his experience “compressed by half” in any strict sense. It is evidence that under monotony and disorientation, prospective timing can skew. His diary supports the qualitative finding. In unbroken darkness, he said, memory stopped capturing the passage of days, which is why the whole period felt like one long day. And a caveat belongs here. Introspection and counting exercises segment experience by their very method, so the act of measuring can alter the flow it aims to describe. Still, the safe claim is clear enough. Environment, attention, and biological rhythm jointly shape how duration is felt and later remembered. The cave isolates those variables and lets us watch lived time loosen from mechanical time.
•
Buddhist sources approach time through impermanence, nonself, and close analysis of experience. Early canonical verses in the Dhammapada put it bluntly: all conditioned things are impermanent, unsatisfactory, not-self. The Anattalakkhaṇa Sutta argues that the five aggregates that make up experience cannot be self precisely because they are changeable and not under mastery. These texts do not offer a mathematical theory of seconds, since their aim is soteriological rather than physical explanation. They train attention to how phenomena arise and pass in immediate experience.
Later scholastic traditions develop this into a doctrine of momentariness, kṣaṇikavāda, where mental and physical events occur in discrete instants that perish as they arise. That thesis is not uniform across Buddhism, and it belongs to Abhidharma debates more than to the earliest suttas. A careful formulation is better. Many Buddhist analyses treat experiential time as successive occurrences and teach practices for noticing the arising and vanishing of those occurrences.
Two touchpoints link this to Siffre without overreach. First, practice. Mindfulness instructions cultivate close noticing of breath, sensation, feeling, and thought as they change from moment to moment. That is an intentional training. Siffre’s cave was the opposite. He was disoriented, not meditating. So it would be wrong to claim he lived pure moment-to-moment awareness. The thinner claim holds. When external markers fall away, his reports match what Buddhist analyses predict about untethered experience. Memory carries little segmentation, and the present thickens into an undifferentiated now that resists counting.
Second, philosophical contour. Dōgen’s essay “Uji” or “Being-Time,” from the Shōbōgenzō, treats being as time and time as the dynamic enactment of being in each occasion. Every now is the whole of being-time as it is, and it never repeats. That does not map one-to-one onto circadian science, but it does echo the intuition Siffre makes vivid. When convention falls away, what remains is not a line of identical ticks but the event of a moment showing itself and then disappearing.
What follows is simple. Early texts ground the claim that experience is constituted by change. Scholastic analysis sharpens it into momentariness. Dōgen radicalizes it into an ontology of occasions. Against that background, the cave reads as a case study in how the segmentation of time is a practice and a scaffolding, not a property built into the moments themselves.
•
Martin Heidegger approaches time from the side of existence. Human beings are Dasein, the being that understands its own being. We always find ourselves thrown into a world we did not choose, already amid projects, relationships, and concerns. Heidegger calls this structure Care. We are ahead of ourselves in possibilities, already alongside things and others, and still carrying what has been. Time shows up for us through this caring involvement. In Being and Time from 1927, Heidegger argues that the usual picture of time as a sequence of identical now-points is a derivative abstraction. What is primary is lived temporality, where future, past, and present are interwoven dimensions of existing. We project toward a future, we have-been, and we make-present, all at once, in the way our activities actually hang together.
Heidegger also distinguishes authentic from inauthentic modes. In inauthentic everydayness we drift with the crowd, keep busy, and measure days by the clock. In authentic existence we confront our finitude, choose, and let the meaning of our projects gather time around them. That contrast clarifies Siffre’s case. The cave is not an example of existential insight. It is what happens when world time and projects thin out. Deprived of cues and goals, his days blur. The structure Heidegger describes still applies. Only the content is stripped down, so making-present collapses into a floating now, having-been records little, and projection has almost nothing to organize. The result is a phenomenology of time that feels empty and undifferentiated, which is exactly what Siffre reports.
There is a deeper tension here, and it clarifies rather than undermines Heidegger. Temporal articulation depends on meaningful projects, yet the capacity to articulate at all seems to rest on a biological floor. The cave reveals that floor. When circadian rhythm and environmental cues are disrupted, the existential structure that usually gathers time can falter. This does not refute Heidegger. It locates a boundary condition. The phenomenology of time presupposes an organism able to stabilize wake, sleep, and attention long enough for Care to weave a story. Biology is not the whole of temporality. It is a precondition for it.
•
Put the pieces together and a sharper picture emerges. Human time arises where biological rhythm meets existential structure and attentional practice. The cave isolates the biological. A pacemaker drifting near 24.2 hours supplies tempo but not meaning, as the Science study shows. Heidegger’s analysis captures the existential. Projects and finitude organize that tempo into a narrative structure, shaping how duration is felt and remembered. Buddhist training addresses the attentional. Practice can sharpen the texture of each moment or let it blur into automaticity. None of these alone is sufficient. Biology without projects yields Siffre’s disorientation. Projects without biological stability fragment under poor sleep. Attention without structure diffuses. The lived picture is ecological, a negotiated fit.
The early pandemic offers a real-world case study that Siffre would recognize. Many people reported the blursday effect, where weekdays and weekends became indistinguishable. Research in Frontiers in Psychology and the Journal of Sleep Research found that changes in emotion and routine predicted the perceived passage of time. Boredom and negative affect were linked to time dragging, while high arousal and novelty complicated the picture. Sleep timing shifted, screen time rose, and people reported distortions in duration and sequence. In short, we removed many zeitgebers, rearranged projects, and flooded attention with screens. The clock kept pace. Lived time changed.
There are costs and limits here. It is tempting to romanticize life beyond the clock. Siffre’s record warns against it. Extended isolation brought strain, including low mood and cognitive slowing, in later cave studies he undertook. Free-running may reveal something true about us, yet it is not a recipe for flourishing.
Culture adds another dimension. Many Indigenous and small-scale societies use event-based or cyclical schemas where activities are keyed to happenings and seasons rather than uniform hours. E. E. Evans-Pritchard’s account of the Nuer shows time organized by tasks and cattle. John Mbiti analyzes orientations that privilege the present and recent past, with a thinner sense of distant future. These examples should not be romanticized. They illustrate a core point. There are multiple workable ways to scaffold time, and the industrial clock is only one of them.
These insights invite a rethink of temporal design. Circadian research shows that light exposure and consistent sleep stabilize entrainment. Phenomenological analysis suggests that temporal landmarks, such as rituals and transitions, restore articulation to otherwise flat stretches. Buddhist methods offer techniques for bringing texture back to minutes that otherwise wash together. The goal is not a universal recipe but an ecological sensibility. We can adjust the relation among biological rhythm, meaningful structure, and attentional practice until the hours we count and the hours we feel begin to converge.
•
Return to the cave with these lenses on. Siffre’s clockless life does not reveal chaos. It reveals a default phenomenology that diverges from the dial. Biology supplies a tempo just off twenty-four hours. Projects thin, so temporal articulation weakens. Attention floats, so the present thickens. Buddhist analysis explains why the present expands or contracts with practice. Heidegger’s framework shows why meaning and finitude organize temporal structure. Circadian science tells us why the day can slide when light and schedule fall away.
The upshot is both theoretical and practical. None of these accounts is enough on its own. Together they show why clock time cannot be ultimate for creatures like us. We can use that insight to design time we can live. Keep the clock for trains and meetings. Build projects that gather meaning. Train attention so the present has texture. Then the hours the clock counts and the hours we feel need not be enemies. They can move toward a fit. Which is another way of saying that time can again become a medium for living, not just a measure of it.
Further Reading
Michel Siffre and cave time
- Cabinet Magazine, “An Interview with Michel Siffre,” Issue 30. Long, primary-source conversation covering the 1962 cave experiment and later isolation studies. https://www.cabinetmagazine.org/issues/30/siffre.php
- BBC Future, “The man who lost time in a cave” (2021). Accessible overview of Siffre’s work and public reception. https://www.bbc.com/future/article/20211005-the-man-who-lost-time-in-a-cave
Circadian science
- Czeisler, Charles A., et al., “Stability, precision, and near-24-hour period of the human circadian pacemaker,” Science 284.5423 (1999): 2177–2181. Definitive lab study of free-running human rhythms. https://doi.org/10.1126/science.284.5423.2177
Buddhist philosophy of time
- Dhammapada 277–279. Early verses on impermanence, unsatisfactoriness, and not-self. Any standard translation.
- Saṃyutta Nikāya 22.59, Anattalakkhaṇa Sutta. Canonical argument that the aggregates are not self because they change. Any standard translation.
- Dōgen, “Uji” or “Being-Time,” in Shōbōgenzō. A radical meditation on the interpenetration of being and time.
- Ronkin, Noa, Early Buddhist Metaphysics: The Making of a Philosophical Tradition (Routledge, 2005). Clear treatment of Abhidharma debates about momentariness.
Heidegger and phenomenological time
- Heidegger, Martin, Being and Time (1927), trans. Macquarrie and Robinson. Division II, especially sections 65–83, for temporality, authenticity, and ordinary time.
- Stanford Encyclopedia of Philosophy, “Heidegger’s Being and Time.” Scholarly overview that situates the key claims. https://plato.stanford.edu/entries/heidegger/
Pandemic time and time perception
- Droit-Volet, Sandrine, et al., “Time and Covid-19 related stress during lockdown: The role of emotions,” Frontiers in Psychology (2020). Explores the link between affect and perceived time during lockdown.
- Cellini, Nicola, et al., “Changes in sleep pattern, sense of time, and digital media use during COVID-19 lockdown in Italy,” Journal of Sleep Research (2020). Connects sleep shifts and temporal distortion empirically.
Anthropology of temporal scaffolding
- Evans-Pritchard, E. E., The Nuer (Oxford University Press, 1940). Classic account of event-based temporal organization.
- Mbiti, John S., African Religions and Philosophy (Heinemann, 1969). Influential analysis of African temporal orientations.
