The brain is wider than the sky,
For, put them side by side,
The one the other will include
With ease, and you beside.
Emily Dickinson
ON THE ANTARCTIC RESEARCH STATION where I lived as base doctor for a year there were almost four months of sunlessness, while the planet’s winter tilt put the continent in shadow. But it wasn’t perpetually dark: there was plenty to see and the sky was always changing.* On emerging from Halley base I became accustomed to looking up and seeing the wheel of the stars and planets, meteor showers, or the slow creep of satellites. The ice was usually moonlit, and at that latitude there were weekly and sometimes daily auroras, granting depth and spectacular brilliance to the sky. On midwinter’s day, almost two months into the dark time, we added another source of light – we lit a fire. We piled up wooden packing crates and set them ablaze.
To warm yourself by a bonfire built on ice is a distinctive experience. The floating ice shelf beneath our feet was hundreds of metres thick, fixed to the shoreline, and composed of snow that had fallen further into Antarctica over millennia, and then flowed slowly, as a glacier, out over the Weddell Sea. As the fire gathered intensity, the compacted snow melted and seeped away, the flames sinking their own firepit deeper into the oblivious ice. To the south of the base we could see the contours of the continent rising towards the South Pole, its immense weight settling beneath the stars and auroras as if in obeisance. On midwinter’s night we kept our backs to it, holding our beer bottles towards the fire to keep them from freezing. For a few hours we bathed in heat and light, trying not to think how alien an environment we were living in, and how far we were from those we loved.
For some, the winter so far had been particularly tough. Sleep had become restless and unrefreshing: as Homo sapiens we’re best adapted to the rhythms of tropical skies, and the lack of sunlight month after month was sending our body clocks awry. Some of my base-mates experienced ‘free-running’, when the body’s internal rhythm loses its purchase on the celestial twenty-four-hour clock and slips to a shorter, or longer, internal timer. Free-running can lead to a bewildering, exhausting sensation of perpetual jetlag, as the body tries to run to a rhythm shorter, or longer, than twenty-four hours.
The body’s internal clock is called ‘circadian’ (Latin for ‘almost a day’) and is characterised by the secretion of melatonin at night from the pineal gland of the brain. When we’re in temperate or tropical latitudes, the pineal’s own rhythms are calibrated by the sky’s alternation of light with dark. Deprived of natural light during a polar winter, the pineal gland of those who by nature are early-rising larks defaults to a shorter internal ‘day’ of just twenty-two or twenty-three hours, while night owls may default to twenty-five or twenty-six.* To get up or to try to sleep on schedule when your circadian rhythm is running faster or slower than twenty-four hours was to put yourself out of synchrony with the rhythms of the base. But to sleep as you pleased would cause havoc to base routine, and upset the delicate harmony of its little society – there were just fourteen of us for the ten months the base was isolated. My role as the doctor was to look after the well-being of those on base, but also to investigate whether supplementing the dim fluorescent lighting on base with additional light boxes could keep everyone’s body clocks to time, alternating white light with blue-enriched as the winter progressed.
Circadian rhythms influence more than just our waking and sleeping – they govern body temperature, blood pressure and aspects of our bodies from the biochemical level right up to the psychological. Light is the best stimulus to mould our sense of time, but exercise after waking can help, as can rigid mealtimes (the liver has a distinct body clock calibrated to customary mealtimes, just as the brain’s clock is timed to sleep cycles). The pineal gland gets its knowledge about the seasons, and ambient light conditions, via ‘ganglion cells’ arising within the intricate weave of the retina and running into a part of the primitive brain called the ‘supra-chiasmatic nucleus’, or ‘SCN’. These neurons are a ‘third eye’, keeping the body aware of the passage of night and day in an entirely unconscious way, and they respond better to light at the blue end of the spectrum.†
The temperature outside reached the fifties below zero, but every ‘afternoon’ I would go skiing on a marked track around the three-kilometre perimeter of the base. I’d ski by moonlight if the moon could be seen, or starlight when it could not. Sometimes I’d ski by the light of auroras. Gathering light into my eyes at the same time each day, I hoped to convince my brain that there was still a shape to the day.
THE SIMPLEST and most archaic organisms on earth, blue-green algae, have circadian rhythms: during daylight, special proteins gather like parasols over their DNA to prevent damage by the sun’s radiation (in darkness those proteins move away to let DNA do its work). It’s likely that the earliest organisms in the primordial ocean worked to a shorter rhythm than we’re used to today, just twenty-two hours, because the earth was spinning faster when they first evolved. There was no ozone layer then, making it even more crucial that DNA be protected against the harsh, unfiltered sunlight. Many of the genes that govern our body’s sense of time look as if they have evolved from primitive proteins involved in this ancient cycle of protecting and repairing DNA.
Many of our own cells – not just in the pineal gland or the liver – have what’s called a ‘molecular oscillator’, showing a twenty-four-hour pattern to the genes they express, and varying throughout the day in terms of their electrical activity. At the molecular level the body is chemistry, and as a general rule chemical reactions go faster in the heat and slower in the cold. But body clock genes and the proteins they express can keep to time irrespective of background warmth – something of critical importance to insects, plants and other organisms that have no temperature control.
Jetlag exists because our bodies have a brake that slows adjustment whenever we move into a new rhythm of darkness and light. It’s a form of resistance to change: the body shifts cautiously into the new rhythm, and it is that caution that prevents our rapid adjustment to a new ambient time zone. If body clocks were able to reset quickly and easily our ancestors might have been thrown out of kilter by a full moon, or whenever they enjoyed a late night around their Palaeolithic fires. But our body clocks have to be able to shift – without that malleability we could never have moved from the tropics to the temperate and polar latitudes as a species, where there are rapid swings in sunrise and sunset times around each equinox. Adaptability of the body’s sense of time made it possible for humanity to move across immense distances of latitude, just as today it facilitates the jet-age shifts in longitude.
A few years ago, a group of cell biologists in Oxford found the cause for this ‘brake’ on adjustment to jetlag: when light shines on the ganglion cells within our retinas, the cells of the SCN begin to express hundreds of genes that transform cell timing to fit the new ambient light conditions. But then another protein kicks in, switching those genes off again almost as soon as they’re active.* Adjustment to the new rhythm is delayed until the pressure of light exposure, day after day, becomes irrepressible. The researchers created transgenic mice without this molecular brake; the new mice adapted to an artificially induced jetlag of six hours within just a day or two, raising their hopes that one day there could be a drug that could cure jetlag, or help shift workers adjust to switching between night and day shifts.
IT’S MORE THAN A DECADE since I practised medicine in Antarctica, but I still meet with circadian problems in clinic. The rhythms of our bodies are often discordant with the rhythms of our communities and our working lives; people in the West spend on average an hour less a day out in natural light than they did twenty years ago, and screen time has burgeoned over the same period, cramming our brains with its blue-enriched light. Shift-working is endemic – particularly in healthcare – and to work rapidly alternating shifts is to condemn yourself to perpetual jetlag. Shift-working is known to lead to poorer concentration, as well as obesity – you get hungrier when your sleep is mistimed, crave more carbohydrate, and a sluggish, out-of-kilter metabolism exacerbates and accelerates diabetes and heart disease.
When the clocks change for winter, for many it’s as if a door is gradually closing, or a curtain is being drawn across their mood and ability to concentrate. ‘Winter blues’ is one name for it, ‘Seasonal Affective Disorder’ another. Herman Melville described it in Moby Dick: ‘Whenever I find myself growing grim about the mouth; whenever it is a damp, drizzling November in my soul …’ To get away from winter blues Melville’s narrator Ishmael took off to the South Seas, but most of us don’t have that opportunity – we have to find a way to make our peace with the winter.
It can feel as much of a struggle to keep one’s body clock running to time through a Scottish winter as it did through an Antarctic one. The research I conducted in Antarctica showed that the sky-blue light boxes offered a slight improvement in the quality of sleep, but didn’t help any of our small group stay more closely to the twenty-four-hour clock. The best ways to beat winter blues, keep the body clock to time, as well as get over jetlag, remain the same wherever you are in the world: stick to a routine, eat well-spaced healthy meals, get daily exercise and, crucially, get as much light through the day as possible – natural light from the sky is usually many factors of magnitude brighter than artificial light. When I remember my time in Antarctica, skiing day after day beneath heavens as wide and dark as a dilated pupil, I was grateful for the spectacle of meteors and auroras, the phases of the moon and the ceaseless turning of the stars. My eyes, as organs of light, granted visions of great beauty there, but I appreciate them too, now, as organs of time.