Imagine the whole of human evolution were squeezed into a single day. You’d learn to walk on two legs just in time to stumble out of bed, then spend most of the day charging around after wild boar, until 11.58pm when you’d begin farming, learn to write, and – in the final seconds
before midnight – invent the printing press, the steam
train, the atomic bomb, the light bulb and the LED.
That, in a nutshell, is why light has such an influence
on our body clocks. We’ve spent almost our entire
evolution living by the light of the sun, and although
electrical illumination has turned out to be awfully
handy, it confuses the hell out of our stone-age brains.
We all know how a light left on can keep us awake and
how it feels to step off a plane into bright sunshine when
your brain is telling you it’s the middle of the night. But
it’s only very recently that we’ve understood the reasons
for this, and just how big an influence light has on our
bodies and minds.
In fact, leading researchers suggest that we start thinking
about light as a drug, such is its potent effect on our
bodies and its rhythms.
On 4 November 2011, six astronauts touched down
after a year-and-a-half long journey to Mars and
stepped, blinking, from their spacecraft. But they hadn’t
really been to Mars – the ‘spacecraft’ was in a scientific
institute in Moscow, part of a $23 million (£ 15 millon)
experiment to see how our bodies and minds might be
affected by spending that long in a metal box.
During the mock voyage, scientists monitored the
participants’ daily activity, sleep patterns and various
physiological indicators, and gave them regular tests
and questionnaires to see how they were coping.
One of the biggest issues turned out to be sleep. A study
published in December 2012 found that the astronauts’
body clocks quickly slipped out of sync – not least
because they had no exposure to natural light. Four
of the six astronauts had their sleep patterns severely
disrupted, causing various problems with their physical
and psychological health – bad news at the best of times
and potentially disastrous in space.
Over the past decade, scientists have made the key
discovery behind biodynamic lighting. We are all,
effectively, fitted with a blue-sky detector: special
receptors in our eyes react to the blue content in
daylight, see it decreasing as the day goes on, and prepare
us accordingly for activity or rest. Our daily cycle takes
its cues from the rising and setting of the sun, but
Deprived of the cues provided by daylight, the body clocks of astronauts
taking part in an 18-month-long Russian study quickly fell out of sync
with actual daily rhythms