This book was in part inspired by my mother, Isobel Geddes, who for as long as I can remember, has divided the year along calendrical fault lines based on the availability of sunlight. Thanks to her for getting up in the blackness of midwinter and accompanying me to mark the sunrise at drizzly Stonehenge and Newgrange; for sharing her extensive knowledge about prehistoric monuments; and for being a valuable first reader.
This book couldn’t have been written without the fantastic patience and parenting skills of my husband, Nic Fleming, who bravely held the fort while I ventured off on multiple trips to Scandinavia, the US, Germany and Italy; read my (very long) first draft and helped improve it; and provided encouragement during moments of literary despair. Thanks also to Nic and to our children, Matilda and Max, for humouring my ‘darkness experiment’ and spending several weeks during December and January living without any electric light.
I am extremely grateful to my agent, Karolina Sutton, and to Rebecca Gray at Profile Books for believing in my idea and commissioning me to write about it in the first place. Thanks too, to the Winston Churchill Memorial Trust, which funded so much of the travel that was necessary for this book, and to Mun-Keat Looi and Chrissie Giles at the Wellcome Trust’s Mosaic, which also funded several of my overseas trips.
My visit to the Amish community in Lancaster County wouldn’t have been possible without the help, trust and enthusiasm of Teodore Postolache at the University of Maryland, who introduced me to Hanna and Ben King. I’m grateful to Sonia Postolache for her companionship and excellent driving skills – and to Hanna and Ben for allowing me into their home, introducing me to their friends and family, and answering my relentless stream of questions about light, sleep and Amish life.
Neither would I have been able to spend the night on a Milanese psychiatric ward without the trust and assistance of Francesco Benedetti at San Raffaele Hospital in Milan. Grazie molto, also, to those patients who shared intimate details of their illnesses with me and to Irene Bollettini for acting as translator.
Richard Fisher at BBC Future gamely commissioned me to research the effects of living without electric light and provided the funding for some of the scientific tests. I am indebted to Derk-Jan Dijk and Nayantara Santhi at the University of Surrey who helped me to devise the experiment and analyse the data. Thanks also to Marijke Gordijn at Chrono@Work for carrying out the melatonin analysis, and to Frank Scheer at Brigham and Women’s Hospital and Mariana Figueiro at the Lighting Research Center who also helped with the data interpretation.
As a science journalist, I am unceasingly indebted to the various researchers and individuals who spare the time to talk me through their work and experiences, and the same goes for this book: Even if you are not mentioned or quoted directly in these pages, the insights and explanations you have provided have been invaluable. Particular credit goes to Anna Wirz Justice, Derk-Jan Dijk and Prue Hart, for reading various chapters and providing feedback on the scientific accuracy of the material, and to my father-in-law, Andrew Fleming, for his thoughts on the archaeological content.
In researching the science of circadian rhythms, I leafed through countless journal articles and books, but found Rhythms of Life by Russell Foster and Leon Kreitzman; Circadian Rhythms: a very short introduction by the same authors; and Sleep: a very short introduction by Steven Lockley and Russell Foster great starting points. Also, highly recommended are Internal Time by Till Roenneberg and Reset Your Inner Clock by Michael Terman. I’m grateful to Professors Lockley, Terman and Roenneberg for taking the time to meet with me and answer my additional questions – particularly to Professor Lockley, who patiently taught me how to minimise jet lag, and may therefore have spared me this horror for the rest of my life. Matthew Walker’s Why We Sleep was also extremely useful.
For my research into the effects of sunlight on our skin, I drew heavily on a themed collection of papers in Photochemical and Photobiological Sciences: The health benefits of UV radiation exposure through vitamin D production and non-vitamin D pathways. Richard Hobday’s The Healing Sun, meanwhile, provides an excellent historical account of light therapy through the ages.
I spent a ridiculous amount of time researching our historical relationship with sunlight, most of which didn’t make the final cut. However, for further reading about this fascinating subject, I’d highly recommend Stations of the Sun by Ronald Hutton, and Prehistoric Belief by Mike Williams. And for an excellent general overview of mankind’s relationship with sunlight over the ages, Chasing the Sun by Richard Cohen is encyclopaedic in its breadth, while if you’d like to learn more about the evolution of electric light, Jane Brox’s Brilliant lives up to its title.
Finally, thanks to the team at Profile and Wellcome Collection for helping to put together this book and market it – particularly to my editors Fran Barrie and Cecily Gayford, and to my copyeditor Susanne Hillen. There were many trees obscuring the wood, and together, you did an excellent job of clearing them.