'We've got to expose ourselves to sufficient light to keep us alert.' Sleep expert Prof Russell Foster, from Nuffield Department of Clinical Neurosciences (NDCN) and brasenosecollege, explains why we all need a 'photon shower' during winter 🌧️💡 #SleepExpert #SleepHack #SleepPsychology #WinterMornings #SleepScience #SleepResearch