This podcast episode explores the impact of light on sleep and circadian rhythms. The guest, Dr. Michael Gradazar, a renowned sleep researcher, discusses his research on the effects of light, screens, and technology on sleep. He shares personal experiences and experiments related to light exposure and its influence on alertness and sleepiness. The episode covers early 2000s research on the effects of different wavelengths of light on circadian rhythms, as well as the concept of phase delay and its implications for sleep timing. Light therapy as a treatment for insomnia and the science behind its effectiveness are also discussed. The episode provides a comprehensive overview of the fundamentals of light and its influence on sleep, emphasizing the importance of factors such as brightness, color temperature, and distance. The impact of light color on sleep is explored, debunking the misconception that blue light from screens significantly suppresses melatonin production. Dr. Gradazar highlights the need for a more nuanced understanding of the effects of light on sleep and promotes further exploration of the science in this field.