And it’s becoming clear that the lights we live under may be upsetting the balance. In the past couple of decades, we’ve switched from incandescent halogen lighting to energy-saving LEDs. A report by the House of Lords Science and Technology Committee published in 2023 cites artificial lighting as a “hidden pollutant” and identifies the invisible LED “flicker” as an issue for many people — it overstimulates our brains. Plus, LEDs are primarily made from blue light, which affects our circadian rhythm. “Just because we can invade the night, doesn’t mean we should,” says Russell Foster, professor of circadian neuroscience and the head of department of ophthalmology at Oxford.