ABSTRACT
The human body evolved in the diurnal cycle of light and dark, and is tuned to the spectrum of the sun’s radiation. We respond to daylight in many ways: our luminous environment affects our health; it triggers responses in us that can be traced to requirements for safety and survival; it affects our interaction with other people; it determines the ease with which we carry out visual tasks. Crucial to all of these is that daylight is not a constant flow of light but something dynamic, varying with time and place.
