Sunlight makes us cheerful. The pineal gland in the brain is responsible; in bright light it releases hormones such as melatonin more strongly. Melatonin is a mood enhancer and sexual stimulant. One consequence is seasonal affective disorder, or SAD, whose sufferers are peculiarly depressed and unsexy during the winter. The short, dull days fail to stimulate their pineal glands. Brief daily exposure to intense light reduces the SADness.

In this connection, Daedalus recalls the theory that the pineal gland is the relic of a third eye possessed by our distant reptilian ancestors. Presumably it still retains a vestigial sensitivity to light. Indeed, it must be amazingly light-sensitive. It is stuck almost in the middle of the brain — how can light reach it? Through the ears, says Daedalus. The pineal gland is almost exactly on the right level, and the ear hole is a excellent entry point for light. It is formed of soft, translucent tissue, and is close to the carotid canal and several nerve pathways into the brain. Light could diffuse along these paths quite well, without being blocked by opaque bone.

This notion has many implications. It explains the sexual allure of the world's tropics and sunlit regions, despite the dark glasses which are de rigueur for their devotees. It explains the ear-concealing headgear of monks and subservient groups in some traditional societies: the garb must serve to damp dangerous feelings, and encourage a grave and humble mien. It also suggests a simple method of countering SAD and depression. Daedalus's ‘Earlight’ is a headband carrying two well-focused lamps to beam light into the wearer's ears. Human tissue is most translucent to red light, so small red lasers or LEDs are the lamps of choice. Accurately aimed, they will illuminate the pineal gland far more effectively than the fiercest daylight. The Earlight should bring cheer and erotic interest to the saddest of SAD sufferers.

More cunning still, the Earlight could illuminate one ear more than the other, thus biasing pineal output into the more illuminated hemisphere. Left-brain-dominated rationalists could boost their emotional awareness, and right-brained dreamers could get a grip on reality. And combined with a personal stereo system, the Earlight could cure the glum truculence of so many teenagers, whose melatonin level is clearly lowered by their permanent wearing of ear-blocking audio equipment.