How the Eye Sees at Night

The retina uses two kinds of receptors. Cones are packed in the center of vision and give you sharp, colorful daylight sight, but they are nearly useless in darkness. Rods surround the cones, respond to dim light and motion, and see only in shades of gray. Because the center of your vision goes nearly blind at night, staring straight at a dim object can make it vanish — the cure is off-center viewing, looking about 5 to 10 degrees to the side so the image lands on the rod-rich outer retina. The rods take roughly 30 minutes to fully adapt to darkness, and one flash of bright white light undoes that adaptation in an instant, which is why pilots use dim red or low-intensity cockpit lighting and scan the sky in slow, overlapping steps.