Definition
The gradual physiological process by which the eyes adjust to low-light conditions, increasing their sensitivity so that objects can be seen in dim or dark environments. Full dark adaptation typically takes about 30 minutes and can be quickly destroyed by exposure to bright light.
Plain English
It's the slow process your eyes go through to start seeing properly in the dark. It takes around half an hour, and a single bright light can undo most of it in seconds.
Context Anchor
Used in night vision discussions, especially before and during night flight when a pilot is trying to preserve the ability to see outside in low light.
Derivation
From 'dark' (without light) and 'adaptation' (the act of adjusting to new conditions, from Latin 'adaptare' — to fit). Together: the eye fitting itself to function in the absence of light.
Why Pilots Care
Full dark adaptation is essential for seeing outside references and instruments at night; bright lights can reset the process and create temporary blindness.
Analogy
It is like walking from bright sunlight into a dark room. At first you see very little, but after a while shapes and details begin to appear.
Grounding Statement
Picture stepping from a bright room into a dark hallway — at first you see almost nothing, and only after several minutes do shapes start to appear. That gradual recovery is dark adaptation.
Intuition Check
Dark adaptation is not just your pupils opening wider. It is a slower change in how well your eyes detect weak light.
Example Sentence 1
The pilot used a dim red flashlight in the cockpit to preserve dark adaptation during the night cross-country.
Example Sentence 2
A flashlight pointed at the chart can interrupt dark adaptation and force the pilot to restart the adjustment process.