Tuesday, October 28, 2014

Your night vision

When your eye has to "adjust" to the dark, what is actually happening is that the retina is activating its night-vision mode. This requires chemically recalibrating the neural networks in the eye to turn on the "scotopic vision" circuits, which are normally off during the day and which take around 20 minutes to activate. The night vision receptors (the "rods") are blue-sensitive and don't work in color, which is why everything at night looks "blue".

And there are no night receptors at the high-resolution center of the retina, which is why it is difficult to read in the dark. The rods are very sensitive to light fluctuation, which is why you can see the stars twinkle at night, but only the ones you are not looking at (because there are no rods at the eye center).

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