Q: Why can you sometimes see a star out of the corner of your
eye, but not when you look directly at it?
Q: Why can you sometimes see a star out of the corner of your eye, but not when you look directly at it?
A: Light comes through the lens of the eye and focuses on the retina, where there are two types of light-sensitive cells: rods and cones. Directly behind the lens are both rods and cones, but a few degrees away from the center, there are mostly rods, which are more densely packed than those at the center. This means the area of the retina away from the center is more adept at detecting faint light than the area at the center of the field of vision. That’s why the eye sees very dim light when it strikes these densely packed rods, but when you turn your head and look at it straight on, it strikes the part of the retina with fewer rods and seems to disappear.
– Douglas B. Smith,
‘Ever Wonder Why?’
