Narrabri-based scientist Dr Bec Thistlethwaite contributes a column to The Courier on the science in our daily lives. Readers are invited to send their science questions in to Dr Bec via [email protected]
If you’ve ever seen a cat’s eyes shining at night, you’ve spotted one of nature’s clever vision tricks.
Cats, like many animals that are active in the dark, have a special structure in their eyes called the tapetum lucidum, which means ‘bright carpet’ in Latin.
This layer sits just behind the retina, the part of the eye that detects light and turns it into signals for the brain.
When light enters a cat’s eye, it passes through the retina.
If the retina doesn’t absorb all of it, the tapetum acts like a mirror, reflecting the light back through the retina for a second chance.
That ‘double pass’ gives the light-sensitive cells more opportunity to capture every bit of brightness.
The result is outstanding night vision.
Cats can see in conditions about six times dimmer than humans can, which makes them excellent at hunting or exploring at night.
The glow you see is simply the reflected light bouncing back out of their eyes.
Depending on the angle and the animal, it can appear green, yellow, blue, or even reddish.
Humans don’t have this reflective layer, which is why our eyes don’t glow in the dark.
The closest effect we get is ‘red-eye’ in flash photography, where light bounces off blood vessels at the back of our eyes.
So, when you notice a cat’s eyes gleaming in torchlight or car headlights, what you’re really seeing is a brilliant piece of natural engineering.
The glow is evidence of a built-in system that helps cats stretch even the faintest light into a clear picture of their world at night.
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