Animals, Plants & Seasons 3-minute video · ages 4-8 · free coloring page
Why do cats' eyes glow in the dark?
At night, when a light shines on a cat, its eyes glow like two little lanterns. Do cats have lights inside their eyes?
3 min
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The scene from the video as a coloring page, plus the three-sentence answer, the experiment, and a QR code back to this page. One sheet, US Letter, black and white.
The answer in three parts
Why?
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Nope, there are no lights inside!
A cat's eyes don't make any light. They bounce light back, like a mirror.
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Cats have a shiny mirror at the back of each eye.
Light that slips past the seeing layer bounces off the mirror and goes through the eye a second time. So cats can see in very dim light, about six times dimmer than what you need.
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Some of that bounced light comes back out.
When a flashlight or a car light shines at a cat, you see the light coming back. That is the glow!
For grown-ups: The "mirror" is a layer called the tapetum lucidum behind the retina. The video keeps it as "a shiny mirror", and it also shows how the pupil works: in bright sun a cat's pupils squeeze into thin slits; in the dark they open wide and round to let in as much light as they can.
Who else has the mirror?
- Dogs
- Deer
- Raccoons
- Foxes
Their eyes can glow green, yellow, or even blue.
A tiny experiment
Try it!
Watch your pupils grow
You need: a mirror and a grown-up
- Stand in front of a mirror in a bright room. Look at your pupils, the dark dots in the middle of your eyes.
- Ask a grown-up to dim the lights. Wait a little bit.
- Look again. Did your pupils get bigger?
What happened? Pupils open wide in the dark to let in more light, just like a cat's.
Did you know?
Even cats can't see in total darkness. They need at least a tiny bit of light. No light at all means no seeing, for everyone!
People don't have the shiny mirror. But if a camera flash hits your eyes, they can look red in the photo. That is light bouncing off the back of your eye, which is full of tiny blood vessels.
Your guide in this video
I'm Midnight, a little black cat. Let me tell you my shiny secret.
Midnight has green eyes and a white chest patch, and hosts all of our pet questions.
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