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Cats see in the Dark ?
The mystery explained by experimental evidence, a personal account.
As well as having nine lives, and always landing the right way up, cats are credited with the ability to See In The Dark. Is that true? Can cats really see in the dark? I have some interesting evidence which sheds light (!) on this curious question. Some time ago a cat tried to leap right through me, like you might imagine a cat trying to leap through an invisible person! It was a dark night and I had the bedroom curtains shut, and I was standing by the bedside in a dark dressing-gown, and along came the cat and tried to leap onto the bed! Not aware I was there, the cat's trajectory onto the soft bed was interrupted by the person quietly standing there. The sudden change of flight plan resulted in the emergency deployment of claws, which was not pleasant. However it was the shock which was worse than the pain, as you just don't expect to be suddenly attacked by a relatively tame well house-trained pet cat when about to go to bed.
It's a known fact that cats can see well in low light conditions, certainly much better than humans can, but cats definitely can not see in total darkness. Outdoors by dim moonlight, cats can mooch around confidently knowing where they are going. But indoors at night with the curtains closed, they can make mistakes.
The ability of cats to cope with darkness is improved by other factors. Without going into too many experimental details, I have observed a cat walking around without any ability to see, and what I noticed was that the four footed configuration is much more stable and less likely to trip over things than the two footed mode of walking. Even if a cat tripped up, there would still be three feet on the floor, whereas a human tripping up has just one foot remaining in place, and the centre of gravity not over that place. Also the cat has less far to fall. These dynamic factors give the cat much more confidence to walk around in the dark.
Cats have eyes which show up in headlights, hence the expression "cats eyes". The reflectiveness of the eyes of cats is because of some sort of organic mirrors behind their light-sensitive retinas. This gives the eyes even more light-gathering ability as the photo-sensors have a second chance to pick up a photon.
In addition to cats' excellent night vision and four footed gait, cats also have other senses useful at night. Smell, and also sound visualisation. Having twin independently steerable directional dishes for ears, the cat's world of sound takes on a 3D stereo appearance. It's not as good as sonar by bats or dolphins, but it's more than the term "hearing" would suggest. I have experience of visualisation in sound, but that's another story!
So to sum it up, cats can see well even on a dark night, and cats can see in the dark as humans might describe it. Cats can't see in total darkness, but they can walk around in total darkness and are very good at making guesses (usually!).
If you'd like to see some pictures of cats, there are some here.
Another vision-related speculative page here is about whether we dream in black and white. Again, experimental evidence beats misconception of commonplace belief.