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Cats purr at the same frequency as an idling diesel engine, about 26 cycles per second.

That's why it's so relaxing.

A cat sees about 6 times better than a human at night, and needs 1/6 the amount of of light that a human does - it has a layer of extra reflecting cells which absorb light.

Cats' hearing stops at 65 khz (kilohertz); humans' hearing stops at 20 khz.

I wonder what they hear.

A healthy cat has a temperature between 38 and 39 degrees Celcius.