Search: why do cats sleep so much
Why: I got up for 30 seconds and came back to this:
Answer: Nobody knows! They are crepuscular (most active at dawn and dusk), since most of their prey is active at these times. This gives them plenty of time to sleep during the middle of the day.
When domestic kitties sleep, their finely tuned senses remain active. The ears rotate as they stay in touch with the environment, and if they hear a noise or sense that someone is approaching, they will open their eyes to assess the situation before falling back to sleep. If you try to wake a sleeping cat, she can transform from deep sleep to full alertness in a matter of seconds – and then back again.
The More You Know: Cats (and dogs and birds and reptiles and most other animals) have a third eyelid called a nictitating membrane that swings in horizontally from the middle. If your cat's third eyelid is visible at all times (not just during naptime), take it to the vet. Sick pet.