Why is cat urine fluorescent?
It isn't. Cat urine is not fluorescent, and it does not glow in
the dark. I'm not sure where this myth comes from. Cat urine is
yellow, like human urine. To the naked eye, it is indistinguishable
from human urine, except for the smell. Cat urine is ammonia-based
(unlike human urine) so it smells of ammonia.