I was reading one day and was wondering about how Kryptonite became so well known with the populace of Metropolis...and the world. When it comes to Superman's weaknesses like red sunlight sapping his powers, or him not being able to see through lead, how well known are they in universe? I mean magic is easy to guess as it's not a weakness specific to Superman, but to everyone. However with his other weaknesses, how much does the general public know about Superman's weaknesses? Why does everyone know?