Where in physics does randomness occur?

[Jarfi]

Main Question or Discussion Point

Electrons appear randomly in quantum physics, but are there any other places where particles behave randomly, is there any other true randomness in the universe, something we can not predict?

 

[phyzguy]

How about radioactive decay? A uranium nucleus happily sits there for a billion years, then one day emits and alpha particle and decays. Why? There is no known reason.