Found this question while think of determine&random. If a system if very complex, it may looks like random. Even GUT is found, it is still impossible to tell what a determined system will be after a long period because of Heisenberg's uncertainty principle. An error in initial conditions, even it's smaller than any number which can be imagined, will be zoom out to be seen very soon in a chaotic system. Then what is the difference between chaos and randomness? Or, are they exactly the same thing since uncertainty principle kills any experiment to tell the difference?