On Thu, Jul 27, 2017 at 07:56:29PM +1200, Lawrence D'Oliveiro wrote:
On Thu, 27 Jul 2017 19:08:31 +1200, Michael Cree wrote:
What is "truly random" when pseudo random number generators can pass all statistical tests for randomness? If there is no known test for distinguishing "truly random" from a known deterministic process that generates a sequence of numbers that passes the tests for randomness, then how can we claim that "truly random" actually exists?
Quantum theory says that, when a superposition of states collapses, you cannot know in advance which of the possible states it will collapse into. This theory has passed all known experimental tests so far.
All sorts of theories say all sorts of things. The question is how much do they actually correspond to reality. What quantum mechanics (QM) says is a little more subtle than the way you put it, but it will suffice for discussion here. Interestingly there are other theories (such as Bohm's pilot wave) that predict exactly the same results as QM. Bohm sacrifices locality (that effects cannot have distant consequences) to retain realism (the ability to predict with certainty the properties of the system given sufficient knowledge of the system at some prior time). It's only for philosophical reasons, not experimental evidence, that most scientists choose QM over Bohm's approach. And while QM has passed all known experimental tests so far, that does not necessarily mean that QM will pass all future experimental tests, and it does not mean that the tests done to date are not subject to flaw or critique. Indeed they are subject to very real problems, such as the sensors are not 100% efficient but the theorems (such as Bell's inequalities) assume perfect sensors. The theorems can be generalised to imperfect sensors but that requires extra assumptions which weakens the test and has opened them to critique. For the record, I kind of like QM and the fact that it is strong evidence demolishing reductionist, realistic and deterministic views of the universe, and, yes, I think it leaves open the door that "truly random" might well exist. But I would not yet take it as proof, particularly when there is still significant debate over the measurement problem in QM. Once again (quoting myself): If there is no known test for distinguishing "truly random" from a known deterministic process that generates a sequence of numbers that passes the tests for randomness, then how can we claim that "truly random" actually exists? Cheers Michael.