Unpredictability vs Randomness

[coktail]

Hi All,

How do we tell the difference between something being random and something being deterministic but unpredictable because of limitations without with our tools/technology or methods of knowing (e.g. uncertainty principal)?

Are there cases where we cannot tell the difference? For example, in sub-atomic uncertainty where we can't predict an objects position and momentum at the same time, do we think that its position is random, or is it deterministic but just unknowable. Or, are we uncertain which of these two it is?

Thanks!

 

[HallsofIvy]

As for your last question, "For example, in sub-atomic uncertainty where we can't predict an objects position and momentum at the same time, do we think that its position is random, or is it deterministic but just unknowable. Or, are we uncertain which of these two it is?", there are fundamental theories of quantum physics that argue both ways. We don't know, yet, which is true, although I believe that most physicists are inclined to the idea that there are no "hidden variables" and the position of a sub-atomic particle really is random- until it is measured.

 

[schip666!]

In the classical world, deterministic chaos is un-predictable but not random. Have a look at the Logistic Map for starters: http://en.wikipedia.org/wiki/Logistic_map

There are regimes whose exact behavior are un-predctable, but we _can_ predict where they are...