To generate a random result we use a coin or a die.But if you have a sequence of numbers, when can you say that they are random? When you cannot find any recipe, any algorithm that will allow you not only to reproduce the sequence but also to predict the next number in the sequence. Before quantum mechanics there was common agreement among scientists
that Quantum mechanics has shown that God does indeed play dices: the behaviour of matter at microscopic scale is unpredictable. There is no way to predict when a radioactive nucleus will decay.For this reason we can use quantum phenomena to produce a sequence of true random numbers. The discovery of deterministic chaos has shown in more recent years that also in classical physics we get randomness and unpredictability. A simple cause can also produce chaos.
We have a simple recipe to produce our numbers but there is no way to predict future values. This allows us,for example,to produce with a simple algorithm a sequence of "pseudorandom" numbers that behaves exactly like a random sequence. This is how a computer generates random numbers. This algorithmically produced pseudo-randomness is so surprising that von Neumann's said (cited by Knuth in his volume 2: Semi-numerical Algorithms)
device that
gathers non-deterministic events in the computer environment, like:
- Mouse movement
- rate of packets coming in or out of system
- interrupts timing
## Randomness and coincidenceThere is a fascinating link between randomness and coincidence. Coincidences are the result of randomness! How can this be?The problem is that if you have a truly random phenomenon than each occurence of it must be completely new.Let's put it in this way. A perfect random die must have an infinite number of faces and each time you cast it the result must be a completely new face, a face never cast before. Now, what happens with real dice:the phenomenon is random but the outcome can be only one of six. The die must decide for one of the six faces. The distribution of the frequencies of the six numbers must now follow some precise laws otherwise THE PHENOMENON IS NOT RANDOM. One of these laws dictates the presence of coincidences like the number 6 cast ten times continuosly. Strange eh... |

The Big Table of Everything Random is also an invitation to find more about this fascinating concept. In the following table,connected to each entry you will find a search on Alta Vista on the most important concepts connected to chance and randomness.

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