How Random Is Random? Limits & Predetermination

[Kazza_765]

What about a decaying nucleus? Two nuclei that are completely identical in every single respect. One of them decays, and one of them doesn't. This doesn't follow cause and effect. And its completely random, no way of ever predicting which will decay and which won't, no matter how good your measuring instruments.

And its also my understanding in the double slit experiment that the point of detection of any individual electron/photon is completely random. All we can ever know about the particle is its wave function, and all that gives us is probabilities. But where it actually hits is completely unpredictable.

Ok , so you can't measure the position and momentum of a body with absolute certainty.
But is it not quite certain that the particle indeed exists somewhere in some state which cant't be predicted through measurement or do we also have to take its dual nature into account ?

Nope, this is what Heisenberg was trying to point out. Its not the case that the particle has a definate position and we just can't measure it. The particle actually doesn't have a clear position and momentum. When you take into acount the dual nature, and you represent the particle as a wave packet, in order to localize that wave packet over an increasingly small area, you must necessarily increase the uncertainty in its momentum.

 

[Hanny]

Reviving an old thread

Firstly, I'm totally new here so what I say may be rubbish.

What about a decaying nucleus? Two nuclei that are completely identical in every single respect. One of them decays, and one of them doesn't. This doesn't follow cause and effect. And its completely random, no way of ever predicting which will decay and which won't, no matter how good your measuring instruments.

I think that the notion of nucleus decay being random is not due to the decay occurring at that exact moment by chance, but rather that we don't have sufficient knowledge to determine what the trigger for nuclear decay really is.

Take the example of a random number generator from a computer. Although the numbers that come from it are seemingly random to an observer, once the algorhythm for generating the numbers is revealed, any observer with an identical computer can "predict" the next number by punching the same input conditions into an identical machine. In the same way, if we knew the causes of nuclear decay and were able to measure them, it would be possible for a complex algorhythm for predicting the nuclear decay to be set up based on the input conditions (the state of the atom).

An even more interesting point that stems from this idea is the notion of predestination. If everything in the universe followed a fixed set of rules governing their behaviour, it would mean an infinite number of universes created from an identical big bang would follow the exact same path of development.

The implications of this would be that everything in this current universe is following a path of reactions that cannot be deviated from. I am aware, however, that there is a notion of human free will that would technically create "randomness" and destroy such a predestination. However, once you look at humans as simply a complex interaction of energy and mass this notion disappears; why should the reactions between the particles in the human brain be any less predictable than the reactions of the particles inside a cooking loaf of bread?

It seems that everything is predestined?

I know that this argument is probably hugely flawed somewhere.. or everywhere! I'd love for you guys to come and tear it apart :)

Cheers,
Hanny

 

[tribdog]

Go back to Schroedinger's Cat. The original experiment was designed to make sure it was random whether or not the particle decayed.

 

[tribdog]

the outcome of a roll of a die is also random no computer, no matter how fast and accurate can predict what it will be before it is rolled.

 

[rcgldr]

Any algorithm that calculates the "nth digits" of pi or similar constants generates random sequences, and there are programs to do this, so computers can be used to generate random sequences. Go to the link below, click on algorithms, then "nth digit ...":

constants.html

 

[TuviaDaCat]

so a chaotic pendulum has no physical value which has a measurable chance to happen?

 

[Pythagorean]

http://www.myphysicslab.com/pendulum2.htmlEdit: this is not my physics lab

 

[AO eye 5]

A small contribution for the thread.

Since this is still in general discussion, there was something interesting I recall on how a mathematican considers the random nature of pi; that is it not random, but displays every pattern possible.

I feel this thread needs to be where it should.