Why is quantum mechanics random?

[zensunni]

I watched "the elegant universe" and it said that quantum mechanics is based on probability calculations. So, to predict something, you calculate the probability of it happening.

 

What experiment has been done that shows sub-atomic particles behaving this way? How did they conclude these things?

 

Thanks for any help! This forum is awesome.

[Klaynos]

It's not "random"...

 

The most common experiment used to say that QM is real, and specifically probability waves and wave-particle duality... is the young's two slit experiment. Where you fire particles at two very thin slits and they act like waves and you get interference between the particles/waves from the two slits.

 

That's all well and good, a bit weird but ok.

 

But now if you send 1 particle at a time (it's been done with buckyballs which are really rather big (60 carbon atoms) you find that you get an interference pattern so the particle not only interferes with itself but must also pass threw both slits at the same time.

 

This is only possible using quantum mechanics.

 

QM is one of the most tested theories in science, mostly because it's just so weird. But you will own devices that rely on it, well assuming you own any modern electronic device.

[pioneer]

One irony in this statement is that the quanta themselves, like photons, are totally reproducible and therefore have a probability of 1, which means the quanta themselves are rational. Another example are the substructures of matter is composed of very distinct combinations of quantized particles, always the same. The proton is a proton and not a distribution function. This suggests the rational laws have yet to be discovered and we use probability as a good first approximation.

[Sisyphus]

One irony in this statement is that the quanta themselves, like photons, are totally reproducible and therefore have a probability of 1, which means the quanta themselves are rational. Another example are the substructures of matter is composed of very distinct combinations of quantized particles, always the same. The proton is a proton and not a distribution function. This suggests the rational laws have yet to be discovered and we use probability as a good first approximation.

 

How does that suggest that? If I understand you, you're just saying that particles exist in specific numbers (hence the "quantum"). What does that have to do with their position/momentum?

[I_Pwn_Crackpots]

I watched "the elegant universe" and it said that quantum mechanics is based on probability calculations. So, to predict something, you calculate the probability of it happening.

 

What experiment has been done that shows sub-atomic particles behaving this way? How did they conclude these things?

 

Thanks for any help! This forum is awesome.

 

 

It's not random, it's just very counterintuitive. On the one hand, all objects have a wave-particle duality. And then there's the fact that you can't know precisely the speed and position of a subatomic particle, the photons are too energetic. That's why probability is a must when modeling the subatomic world. Otherwise, quantum mechanics is very deterministic, and one of the best tested theories ever formulated.

 

But if you really must insist on an ontology, read up on the Copenhagen Interpretation, that might make quantum mechanics make much more sense.

[big314mp]

I would also recommend the book "Schrodinger's kittens", as that provides a good look at the different interpretation of QM.

 

I would be careful of the Copenhagen Interpretation (not exclusively this one, but since this is the most common one, I mention it) as it is just an interpretation. There are many different interpretations out there.

 

"Schrodinger's kittens" is the sequel to the book "Schrodinger's cat", which I have not read, and thus cannot make any statements about. Kittens will stand on its own, however.