On 12/20/2012 03:15 AM, Michael Press wrote: > In article<email@example.com>, > Phil Carmody<firstname.lastname@example.org> wrote: > >> Michael Press<email@example.com> writes: >>> In article >>> <0.ef56b5652decd19bb478.20121128013501GMT.firstname.lastname@example.org>, >>> Ben Bacarisse<email@example.com> wrote: >>> >>>> Good quality, hardware-generated random number sequences (if our current >>>> understanding of quantum effects is correct) are random in a different >>>> way to the digits of pi. It helps if the terminology is be able to >>>> distinguish between them. >>> >>> I do not see how quantum effects can be used to generate >>> random sequences. Coherent systems are stable and highly, >>> if not perfectly, predictable. >>> >>> Hardware generated random sequences usually read Schottky >>> noise off some device (a sound card in a computer) and use >>> that. This can be modeled using entirely classical physics. >> >> Are you sure? Shottky noise is white noise, and thus is >> indistinguishable from thermal (Johnson-Nyquist) noise. >> So you can statistically model it the same way, but that >> doesn't mean it's actually caused by classical mechanics. >> I can't find any references to Shottky noise that don't >> mention some quantum effect. > > _What_ quantum effect? So far I am the only one who > does not gloss over this question. That `quantum > effects' are involved does not imply that they > beget stochastic effects. > > Experiment and analysis of time series show that > radioactive decay has an unexplained component. Further > this unexplained component is no more complicated or > less simple than diffusion across a membrane. Bluntly, > equivalent to deflation of a bicycle tire. > > By `quantum' I read `wave theory of matter'. The > original Bohr theory is as good as we have for what > might actually be happening. > > (Personally I do not adhere to any interpretation used > to psychologically make the experiments more palatable; > preferring to confront as best my faculties allow the > raw facts.) >
We tend to take "measurement" as an objective practice. But I think there's a subtle interplay between theory and practice or experimental physics.
Measuring is a phenomenon involving physicists, their apparatus and what they're observing. (maybe? )
In practice, a sophisticated measurement relies on a long chain of observations, calculations and assumptions on what's negligible. These days, it will likely invoke electro-magnetic theory, since digital measurements are so common .
The statistics of quantum mechanics has to do with "observed things", the result of measurement in the wider sense (approximately).
What is "measuring" in physics, in a once-and-for-all definition?