Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Emc2 on 08/09/2012 06:15:32

Title: experiments have cast doubt on a founding idea of the branch of physics
Post by: Emc2 on 08/09/2012 06:15:32

good article

http://www.bbc.co.uk/news/science-environment-19489385

Title: Re: experiments have cast doubt on a founding idea of the branch of physics
Post by: yor_on on 08/09/2012 15:09:00

That's weak measurements E, and using them you can apply whatever logic you like, the trend of today becoming a 'truth' until revealed of lacking by some new experiment. A weak measurement is the idea that there is a hidden logic that we can't see directly, but can be revealed through carefully chosen experiments in where we try to avoid 'looking directly' but instead infer it from logical principles. Where it fails is in implying that causality chains is 'what exists'. I don't think so myself. I expect, as 'time' becomes a description of the room relative frames of reference, that we are a symmetry break in something more, or less :) which may be closer to the truth, and that the way that 'reality' works is better described by indeterminism than 'causality-chains'.

Title: Re: experiments have cast doubt on a founding idea of the branch of physics
Post by: imatfaal on 10/09/2012 13:42:29

Not really EMC2 - what the experimenters showed was that Heisenburg's initial measurement-disturbance relationship was incorrect.  But this relationship has been ignored for a while - the mathematical formalism of quantum mechanics has shown than Heisenberg Uncertainty principle is intrinsic and not a product of measurement.  This experiment does not touch the HUP - and I think most physicists still think that the HUP is correct and will not be shown to be avoidable through weak measurement.  To be clear the measurement-disturbance idea was an old chestnut - I have written on this forum about how it is the maths and not the technique that demonstrates the HUP.  If you have a maths background and very simplistically it is the non-commutative nature of certain matrices that allows quantum physicists to be sure that the HUP is not just bad measurement

What the UofT researchers showed was that weak measurement can be so weak that the measurement would not be disturbing enough to create the uncertainty - but they do not deny that the uncertainty is still there.

Lee Rozema was quoted saying
"The quantum world is still full of uncertainty, but at least our attempts to look at it don't have to add as much uncertainty as we used to think!"

Title: Re: experiments have cast doubt on a founding idea of the branch of physics
Post by: JP on 10/09/2012 16:42:51

Ugh!  Bad science journalism!  I'm pretty familiar with the experiment they cite here:

Quote

Prof Steinberg and his team are no stranger to bending quantum mechanics' rules; in 2011, they carried out a version of a classic experiment on photons - the smallest indivisible packets of light energy - that plotted out the ways in which they are both wave and particle, something the rules strictly preclude.

QM actually predicts exactly what their experiment showed, so there was no "rule bending." 

It sounds as if, as Matthew says, their "rule bending" of the Heisenberg uncertainty principle isn't bending any rules whatsoever.  (If the uncertainty principle turned out to be wrong, most wave theories would break down!)

Title: Re: experiments have cast doubt on a founding idea of the branch of physics
Post by: imatfaal on 10/09/2012 18:02:16

Exactly JP - and it seems that, once again, it was the journos and the university publicity machine over-hyping and the scientists being swept along.