Is the uncertainty principle culturally deranging?

[Paul Mackin]

On 8/1/2012 9:47 PM, Prashant Kumar wrote:
> The uncertainty principle as mentioned (as opposed to used) in 
> postmodernism and elsewhere is not the physicist's uncertainty 
> principle. If one misunderstands something aggressively enough it 
> takes on a life of its own.
>
> Just for clarity, I should differentiate between two versions of the 
> HUP which have popular currency, and are (consequently) almost always 
> conflated.
>
> Some people will tell you that the HUP forbids you from exactly 
> specifying position and momentum (think of momentum as how much 
> something hurts when it hits you); if I have a quantumball, I can't 
> get both pieces of information at a given instant. A more useful way 
> of restating this is that I can't /measure/ both simultaneously. If I 
> measure position, then momentum, I don't get the same results as if I 
> measure momentum then position. This isn't true in classical physics.
>
> In QM we don't know exact values of things like position and momentum. 
> Instead we work with probability distributions. HUP tells you that if 
> you know one quantity with some (statistical) degree of specificity, 
> then the other quantity is limited in a particular way. If I give you 
> the position of our quantumball exactly, you will have no idea of its 
> momentum. This is a consequence of the way wavefunctions work. It does 
> /not/ mean that our knowledge is imperfect or incomplete. It means 
> that there is no more there to know. This is the modern understanding 
> (modulo technical mathematical caveats).
>
> Usually something called Heisenberg's (the guy was prolific) 
> microscope enters the picture at this point. This thought experiment 
> tries to imagine the actual /process/ of measurement, and see whether 
> we can find some physical reason for HUP. At the time of its 
> formulation, the only known way to measure a quantum state was to 
> subject it to photons, measure it directly or indeed just get in there 
> and rustle around till you got what you came for, leaving the quantum 
> state spent and shivering under the sheets. The argument was that the 
> act of measurement, and the requisite interaction, was responsible for 
> the uncertainty principle: you changed the state by mucking round with 
> it, so you're not going to get exact results.
>
> Problem is, today we know there is a class of measurements which are 
> known as /interaction-free, /you get information seemingly for free/, 
> without/ directly addressing the state/. /And these measurements are 
> also subject to the HUP. This is a particularly dark kind of magic and 
> I won't go into it, but if you're interested check out the 
> Elitzur-Vaidman bomb tester. Interaction-free measurements have 
> actually been performed in a lab.
>
> So if someone at a party tells you that the uncertainty principle 
> implies something about our knowledge of the universe, fundamental 
> inconsequentiality of human endeavour etc., you should shank them with 
> your champagne flute, then patiently explain the failure of 
> Heisenberg's microscope.

Thanks, Preshant.  Helpful explanation.

If people want to talk about the uncertainty of knowledge, they still 
have "il n'y a pas de hors-texte" to fall back on.

P


>
>
>
> On 2 August 2012 07:10, Paul Mackin <mackin.paul at verizon.net 
> <mailto:mackin.paul at verizon.net>> wrote:
>
>     On 8/1/2012 4:33 PM, Madeleine Maudlin wrote:
>>     Oh der/anging/.  Mr. Kohut is certainly /that/.  I would never
>>     use that word though, or any deranged derivative there, hem, of.
>>      If I did it would be in the best sense possible, which for me
>>     would be exceedingly /good/.
>
>     Vidal claims he was using the word, if not necessarily in the best
>     sense possible, not the worst sense either.
>
>     Writing of the author of GR:  "Only a physicist who wrote good
>     prose could tell us if, say, Heisenberg’s famous and culturally
>     deranging principle is correctly used in these many, many pages."
>
>
>
>     P
>>
>>     Does anybody write here?  I just got an email, who knows why I'm
>>     on their list, I haven't tried to publish anything in years, from
>>     a place called AuthorHouse, subject says Publish today and get a
>>     no-cost bump-up.  So I guess it's free, today, if you want to get
>>     published.  I'm currently stuck on page 400 hell with no end in
>>     sight.  432.  What is it about 400?  The Moon is 400 times
>>     smaller than the Sun and 400 times closer to it than the Earth,
>>     or something.  Bumping-up, m
>>
>>     On Wed, Aug 1, 2012 at 2:58 PM, Paul Mackin
>>     <mackin.paul at verizon.net <mailto:mackin.paul at verizon.net>> wrote:
>>
>>         On 8/1/2012 10:23 AM, Prashant Kumar wrote:
>>>         Yes.
>>
>>
>>         but not pejoratively so I hope
>>
>>         P
>>
>>
>>>
>>>         P.
>>>
>>>         On 1 August 2012 23:52, Paul Mackin <mackin.paul at verizon.net
>>>         <mailto:mackin.paul at verizon.net>> wrote:
>>>
>>>
>>>
>>>             http://www.nybooks.com/articles/archives/1976/oct/28/plastic-fiction-3/
>>>
>>>
>>
>>
>
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://waste.org/pipermail/pynchon-l/attachments/20120802/60564592/attachment.html>