Talk:Uncertainty principle/Archive 1

message: I've always understood it needed to be calculated from two distances at two times to get speed and a measurement of mass, in order to fulfill the equation momentum=mass*speed  --Hackwrench
:You can simply measure the force exerted within a certain time period.  See the impulse section of momentum.   — Cortonin | Talk 18:46, 20 Apr 2005 (UTC)
replies: text: Get a friend, put him on roller skates, close your eyes, and throw a softball at him.  You can examine the momentum imparted by the softball without concern for where it hit him.  All you need to know is your friend's mass and how fast he was going after the ball hit him.  (Yes, the position must be precise enough to be in your measurement device, but this is pretty huge compared to the scale of the uncertainty principle.)  (And please do not hurt your friends.)   — Cortonin | Talk 22:08, 21 Apr 2005 (UTC)

text: Yes, you can measure the momentum of a baseball as well.  The uncertainty principle does not say that either mass or position are unmeasureable.  In fact, both are measureable.  It only says that they cannot both be measured with extremely high precision at the same time, and that if one of momentum or position is measured with extremely high precision, then the other must become uncertain.   — Cortonin | Talk 03:30, 23 May 2005 (UTC)

text: The formulation in your above discussion is the reason why I said that either one can be measured with "extremely high precision", rather than "exactly".  Is there some point you are trying to make relating to the article?  If so, what is it?   — Cortonin | Talk 14:54, 25 May 2005 (UTC)
thread_title: How is momentum even measurable.

message: Can someone clear this up for me. Someone has said that the "uncertainty principle" is a result of mathematics and NOT a result of the physical world/physics. And that if the physical world did not exist there would still be the uncertainty principle in mathematics.
The article did not clear this up one way or the other.
----
: I guess both are true.  In the physical world/physics (to use yor term) the position and momentum observables can be modelled by self adjoint operatprs P, Q which satisfy a commutation relation
:: [P, Q] = r I 
: for some r. That's a fact of physics.  The rest is mathematics. Now in the historical development of quantum mechanics, the sequence of events is more complicated. CSTAR 00:26, 18 Nov 2004 (UTC)
replies: text: The uncertainty principle is measureable, and thus it's real.  That's the important point.  It is commonly observed in things like quantum tunneling.  When we say the uncertainty principle "comes from" a particular equation or mathematical formulation, that doesn't mean this is the reason for it, it just means this is how the correct result is derived.  It comes from reality, ultimately, it's just that in a descriptive sense, the uncertainty principle is not a postulate itself, but a result of other postulates.  Cortonin 02:05, 18 Nov 2004 (UTC)
replies: text:  Of course, Cortonin is right. The uncertainty principle for QM is an experimentally verifiable fact and historically the experimental verification (probably) preceded  derivations of it from first principles. (However, history of science is always tricky, so seemingly obvious assertions about precedence of discoveries are often wrong.) Nevertheless, in this article, the uncertainty principle has a somewhat different status from the purely QM expression of it since it has manifestations in other areas of physics and mathematics.CSTAR 04:13, 18 Nov 2004 (UTC)

text:  In summary, the stated uncertainty relation applies to position and momentum whenever you're dealing with the position and momentum involving a wave packet.  The gaussian is the minimization of the product of the uncertainty of these two things, and thus, you get the relation stated in the article.  I believe Jackson's E&M has a discussion on uncertainty of x and k of electromagnetic waves from a classical perspective, since this also applies. Cortonin 05:05, 18 Nov 2004 (UTC)
thread_title:  source of the uncertainty principle. 

message: Your addition in the corresponding subsection to the article requires a little more explanation.  ALso for the angular momentum operators Jx you wrote the commutation relations not the uncertainty relations.  Could you add this or should I?  CSTAR 04:13, 18 Nov 2004 (UTC)
thread_title:  Examples of observables which satisfy the commutation relations

message: One other remark regarding this section, specifically, on the time-energy uncertainty relation. One has to be more careful about the meaning of a time operator.  See for instance the discussion by John Baez .CSTAR 02:19, 19 Nov 2004 (UTC)
thread_title: Common observables which obey the uncertainty principle

message: The link points to classical angular momentum.  There doesn't seem to  be any page on quantum angular momentum.CSTAR 21:52, 24 Nov 2004 (UTC)
thread_title:  Total angular momentum 

message: An anonymous user (who probably didn't understand what a talk page is for) added this text to the page after "...transmit information to each other to ensure that the correlations in behavior between particles occur." I'm moving it here, because it's, well, talk. (I don't know enough about quantum mechanics and am not awake enough right now to do anything about what he's commenting on.)
(This directly contradicts Copenhagen Interpretation page which states: "The completeness of quantum mechanics (thesis 1) has been attacked by the Einstein-Podolsky-Rosen thought experiment which was intended to show that there have to be hidden variables in order to avoid non-local, instantaneous "effects at a distance". Deterministic hidden variables avoid the problem of spooky action at a distance.)
-℘yrop (talk) 06:13, Jan 14, 2005 (UTC)
::The anonymous user makes a good point, but it's the Copenhagen article which was unclear.  I corrected it.   — Cortonin | Talk 09:08, 14 Jan 2005 (UTC)
thread_title:  Anonymous comment 

message: Other (equally misleading) analogies with macroscopic effects have been suggested to explain the uncertainty principle: One such involves pinpointing a watermelon seed with one's finger. The effect is well known - one cannot predict how fast or where the seed will disappear. This random outcome is based entirely on randomness that can be explained in purely classical terms.
What does this para actually mean?? Anyone care to explain so I can rewrite it?--Light current 23:23, 3 October 2005 (UTC)
replies: text:  It doesn't mean anything that I know of. Somebody kept reinserting it, so rather than continue with a revert war, I just put it in a paragraph on misconceptions. You can delete the whole paragraph as far as I'm concerned. --CSTAR 00:43, 4 October 2005 (UTC)
replies: text:  Thanks. --CSTAR 02:18, 4 October 2005 (UTC)
replies: text:  Re: your edit summary for your edits to the article: you don't need to "get anybody's approval" to make a change. On the other hand, I (or anybody else) can legitimately revert if the change is not regarded as an improvement. Generally, changes are improvements so long as the technical accuracy is not sacrificed -- people generally want to improve readability.  At other times, dealing with individuals that insist on inserting some text (such as the one that inserted the watermelon business which you thankfully deleted) is just too much trouble. All your changes so far have been reasonable and I am certainly happy to see the article improve.--CSTAR 02:48, 4 October 2005 (UTC)
thread_title:  What?? 

message: Does anyone know whether the dimensions of any relation have to be the same on both sides of the inequality? I would think they do-- but I dont know.--Light current 06:00, 4 October 2005 (UTC)
replies: text: Yes, they have to be. Note that the uncertainty relation is an identity for Gaussian states.--CSTAR 14:30, 4 October 2005 (UTC)
thread_title:  Dimensions in uncertainty relations 

message: This is drawn from research into GUT. Reference to be added when made available to public.
: If it's not public, it doesn't belong here. When it becomes public and you can cite sources, then by all means put it in. --CSTAR 05:06, 16 October 2005 (UTC)
thread_title:  Near-Complete Relativisitic Uncertainty Principle 

message: 24.226.10.99 changed \Delta x \Delta p \ge \frac{\hbar}{4}  to \Delta x \Delta p \ge \frac{\hbar}{2} . However, due to this user's behaviour on many other pages, I am reverting this change. My apologies if it was legit.  --  user:zanimum
:: There were two successive changes made by that user. The last change, that is the one you mentioned, reverted back to the correct form, from the previous incorrect form.--CSTAR 22:49, 17 October 2005 (UTC)
thread_title:  Vandalism? 

message: This entire debate is completely pointless. Yes x,p are observables in NRQM. Yes t is not an observable, but an externally provided parameter in NRQM. But this is not an article about observables and external parameters and how NRQM is ultimately dumb. These are problems carried over from NRCM not being covariant. The fact is that the wave nature of QM and Fourier analysis provide the exact same inequality relationship for x,p and for t,E. And both are useful. Particle physicists use dtdE>hbar/2 all the time to rationlize things, and they use it in the exact same manner as dxdp. The full relativistic uncertainty principle for x,p derives from the commutator [x_\mu,p_\nu] = i \hbar \eta_{\mu,\nu}. It is a property of the manifold's tangent bundle and fundamental QM principles that transcend the assumptions of NRQM. CHF 23:09, 11 December 2005 (UTC)
thread_title:  dE dt >= h/2 debate