Re: Understanding the HUP

"Ranando King" <rk@xxxxxxxxxxxxxxxxxx> wrote in message
news:430a0cfd$1_2@xxxxxxxxxxxxxxx
|
| "FrediFizzx" <fredifizzx@xxxxxxxxxxx> wrote in message
| news:3mmmu3F17mluaU1@xxxxxxxxxxxxxxxxx
| > "Ranando King" <rk@xxxxxxxxxxxxxxxxxx> wrote in message
| > news:43060cc4_1@xxxxxxxxxxxxxxx
| > | Too many times I've seen this formula:
| > |
| > | dx * dp > h_bar/2 (Heisenberg Uncertainty Principle)
| > |
| > | accompanied by a description like this:
| > |
| > | The better you know the position x, the larger the momentum p
becomes,
| > and
| > | the better you know the momentum p, the larger the position x
becomes.
| >
| > Nope.
| >
| > | Don't those of you spouting this realize that
| > |
| > | 1. this makes no sense! and
| > | 2. this is NOT what that formula states?
| > |
| > | How can a POSITION as defined by a single coordinate in space ever
| > become
| > | large? It's a theoretical point. Points are by definition
| > infinitesimally
| > | small. Further, how can it be possible that the momentum of a
| > stationary
| > | elementary particle can become larger than the total momentum of
our
| > entire
| > | galaxy? Since momentum requires motion, how can a stationary
particle
| > even
| > | have an momentum?
| > |
| > | Don't try to answer these questions. They only come up because of
a
| > | misunderstanding of what the HUP means. Here's the real
breakdown...
| >
| > No one that has studied QM correctly misunderstands HUP. Apparently
you
| > have been suffering from the misunderstanding.
| >
| > | dx <-> the error of the position value
| > | Put another way, dx represents the range of possible values for
the
| > position
| > | of the particle. It's not the actual position, but rather just a
delta
| > | corresponding to the experimental uncertainty in the position.
| > |
| > | dp <-> the error of the momentum value
| > | Much like dx, dp is just another range of values that might be the
| > actual
| > | momentum of the particle.
| >
| > Anyone that has studied QM already knows this.
| >
| > | It's actually a matter of common sense why you cannot know x and p
| > with near
| > | absolute accuracy at the same time. Consider the formula for
momentum:
| > |
| > | p = m * v
| > |
| > | Of course, there's a different formula for massless stuff, but
this
| > one
| > | works well enough. Where
| > |
| > | p <-> momentum
| > | m <-> particle mass
| > | v <-> particle velocity
| > |
| > | we can replace v with dx/s where
| > |
| > | dx <-> change in position
| > | s <-> elapsed time
| > |
| > | This leaves us with
| > |
| > | p = m * dx / s
| > |
| > | So for low values of dx, p will become less and less accurate.
After
| > all,
| > | our experiment equipment is only just so accurate. Therefore dp
will
| > | increase as dx decreases. Likewise dp will decrease as dx
increases.
| > Similar
| > | simple observations can be used to verify this interpretation of
the
| > HUP for
| > | all of its variations.
| > |
| > | Remember, the bottom line is that the HUP doesn't determine the
| > values, or
| > | for that matter even constrain them. The only thing the HUP does
is
| > give a
| > | reasonable minimum MARGIN OF ERROR in measuring the values of
certain
| > | property pairs. Nothing more. Nothing less.
| >
| > Uncertainty is a natural phenomenon of wave mechanics.
| >
| > FrediFizzx
|
| I have no misunderstandings regarding the HUP. However, in reading
1000's of
| posts in this newsgroup, I have noticed that others have stated the
exact
| same misconception that I mentioned above. Seeing as how the
information in
| my post does indeed state the proper understanding of the HUP, I do
not
| understand your reason for even interjecting those somewhat trifling
| comments.
|
| It is not true that anyone who has studied QM already understands the
HUP.
| This should be very evident from the number of students taking a
course in
| the subject and walking away confused, and even in observing pop
scientists.
| And as for Uncertainty being a natural phenomena of wave mechanics, I
will
| agree only in the contingency that you are referring to the *study and
| research of* wave mechanics since the actual physical phenomena
involves no
| provable uncertainties that cannot be shown to be simple physical
| limitations in the human ability to study the physical phenomena.
|
| The physical cause of the Heisenberg Uncertainty Principle is that
humans
| are incapable of physically studying a quantum system without
involving a
| controlled secondary quantum system in the form of a measuring device
or
| interactive catalyst. Such a limitation means that all we can know of
a
| quantum system is contained within those brief moments of interaction.
The
| nature of anything occuring outside of those moments can only be
speculated
| upon.

So what? If our "speculations" guide us to producing the correct real
results, we then have some verification that they could be correct.

| This is the ugly truth. QM, for all of its successes, will always come
up
| short and leave uncertainties in our knowledge. For now, this is an
| unavoidable truth.

Perhaps, but I highly doubt it.

FrediFizzx

.

Relevant Pages

  • Re: Understanding the HUP
    ... > | the better you know the momentum p, the larger the position x becomes. ... > No one that has studied QM correctly misunderstands HUP. ... > Uncertainty is a natural phenomenon of wave mechanics. ...
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