🚀 go-pugleaf

In article <1NOV199211204351@csa2.lbl.gov>, sichase@csa2.lbl.gov (SCOTT I CHASE) writes:
> In article <329@mtnmath.UUCP>, paul@mtnmath.UUCP (Paul Budnik) writes...
> >In article <30OCT199211272273@csa3.lbl.gov>, sichase@csa3.lbl.gov (SCOTT I CHASE) writes:
> >> ... The "size" of an electron is a matter of definition.
> >> Particle physicists like to call an electron a "point particle", implying
> >> that it has zero size.  Due to quantum mechanics, it has a wavelength however,
> >> which *does* shrink with energy. ...
> >> On the other hand, there is no such thing as an electron's "shape."  
> > 
> >Just as the wavelength can be thought of as determining a size for an
> >electron, the spatial distribution of the wave function could be thought
> >of as a shape. In both cases it is a matter of definition and in both
> >cases the value changes with experimental conditions.
> 
> This definition won't really work.  Shape is an intrinsic property.  The
> wavefunction determines the probability distribution for the position of the
> object.  Where an object is (or might be) does not determine it's shape.
> And, as I said, the size of an object is best defined in terms of the
> limiting cross-section as the wavelength goes to zero.  At very high energy,
> a proton is still about 1 fermi across, while an electron is (to the best
> of our knowledge) immeasurably small.

But size is as much of an `intrinsic' property as shape is. If you are going to
consider the frequency as defining a size in some sense, then I don't see
how you can exclude the spatial distribution of the wave function as
defining a shape in a similar sense.  Of course the size of this `shape'
is not the same thing as the size determined by frequency which in turn is
not the same thing as the cross section seen in particle physics.

It would be silly to argue about such semantic hair splitting, except I think
it is of physical relevance. Physicists do not think of the spatial
distribution as defining a shape because they think of it as you suggest
as only defining where the particle might be. However, for the
photon, the QM wave function and the electromagnetic field are identical.
It is certainly reasonable to speak of the shape of this field at least in
classical physics. It is the notion that there is no objective physical
reality to the wave function that is why one does not think of
the QM wave function as defining a shape. I think this is a fundamental
flaw in the way most physicists interpret quantum mechanics.

Paul Budnik