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Re: [Phys-l] Relativity Question about spring

I usually don't "top post" my responses, but this is getting complicated and posting the originals at the top would mean that everyone has to weed through a long preliminary before getting to what I have to say, so I'll leave the material below for those who need the reference to scroll down to.

First, I more or less agree with Jeff's comment about Scheider's explanation of the "reduced mass" involved with bound systems. The implication of Scheider's position is that the mass of these particles is due to the energy contained in the fields surrounding them. I'm not sure that is possible. Assuming that the electron is truly a point particle (zero radius), which may or may not be the case, since we have not been able to find a core particle at the heart of the electron field as of yet, then the self energy of the electron is infinite, which implies that the mass of the electron is also infinite, which is clearly not so. I am not a particle physicist so I cannot provide an explanation of this in QED terms, but I believe that it has not been completely resolved, rather, it has been "swept under the rug," in Feynman's terms by the renormalization process.

Others more well-versed in particle theology might be able to provide more light on this issue.

Now let me go back to some of Alphonsus's comments on my response to his earlier posting. He says:

What if some physicists and physics teachers have said something to
> that effect? [That one can talk about the individual masses of nucleons bound into the nucleus]
>
In fact, some astrophysicists are interested in the effective neutron
mass; for those neutrons which are present in the neutron stars...

I'm sure some have talked about the individual masses of the particles, but so far, to my knowledge, no one has figured out how to assign those masses. The possibility I suggested of doing it in proportion to the known mass of the free particle is pure conjecture on my part and I have no idea whether it is valid or not. So at the moment, all we can do is talk about the average mass of each nucleon, and compare it with the average mass of the free nucleons, taking the difference to be the binding energy (or as I prefer, the interaction energy). It is sometimes quaintly referred to, especially in older texts, as the "mass defect."

As to the effective masses of neutrons in a neutron star, I wish those astrophysicists luck. Since the neutrons are fermions, it is the repulsion between the neurons induced by the exclusion principle that keeps the neutron star from collapsing to a black hole, and calculating the binding energy of any given neutron is not going to be easy. It may not even make much sense to talk about individual neutrons in such a collection. I doubt that we know the mass of any neutron star well enough to be able to estimate the number of neutrons it contains to better than a couple of orders of magnitude or so, in which case I would guess (without trying to do the calculation) that the uncertainty in such an estimate would be much larger than the value obtained.

Then Alphonsus quotes Scheider:

"Now, back to the question: what got smaller? (We don't mean smaller
in size, necessarily, but in mass.) Did some of the protons get
smaller? Did some of the neutrons get smaller? Did some of the
electrons get smaller?

In fact, the answer to that question is "yes." But, you will respond,
we've been taught that a proton has a definite mass, the mass that is
listed in the tables to seven decimal places. Same for the neutron,
and the electron. Surprisingly it's not quite like that......"

Having not read Scheider's book or looked at the web site Jeff cites, I cannot comment on the context of these remarks, or the further conclusion, but I think Scheider is pushing what we can know too far here. The known masses that he talks about are clearly the masses of the free particles, and so I question the relevance of his comment.

As I see it, the response to the question "what got smaller" is, "the total mass of all the bound particles, compared to their total mass as unbound particles." And it makes little sense to try to talk about the masses of any of the individual particles involved. Since each is existing within the field of the others, they are mutually interacting and so the effect is mutual, and there is simply no effective meaning to the question of what happens to any individual particle, since there seems to be no possible way to measure the mass if that individual particle while it is in such a bound state.

Hugh

At 11:44 -0400 5/15/07, Jeffrey Schnick wrote:

Thank you Alphonsus for the link to the excellent site of Walter
Scheider. I read the material there up to the part to which you
referred (regarding the lower mass of a bound system resulting from a
reduction in the masses of the constituent particles). I actually found
Walter Scheider's arguments:

------------------------Walter Scheider--------------------------------
An electron is surrounded by an electric field. At each point in the
surroundings of the electron, the electric field contains energy, with
an energy density measured in Joules/cm3, that is well known. Energy and
mass are one and the same (Einstein), so that the energy that is in the
electric field is also an equivalent amount of mass. That mass is part
of the electron. When the electron forms a hydrogen atom by forming a
bond with a proton, the field surrounding them is diminished. Both the
electron and the proton lose some of their field energy, and that loss
represents some diminution in the total mass of the two particles.
------------------------------------------------------------------------

to lend more support to the opposing view (that the lower mass is a
characteristic of the bound system as a whole). I would agree that the
field surrounding the proton and the electron discussed by Walter
Scheider is diminished, but I would argue that neither the field of the
electron nor the field of the proton is weaker at any point in space
than it would be in the absence of the other particle but rather that
the two undiminished fields add up to something that is of smaller
magnitude than either field by itself at points in space surrounding the
pair of particles.

Jeff Schnick

-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
> bounces@carnot.physics.buffalo.edu] On Behalf Of
> carmelo@pacific.net.sg
> Sent: Thursday, May 10, 2007 9:50 AM
> To: Forum for Physics Educators
> Subject: Re: [Phys-l] Relativity Question about spring

Hugh wrote:
> I don't think so. The issue is, what is the system.

Have not we defined an electron or a muon as a system before? This is
also known as "one-particle system". You may not have answered the
question.

> But no one says that the neutron "loses such and such a
> mass" when it becomes bound to a proton, we only talk about the
> deuteron mass being less than the collective masses of the proton
and
> neutron as free particles.

> What if some physicists and physics teachers have said something to
that effect?

In fact, some astrophysicists are interested in the effective neutron
mass; for those neutrons which are present in the neutron stars...

> In addition, physics teachers such as Walter Scheider, the
"Presidential award winning teacher", describe this in his book and
website:

> "Now, back to the question: what got smaller? (We don't mean smaller
in size, necessarily, but in mass.) Did some of the protons get
smaller? Did some of the neutrons get smaller? Did some of the
electrons get smaller?

In fact, the answer to that question is "yes." But, you will respond,
we've been taught that a proton has a definite mass, the mass that is
listed in the tables to seven decimal places. Same for the neutron,
and the electron. Surprisingly it's not quite like that......"

> For more details, please refer to
http://www.cavendishscience.org/energy-flash/flash-index.htm

Alphonsus
>

--

************************************************************
Hugh Haskell
<mailto:haskell@ncssm.edu>
<mailto:hhaskell@mindspring.com>

(919) 467-7610

Hard work often pays off after time. But Laziness always pays off now.

February tagline on 2007 Demotivator's Calendar