definition of a particle?

[Tim_Lou]

i have been thinking about this thing for a while.

seeing how fields are always not well defined approaching the position of a particle, perhaps a particle can be defined as a discontinuity of field (any kind of force field)

but then.... a photon, there is no discontinuity of electromagnetic field. perhaps this is something different.

as I am not so good with quantum mechanics... knowing that position is not very well defined, the position of the "discontinuity" wouldn't be very well defined as well....

What other ways can a person detect/define a particle otherwise? besides observing severe distortion of force fields? hmm.... and how would a person observe a particle without another particle? if a particle is only well defined in relation with another particle, what does it mean?

[Mercedes Benzene]

Those are some good points...
I've never really thought of that before.
Good questions!

[ronthepon]

Well, for one thing, the photon is better defined as a travelling disturbance in the electric and magnetic feilds.

More like fluctuations in the magnitudes of the two feilds, a fluctuation that moves. (Transverse wave style, only that the crests and troughs are in the magnitudes of the feilds)

So it cannot be a particle in the same sense as the other ones.

I know that you know all of this... but we all tend to keep the elementary things in the back of our minds normally. Am I mistaken by any chance?

[Mercedes Benzene]

Well... I've only just recently started to study particle physics...
...so I do not claim to be an expert to any degree of the definition.
I mostly work with subatomic particles that are a result of radioactive decay...
...that area, I can claim some knowledge...

I'm interested in seeing how this thread turns out.

[Tim_Lou]

Well, planck's energy distribution of black bodies can be derived perfectly from the assumption that energy exists in discrete packages. the only explaination for this is that photon is discrete particles, so that 1 energy package= 1-photon package, 2 enerage package= 2-photons package

planck's finding really is mind boggling... I'm still trying to understand it fully... i read the above in a book from barnes 'n nobles, it shows the how planck first "accidently" derive it when trying to improve Wilhelm Wien's distribution, then comin up with a explaination to it.... nice free learning from barnes n' nobles.

this has indeed shaken my understanding of continuum...it troubles me to think that one almost perfectly validated concept does not go with another almost perfectly validated concept...

Anyway, how is electromagnetic field defined? another test "particle"... well the existence of photon must still rely on other "particles" regardless of whether not it is a particle...

i think that something is missing regarding fundamental definitions here.

[Tim_Lou]

perhaps the existence of a particle can be defined by gauss law? (neglect strong and weak force as i have no idea what the equations behind them are)

as long as the surface integral of E field is non-zero, we say a charged particle exists within that region. or even better, using divergence (only for "density" though). (same for gravitational field)

but then the definition of "fields" have to be re-written (so that it does not use a "test" particle)

[ronthepon]

The gauss law definition of a particle won't hold for neutral ones.

The electrical feild is defined that way so that it becomes totally rigid. However, we can imagine it to be a property of that portion of space... And it's induced by the presence of particles with special properties nearby.

We merely simplify it by calling these nearby particles as 'charged'. However, if there is merely one charged particle in the entire universe, there is no significance of this concept. So, the test charge thing is just a process of clearing it up.

[Erasmus00]

In quantum field theory, all particles are defined like the photon: excitations in a field. Electrons are excitations in the dirac field just as photons are excitations in the Maxwell field.
-Will

[Tim_Lou]

and all massive particles are "excitations" in "gravitational" fields?

so what exactly is this "excitation"?

[Turtle]

Originally Posted by Tim_Lou

What other ways can a person detect/define a particle otherwise? besides observing severe distortion of force fields? hmm.... and how would a person observe a particle without another particle? if a particle is only well defined in relation with another particle, what does it mean?

String theory is an attempt to describe a "particle" as other than a speherical dimensionless point. It describes the particle as a vibrating string and/or membrane.
A person would not, could not, should not, observe a particle without another particle. Chirality rules duality.