i.e. is an electron bigger/smaller than a strange quark? Is a strange quark bigger/smaller than an up quark? Or are they all the same size?
Leading on, are electrons the same size (as in physical size or mass) as protons and neutrons?
To clarify: Say if an electron was mass x. Is it possible that a certain quark could be mass x+1, 1/2x, etc?
Lizzie, there is no definite answer to this question.
If you think about it, when we first measured the size of the atom, or rather the structure of it, we fired in electrons as probes, but what we found was an idea of by how much electron was deflected, not the actual size of the electron. This is because it is the charge that we are always really measuring, not the physical size of the particles.
So we can't measure the size of particles directly, even in the LHC, we can only measure how far the electric charge (or other charges) on them extends outwards from a point, and how this charge changes with distance from a point.
This is something like if you were pushed in the dark, by one of your friends, you could judge which friend it was by how hard you were pushed, and how strong they were, but you could not actually not see the size of them at the time.
Protons are not particles in themselves, they are believed to be collections of three quarks, but you can look this up on Wikipedia.
So it's indirect measurements we do, to determine the size, and the size of elementary particles could all be the same, that is they are dimensionless points.
If you try to imagine a dimensionless point, you will just get a headache, because there is nothing in the real world to compare this to.
As far as mass of particles goes, you can look up on Wikipedia the differing masses, but this definitely does not mean they are larger in physical size, just that they can "push back harder", when you fire things at them, if you follow me.
How is it that we have a standard model of particle physics? and this model has a particles table that contains different mass point particles , i.e. zero dimensional?
It is because we have gathered measurements, data, from innumerable experiments and have fitted them mathematically with these axiomatic propositions, and not only fitted them, but can use the model to predict new measurements.
These elementary particles
are axiomatically in the mathematical theory without dimensions, point like.
Protons and neutrons are composites of the quarks of this table, and they have measured dimensions.
One can look at a simple measurement of a bubble chamber picture, and one can see tracks identified with electrons and muons ( both elementary particles) but that is just the dimensions of their interactions with the medium of the bubble chamber, their foot print.
Is the standard model the theory of everything? No, we have strong indications that it has to be extended or even changed. At the moment our research tools have elementary particles point like. New theories are proposed to be tested in future experiments as:
. String theories have a one dimensional string as the only elementary particle, whose vibrational states describe the table above and predict much more.
. Preon theories give a substructure to the particles in the table, going to a lower level of point elementary particles, and then one can talk of dimensions for the ones in the table above.
In the accepted standard model elementary particles are point like, all the same size in space.
