At school we learn about protons, neutrons and electrons. However, I can not believe that these are solid balls. So the question arises of what those protons, neutrons and electrons are made of, and what those particles consist of. I also have doubts about the so-called ‘nothing’ that is between the electrons and the atomic nucleus. Is this really a vacuum?
So I am looking for the limit of current scientific knowledge about the structure of atoms.
Answer
There is indeed another smaller sub-atomic level of matter, namely the quarks. Protons and neutrons each consist of three quarks. These are currently the smallest particles we know of.
Quarks exist in different “flavours” : the two most important are the UP quark (with charge 2/3) and the DOWN quark (with charge 1/3). For example, a proton consists of two UPs and one DOWN, so that the total charge is indeed +1. A neutron consists of two DOWN’s and one UP so that the total charge is 0. In addition, there are four other “flavors”, which do not occur in normal everyday matter and can only be observed briefly under extreme conditions in particle accelerators. They also occur in the universe, always under extreme conditions. They are called STRANGE, CHARM, BOTTOM and TOP.
Each quark can occur in three variants, the “colors”, so that there are 18 quarks. Each quark also has an ant-particle, an anti-quark.
Quarks are constantly exchanging “gluons”, which also have one of these three colors. When a quark captures a gluon, its color changes, depending on its own color and that of the gluon. The gluons are force-transmitting particles, just like the photon is for the electromagnetic force.
The gluons are thus constantly exchanged and form a force that holds the quarks together. That force increases with distance, in contrast to gravity, for example. You cannot isolate a quark individually, because then you would have to extract it from a proton or neutron, and that takes so much energy that you simply use that energy to make a new couple of quarks instead of pulling that one quark loose.
In addition to particles consisting of three quarks such as the proton and the neutron, there are also elementary particles consisting of a quark and an anti-quark.
The space between quarks must be regarded as a vacuum, because the gluons are considered to be massless, just like photons.
Have a look at: http://en.wikipedia.org/wiki/Quark
for a good starting point in this fascinating world.
Answered by
prof.dr. Paul Hellings
Department of Mathematics, Fac. IIW, KU Leuven
Old Market 13 3000 Leuven
https://www.kuleuven.be/
.