An helium nucleus

Size: 10-15 m.

A helium nucleus has a charge +2.

It has a big mass.

Now we can see structure.

A helium nucleus is made of two protons and two neutrons.

A proton has charge +1 and a big mass.
A neutron has charge 0 and a big mass.
They both have strong interactions.

Protons and neutrons are made mostly of up-quarks down-quarks and gluons.

At the limits of experiments so far, quarks and gluons are pointline particles and are not made of anything else.

(The current limit is about 10-18 m.)

Davison E. Soper, Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA