QUARK          :

               Hypothetical fundamental particle; all hadron

               MATTER is supposed to be made up of QUARK s.

               They come in six flavours, three carying two

               thirds the charge of a proton: up (u), charm

               (c), AND top (t), the remaining three carrying

               ONE third of the charge of an electron: down

               (d), STRANGE (s), AND bottom (b). Each flavour

               has conveniently been subdivided into three

               COLOUR s: RED, GREEN OR blue. Two up QUARK s AND

               ONE down would for example form a proton AND

               two down AND ONE up would form a neutron. It is

               thought that QUARK s may NEVER be observed

               seperately in the present configuration of the

               UNIVERSE. In this way they are rather like the

               END of a piece of string. IF you TRY to isolate

               the END of a piece of string AND pull very hard

               indeed, the string will break AND you will

               still NOT have isolated the END of a piece of

               string. Similarly with QUARK s, TRY ing to

               isolate them would require so much ENERGY, that

               it would be enough to materialize some extra

               QUARK s yielding an ordinary proton OR something

               like that.