1. The problem statement, all variables and given/known data In electromagnetic interactions, the force carrier is the photon, and it interacts with anything which has electric charge. Electric charge can be represented by the integers on a single number line and photons themselves carry no electric charge. (a) In the case of the strong interaction, explain what is analogous to the number line representing electric charge in electromagnetism. (b) Do gluons carry the charge associated with the strong interaction? (c) What important feature of the strong interaction follows from your answer to (b)? 2. Relevant equations 3. The attempt at a solution (a) The colour charge associated with gluons? (this is the one i'm not sure of, what does this mean?) (b) Yes- colour charge (c) Colour charge is conserved in strong interactions. Thanks for any help with a), and if the other are correct.