What is wrong with the following proof: Theorem Quark transformation is impossible. Proof: Assume a quark can transform. A particular quark exists: top and this transforms into an anti-b quark while emitting a W-. Then the intermediate state exists: t-anti-b-W- / t-W-anti-b. This is impossible since a t quark is a fundamental particle. Similar reasoning holds for the other qaurks and antiquarks. Alternatively this is circumventable by assuming there is no intermediate state: the t exists and the next instant (one planck time) the W- and anti-b exists. Then there is no causal link between the t and anti-b so the reaction couldn't have happened. QED.