Professor Positron's Tiny Quiz

Neutrons have no antiparticles because they are composed of three quarks (two down quarks and one up quark) and have no net electric charge. Antiparticles are the counterparts of particles with opposite charge, but since neutrons have no charge, they do not have antiparticles. Protons, on the other hand, are composed of two up quarks and one down quark, resulting in a positive charge, and therefore have antiparticles called antiprotons.

The graviton is the only particle listed that does not fit into the current standard model of physics. The standard model describes the fundamental particles and forces of nature, but it does not include a particle for gravity. The graviton is a hypothetical particle that is predicted by theories of quantum gravity, which aim to unify gravity with the other fundamental forces. However, the graviton has not been observed or confirmed by experimental evidence, and its existence is still a subject of ongoing research and speculation.

The mass of an up quark is 2.4MeV/c^2. This measurement is given in units of energy divided by the speed of light squared, which is a common way to express mass in particle physics. The mass of an up quark is relatively small compared to other particles, such as protons and neutrons, which are composed of up and down quarks.

The strange quark has the highest positive charge among the given particles. Quarks are elementary particles that make up protons and neutrons. The strange quark has a charge of +2/3, while the tau neutrino, photon, and electron have charges of 0, 0, and -1 respectively. Therefore, the strange quark has the highest positive charge.