Quick questions on The four fundamental forces (QCE Physics Unit 4)

Mediator. Gluon (8 types). Massless. Carry colour charge.

Mediator. Photon. Massless. No charge.

Mediator. W$^+$, W$^-$, Z$^0$ bosons. Massive (80-91 GeV/c$^2$). Charged or neutral.

Mediator. Graviton (hypothesised, not observed). Would be massless, spin 2.

Gluon (8 types). Massless. Carry colour charge.

Quarks (and hadrons by extension).

$\sim 1$ (the reference strength; about 100 times stronger than electromagnetism at this distance).

About $10^{-15}$ m (one femtometre, nuclear size). Effectively confining for quarks; never observed in isolation.

Binds quarks into hadrons. The residual strong force (sometimes called the nuclear force) binds protons and neutrons into nuclei despite Coulomb repulsion between protons.

Without it, no atomic nuclei beyond hydrogen would be stable (Coulomb repulsion would tear them apart). No stars, no elements heavier than hydrogen, no life.

Without it, no atoms (electrons would not bind to nuclei). No chemistry, no light, no electromagnetism. Most of everyday physics.

Without it, no beta decay; the cosmic distribution of elements would be very different. The hydrogen fusion in the sun begins with a weak-force process (proton-proton fusion via a W boson), so without the weak force, the sun would not shine. Most natural radioactive decays involve the weak force.

Without it, no large-scale structure (stars, planets, galaxies). Negligible at scales below planets, but cumulatively decisive at astronomical scales.

Strong is what binds nuclei (gluon mediator, $10^{-15}$ m range). Weak is responsible for beta decay (W/Z mediators, $10^{-18}$ m range, much weaker).

The photon mediates all electromagnetic interactions, including the static Coulomb force between charges. Virtual photons are exchanged between charged particles even when no light is being emitted.