---
title: "The Standard Model and the Four Interactions"
description: "Matter is built from quarks and leptons in three generations, and forces are carried by exchange particles with characteristic ranges and strengths. The model states which interactions each particle f"
canonical: https://lightmysky.com/learn/science/the-standard-model-and-the-four-interactions-mt_GYB4UMS0D9
source: https://lightmysky.com/learn/science/the-standard-model-and-the-four-interactions-mt_GYB4UMS0D9.md
retrieved: 2026-09-12
---

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# The Standard Model and the Four Interactions

Matter is built from quarks and leptons in three generations, and forces are carried by exchange particles with characteristic ranges and strengths. The model states which interactions each particle feels.

Subject: Science · Area: Quantum & Modern Physics · Ages 20 to 22
Page: https://lightmysky.com/learn/science/the-standard-model-and-the-four-interactions-mt_GYB4UMS0D9

## Ready when they can

- Places a given particle in the standard model and states which interactions it feels
- Relates the range of a force to the mass of its exchange particle
- Uses conservation rules to decide whether a proposed reaction can happen

## Lesson: The particle catalogue and its rules

Matter comes in quarks and leptons, arranged in three generations. Quarks feel all three quantum forces; leptons skip the strong one. Each force has its carriers: gluons carry the strong force, photons carry electromagnetism, and the W and Z bosons carry the weak force.

Range follows carrier mass through the uncertainty principle: a heavy carrier lives briefly and travels far less. Photons are massless, so electromagnetism reaches forever. The W and Z weigh near 80 to 90 GeV, so the weak force dies out around 10 to the minus 18 meters. Gluons are massless too, yet the strong force fades near 10 to the minus 15 meters.

Before trusting a proposed reaction, balance the books: charge, baryon number, and each lepton number must match on both sides. A neutron can never decay into just an electron plus a positron: charge works, but baryon number falls from 1 to 0. Strangeness must also match in strong reactions, though weak decays may break it.

**Example.** Quarks team up color-neutral: three make a baryon like the proton or neutron, while a quark plus an antiquark makes a meson like the pion. Mass itself comes from grip on the Higgs field: stronger coupling means a heavier particle, and the Higgs boson is that field's ripple.

**Recap.** Carriers set each force's reach, and charge plus baryon and lepton tallies decide which reactions may happen.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Exchange Particles and Reading a Feynman Diagram](https://lightmysky.com/learn/science/exchange-particles-and-reading-a-feynman-diagram-mt_7Ka5cVpTVL)
- [Particle Accelerators, Detectors and Cross-Sections](https://lightmysky.com/learn/science/particle-accelerators-detectors-and-cross-sections-mt_euJtxtxXyV)
- [Quarks, Leptons and the Conservation Laws](https://lightmysky.com/learn/science/quarks-leptons-and-the-conservation-laws-mt_kCGc5Neub_)

## Opens up

- [Hydrostatic Equilibrium and the Structure of a Star](https://lightmysky.com/learn/science/hydrostatic-equilibrium-and-the-structure-of-a-star-mt_RKeMW8iX56)