Particle Physics Cosmology Lesson 44 by Owen Borville 1.20.2026
Hideki Yukawa described the idea of virtual particle exchange as the carrier of forces being crucially important, with virtual particles being formed in temporary violation of the conservation of mass-energy as allowed by the Heisenberg uncertainty principle.
The four basic forces and their carrier particles are: (1) Gravity force is carried by gravitons (theoretical). (2) Electromagnetic force is carried by photons as observed. (3) Weak force as observed (W +- bosons, Z bosons, neutral Z bosons) (4) Strong force is carried by gluons (theoretical). The four forces in order of strength are: strong, electromagnetic, weak, and gravitational.
The Standard Model describes interactions between particles through the strong nuclear, electromagnetic, and weak nuclear forces. Particle interactions are represented by Feynman diagrams on a space-time graph.
Electromagnetic forces act over a long range, but strong and weak forces act over a short range. These forces are transmitted between particles by sending and receiving bosons, which carry particle forces.
Feynman diagrams by Richard Feynman are graphs of time versus position and are highly useful pictorial representations of particle processes. The theory of electromagnetism on the particle scale is called quantum electrodynamics (QED).
Particle accelerators have been developed to explore the nature of subatomic particles, their interactions, and to test predictions of particle theories. Modern accelerators used in particle physics are either large synchrotrons, linear accelerators, cyclotrons, and colliding beams. The use of colliding beams makes much greater energy available for the creation of particles, and collisions between matter and antimatter allow a greater range of final products. Colliding beams are used to create massive particles that decay quickly to lighter particles. Multipurpose detectors are used to design all aspects of high-energy collisions. These include detectors to measure the momentum and energies of charge particles and photons. Charged particles are measured by bending these particles in a circle by a magnetic field. Particles are measured using calorimeters that absorb the particles.
All particles of matter have an antimatter particle counterpart that has similar properties but the opposite charge and certain other quantum numbers. These matter-antimatter pairs are otherwise very similar but will annihilate when brought together. Known particles can be divided into three major groups: leptons, hadrons, and carrier particles (gauge bosons).
Leptons do not feel the strong nuclear force and are further divided into three groups: electron family designated by electron family number Le. Muon family designated by muon family number Lµ. Tau family designated by tau family number Lτ . The family numbers are not universally conserved due to neutrino oscillations.
Hadrons are particles that feel the strong nuclear force and are divided into baryons, with the baryon family number B being conserved and mesons.
Quarks are thought to compose hadrons, with baryons having three quarks and mesons having a quark and an antiquark. Indirect evidence for quarks is very strong, explaining all known hadrons and their quantum numbers, such as strangeness, charm, topness, and bottomness. Quarks come in six flavors and three colors and occur only in combinations that produce white. Quarts interact via the strong force, but leptons do not. Both quarks and leptons interact with the other three forces, however (electromagnetic, weak, gravitational force). The six known quarks are up (u), down (d), charm (c), strange (s), top (t), and bottom (b). These particles are fermions with half-integral spin and fractional charge. Baryons consist of three quarks, and mesons consist of a quark-antiquark pair. Due to the strong force, quarks cannot exist in isolation. Evidence for quarks is found in scattering experiments.
Fundamental particles have no further substructure, not even a size beyond their de Broglie wavelength. There are three types of fundamental particles: leptons, quarks, and carrier particles and each type is divided into three analogous families. Quarks and leptons belong to particle families composed of three members each. Members of a particle family share many properties such as charge, spin, participation in forces but not mass.
Elementary particles are classified into fermions and bosons. Fermions have half-integral spin and obey the Pauli exclusion principle, which states that no two identical fermions can occupy the exact same quantum state (like electrons). Bosons have integral spin and do not obey this exclusion principle. Bosons are the force carriers of particle interactions.
Particle conservation laws govern elementary particle interactions and these laws can be used to determine what particle interactions, reactions and decays are possible or not possible. The baryon number conservation law and the three lepton number conservation law are valid for all physical processes. However, conservation of strangeness is valid only for strong nuclear interactions and electromagnetic interactions.
Grand Unified Theories (GUTs) attempt to show unification of the four fundamental forces into one force and have been partially successful, with connections proven between EM and weak forces in electroweak theory. The strong force is carried by eight proposed particles called gluons, which are intimately connected to a quantum number called color, their governing theory is thus called quantum chromodynamics (QCD). Taken together, QCD and the electroweak theory are widely accepted as the Standard Model of particle physics.
Unification of the strong force is expected at such high energies that it cannot be directly tested, but it may have observable consequences in the as-yet unobserved decay of the proton and other topics. Although unification of forces ins generally anticipated, much remains to be done to prove its validity.
The universe is believed to be expanding (The Big Bang Theory) like a balloon so that every point is moving away from every other point. Distant galaxies move away at a velocity proportional to its distance. This rate is measured to be about 70 km/s/Mpc. Thus, the farther the galaxies are from us, the greater their speeds. These 'recessional velocities" can be measured using the Doppler shift of light.
The early universe is believed to be hot and dense and today the universe is believed to be isotropic (uniform) and expanding, according to Hubble's Law (v = Hod, where v is the recessional velocity, d is the distance, and Ho is Hubble's constant, the rate of expansion measured by observing galactic redshift or light stretching. Cosmic background radiation is given as the evidence for the Big Bang Theory. However, most of the properties of the universe, including most of the mass and energy, are not well understood.
Cosmology is the study of the structure and origin of the universe, including the stars and galaxies. The universe is believed to be expanding and the two most common evidences given for this phenomenon are the cosmological red shifts of its galaxies being proportional to distance and its cosmic microwave background radiation (CMBR). Both of these support the idea of a large explosion, called the Big Bang, that caused the universe to appear or become what it is now. Galaxies further away than ours have an average recessional velocity determined by v = Hod, where d is the distance to the galaxy and Ho is the Hubble constant, with the average value of Ho = 20 km/s*Mly.
The concepts of particle physics help explain the characteristics of the universe. Matter has an opposite known as antimatter, which is dominated by matter and its slight abundance allowed the universe to become what it is today (the baryon asymmetry concept). The smoothness of the CMBR are explained by particle physics concepts. The cause of the universe inflation is a topic of mystery and research.
Albert Einstein's theory of general relativity includes accelerated frames and therefore includes special relativity and gravity that were verified by real scientific experiments. One direct result of this behavior of nature is the gravitational lensing of light by massive objects, such as galaxies, and in the microlensing of light by smaller bodies in our galaxy.
Another prediction is the existence of black holes, which are objects for which the escape velocity is greater than the speed of light and from which nothing can escape. The event horizon is the distance from the object at which the escape velocity equals the speed of light c, known as the Schwarzchild radius Rs = 2GM/c^2, where G is the universal gravitational constant, and M is the mass of the body. Physics is unknown inside the event horizon, but wormholes (theoretical tunnels) and time travel have been theorized. Black holes may power the extremely energetic emissions of quasars, distant objects that seem to be early stages of galactic formation.
Neutron stars are stellar remnants, having the density of a nucleus, that imply that black holes could form from supernovas, too.
Gravitational waves are wrinkles in space, predicted by general relativity but not yet observed, caused by changes in very massive objects.
Quantum gravity is an incomplete theory that attempts to include or incorporate general relativity, quantum mechanics, and unification of forces (a theory of everything). One unconfirmed connection between general relativity and quantum mechanics is the prediction of characteristic radiation from just outside black holes.
Superstring theory claims that fundamental particles are one-dimensional vibrations similar to those on strings and this theory is an attempt at a theory of quantum gravity.
Dark matter is non-luminous matter detected in and around galaxies and galactic clusters. Dark matter is believed to be up to ten times the mass of luminous matter in the universe. Scientists have used the amount of dark matter to help determine whether the universe is open or closed (continuous forever or have an edge or ending). The critical density of the universe and the cosmological theoretical constant are determining factors related to expansion and closure of the universe.
The critical density ρc is the density needed to just halt universe expansion and it is estimated to be about 10^-26 kg/m^3. An open universe is negatively curved, a closed universe is positively curved, whereas a universe with the critical density is flat.
Dark matter's composition is unknown. If neutrinos have mass, they will change particle families, called neutrino oscillations, of which there is evidence.
Complexity is a growing field of study in physics that is concerned with complex adaptive systems and their origin, and how their organization occurred. Complexity has applications in physics and biology. Chaos is a field of study concerned with systems whose properties depend extremely sensitively on some variables and whose origin and development is impossible to predict.
High-temperature superconductors are materials that become superconducting at high temperatures above Kelvin. The critical temperature Tc is the temperature below which a material is superconducting. Some high-temperature superconductors have verified Tc above 125K and up to 250 K.
Questions in physics at the macro scale are about dark matter, dark energy, black holes, quasars, and more. At the intermediate scale there are questions about gravity, phase transitions, nonlinear phenomena, high-Tc superconductors, and magnetic effects on materials. At the smallest scale, questions exist about quarks and leptons, fundamental forces, stability of protons, and existence of monopoles.
Hideki Yukawa described the idea of virtual particle exchange as the carrier of forces being crucially important, with virtual particles being formed in temporary violation of the conservation of mass-energy as allowed by the Heisenberg uncertainty principle.
The four basic forces and their carrier particles are: (1) Gravity force is carried by gravitons (theoretical). (2) Electromagnetic force is carried by photons as observed. (3) Weak force as observed (W +- bosons, Z bosons, neutral Z bosons) (4) Strong force is carried by gluons (theoretical). The four forces in order of strength are: strong, electromagnetic, weak, and gravitational.
The Standard Model describes interactions between particles through the strong nuclear, electromagnetic, and weak nuclear forces. Particle interactions are represented by Feynman diagrams on a space-time graph.
Electromagnetic forces act over a long range, but strong and weak forces act over a short range. These forces are transmitted between particles by sending and receiving bosons, which carry particle forces.
Feynman diagrams by Richard Feynman are graphs of time versus position and are highly useful pictorial representations of particle processes. The theory of electromagnetism on the particle scale is called quantum electrodynamics (QED).
Particle accelerators have been developed to explore the nature of subatomic particles, their interactions, and to test predictions of particle theories. Modern accelerators used in particle physics are either large synchrotrons, linear accelerators, cyclotrons, and colliding beams. The use of colliding beams makes much greater energy available for the creation of particles, and collisions between matter and antimatter allow a greater range of final products. Colliding beams are used to create massive particles that decay quickly to lighter particles. Multipurpose detectors are used to design all aspects of high-energy collisions. These include detectors to measure the momentum and energies of charge particles and photons. Charged particles are measured by bending these particles in a circle by a magnetic field. Particles are measured using calorimeters that absorb the particles.
All particles of matter have an antimatter particle counterpart that has similar properties but the opposite charge and certain other quantum numbers. These matter-antimatter pairs are otherwise very similar but will annihilate when brought together. Known particles can be divided into three major groups: leptons, hadrons, and carrier particles (gauge bosons).
Leptons do not feel the strong nuclear force and are further divided into three groups: electron family designated by electron family number Le. Muon family designated by muon family number Lµ. Tau family designated by tau family number Lτ . The family numbers are not universally conserved due to neutrino oscillations.
Hadrons are particles that feel the strong nuclear force and are divided into baryons, with the baryon family number B being conserved and mesons.
Quarks are thought to compose hadrons, with baryons having three quarks and mesons having a quark and an antiquark. Indirect evidence for quarks is very strong, explaining all known hadrons and their quantum numbers, such as strangeness, charm, topness, and bottomness. Quarks come in six flavors and three colors and occur only in combinations that produce white. Quarts interact via the strong force, but leptons do not. Both quarks and leptons interact with the other three forces, however (electromagnetic, weak, gravitational force). The six known quarks are up (u), down (d), charm (c), strange (s), top (t), and bottom (b). These particles are fermions with half-integral spin and fractional charge. Baryons consist of three quarks, and mesons consist of a quark-antiquark pair. Due to the strong force, quarks cannot exist in isolation. Evidence for quarks is found in scattering experiments.
Fundamental particles have no further substructure, not even a size beyond their de Broglie wavelength. There are three types of fundamental particles: leptons, quarks, and carrier particles and each type is divided into three analogous families. Quarks and leptons belong to particle families composed of three members each. Members of a particle family share many properties such as charge, spin, participation in forces but not mass.
Elementary particles are classified into fermions and bosons. Fermions have half-integral spin and obey the Pauli exclusion principle, which states that no two identical fermions can occupy the exact same quantum state (like electrons). Bosons have integral spin and do not obey this exclusion principle. Bosons are the force carriers of particle interactions.
Particle conservation laws govern elementary particle interactions and these laws can be used to determine what particle interactions, reactions and decays are possible or not possible. The baryon number conservation law and the three lepton number conservation law are valid for all physical processes. However, conservation of strangeness is valid only for strong nuclear interactions and electromagnetic interactions.
Grand Unified Theories (GUTs) attempt to show unification of the four fundamental forces into one force and have been partially successful, with connections proven between EM and weak forces in electroweak theory. The strong force is carried by eight proposed particles called gluons, which are intimately connected to a quantum number called color, their governing theory is thus called quantum chromodynamics (QCD). Taken together, QCD and the electroweak theory are widely accepted as the Standard Model of particle physics.
Unification of the strong force is expected at such high energies that it cannot be directly tested, but it may have observable consequences in the as-yet unobserved decay of the proton and other topics. Although unification of forces ins generally anticipated, much remains to be done to prove its validity.
The universe is believed to be expanding (The Big Bang Theory) like a balloon so that every point is moving away from every other point. Distant galaxies move away at a velocity proportional to its distance. This rate is measured to be about 70 km/s/Mpc. Thus, the farther the galaxies are from us, the greater their speeds. These 'recessional velocities" can be measured using the Doppler shift of light.
The early universe is believed to be hot and dense and today the universe is believed to be isotropic (uniform) and expanding, according to Hubble's Law (v = Hod, where v is the recessional velocity, d is the distance, and Ho is Hubble's constant, the rate of expansion measured by observing galactic redshift or light stretching. Cosmic background radiation is given as the evidence for the Big Bang Theory. However, most of the properties of the universe, including most of the mass and energy, are not well understood.
Cosmology is the study of the structure and origin of the universe, including the stars and galaxies. The universe is believed to be expanding and the two most common evidences given for this phenomenon are the cosmological red shifts of its galaxies being proportional to distance and its cosmic microwave background radiation (CMBR). Both of these support the idea of a large explosion, called the Big Bang, that caused the universe to appear or become what it is now. Galaxies further away than ours have an average recessional velocity determined by v = Hod, where d is the distance to the galaxy and Ho is the Hubble constant, with the average value of Ho = 20 km/s*Mly.
The concepts of particle physics help explain the characteristics of the universe. Matter has an opposite known as antimatter, which is dominated by matter and its slight abundance allowed the universe to become what it is today (the baryon asymmetry concept). The smoothness of the CMBR are explained by particle physics concepts. The cause of the universe inflation is a topic of mystery and research.
Albert Einstein's theory of general relativity includes accelerated frames and therefore includes special relativity and gravity that were verified by real scientific experiments. One direct result of this behavior of nature is the gravitational lensing of light by massive objects, such as galaxies, and in the microlensing of light by smaller bodies in our galaxy.
Another prediction is the existence of black holes, which are objects for which the escape velocity is greater than the speed of light and from which nothing can escape. The event horizon is the distance from the object at which the escape velocity equals the speed of light c, known as the Schwarzchild radius Rs = 2GM/c^2, where G is the universal gravitational constant, and M is the mass of the body. Physics is unknown inside the event horizon, but wormholes (theoretical tunnels) and time travel have been theorized. Black holes may power the extremely energetic emissions of quasars, distant objects that seem to be early stages of galactic formation.
Neutron stars are stellar remnants, having the density of a nucleus, that imply that black holes could form from supernovas, too.
Gravitational waves are wrinkles in space, predicted by general relativity but not yet observed, caused by changes in very massive objects.
Quantum gravity is an incomplete theory that attempts to include or incorporate general relativity, quantum mechanics, and unification of forces (a theory of everything). One unconfirmed connection between general relativity and quantum mechanics is the prediction of characteristic radiation from just outside black holes.
Superstring theory claims that fundamental particles are one-dimensional vibrations similar to those on strings and this theory is an attempt at a theory of quantum gravity.
Dark matter is non-luminous matter detected in and around galaxies and galactic clusters. Dark matter is believed to be up to ten times the mass of luminous matter in the universe. Scientists have used the amount of dark matter to help determine whether the universe is open or closed (continuous forever or have an edge or ending). The critical density of the universe and the cosmological theoretical constant are determining factors related to expansion and closure of the universe.
The critical density ρc is the density needed to just halt universe expansion and it is estimated to be about 10^-26 kg/m^3. An open universe is negatively curved, a closed universe is positively curved, whereas a universe with the critical density is flat.
Dark matter's composition is unknown. If neutrinos have mass, they will change particle families, called neutrino oscillations, of which there is evidence.
Complexity is a growing field of study in physics that is concerned with complex adaptive systems and their origin, and how their organization occurred. Complexity has applications in physics and biology. Chaos is a field of study concerned with systems whose properties depend extremely sensitively on some variables and whose origin and development is impossible to predict.
High-temperature superconductors are materials that become superconducting at high temperatures above Kelvin. The critical temperature Tc is the temperature below which a material is superconducting. Some high-temperature superconductors have verified Tc above 125K and up to 250 K.
Questions in physics at the macro scale are about dark matter, dark energy, black holes, quasars, and more. At the intermediate scale there are questions about gravity, phase transitions, nonlinear phenomena, high-Tc superconductors, and magnetic effects on materials. At the smallest scale, questions exist about quarks and leptons, fundamental forces, stability of protons, and existence of monopoles.