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Elementary Particles and the World of Planck Scale

Unifications, A Brief History of Physics

Unification Theories The history of physics is closely linked to the unification of seemingly disparate phenomena. (See Figure 15-05a.) Each stage of unification in turn advanced a new theoretical framework, which provides a deeper understanding of nature. (see Figure 15-05b.) The followings provides a history of the development of physics and the many unifications as depicted in Figure 15-05a. It also contains a brief description of the theoretical concept at each stage.

For those who wish to learn or re-learn elementary physics, there is a website, which uses animations to illustrate many of the subjects commonly taught in high school.

Figure 15-05a Unifications
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Figure 15-05b Theories
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Quantum Gravity A few of the other approaches to quantum gravity may turn out to play significant roles in the final synthesis. Among them will be the twistor theory and the non-commutative geometry. They will provide essential insights into the nature of the quantum geometry of space-time. Quantum gravity will emerge as a more fundamental theory since it will possess more explanatory and predictive powers. Figure 15-05p shows the relationship between quantum gravity and the other branches of physics at the limit of the various universal constants, where the gravitational constant G is associated with gravity, the Planck constant is for quantum, and the velocity of light c comes with special relativity. In quantum gravity, all the fundamental units are expressed in terms of G, , and c: Planck length = (G/c3)1/2 = 1.62x10-33 cm, Planck time = (G/c5)1/2 = 5.39x10-44 sec, Planck mass = (c/G)1/2 = 2.17x10-5 gm, Planck energy = (c5/G)1/2 = 1.22x1019 Gev, and Planck temperature = (c5/GkB2)1/2 = 1.42x1032 oK, where kB is the Boltzmann's constant, which relates energy to absolute temperature on the Kelvin scale.

Figure 15-05p Quantum Gravity [view large image]

The diagram below summarizes the domains of activity in physics:

Phenomenological model is constructed to account for some data, while the theoretical framework encompasses a much wider scope including many phenomena. Usually the development of theories in physics follows the path from step 1 to 4 with constant feedbacks. Rarely does it proceed from Step 4 back to 1. But such is the case from the brilliant insight of P. A. M. Dirac, who just wrote down the wave equation for the electron, the derived predictions were all verified to be correct. In another example, it took a genius like Einstein to start from a little bit of mathematics in the curvature of space (a small part in differential geometries) and works its way backward to Step 1 with predictions way ahead of observations - many of those have been confirmed only recently.

Solvay Conference Figure 15-05q is a group photo for the physicists of yesterday. It was taken in 1927 at the Solvay Conference on Quantum Mechanics, Belgium. Most of the physicists are European males with 2 exceptions from the U.S. and one lady (Madam M. Curie), whoes entry was secured by the fame of pioneering the investigations into radioactivity. Table 15-01b lists all the participants with their nationality, field(s) of study, and the year when the Nobel prize was conferred (if any). Most of their names are linked to various kinds of theory, equation, and formula. It is very difficult to avoid them in a text book for physics. The year 1927 was within a relatively quiet period between the end of World War I (1919) and the onset of Great Depression in 1929. It was the heyday for the developments of quantum theory and relativity. However, all was not well.

Figure 15-05q 1927 Solvay Conference [view large image]

Hitler was on the way to seize power in Germany. Nightmare would soon begin in 1933 when he became Chancellor of the Reich.

Name Nationality Nobel Field(s) of Study
Auguste Piccard* (1884-1962) Switzerland   Stratosphere, Ocean Floor
Émile Henriot (1885-1961) France   Radioactive Elements, High-speed Spin
Paul Ehrenfest* (1880-1933) Austria   Electron Microscope
Édouard Herzen (1877-1931) Belgium   Quantum Statistical Mechanics
Théophile de Donder (1872-1957) Belgium   Thermal Irreversible Process
Erwin Schrödinger* (1887-1961) Austria 1933 Schrödinger Equation
Jules-Émile Verschaffelt (1870-1955) Belgium   Secretary of the Solvay Institute of Physics
Wolfgang Pauli* (1900-1958) Austria 1945 Exclusion Principle
Werner Heisenberg* (1901-1976) Germany 1932 Uncertainty Principle, Particle Physics, QFT
Ralph Howard Fowler (1889-1944) Britain   Stellar Structure
Léon Brillouin* (1889-1969) France   Solid State Physics, Information Theory
Peter Debye* (1884-1966) Netherland 1936 Low Temperature Specific Heat, Physical Chemistry
Martin Knudsen (1871-1949) Denmark   Kinetic Theory of Gases, Knudsen Number
William Lawrence Bragg* (1890-1971) Britain 1915 X-ray Diffraction
Hendrik A. Kramers* (1894-1952) Netherland   Dispersion Theory, Atomic Transitions
Paul Dirac* (1902-1984) Britain 1933 Dirac Equation
Arthur Compton* (1892-1962) U.S.A. 1927 Compton Scattering
Louis de Broglie* (1892-1987) France 1929 Wave-particle Duality
Max Born* (1882-1970) Germany 1954 Probability Interpretation of Wave Function, Born's Rule
Niels Bohr* (1885-1962) Denmark 1922 Semi-classical H atom, Copenhagen Interpretation
Irving Langmuir* (1881-1957) U.S.A. 1932 Atomic and Molecular Structures
Max Planck* (1858-1947) Germany 1918 Quanta of Light, Planck's Constant
Marie Curie* (1867-1934) Poland 1911 Radioactive Elements
Hendrik Lorentz* (1853-1928) Netherland 1902 Lorentz Transformation
Albert Einstein* (1879-1955) Germany 1921 Theories of Relativity
Paul Langevin* (1872-1946) France   Statistical Physics
Charles E. Guye (1866-1942) Switzerland   Mathematics
Charles T. R. Wilson (1869-1959) Britain 1927 Cloud Chamber
Owen W. Richardson* (1879-1959) Britain 1928 Vacuum Tubes
* Attendees

Table 15-01b Physicists of Yesterday

Table 15-01c lists the seven most important equations in physics in sequence of the year of publication. More detail for the equations is just one "click" away (on each of the "Discipline"). It shows that all the important equations had been laid down more than eighty years ago right back to the 17 century. Since then theoretical physicists make use of these tools to explain various phenomena. Some new ideas such as Superstring theory appear to be more intricate and without experimental backup. Theoretical physics just doesn't seem to be what it used to be mainly because we can observe much further and probe into much smaller objects. These kind of objects cannot be explained by an "one liner" as shown in the table.

Year Author Discipline Subject Equation(s)
1687 Isaac Newton Classical Mechanics Motion of Partilce
1865 J. C. Maxwell Electrodynamics Electricity and Magnetism
1872 L. Boltzmann Thermodynamics Tendency toward Disorder
1905 Albert Einstein Special Relativity Constant Velocity of Light
1915 Albert Einstein General Relativity Gravity - Warpped Spacetime
1927 W. Heisenerg Quantum Theory Microscopic Particle
1928 P. A. M. Dirac Quantum Field Theory Free Field Equation for Fermion

Table 15-01c The Seven Most Important Equations in Physics

An idea about the unification of the four distinct interactions is expounded in the 2015 book "A Beautiful Question" by Frank Wilczek. The main thrust is on the unification of the various "Property Spaces". The sum total of the different forms can be represented by a map of the space-time containing information about the electromagnetism, weak and strong interactions at every point (Figure 15-05r shows just one example with the strong interaction in 2-D space). This map looks flat, but it can represent a curve space by labeling the step size dx and dy with different values. The different facets of the various interactions are the result of distortion of a central entity by some sort of medium similar to the anamorphic art which alters the viewing or the anachromic art which changes the color of the object (Figure 15-05s). As shown in Table 15-01d, the
Property Space Distorted Images "Source", "Metric Generator", and "Mediating Particle" conspire together to produce each of the "Property Space". The "Source" is a specific property of matter responsible for generating the "Property Space". The "Metric Generator" is the rule (the mathematical equations - the distorting medium) for its production. The "Mediating Paricle" is the messenger to implement the rule. The "Property Space" is the final product, which could show up in various configurations or states to

Figure 15-05r Property Space [view large image]

Figure 15-05s Distorted Image
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direct the movement of other matter with similar "Source" in that particular "Property Space".

Interaction Sources / Fermions Metric Generator Mediating Particle(s) Property Space
Gravity Energy-Momentum General Relativity Graviton (?)
Space-time with coordinates x, y, z, t
Electromagnetism Electric charges / e-1 Quantum Electrodynamics Photon
U(1) symmetry with one gauge and state u(p,s)
Weak Interaction Hypercharge, 3rd Isospin Component / , e-1 Weinberg-Salam Model Z0, W mesons
U(1)SU(2) symmetry with a total of 4 gauges and isosingle, isodublet states
Strong Interaction Color charges /
6 left-handed ur,b,g , dr,b,g +
6 right-handed ur,b,g , dr,b,g
Quantum Chromodynamics 8 Gluons
SU(3) symmetry with 8 gauges and triplet state

Table 15-01d Unification of the Four Interactions

Meanwhile, proponents of SO(10) unification can explain away the many unobserved mediating particles (emerging from such symmetry including those changing quark to lepton) by heavy mass which tends to decay themselves quickly to the species with lowest mass. They also
Domain of Unification tried to show that all the interactions would merge in the tiny region (corresponding to high probing energy) within which the "central entity" resides. The attempt is not very successful (see left diagram of Figure 15-05w). However, the improvement is drastic (including gravity as shown in the right diagram of Figure 15-05w) if supersymmetry (SUSY) is introduced into the consideration. But none of the partner particles predicted by SUSY has ever been detected despite the deployment of many modern technologies (see dark matter as SUSY/WIMP or some LHC updates).

Figure 15-05w Domain of Unification [view large image]

BTW, MSSM = Minimal Supersymmetric Standard Model, and see more beauty in "Conservation Rules".

1Inertial systems of reference are either at rest or moving with constant velocity relative to each other.

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