Particle Physics...In A Nutshell
Elements and Atoms
(Please refer to the glossary at the end of the article for help with bold, italicized terms.)
Chemistry is not yet a science. We are very far from the knowledge of first principles. We should avoid every thing that has the pretensions of a full system. The whole of chemical science should, as yet, be analytical, like Newton’s Optics, in the form of a general law, at the very end of our induction, as the reward of our labour.—Joseph Black[i]
Developed by Dmitri Mendeleyev in 1869, the Periodic Table of Elements is a chart of all known elements grouped according to chemical composition. Everything in the Universe is composed of elements. (Refer to Figure 1.4 for a basic chart.)
Hydrogen makes up 75% of all known matter in the Universe, helium just under 25%. Less than 1% of all matter makes up the remaining elements listed on the Periodic Table. Hydrogen and helium are the lightest elements and the primary components that fuel stars via nuclear fusion. The remaining heavy elements appeared during the formation of the planets, which allowed for the process of life to begin. Without them, we would not be here.
In 400 BCE, the philosopher Democritus believed all matter consisted of indivisible particles, called atoms. An atom is the smallest particle of an element that can retain the characteristics of that element. Certain combinations of atoms make up the individual elements found throughout the Periodic Table.
[i] Black, Joseph. Lecture on the Elements of Chemistry. Brooklyn: AMS Press, 1982, p. 547.
Constituents of Atoms
The atomic nucleus consists of proton and neutron particles, together known as nucleons. Nucleons consist of even smaller particles, called quarks, which quantum physicists believe are the true elementary particles. Basic constituents of matter, then, are not atoms, but quarks. Quarks, including the gluon holding them together, combine to make up protons and neutrons. Protons, neutrons, and electrons together make up atoms. In essence, all matter is composed of two basic constituents: quarks and leptons. Leptons are light-wave particles and include muons, taus, electrons, and neutrinos.
In 1932, scientists discovered the existence of yet another particle. Its discoverer, Italian physicist Enrico Fermi, called it a neutrino, or little neutron. Neutrinos are leptons with a zero charge. They are small particles with almost no mass but are believed to make up the largest percentage of matter in the Universe.
Electrons, like quarks, are true, elementary, indivisible constituents of matter. They are negatively charged subatomic particles orbiting an atom, unlike the positively charged protons and neutrons found in the center of one.
Quarks come in three varieties, or “colors.” Since quarks are invisible to the naked eye, their color is determined by their theoretical characteristic, not spectra. They carry electric charges of plus or minus two-thirds or plus or minus one-third the electron charge. These constitute up and down varieties of quarks depending on the charge. Quarks combine in threes to make protons, neutrons, and many other particles, called hadrons, or “heavy” particles. Hadrons consist of confined quarks and antiquarks. They combine in twos to make other particles, called mesons.
(*Please click on matching diagram link above for a visual.)
To eliminate some confusion in an inherently perplexing topic, there are three basic families of particles:
1) First family, which is composed of everyday matter: up quark, down quark, electron, and electron neutrino.
2) Second family: charmed quark, strange quark, muon, and muon neutrino.
3) Third family: top quark, bottom quark, tau particle (electron-like), and tau neutrino.
Physicists are able to observe and catalog these particles using a particle accelerator, which is a miles-long pipe that accelerates and agitates particles with centrifugal force at super-fast speeds. Where they converge for observation is a very large and powerful microscope. The faster they can accelerate a particle, the smaller they can expose and observe one. Particle physicists study their angles and velocities to differentiate between one another. At first, they had a difficult time characterizing any since the same type of particle can have a different mass. Physicists called it a particle zoo. Over time, they were able to catalog them based on type, and the number of different families became more manageable.
Why did the Universe end up with more quarks, or particles, than antiquarks, or antiparticles? If the number of antiparticles had outweighed the number of particles, we would be living in a quite normal, antiparticle Universe. If the numbers did not outweigh each other either way, the Universe would be more radiation and less matter, an unfriendly scenario for life. Particles and antiparticles would have combined and annihilated each other until nothing but radiation remained. Fortunately for all life, this did not happen, and the better scenario won out.
(*Please click on matching diagram link above for a visual.)
In addition to matter particles, there are other particles, called force carriers: for the electromagnetic force, it is the photon; for the weak nuclear force, W and Z bosons; for the strong nuclear force, gluon; and for gravity, the graviton, though proof of its existence has yet to surface. A massive particle, called the Higgs boson, also exists. It is responsible for the masses of all other particles. Some scientists believed all mass originated from this single particle, and in July 2012, physicists made this elusive discovery. It was the Holy Grail of particle physics and will be a major asset to scientists in that field. Because of this revelation, they will have the ability to reach into the very fabric of the Universe.
The electromagnetic force is associated with the electron, the strong nuclear force acts between protons and neutrons, the weak nuclear force is associated with the neutrino, and gravity plays a role in the interaction between electrons. These four basic forces of nature are found in all atoms and dictate interactions between individual particles.
Macrocosm to Microcosm
From Largest to Smallest
In retrospect, all matter is composed of atoms. Atoms consist of protons, neutrons, and electrons. Electrons, themselves, are elementary. Protons and neutrons consist of three smaller particles, called quarks. Leptons, like quarks, are basic, fundamental particles and include electrons, muons, taus, and neutrinos. Electrons have no subcategory family like quarks and neutrinos. The different forms of quarks and neutrinos are not critical for the intent of this book.
Switching gears to a larger scale, the following sequence is the “nature of things” from largest entity to smallest: hyperspace, or the all-encompassing, interdimensional container of all possible universes (infinite); the known, visible Universe (28 billion light years across); clusters of galaxies (100 million ly across); galaxies (10,000 ly across); solar systems (one ly across); stars; planets; and finally individual, living beings. Further down the scale on the microscopic level is the individual cell (made up of about 100 trillion atoms); molecules, or aggregates of a particular number of atoms surrounded by the linking electron haze; atoms (one ten-thousandth of a micrometer); and the atomic nucleus.
The nucleus of an atom consists of a particular number of pairs of neutrons and protons, which combine to make up the atomic number for each element. Neutrons and protons combine to make up an atom. Each of these particles consists of three additional particles, or quarks. At last, quarks and electrons are true elementary constituents. In an atom, quarks make up the structure of protons and neutrons, and electrons surround them.
Cosmic Strings, Branes, and String Theory
Some quantum physicists believe quarks and electrons may not be particles at all, rather multidimensional entities, called branes. Some of these constituents manifest themselves as tiny loops of “string,” otherwise known as cosmic strings. According to some theoretical physicists, these thin tubes of high-energy vacuum are the most fundamental portions of matter, far smaller than quarks or neutrinos. A typical loop of string is 100 billion times smaller than an atomic nucleus. In theory, an inch of cosmic string, because of its high-tension energy, would weigh ten million-trillion tons. Their presence, like black holes, act as gravitational lenses that bend the space-time continuum.
String theory, more specifically M-theory, which is the most popular version of string theory, calls for the existence of a new class of elementary particles known as supersymmetric particles, called sparticles. Cosmic strings are a type of topological defect described by string theory and are entities some physicists believe were left over from the big bang following the formation of the Universe. Higher dimensions are related to string theory and appear outside of known existence.
Srinivasa Ramanujan’s Ramanujan function is a set of mathematics that allows for the existence of up to 26 dimensions in string theory. Ramanujan was considered one of the greatest mathematicians ever to live. The magic numbers eight and 24, plus two dimensions from relativistic theory, continue appearing in these equations for no apparent reason, each corresponding to a physical vibration of the string. When his function is generalized, the number 24 is replaced with the number eight (again, plus two), thus the origin of the tenth dimension. Most theoretical physicists add the dimension of time to come up with 11. This mysterious but consistent set of mathematics continues to baffle physicists, yet they persist. (String theory is outlined throughout Chapter 4 and Ramanujan’s unique mathematics in Chapter 8.)
Perhaps a marriage of quantum mechanics and general relativity is the prevailing salvation in all this jumble of particles, elements, strings, and dimensions. The macrocosm of general relativity is difficult enough for many to comprehend, let alone one of incomprehensibly minute quantum particles.
More interesting characteristics of these particles are outlined in later chapters, as this section was more of a basic, rather tedious introduction to particle physics.
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Antiquarks The antiparticle of a quark, or its quantum opposite. Antiparticles are thought to exist in higher dimensions as mirror images to their corresponding particles.
Atom The smallest part of an element able to participate in a chemical reaction. Each is made up of an electron, proton, and neutron. Smaller than a molecule but larger than a subatomic particle.
Bosons Particles associated with the transmission of each force of nature. Those forces include the weak nuclear force, strong nuclear force, electromagnetic force, and gravity.
Branes In string theory, they are layers of multidimensional folds found throughout the fabric of the Universe but in different dimensions. These branes are thought to reside a mere atom’s width apart, but one would need to travel the length of a dimensional fold and back again to observe the other side, or other reality. However, if the folds are just a separator between the dimensions, one could argue the traveler remains limited to the opposite side of the same three-dimensional fold, and the higher or lower dimensions “in between” remain unreachable and unobservable.
Cosmic Strings Hypothetical, one-dimensional, subatomic particles millions of light years long. They are thought to be topological imperfections, or “cracks,” in the structure of the Universe that formed in the early part following the big bang. Also responsible for clumping matter together so stars and galaxies could form.
Electromagnetic Force A force of nature that interacts between electrically charged particles, otherwise known as electromagnetism. One of the four basic forces of nature that explains electromagnetic fields. In layman’s terms, the study of the relationship between lightening and magnets.
Electron An elementary subatomic particle with a negative charge of electricity. It is found in all atoms and is a fundamental constituent of matter, which means it cannot be broken down and has no smaller parts. It is the primary carrier of electricity.
Force Carriers In quantum mechanics, particles that are bundles of energy of various fields. There is a force carrier for each type of elementary particle. Described as quanta, or an electron field for electrons, photons, and more.
General Relativity Albert Einstein’s theory of the association between gravity and geometry, developed in 1916. It is a proven theory accepted by physicists to explain gravity as a geometric property of curved space and time, or space-time. Time is a required component of the association between objects and their gravitational influence on space. You cannot measure gravity without time. If GPS satellites did not take into account general relativity, they would not work properly. Special relativity, on the other hand, deals more with properties of the speed of light. See also special relativity.
Gluons Elementary particles that act like “glue” by binding quarks together within hadrons. (Quarks are the building blocks of hadrons.) Gluons are bosons without mass and have a neutral vector.
Graviton Virtual particle of gravity yet to be quantized. Physicists believe the graviton is spread throughout multiple dimensions and, as a result, gravity appears as the weakest force of nature.
Hadrons A baryon or meson-composite particle made up of bound quarks. Protons and neutrons are the most common examples of hadrons.
Higgs Boson Also called the God Particle. In 2012, scientists discovered this elusive particle, which should be responsible for holding the entire Universe together. It is a massive elementary particle with zero charge and helps explain the masses of all other particles. Its discovery is considered the Holy Grail of particle physics.
Hyperspace Also called zero-dimensional hyperspace. It is the true vacuum of raw interdimensional energy, which is the container of all parallel universes. It has no textures or dimensional properties, so it cannot be observed by three-dimensional beings. It has no causal influence, so one could argue is a non-realm with no discernable properties. Hyperspace is the nothingness that exists “between” each parallel universe yet has the ability to house all lower and higher dimensions outlined in string theory.
Leptons An electron, muon, or neutrino not part of the strong nuclear force, only the weak.
M-theory (Magic, Matrix, or Mystery Theory) An extension of string theory that allows for the existence of up to 11 hidden dimensions, or 10 spatial and one of time. Some versions allow for up to 26, but the math tends to break down above 10. Each dimension exists on its own membrane, or brane, and is an atom’s length apart. The reason we are unable to see these dimensions is because one would have to travel the length of the Universe and back along the dimensional fold to witness anything above three dimensions. Physicists argue these higher dimensions could be similar to ours but may be more dynamic with peculiar properties. Our three-dimensional bodies could not exist in or witness any higher dimension.
Mesons Concerning the strong force of nature, they are hadronic elementary particles composed of a quark and an anti-quark. Their existence is unstable, lasting just a fraction of a second. Charged mesons decay to form electrons and neutrinos, uncharged ones decay to photons.
Muon An elementary particle with a negative charge. Combined with an electron, tau, and three neutrinos, it is classified as a lepton.
Neutrinos Neutral elementary particles that almost never interact with normal matter. Associated particles are electrons, muons, and taus. Italian for little neutron.
Neutrons Subatomic particles similar to protons but with no electric charge. Found in all atomic nuclei except hydrogen.
Nucleons A proton or neutron as part of the atomic nucleus.
Particle Zoo Initial mess of particles physicists had a difficult time differentiating between. Once they discovered the same particle can have a different mass, the number became a lot smaller and more manageable.
Photon An elementary particle of light and electromagnetic radiation. The force carrier for the electromagnetic force.
Proton A subatomic particle in an atomic nucleus with a positive electric charge, in equal magnitude to the opposing electron.
Quantum Mechanics Study of physics dealing with atomic and subatomic particles, in particular their behavior and interactions with energy and matter. Different from classical mechanics, which deals with the interactions and predictable behavior of macroscopic objects.
Quarks Theoretical elementary particles with a small electric charge. They are fundamental constituents of matter that combine to form hadrons, or protons and neutrons.
Quark, Down The second lightest of all quarks. Combinations of up and down-quark varieties make up neutrons and protons.
Quark, Up The lightest of all quarks. One of them plus two down quarks combine to make a neutron. Two of them plus one down quark combine to make a proton.
Ramanujan Function Developed by Srinivasa Ramanujan, an Indian mathematician born in 1887 who died at age 33 from tuberculosis. His function is a set of mathematics with the “magic” number, 24, repeatedly appearing throughout his journals. These equations fit nicely with string theory. His papers are still used today for such fields as polymer chemistry, computer applications, cancer research, and much more. Some of the equations remain baffling to the greatest mathematicians of our day. Srinivasa was self-taught with no formal training and considered one of the greatest mathematicians ever to live. At first, these equations were thrown away by Cambridge mathematician Godfrey Hardy in 1913. Ramanujan tried to explain the visions for these equations appeared in his dreams by the Hindu Goddess of Creativity, Namakkal.
Sparticles Also called supersymmetric particles. They are virtual particles that should be paired with every type of known particle, but physicists have yet to verify their existence. For every quark, there should be a squark; for every gluon, a gluino; and so on. Sparticles may be a necessary component to help complete the standard model in particle physics. Their discovery may help physicists find the graviton and learn the properties of dark matter.
String Theory Its goal is to reconcile incompatible aspects of quantum mechanics and general relativity into a theory of everything. See also M-theory.
Strong Nuclear Force (Color Force) The force between two or more nucleons that binds together protons, neutrons, and atomic nuclei. One of the four known forces of nature.
Taus An elementary particle with a negative electric charge. Combined with an electron, muon, and neutrinos, it is classified as a lepton but may decay into a hadron.
Weak Nuclear Force (Weak Force) As one of the four fundamental forces of nature, it is responsible for the radioactive decay of subatomic particles. Based on the theoretical exchange of W and Z bosons.