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Journey into the Atom: Glossary
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alchemists - People who tried to convert lesser metals such as lead into precious metals, such as gold and silver and who tried to find the source of life. See also: chemists, Briefing Room antiparticle - Each particle has an anti-particle with the opposite electrical charge, color charge, and various other properties of the particle. Antiparticles and particles usually annihilate each other when they come close, releasing vast amounts of energy. Anti-matter and even some atoms of anti-hydrogen have been created in high energy particle accelerators. See also: particle, Debriefing, Journey - Anti-matter
atom - the smallest portion of a chemical element that can exist and still retain its characteristic chemical properties. See also: element, Briefing Room atomic theory - 1 the theory that all matter is made up of fundamental particles called atoms. 2 the concept of an atom as being composed of subatomic particles. See also: Briefing Room atomos - Greek word meaning "indivisible". Leucippos used the term to describe the smallest portion of matter. See also: atom, Democritus of Abdera, Leucippos, Briefing Room
baryons - A group of hadrons that are made with 3 quarks. Examples include protons and neutrons. See also: hadron, quark, proton, neutron, Debriefing bosons - A family of particles that have integral spins (1, 2, ...) and do not obey the Pauli Exclusion Principle. Bosons can also be made from an even number of fermions. Examples: mesons, gague bosons, the helium nucleus in the journey. See also: spin, fermions, mesons, gauge bosons, Debriefing Boyle, Robert - Chemist of the early 1600's who, in his paper The Skeptical Chymist, defined the term "element." See also: element, Briefing Room
chemists - People who study normal matter (electrons, neutrons, and protons) and how it interacts (electromagnetic force). See also: alchemists, Briefing Room color charge - A property of certain particles completely separate from electrical charge. Particles with color charge respond to the strong force. It has three values for matter particles (red, green, and blue). Anti-matter particles have color charges of anti-red, anti-green, and anti-blue. See also: strong force, quantum chromodynamics, Debriefing
Dalton, John - Chemist during the 18th century who reasoned that "atomos" (changed to atoms) are what make elements. In a paper, he described the laws that applied to elements and their atoms. See also: atomos, atom, Briefing Room Democritus of Abdera - A Greek philosopher who hypothesized that matter was made up of pieces (It can only be broken down to a specific size). See also: atomos, Leucippos, Briefing Room De Broglie, Louis - A scientist of the 20th century. Louis De Broglie reasoned that if light waves can behave as particles, matter particles could behave as waves. See also: wave-particle duality, Advanced Topics Dirac, Paul - Physicist who, in a paper called The Principles of Quantum Mechanics, introduced the theories behind antiparticles. See also: antiparticles, Physicists
fermions - A category of particles that have "odd-half-integer" spins (1/2; 3/2; ...) and obey the Pauli Exclusion Principle. Examples include electrons, electron neutrinos, and quarks. See also: spin, Pauli Exclusion Principle, electron, quark, neutrino, boson, Debriefing Fermi, Enrico - In 1942, he created the world's first controlled nuclear reaction. Since his death, the Enrico Fermi award is annually given to the one person who has made the largest contribution to the use, development, or control of atomic energy. See also: Physicists Feynman, Richard - Feynman has been called the greatest physics lecturer ever. His book QED contains four of his lectures which were an attempt to teach non-scientists how to use the principles of the quantum theory of light and electricity. His greatest contributions include his work on Feynman diagrams, which help physicists visualize the mathematics behind the interactions of particles similar to the way that a pie chart can help us visualize the results of a survey. See also: Physicists frequency - The number of times every second something repeats itself. In a wave, a "repetition" is one time up and one time down. Its unit is called Hertz, or Hz for short. See also: speed of light, Advanced Topics fundamental particle - A particle that can not be broken down any further. The list of particles we call fundamental has changed through time as we see that certain particles are really composites of more fundamental particles. See also: Debriefing
hadron - A type of matter particle made up of quarks bound together by gluons. See also: quark, gluon, baryon, meson, Debriefing Hawking, Stephen - Referred to as the Einstein of our time, Hawking has made discoveries in both particle physics and astrophysics, specifically black holes. Hawking has also made the effort to make it easier for non-scientists to understand these subjects in his book, A Brief History of Time. See also: Physicists Heisenberg Uncertainty Principle - Principle that states there is a fundamental limit to how precisely both the position and velocity of a particle can be measured at the same time. See also: particle, Advanced Topics Hertz /hurts/ - See frequency
lepton - The fundamental matter particles that do not carry color charge. They are all spin 1/2 particles, and include the electron, muon, tau, and their corresponding neutrinos. See also: fundamental particle, spin, electron, neutrino, Debriefing Leucippos - Another philosopher of Democritus' time. He coined the term "atomos" for the tiny pieces of matter Democritus hypothesized about. See also: Democritus of Abdera, atomos, Briefing Room
meson - A family of particles that are made up of a quark and an anti-quark bound by gluons. They are all bosons and carry the residual strong force, which keeps baryons (especially the proton and neutron) together. See also: boson, quark, gluon, strong force, Debriefing, Journey - Meson
neutrino - A group of leptons that have little, if any, mass. Since they are also electrically neutral, their most important interaction with other particles is the weak force. There is one neutrino for each of the charged leptons. See also: lepton, weak force, Debriefing, Journey - Neutrino
neutron - A baryon that carries no charge. It is made of two down quarks and one up quark. The neutron is located in the nucleus and is "stuck" to the protons by the residual strong force. See also: nucleus, proton, quark, Journey - Neutron
nucleus - At the center of an atom, the nucleus makes up over 99% of its mass and carries the positive charge of the atom. See also: atom, proton, neutron, electron, Journey - Atom, Journey - Nucleus
quantum - Quantum means "a specific amount (quantity)". Max Planck suggested in 1900 that the energy in a wave of electromagnetic radiation comes in quanta (plural). He found that multiplying a constant by the frequency gives the energy of a single photon of light. See also: Planck, Max, electromagnetic radiation, frequency, photon, Planck's constant, Advanced Topics quantum chromodynamics - A set of equations and rules describing the strong force, which is carried by gluons and acts on all particles with color charge. See also: color charge, gluon, quark, Debriefing quantum electrodynamics - A set of equations and rules describing the electromagnetic force. See also: electromagnetic force quark - A group of fundamental, spin 1/2 particle that have color charge and fractional electric charge. It makes up such particles as neutrons, protons, and pions, all of which are hadrons. In German "quark" means liquid cheese. See also: spin, hadron, Debriefing
speed of light (c) - 3×108 meters per second (over 186,000 miles per second), represented by the letter 'c' in physics (as in E=mc2). Pretty fast, huh? Einstein's theory of relativity says that massive particles can never reach the speed of light. See also: Einstein, Albert, Advanced Topics spin - Spin is a detailed subject, but its definition is this: a property of particles that is similar to the idea of angular momentum in classical physics. You might want to read some of the books in the Individual Exploration for a more complete description that we give here. See also: Debriefing Standard Model - The most widely accepted theory of particle physics. It is the only one covered in this site.
strong force - The strongest of the forces. It is carried by the gluon and keeps quarks together in hadrons. There is also a residual strong force that is carried by mesons, keeping protons and neutrons together in the nucleus of an atom. gluon, quark, nucleus, proton, neutron, Quantum Chromodynamics, Debriefing
Theory of Everything (TOE) - The final theory of particle physics. It will describe the electromagnetic, weak, strong, and gravitational forces as different aspects of the same force. It will not end all of physics, however. Just because you can describe how all of the quarks, electrons, photons, etc. interact in the human body does not mean that you can describe how a person will react if he has his head smashed by a hammer. It would take too long to calculate the result of every interaction between every particle in the body. See also: strong force, electromagnetic force, gravitational force, Grand Unified Theory Thomson, J.J. - Discovered the electron in 1897. This finding made others search for more sub-atomic particles and eventually the field of particle physics was born. This site is dedicated to him for what his discovery precipitated. See also: electron, Physicists
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