Astronomy 10 Exam 1- Ch.16 – Flashcards
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Cosmology
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study of the universe on the very grandest of scales, including its nature, origin, evolution, and ultimate destiny
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Hubble Time
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an estimate of the universe's age: 13.8 billion years
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Big Bang
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The event that occurred 13.8 billion years ago that marks the beginning of time and the universe. - created space time - started with singularity
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4 forces
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gravity, electromagnetic, weak/strong nuclear forces
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observable universe
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the part of the universe that we can see.
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Ralph Alpher (1921-2007), Robert Herman (1914-1997), and George Gamow (1904-1968)
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reasoned that because a compressed gas cools as it expands, the expanding universe should also be cooling
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cosmic microwave background (CMB) radiation
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Isotropic microwave radiation from every direction in the sky having a 2.73-kelvin (K) blackbody spectrum. The CMB is residual radiation from the Big Bang.
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recombination
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1. The combining of ions and electrons to form neutral atoms. 2. An event early in the evolution of the universe in which hydrogen and helium nuclei combined with electrons to form neutral atoms. The removal of electrons caused the universe to become transparent to electromagnetic radiation.
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critical density
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The value of the mass density of the universe that, ignoring any cosmological constant, is just barely capable of halting expansion of the universe
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cosmological constant
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A constant, introduced into general relativity by Einstein, that characterizes an extra, repulsive force in the universe due to the vacuum of space itself.
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dark energy
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A form of energy that permeates all of space (including the vacuum) producing a repulsive force that accelerates the expansion of the universe.
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electromagnetic force
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The force, including both electric and magnetic forces, that acts on electrically charged particles. One of four fundamental forces of nature. The force mediated by photons
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weak nuclear force
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The force underlying some forms of radioactivity and certain interactions between subatomic particles. It is responsible for radioactive beta decay and for the initial proton-proton interactions that lead to nuclear fusion in the Sun and other stars. One of the four fundamental forces of nature, mediated by the exchange of W and Z particles.
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electroweak theory
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the electromagnetic force and the weak nuclear force have been combined into a single force that predicts the existence of three carrier particles that mediate the weak nuclear force.
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quark
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The building block of protons and neutrons.
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Higgs field
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responsible for breaking the symmetry between different kinds of carrier particles.
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standard model
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The theory of particle physics that combines electroweak theory with quantum chromodynamics to describe the structure of known forms of matter. - excluding gravity
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antiparticle
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An elementary particle of antimatter identical in mass but opposite in charge and all other properties to its corresponding ordinary matter particle.
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pair production
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The creation of a particle-antiparticle pair from a source of electromagnetic energy.
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grand unified theory (GUT)
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A unified quantum theory that combines the strong nuclear, weak nuclear, and electromagnetic forces but does NOT INCLUDE gravity.
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Planck era
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The early time, just after the Big Bang, when the universe as a whole must be described with quantum mechanics.
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theory of everything (TOE)
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A theory that unifies all four fundamental forces of nature: strong nuclear, weak nuclear, electromagnetic, and gravitational forces.
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string theory
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The theory that conceives of particles as strings in 10 dimensions of space and time; the current contender for a theory of everything.
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flatness problem
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The surprising result that the sum of Ωmass + ΩΛ is extremely close to unity in the present-day universe; equivalent to saying that it is surprising the universe is so close to being exactly flat.
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horizon problem
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The puzzling observation that the cosmic background radiation is so uniform in all directions, despite the fact that widely separated regions should have been "over the horizon" from each other in the early universe.
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inflation
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An extremely brief phase of ultrarapid expansion of the very early universe. After inflation, the standard Big Bang models of expansion apply.
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multiverse
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A collection of parallel universes that together comprise all that is.
