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29.9: Key Terms

Last updated

Jul 28, 2023
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- 29.8: The Anthropic Principle
- 29.10: Summary

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anthropic principle: idea that physical laws must be the way they are because otherwise we could not be here to measure them

Big Bang: the theory of cosmology in which the expansion of the universe began with a primeval explosion (of space, time, matter, and energy)

closed universe: a model in which the universe expands from a Big Bang, stops, and then contracts to a big crunch

cosmic microwave background (CMB): microwave radiation coming from all directions that is the redshifted afterglow of the Big Bang

cosmological constant: the term in the equations of general relativity that represents a repulsive force in the universe

cosmology: the study of the organization and evolution of the universe

critical density: in cosmology, the density that is just sufficient to bring the expansion of the universe to a stop after infinite time

dark energy: the energy that is causing the expansion of the universe to accelerate; its existence is inferred from observations of distant supernovae

dark matter: nonluminous material, whose nature we don’t yet understand, but whose presence can be inferred because of its gravitational influence on luminous matter

deuterium: a form of hydrogen in which the nucleus of each atom consists of one proton and one neutron

flat universe: a model of the universe that has a critical density and in which the geometry of the universe is flat, like a sheet of paper

fusion: the building of heavier atomic nuclei from lighter ones

grand unified theories: (GUTs) physical theories that attempt to describe the four forces of nature as different manifestations of a single force

inflationary universe: a theory of cosmology in which the universe is assumed to have undergone a phase of very rapid expansion when the universe was about 10^–35 second old; after this period of rapid expansion, the standard Big Bang and inflationary models are identical

lithium: the third element in the periodic table; lithium nuclei with three protons and four neutrons were manufactured during the first few minutes of the expansion of the universe

multiverse: the speculative idea that our universe is just one of many universes, each with its own set of physical laws

open universe: a model in which the density of the universe is not high enough to bring the expansion of the universe to a halt

photon decoupling time: when radiation began to stream freely through the universe without interacting with matter

weakly interacting massive particles: (WIMPs) weakly interacting massive particles are one of the candidates for the composition of dark matter

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