29.9: Key Terms
- Page ID
- 66785
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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