Chapter 19 In The Beginning term anthropic principle

Chapter 19 In The Beginning

term: anthropic principle [ click for answer ] 1 of 21

definition: The idea that since we exist, the Universe must have certain properties or it would not have evolved so that life formed and humans evolved. [ click for next term ] 1 of 21

term: cosmic microwave radiation [ click for answer ] 2 of 21

definition: Isotropic millimeter and submillimeter radiation following a black-body curve for about 3 K; interpreted as a remnant of the big bang. [ click for next term ] 2 of 21

term: electromagnetism [ click for answer ] 3 of 21

definition: The combined force of electricity and magnetism, which follows the formulae unified by Maxwell. [ click for next term ] 3 of 21

term: electroweak force [ click for answer ] 4 of 21

definition: The unified electromagnetic and weak forces, according to a recent theory. [ click for next term ] 4 of 21

term: flatness problem [ click for answer ] 5 of 21

definition: One of the problems solved by the inflationary theory, that the Universe is exceedingly close to being flat for no obvious reason. [ click for next term ] 5 of 21

term: grand unified theories (GUTs) [ click for answer ] 6 of 21

definition: Theories unifying the electroweak force and the strong force. [ click for next term ] 6 of 21

term: gravity [ click for answer ] 7 of 21

definition: The tendency for all masses to attract each other; described in a formula by Newton and more recently described by Einstein as a result of a warping of space and time by the presence of a mass. [ click for next term ] 7 of 21

term: horizon problem [ click for answer ] 8 of 21

definition: One of the problems of cosmology solved by the inflationary theory: why the Universe has the same average temperature in all directions, even though widely separated regions could never have been in thermal equilibrium with each other since they are beyond each other's horizons. [ click for next term ] 8 of 21

term: inflation [ click for answer ] 9 of 21

definition: The theory that the Universe expanded extremely fast, by perhaps 10 to the 100 th power, in the first fraction of a second after the big bang. The concept of inflation solves several problems in cosmology, such as the horizon problem. [ click for next term ] 9 of 21

term: multiverse [ click for answer ] 10 of 21

definition: The set of parallel universes that may exist, with our observable universe as only one part. [ click for next term ] 10 of 21

term: perfect cosmological principle [ click for answer ] 11 of 21

definition: The assumption that on a large scale the Universe is homogenous and isotropic in space and unchanging in time. [ click for next term ] 11 of 21

term: phase transition [ click for answer ] 12 of 21

definition: Change from one state of matter to another, as from solid to liquid or liquid to gas; phase transitions in the early Universe marked the separation of the fundamental forces. [ click for next term ] 12 of 21

term: Planck time [ click for answer ] 13 of 21

definition: The time very close to the Big Bang, 1043 seconds, before which a quantum theory of gravity would be necessary to explain the Universe and which is therefore currently inaccessible to our computations. [ click for next term ] 13 of 21

term: primordial nucleosynthesis [ click for answer ] 14 of 21

definition: The formation of the nuclei of isotopes of hydrogen (such as deuterium), helium, and lithium in the first 10 minutes of the Universe. [ click for next term ] 14 of 21

term: quark [ click for answer ] 15 of 21

definition: One of the subatomic particles of which modern theoreticians believe such elementary particles as protons and neutrons are composed. The various kinds of quarks have positive or negative charges of 1/3 e or 2/3 e, where e is the unit of electric charge. [ click for next term ] 15 of 21

term: steady-state theory [ click for answer ] 16 of 21

definition: The cosmological theory based on the perfect cosmological principle, in which the average properties of the Universe are unchanging over time. [ click for next term ] 16 of 21

term: strong nuclear force [ click for answer ] 17 of 21

definition: The strong force. [ click for next term ] 17 of 21

term: supercooled [ click for answer ] 18 of 21

definition: The condition in which a substance is cooled below the point at which it would normally make a phase change; for the Universe, the point in the early Universe at which it may have cooled below a certain temperature without breaking its symmetry; the strong and electroweak forces remained unified. [ click for next term ] 18 of 21

term: superstring (string) theories [ click for answer ] 19 of 21

definition: A possible unification of quantum theory and general relativity in which fundamental particles are really different vibrating forms of a tiny, onedimensional "string" instead of being localized at single points. [ click for next term ] 19 of 21

term: symmetric [ click for answer ] 20 of 21

definition: A correspondence of shape so that rotating or reflecting an object gives you back an identical form; symmetry of forces in the early Universe corresponds to forces acting identically that now act differently as the four fundamental forces: gravity, electromagnetism, weak nuclear force, and strong nuclear force. [ click for next term ] 20 of 21

term: weak nuclear force [ click for answer ] 21 of 21

definition: One of the four fundamental forces of nature, weaker than the strong force and the electromagnetic force. It is important only in the decay of certain elementary particles, such as neutrons. [ End of chapter 19] 21 of 21