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an accepted source of expert information or advice


the act or faculty of knowing or sensing without the use of rational processes; it involves immediate cognition


the capacity for logical, rational, and analytic thought- intelligence

sensory data

knowledge obtained through the senses


a tentative explanation for an observation, phenomenon, or scientific problem, that can be tested by further investigation


a set of statements or principles devised to explain a group of facts or phenomena, especially one that has been repeatedly tested or is widely accepted and can be used to make predictions about natural phenomena


a well-tested theory, so firm as to be unquestioned by science


a schematic description of a system, theory, or phenomenon that accounts for its known or inferred properties and may be used for further study of its characteristics


a fact or state of having actual or real being


cause must always precede the effect

position symmetry

the laws of the universe are not different at different locations

time symmetry

the laws of the universe do not change with time

principle of noncontradition

of two contradictory propositions, both cannot be true

Occam's Razor

simpler explanations are more likely to be true than complex ones


any of the four fundamental ways in which elementary particles and bodies can influence each other


a push or pull on an object

strong nuclear interaction

the interaction between nucleons that gives rise to the strong force

electromagnetic interaction

the interaction between charged objects that gives rise to the electromagnetic force

weak nuclear interaction

the interaction between nucleons that gives rise to the weak force


the interaction between anything with mass that gives rise to the gravitational force

atomic nuclei

the positively charged central region of an atom composed of protons and neutrons


a composite, strongly interacting particle made up of three quarks; protons carry a positive electrical charge and is a constituent part of the nucleus of atoms


a composite, strongly-interacting particle made up of three quarks, but which carries no net electrical charge; neutrons area constituent part of the nucleus of the atom


a generic name for either a proton or neutron


the elementary particles of which protons and neutrons consist; a proton and neutron each consist of three quarks


a term referring to atoms whose nuclei can spontaneously change under the influence of the weak nuclear force


an elementary particle in atoms having a negative charge; electrons are located outside atomic nuclei


a substance composed of atoms that have an identical number of protons in each nucleus; elements cannot be reduced to simpler substances by normal chemical means


the fundamental unit of an element


the microscopic structure usually made up of more than one atom

solar system

the sun and all planets, comets, asteroids, and other bodies that orbit about it under the pull of gravity

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