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gravitation
(Encyclopedia)gravitation, the attractive force existing between any two particles of matter. The term gravitygravity is commonly used synonymously with gravitation, but in correct usage a definite distinction is...mechanics
(Encyclopedia)mechanics, branch of physics concerned with motion and the forces that tend to cause it; it includes study of the mechanical properties of matter, such as density, elasticity, and viscosity. Mechanics...pulsar
(Encyclopedia)pulsar, in astronomy, a neutron star that emits brief, sharp pulses of energy instead of the steady radiation associated with other natural sources. The study of pulsars began when Antony Hewish and h...atomic clock
(Encyclopedia)atomic clock, electric or electronic timekeeping device that is controlled by atomic or molecular oscillations. A timekeeping device must contain or be connected to some apparatus that oscillates at a...binary star
(Encyclopedia)CE5 A. Eclipsing binary: Primary component passing behind secondary (dimmer) component B. Light curve for eclipsing binary binary star or binary system, pair of stars that are held together by the...skepticism
(Encyclopedia)skepticism skĕpˈtĭsĭzəm [key] [Gr.,=to reflect], philosophic position holding that the possibility of knowledge is limited either because of the limitations of the mind or because of the inaccess...Mercury, in astronomy
(Encyclopedia)Mercury, in astronomy, nearest planet to the sun, at a mean distance of 36 million mi (58 million km); its period of revolution is 88 days. Mercury passes through phases similar to those of the moon a...quantum electrodynamics
(Encyclopedia)quantum electrodynamics (QED), quantum field theory that describes the properties of electromagnetic radiation and its interaction with electrically charged matter in the framework of quantum theory. ...time , sequential arrangement of all events
(Encyclopedia)time, sequential arrangement of all events, or the interval between two events in such a sequence. The concept of time may be discussed on several different levels: physical, psychological, philosophi...cosmology
(Encyclopedia)cosmology, area of science that aims at a comprehensive theory of the structure and evolution of the entire physical universe. The earliest pre-Ptolemaic theories assumed that the earth was the cent...Browse by Subject
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