Browse Reference Articles
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Doppler effect
The Doppler effect, named after Christian Andreas Doppler, is the apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves. The ... > more -
Precession
Precession refers to a change in the direction of the axis of a rotating object. In certain contexts, "precession" may refer to the precession that the Earth experiences, the effects of this type of ... > more -
Light-year
A light-year or lightyear (symbol: ly) is a unit of measurement of length, specifically the distance light travels in a vacuum in one year. While there is no authoritative decision on which year is ... > more -
Gravitation
Gravity is a force of attraction that acts between bodies that have mass. Gravity is the reason for the very existence of the earth, the sun and other celestial bodies; without it matter would not ... > more -
Solar System
The Solar System consists of the Sun and the other celestial objects gravitationally bound to it: the eight planets, their 165 known moons, three dwarf planets (Ceres, Pluto, and Eris and their four ... > more -
Galaxy formation and evolution
The formation of galaxies is still one of the most active research areas in astrophysics; and, to some extent, this is also true for galaxy evolution. Some ideas, however, are now widely accepted. ... > more
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