天文学(astronomy)
研究宇宙（universe）内所有天体和散布其中的一切物质的起源、演化、组成、距离和运动的科学。天文学是一门最古老的科学，自有记载的文明之初就已出现。许多最早关於天体的知识往往被认为源出巴比伦人。古希腊人提出了多种对後世有影响的宇宙学概念，包含地球与宇宙其他地方的相关理论。西元2世纪，托勒密致力传播宇宙地心说，这一天文思想影响了一千三百多年。16世纪，哥白尼（Nicolaus Copernicus）提出日心说（参阅Copernican system），象徵了现代天文学时代的来临。17世纪出现了几项重大进展：克卜勒发现行星运动原理，伽利略（Galileo）应用望远镜（telescope）於天文观测，牛顿建立运动定律和引力定律。19世纪，分光方法和照相术都用於天文研究，使天文学家能够研究所有天体的物理性质，从而导致天体物理学的发展。1927年哈伯发表宇宙膨胀论。1937年完成第一座无线电望远镜。1957年苏联发射第一颗人造卫星「史波尼克」（Sputnik）号。1960年代展开第一次深入太空探测（参阅Pioneer）。亦请参阅cosmology、infrared astronomy、radio and radar astronomy和ultraviolet astronomy。
English version：
astronomy
Science dealing with the origin, evolution, composition, distance, and motion of all bodies and scattered matter in the universe. The most ancient of the sciences, it has existed since the dawn of recorded civilization. Much of the earliest knowledge of celestial bodies is often credited to the Babylonians. The ancient Greeks introduced influential cosmological ideas, including theories about the earth in relation to the rest of the universe. Ptolemy's model of an earth-centered universe (2nd century AD) influenced astronomical thought for over 1,300 years. In the 16th century, Nicolaus Copernicus assigned the central position to the sun (see Copernican system), ushering in the age of modern astronomy. The 17th century saw several momentous developments: Johannes Kepler's discovery of the principles of planetary motion, Galileo's application of the telescope to astronomical observation, and Isaac Newton's formulation of the laws of motion and gravitation. In the 19th century, spectroscopy and photography made it possible to study the physical properties of planets, stars, and nebulae, leading to the development of astrophysics. In 1927 Edwin Hubble discovered that the universe, hitherto thought static, was expanding. In 1937 the first radio telescope was built. The first man-made satellite, Sputnik, was launched in 1957, and the first deep-space probes (see Pioneer) were launched in the 1960s. See also big bang, cosmology, gamma-ray astronomy, infrared astronomy, radio and radar astronomy, ultraviolet astronomy, X-ray astronomy.