什麼是天文學

研究宇宙（universe）內所有天體和散佈其中的一切物質的起源、演化、組成、距離和運動的科學。天文學是一門最古老的科學，自有記載的文明之初就已出現。許多最早關於天體的知識往往被認為源出巴比倫人。古希臘人提出了多種對後世有影響的宇宙學概念，包含地球與宇宙其他地方的相關理論。西元2世紀，托勒密致力傳播宇宙地心說，這一天文思想影響了一千三百多年。16世紀，哥白尼（Nicolaus Copernicus）提出日心說（參閱Copernican system），象徵了現代天文學時代的來臨。17世紀出現了幾項重大進展：克卜勒發現行星運動原理，伽利略（Galileo）應用望遠鏡（telescope）於天文觀測，牛頓建立運動定律和引力定律。19世紀，分光方法和照相術都用於天文研究，使天文學家能夠研究所有天體的物理性質，從而導致天體物理學的發展。1927年哈伯發表宇宙膨脹論。1937年完成第一座無線電望遠鏡。1957年蘇聯發射第一顆人造衛星「史波尼克」（Sputnik）號。1960年代展開第一次深入太空探測（參閱Pioneer）。亦請參閱cosmology、infrared astronomy、radio and radar astronomy和ultraviolet astronomy。

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.