What is astronomy?

Astronomy is the discipline of observing and studying celestial bodies in the universe. It studies the distribution, movement, position, state, structure, composition, nature, origin and evolution of celestial bodies, and is a basic subject in natural science. A remarkable difference between astronomy and other natural sciences is that the experimental method of astronomy is observation, through which all kinds of information of celestial bodies are collected. Therefore, the study of observation methods and means is a direction that astronomers strive to study. In ancient times, astronomy was also closely related to the formulation of calendars. Modern astronomy has developed into the science of observing all electromagnetic waves.

Astronomy is an ancient discipline with a history of at least several thousand years. Gu's "Rizhilu" has a cloud: "For more than three generations, everyone knows astronomy: July is a fire, and the words of farmers are also; Samsung is at home, and the language of women is also; The moon is gone, and the work of guarding the pawn is finished; Children's stories "[1]. Astronomy occupies a very important position in early human civilization. In ancient times, people determined the time and direction by observing the sun, moon and stars with naked eyes, made calendars and guided agricultural production, which was the earliest beginning of astrometry. On this basis, astrology was born, that is, predicting bad luck, natural disasters, winning or losing wars and personal destiny through the operation of celestial bodies.

In the 2nd century A.D., Ptolemy, an ancient Greek astronomer, put forward the geocentric theory that cosmic objects, including the sun, revolve around the earth. This theory was welcomed by the church and dominated the western society's understanding of the universe for more than 1000 years. /kloc-in the 6th century, Copernicus, a Polish astronomer, put forward a new theory of cosmic system-Heliocentrism. 16 10, Italian astronomer Galileo made astronomical observations with a telescope for the first time, observing sunspots, the surface of the moon, the planets' losses and the four moons of Jupiter. Newton, a famous British physicist, put forward the law of universal gravitation and founded classical mechanics, which promoted the birth of a new branch of astronomy, celestial mechanics, and made astronomy enter a new stage of studying the interaction and motion reasons between celestial bodies from simply describing the geometric relationship and motion of celestial bodies, which was a huge leap in the history of astronomy.

/kloc-The invention of astrophotography and spectral technology in the mid-9th century enabled astronomers to further study the physical properties, chemical composition, motion state and evolution law of celestial bodies, thus deepening the essence of the problem, thus resulting in a new branch of astrophysics. This is another leap in astronomy.

After the end of the Second World War in the 20th century, radio telescopes began to be widely used in astronomical observation, opening a new window of electromagnetic spectrum except visible light, and made new achievements called "Four Great Discoveries in Astronomy" (microwave background radiation, pulsars, quasars and interstellar organic molecules) in the 1960s. With the continuous improvement of human technology, space astronomy has developed rapidly. Humans can break through the barrier of the earth's atmosphere and observe celestial radiation in ultraviolet, infrared, X-ray, γ-ray and other bands outside the earth, and astronomy has entered a new era of full-band development. At the same time, new technology makes the aperture and resolution of ground-based telescopes continuously improved, from 4-meter, 5-meter and 6-meter telescopes to some 8-65 and 438+00-meter telescopes in 1960s. Together with space astronomical satellites, these telescopes have accumulated a lot of observation data and found active galactic nuclei, gamma-ray bursts, X-ray binaries, gravitational lenses, dark matter and dark energy.