[导入]Unit 1 Astronomy, space exploration [Article 1 introduction]

Unit 1 Astronomy, space exploration

Article 1 introduction

Reading assignment

1. What does astronomy deal with?
2. What does astrophysics deal with?
3. Please list the names of some spacecraft.

　　Astronomy Astronomy is the science that deals with the origin, evolution, composition, distance, and motion of all bodies and scattered matter in the universe. It includes astrophysics, which discusses the physical properties and structure of all cosmic matter.

　　Until the invention of the telescope and the discovery of the laws of motion and gravity in the 17th century, astronomy was primarily concerned with noting and predicting of the positions of the Sun, Moon, and planets. The catalog of objects now studied is much broader and includes, in order of increasing distances, the solar system, the stars that make up the Milky Way Galaxy, and other more distant stellar objects and galaxies. With the advent of scientific space probes, the Earth also has come to be studied as one of the planets, though its more detailed investigation remains the domain of the geologic sciences.

　　During the 20th century astronomy has expanded to include astrophysics, the application of physical and chemical knowledge to an understanding of the nature of celestial objects and the physical processes that control their formation, evolution, and emission of radiation. Study of the nuclear reactions that provide the energy radiated by stars has shown how the diversity of atoms found in nature can be derived from a universe that originally consisted exclusively of hydrogen. Concerned with phenomena on the largest scale is cosmology, the study of the evolution of the universe. Astrophysics has transformed cosmology from an almost purely speculative activity to a modern science capable of predictions that can be tested.

　　In spite of its great advances, astronomy is still subject ot a major constraint; it is inherently an observational rather than an experimental science. Almost all measurements must be performed at great distances from the objects of interest, with no control over such quantities as their temperature, pressure, or chemical composition. There are a few exceptions to this limitation -- namely, meteorites, rock and soil samples brought back from the Moon, and interplanetary dust particles collected in or above the stratosphere. These can be examined with laboratory techniques to provide information that cannot be obtained in any other way. But much of astronomy appears otherwise confined to Earth-based observations.

　　Space exploration Space exploration is the investigation, by means of both manned and unmanned spacecraft, of the reaches of the universe beyond the atmosphere of the Earth. Spaceraft, vehicles that operate above the Earth's atmosphere, include sounding rockets, Earth satellites, and lunar, planetary, and deep space probes.

　　 On October 4,1957, the Soviet Union launched the world's first artifical satelite, Sputnik 1, and set in notion a series of programs of space exploration. The first U.S. satelite, Explorer 1, was launched on january 31, 1958, not quite four months after Sputnik 1. Both nations participated during the next decades in a space race, with more than 5 000 sucessful launches of satelites and space probes of all varieties: scientific research, communications, meteorological, photographic reconnaissance, and navigation satelites, lunar and planetary probes, and manned space flights. The Soviet Union launched the first man into orbit around the Earth on April 12, 1961. On July 20, 1969, the United Sates landed two men on the surface of the Moon. On April 12, 1981, the 20th anniversary of manned space flight, the United Sates launched the first reusable manned vehicle, the space Shuttle.

　　Many of the spacecraft, such as manned and reconnaissance vehicles, are designed for recovery. Most operational satelites become inert after a few months or years of operation. The North American Air Defense Command (Norad) keeps a constant watch on the thousands of objects of human orgin circling the Earth in a variety of orbital paths. Both radar and optical telescopes are used.

　　For some years the launching of spacecraft was limited to the United States and the Soviet Union. The reason was that the rocket-powered launch vehicles ware based on long-range ballistic missiles. which only these countries had developed. France was the third nation to launch a satelite (1965), followed by Japan (1970), the People's Republic of China (1970), and the United Kingdom (1971), under the auspices of the European Space Agency (ESA), the nations of western Europe developed their launcher during the 1970's to assure themselves of independent launch capability.

 

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