Exclusive! How mysterious is the FAST telescope that the media has been speculating about?

Recently, foreign media said that China plans to build the world's largest caliber radio telescope in Guizhou in order to find extraterrestrial life, and said that "according to scientific requirements, the super astronomical telescope will generate electromagnetic waves, which will have an impact on human health. Residents have to move 5 kilometers away. " In fact, foreign media refers to the world's largest single-aperture radio telescope-the 500-meter spherical radio telescope (FAST). This project is located in Jinke Village, Kedu Town, Pingtang County, Guizhou Province, China. What is a radio telescope? Is it really used to find aliens? The generated electromagnetic waves are harmful to human body? The correspondent of "Knowledge is Power" interviewed the FAST Engineering Office of the National Astronomical Observatory of Chinese Academy of Sciences exclusively. Your doubts may be answered here.

The world's largest single-aperture radio telescope is like this.

Doubt 1: Why do you want to do the FAST project?

Zhili: When it comes to telescopes, we are no strangers. It can bring distant scenery closer to our eyes and make people see it more clearly. Now everyone is familiar with the optical astronomical telescope, but what is the radio telescope?

Office of Rapid Engineering: As we know, light and radio and television signals are electromagnetic waves that travel at the speed of light, and the difference is only in wavelength. For thousands of years, human beings have only observed the universe through the visible light band, while the radiation of actual celestial bodies covers the entire electromagnetic wave band. Radio emission is the radiation of celestial radio band (wavelength 3000m ~ 0.3mm). It can be said that this discovery has created a new era of studying celestial bodies through radio waves. Why do you say that? Because radio waves can penetrate a large number of interstellar dust substances existing in the universe, but light waves can't, radio telescopes can observe more distant unknown universe through interstellar dust and have a deeper understanding of the known interstellar world. Radio waves are basically unaffected by light and weather, and radio telescopes can work almost all day.

The basic structure of radio telescope includes directional antenna for collecting radio waves, high-sensitivity receiver for amplifying radio signals, information recording, processing and display system, etc. The radio signals of celestial bodies in space are extremely weak, and the energy collected by all radio telescopes in the past 70 years can't turn a page. In order to get more information about cosmic objects, it is necessary to design the aperture of the radio telescope as large as possible. However, due to the deformation caused by self-weight and wind, the maximum aperture of the traditional full-motion telescope can only reach 100 meter.

Zhili: Compared with other international radio telescopes, what are the advantages of China FAST radio telescope?

FAST Engineering Office:1At the end of 995, led by Beijing Astronomical Observatory (now National Astronomical Observatory) of Chinese Academy of Sciences, more than 20 universities and research institutes in China set up the China Promotion Committee of Radio "Large Telescope", and put forward the concept of "karst project" to construct spherical reflector by using karst depression in Guizhou, China. After learning from the experience of large foreign radio telescopes, astronomers in China further promoted the concept of "karst engineering" and proposed to build the world's largest single-aperture radio telescope-a 500-meter spherical radio astronomical telescope. Compared with similar large-aperture radio telescopes, it has three unique independent innovations:

1. Using natural karst potholes in Guizhou as the site greatly reduces the cost of telescope engineering;

2. Thousands of units are laid in the pit to form a 500-meter spherical cap active reflector, and the spherical cap reflector forms a 300-meter instantaneous paraboloid in the direction of radio power supply, so that the telescope receiver can focus like a traditional paraboloid antenna;

3. The high-precision positioning of telescope receiver is realized by using optical cable traction mechanism and parallel robot. Brand-new design ideas and unique site advantages enable FAST to break through the 100-meter limit of radio telescopes and create a new mode of building giant radio telescopes.

Its receiving area is equivalent to 30 football fields and it will be the largest single aperture telescope in the world. Compared with Bonn 100 meter telescope, which is known as "the largest machine on the ground", the sensitivity is improved by about 10 times. Compared with the American Arecibo 300-meter radio telescope, which was listed as the first major project in the 20th century 10 before Apollo landed on the moon, its comprehensive performance was improved by about 10 times. As the largest single-aperture telescope in the world, FAST will maintain its position as a world-class equipment in the next 20 to 30 years.

Doubt 2: Why is FAST located in Guizhou? The generated electromagnetic waves are harmful to human body?

Zhili: Guizhou is mountainous. Why is FAST located in Dawodang, Guizhou? What impact will the construction of FAST have on the local environment?

FAST Engineering Office: The reason why we chose "Dawodang" as a natural giant mountain depression is because the construction of FAST requires the use of natural potholes, which are only developed in karst areas. Since 1994, the project team has carried out multidisciplinary site evaluation in karst areas in southern Guizhou. A preliminary evaluation is made from the aspects of physical geography, controlling factors of landform development, morphological characteristics of depressions, hydrogeology, engineering geology, meteorology and radio wave environment. Many experts at home and abroad, including two former directors of Arecibo Observatory, have visited the FAST pre-selection area, and experts from the FAST project team have also visited Arecibo in 1999. Everyone agrees that the depression in Guizhou preselection area is unique in the world as the location of large spherical radio telescope.

Among these numerous depressions, we selected 400 depressions as candidates and input their data into the database. Then, according to the excavation volume, sealing degree, opening angle, radio wave environment, traffic, earthquake, hail and other conditions, Dawodang depression in Pingtang County, Qiannan Buyi and Miao Autonomous Prefecture, Guizhou Province was selected as the location of FAST. The slope here is stable and the rock has enough bearing strength; Karst geological conditions can ensure that rainwater penetrates underground and will not be deposited on the surface to damage and corrode the telescope; No record of major natural disasters; There is no township within 5km of Fiona Fang near Dawodang, and there is only one county within 20km of Fiona Fang. /kloc-the monitoring of radio interference environment for more than 0/0 years shows that Dawodang radio wave environment is quiet, accessible and isolated, and the radio environment is the most ideal. In addition, there are a number of electronic industrial enterprises in Guizhou, which have the production capacity of manufacturing large-scale radio antennas, convenient transportation and sufficient water and electricity, providing a superior engineering environment for rapid construction.

Because the main function of FAST project is observation and research, environmental factors are relatively simple. In addition, FAST has no electromagnetic pollution to the surrounding environment, and the project has no sensitive pollution links. During the operation of FAST, hundreds of technicians will work and live in the site area. We analyzed and thought about the treatment of domestic sewage and garbage. Domestic sewage is discharged up to standard after being treated by sewage treatment facilities, and domestic garbage is regularly collected and transported to Pingtang County garbage treatment station for unified treatment.

Zhili: When will such a huge FAST be completed?

FAST Engineering Office: Since the establishment of the FAST project, it has experienced intense research and experiments. By 20 16, the telescope system will be adjusted. At present, resettlement houses at four points, including Laoyanjiao, Kedu Town, Pingtang County, are under construction, and the whole project is expected to be completed in September 20 16.

The FAST project is a combination of scientific research and engineering. Without ready-made specifications and mature technology, every step is very groundbreaking. In building technology, we have been studying new materials and technologies. For example, due to the requirement of cable fatigue, a special steel cable exceeding the national standard has been developed; The optical fiber that transmits the cosmic radio signal received from the feed to the terminal processing equipment is always in a bending state because the feed is always moving, so this new type of optical fiber is independently developed. It can be said that the development and construction of FAST reflects China's independent innovation ability, and will also promote the development of China in many high-tech fields such as antenna manufacturing technology, microwave electronics technology, parallel robot, large-scale structural engineering, and high-precision dynamic measurement within a kilometer.

Doubt 3: Is FAST built to find extraterrestrial life?

Zhili: Is FAST really built to find extraterrestrial life?

Office of Rapid Engineering: Its function goes far beyond this. Generally speaking, the completed FAST will provide opportunities for discovery and breakthrough in many fields of basic research such as large-scale physics of the universe, deep structure and laws of matter, and will also play an irreplaceable role in solar-terrestrial environmental research, national defense construction and national security.

Main functions of FAST project

Zhili: Besides scientific research, what role will FAST play in popular science?

FAST Engineering Office: The construction and operation of FAST will promote the economic prosperity and social progress in western China, which is in line with the overall strategy of national regional development. With FAST, the remote and isolated karst mountain area in southern Guizhou will become a world-renowned international astronomical academic center and a new window to show Guizhou to the world. In addition, the National Astronomical Observatory also cooperates with local universities such as Guizhou University and Guizhou Normal University to jointly cultivate technical talents, increase local higher education and strengthen educational resources. In addition, the astronomical popular science base with FAST as the main body will promote the popular science work in China, stimulate young people's enthusiasm for astronomy and science, and publicize it to the public and decision-makers to serve the long-term strategic goal of rejuvenating the country through science and education.

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(This article comes from the article "Fast: Eyes with a Diameter of 500 meters" published by Knowledge is Power magazine in July 20 14, which was exclusively edited by Zhili. Scientific Consultant: Quick Work Office, original works, please indicate that it comes from knowledge is power WeChat official account).