If there is only one “eye in the sky” in the world

There were two “big eyes” on the earth, and human beings used them to explore the unknowns and mysteries in the galaxy of the universe. Unfortunately, a sudden news caused a shock in the world of astronomical exploration-on December 1, 2020, the National Science Foundation (NSF) confirmed that Puerto Arecibo, one of the “two big eyes” of the earth (Arecibo) The radio telescope collapsed and it can no longer be used. From now on, the important task of walking side by side with humans will fall on the other “big eye”.

The remaining “big eye” is called FAST (Fivehundred-meter Aperture Spherical radio Telescope), short for “500-meter spherical radio telescope”. In 1994, the FAST project concept was proposed. After 22 years of construction, it was put into use on September 25, 2016; on January 11, 2020, FAST passed the national acceptance and was officially put into operation.

FAST is located in Kedu Town, Pingtang County, Qiannan Buyi and Miao Autonomous Prefecture, Guizhou Province. It is located in a karst crater called Dawodang. It is far away from cities and people, surrounded by green trees and green mountains. At present, it is the largest single-aperture radio telescope in the world. It consists of 4,450 reflector units and covers an area of ​​about 250,000 square meters. It has a receiving area equivalent to 30 standard football fields.

In order to install this giant “sky eye”, scientists can be described as painstakingly. They led a team across the large and small mountains and ridges in the southwestern region of the motherland and surveyed the site with the help of local residents. After rigorous multiple surveys and screenings, the karst crater located in Guizhou Province was finally elected as the “eye socket” of this huge “eye of the sky”. There are three main reasons for choosing the site of “Dawotai”: First, its topography is closest to the shape of FAST. The surrounding three peaks are in a “three-legged” trend. The distance between each is about 500 meters, and the middle is about 500 meters. The topography of the depression resembles a natural “pot rack”, which can just steadily set up the “cauldron” of FAST, so the amount of excavation is relatively minimal; the second is that the karst geology here can ensure that rainwater penetrates into the ground. Rainwater is silting up and damages the telescope; third, the working principle of the radio telescope is to use electromagnetic waves with a frequency lower than visible light, which requires a “static soil” to avoid interference from other wireless signals. And there is no town within 5 kilometers of Tai Wo Tai, which is an excellent site.

A radio telescope is not an ordinary telescope for observation with the naked eye. It is the basic equipment for observing and studying radio waves from celestial bodies, and it is the world’s top space telescope. However, if you want to understand what a radio telescope is, you must first figure out what a radio telescope is. Radio generally refers to wireless, electromagnetic waves that can propagate in all free spaces (including air and vacuum). The radio telescope is similar to the “antenna pot” that receives satellite signals. It can focus on the spherical reflection of the bottom of the pot and gather signals from several square meters to thousands of square meters on a single point. Therefore, the larger the area of ​​the “pot”, the stronger the gathered signal, and the farther and weaker signal can be detected.

Nan Rendong, chief scientist and chief engineer of the FAST project of the National Astronomical Observatory of the Chinese Academy of Sciences, once said: “The universe is mixed with various radiations, and distant signals are like cicadas in thunder. Without super sensitive ears, they can’t be distinguished at all.” And FAST serves as the “eyes” and “ears” for the earth to explore the universe.

So, what exactly can this “eye of heaven” “see”? Can you see aliens? In fact, the “Sky Eye” is more built for exploring the pulsar signals of the universe. In theory, FAST can receive electromagnetic signals 13.7 billion light-years away, which is close to the edge of the universe. At the same time, FAST’s function of receiving cosmic pulse signals is also extremely sensitive. This can be used to achieve large-area, high-density astronomical observations, including patrolling neutral hydrogen in the universe, observing pulsars, detecting interstellar molecules, and searching for possible interstellar communication signals. And so on, to provide coordinates and point out the direction for the exploration of the universe. But in this process, the “eyes of the sky” will only receive signals from the universe, and will not output any information from the earth, so there will be no “talking” with the “aliens”.

Since it was officially put into operation, FAST has achieved extraordinary results. As of November 2020, its observation service has exceeded 5,200 machine hours, which has reached nearly twice the expected design goal; cumulatively discovered more than 240 pulsars; based on observational data published high There are more than 40 level papers. Recently, in the international scientific journal “Nature”, FAST has successively published research results on fast radio bursts. In the long river of history, mankind has never stopped exploring the mysteries of the universe. China’s “Sky Eye” will be opened to the world and become the “Earth Eye”, continuing to explore the mysteries of the origin, evolution and unknown of the universe for mankind.