According to Professor Huang Yongfeng from the Institute of Astronomy at Nanjing University, there are currently three ways to search for extraterrestrial civilisations. The most common is to try to catch signals or radio emissions from an extraterrestrial civilisation. Even if the celestial body is far from the Earth, its radio emissions can reach the planet, and we can receive radio signals with radio telescopes.
"Celestial bodies, such as the Sun, the Moon, planets and stars, can generate radio emissions. The telescopes used by astronomers to receive this radiation are called radio telescopes", he said.
Moreover, providing that extraterrestrial life does exist, they can transmit signals to us.
"FAST can study radio signals from space, or those coming from the bowels of the planet. However, the intensity of these signals’ radio emissions is very high, so it’s quite difficult for us to find which of the many signals are traces of extraterrestrial civilisations. Nevertheless, the difference in signals can tell us whether extraterrestrial life exists. Radio waves emanating from artificially created objects differ from natural radiation, etc."
Today, this method is considered the most practical and accurate, this is exactly how the Chinese FAST telescope works.
There are dozens of various radio telescopes in the world, while Puerto Rico's Arecibo and the Chinese "celestial eye" FAST are considered the most promising projects.
"By far, the world’s most famous project to study extraterrestrial life is the SETI @ home project (a scientific nonprofit voluntary computing project on the BOINC platform, created by the SETI Research Centre at the University of California at Berkeley). It uses the Arecibo radio telescope to detect radio signals emitted by celestial bodies. However, the data observed by the Arecibo radio telescope has failed to find any concrete evidence confirming the existence of alien signals".
The FAST telescope was officially put into operation on 11 January 2020. But back in 2016, its sensitivity was 10 times higher than that of the former record holder, the Arecibo Observatory. After the project had been improved, a network of 10 extra 30-to-50-metre-diameter telescopes was deployed around the main one. Thanks to the innovations, FAST has become six times more sensitive and can now work 19 times faster.
"Compared to the Arecibo radio telescope, FAST really has advantages due to its large size. It’s a very good device to find extraterrestrial life forms. However, given that a lot of work has been done with Arecibo, which failed to detect a single confirmed signal of extraterrestrial life, we cannot expect a breakthrough in the FAST telescope in the short term. Some progress will be made in the future, especially in the search for aliens, but for now we need to wait for some results".
Over the course of its operation, FAST has discovered about 102 new pulsars, unidentified radio emission sources coming to Earth in the form of recurrent bursts.
There is another method that is quite demanding in terms of technology and resources, so it doesn’t justify itself at this stage of development. This method proposes sending spaceships with information about our civilisation, videos, and graphic diagrams, to search for extraterrestrial life.
"Such spaceships must have high speed to reach the solar system's limits and go to the nearest stars. So, extraterrestrial civilisations can intercept this object, a kind of 'visiting card' from Earthlings. However, it will take 4.2 light years to reach the nearest star".
The third way is to send radio signals to planets, which, we assume, could be inhabited, hoping that one day they will respond.
"If sapient life exists, it can intercept these signals. But even if they are intercepted, decoding and restoring the information we send will be quite difficult".
However, many supporters of “conspiracy theories” believe that if the signal reaches a civilisation that is superior to us in development, they will attack our planet. And then the scenario of the Chinese bestseller “The Three-Body Problem” by Liu Cixin could unfold on Earth. (The book talks about the first contact between Earthlings and an alien civilisation and its unpleasant consequences. In 2015, the author was awarded with the prestigious Hugo Prize for best science fiction novel).
The Pentagon has recently added fuel to the fire by publishing videos of UFOs that the US Air Force allegedly managed to record. However, Huang Yongfeng doesn’t consider the release of these videos as evidence of the existence of aliens:
"These so-called UFOs are hardly a manifestation of extraterrestrial life. Of course, I have no doubt that other life forms exist in the galaxy or planets of the universe. But the main problem is that even if there is life somewhere in the galaxy, due to the great distance between us, the probability that another civilisation will reach Earth is very small. I personally prefer to think that these UFOs could be atmospheric or natural phenomena, artificial flying objects, hallucinations or even artificially created hype content".