Radio signals unlikely to be extragalactic aliens saying 'hi'

Gou Lijun, a research professor at the National Astronomical Observatories, Chinese Academy of Sciences

Fast Radio Bursts are a rather new concept in astronomical studies. It was discovered by accident in 2007 from the SMC archival data by Professor Duncan Lorimer at West Virginia University. Afterwards, within the following five years astronomers did not detect any more, and started to doubt their existence. Until 2012, when another FRB was finally observed, the doubt finally disappeared. Although dozens of events have been observed, astronomers still have no idea about the cause of the events.

Yuan Lanfeng, an associate professor at University of Science and Technology of China

On micro blogs and other social media platforms, readers have been associating the signal with the famous science fiction The Three-body Problem, in which the Earth replied to a signal from the space and faced the threat of invasion from the latter. That's why many readers jokingly write "Don't answer!" three times on micro blog, which is a famous scenario of the novel.

Their concern is understandable. However, even if you hope to answer the signal, there is no way of doing that with our current technology.

Yu Jun, a senior editor on space at pop-science website guokr.com

The long distance means a high attenuation rate. In other words, the burst at the origin of the signal must be extremely powerful so that we can receive it. There is no way to calculate the exact amount of energy needed this time, but we can compare it to the sun: It is like bursting out the energy radiated by the sun for dozens to tens of thousands of years within 0.01 second.

Since the discovery of the first FRB in 2007, humans have only observed about 60 of them. As a result of insufficient observation data, there is no confirmed theory on what phenomenon produced them.

However, considering the extremely high amount of energy they need, the number of "suspects" is limited, too. According to existing theories, there are at least several possible causes of FRBs, such as the merging of black holes or neutron stars, hyperflares of magnetars, especially energetic supernova, or the collapse of the magnetospheres of Kerr–Newman black holes.

Strictly speaking, the possibility of a super extraterrestrial civilization sending such a signal cannot be excluded, but the possibility is really low considering the high amount of energy needed. Besides, there is no evidence leading specifically to this possibility. So there is no need to exaggerate it.