The origin of so-called 'Fast Radio Bursts' has remained a cosmic mystery since the first 'FRB' was detected in 2007. But while explanations have included phenomena such as colliding black holes and dark matter-induced collapse of pulsars, a new theory suggests that FRBs could, perhaps, be a sign of intelligent alien life.
In the newly posted arXiv.org paper "Fast Radio Bursts from Extragalactic Light Sails", distinguished physicist and cosmologist Abraham (Avi) Loeb and co-author Manasvi Lingam put forward the suggestion that FRBs could be "artificial beams which have been set up as beacons, or for driving light sails".
Currently, only 17 FRBs have been recorded... Despite the diversity of explanations advanced for FRBs, the possibility that they may be of artificial origin has not been investigated, except for a brief consideration in Luan & Goldreich (2014).
...[The idea that extraterrestrial civilizations may be using radio beams is certainly not a new one, as it dates back to the pioneering paper by Cocconi & Morrison (1959). This idea was quickly picked up and extended by researchers engaged in the Search for Extraterrestrial Intelligence (SETI)
...[S]ome of the major observables for FRBs are consistent with the idea that they may be manifestations of extragalactic beams. However, this still fails to answer the important question of why they exist in the first place.
The authors firstly consider the idea that FRBs might serve as ‘beacons’, meant to broadcast the presence of alien civilizations. However, given the massive power expenditure involved in creating the beam, they then suggest that perhaps it is more likely such high-powered beams might instead be employed to propel spacecraft to "mildly relativistic speeds" using light sails.
Entertaining this idea and working through the relevant equations, the researchers were surprised to find that the beam frequency that would be optimal to power a light sail falls within the range of FRB frequencies. Thus, they note, "it seems quite reasonable to hypothesize that the beams are being used to power light sails".
(Another conclusion was that the likely size of a light sail using Fast Radio Bursts for propulsion would have a mass of approximately 1 million tons - a value "extremely high by human standards" - suggesting that the spaceship involved would likely be an “interstellar ark” or “world ship” of sorts.)
If the theory sounds familiar, it might be because we humans are currently working on a similar idea (though on a much smaller scale). The Breakthrough Starshot project, funded by Russian entrepreneur Yuri Milner's $100 million investment in 2015, aims to send tiny space probes to our nearest star system at a fifth the speed of light, using light sails propelled by Earth-based lasers.
So it's perhaps worth noting that the research on this new FRB paper was "supported in part by a grant from the Breakthrough Prize Foundation for the Starshot Initiative", and also that Abraham Loeb is the Chair of the Advisory Committee for Breakthrough-Starshot.