Is there anybody out there?

DAVID HAMBLING wonders if geeky mathematical messages are going to get the aliens’ attention

Scientists have been scanning the heavens for alien radio signals for decades [ FT346:16], but the Search for Extra-Terrestrial Intelligence (SETI; see FT157:42-46) has only yielded one tantalising hit, and that was 40 years ago. More recently there has been growing excitement around whether the dimming of a stellar object known as Tabby’s Star indicates alien activity [ FT348:14]. In the last few months scientists have gained some surprising new insights relating to both of these, and to the quest for alien life in general.

In August 1977, the Ohio State University’s SETI program picked up a powerful signal at 1,420 MHz, the hydrogen band where alien communication seemed most likely. Astronomer Jerry Ehman wrote “Wow!” on the printout, and the radio telescope was swiftly pointed at the area of the sky where the signal had originated, but nothing else was ever received.

Researchers from the Centre of Planetary Science now claim that a comet may have been the source. Comets carry a hydrogen cloud that might emit radiation on the hydrogen frequency, and two comets, both undiscovered at the time, were passing through the area being scanned. Astronomical observations early this year confirmed comets can emit on exactly the right frequency, and they are a moving point source, so if a radio telescope is even one degree out it will see nothing. The moving comet will show up as a brief, elusive, intense signal. This now looks like the best explanation for the “Wow!” signal.

Meanwhile there has also been further study of Tabby’s Star. This had showed a pattern of dimming that doesn’t fit with normal astronomical objects (such as comets and asteroids) passing in front of the star. Some suggested that the shadows were cast by colossal alien building work – a megastructure encompassing Tabby’s solar system.

Fernando Ballesteros and colleagues at the University of Valencia in Spain have recently suggested an alternative solution, although it may seem just as far-fetched. Their theory is that the initial dimming in 2011 was the result of a huge ringed planet, like a giant alien version of Saturn, partially eclipsing Tabby’s Star. The tilt of the rings might produce the sort of asymmetric dimming which was observed. After that, the 2013 dimming may have been caused by a vast swarm of asteroids trailing in the giant planet’s wake, just as Jupiter pulls the Trojan asteroids after it in our Solar System.

Finally, the latest, comparatively minor dimming event might have been caused by the ringed planet passing behind Tabby’s Star. When this happens, light reflected from the planet is invisible to us, and the overall brightness of the star system is reduced.

Ballesteros’s model does not require any bending of laws of physics. Furthermore, it predicts there will be another dimming event in 2021 as the alien Saturn swings around again. Testable predictions are one of the hallmarks of good science. If these latest theories are correct, then SETI seems to be getting nowhere and there are no traces of aliens out there. As physicist Enrico Fermi famously asked in the 1940s: “Where is everybody?” One possibility is that there are no aliens, at least not technologically advanced ones who wish to communicate. The chances of life developing, or intelligence evolving from life, may be much less than scientists assume.

Another suggestion is that we are simply listening to the wrong thing. Radio broadcasts on the hydrogen frequency might seem obvious to us, but as the recent comet discovery revealed, such signals may have more than one cause. Aliens might prefer to communicate via neutrinos, a technology which we have yet to master, or via what scientists term “Zeta rays” – forms of radiation that we do not even suspect. If this is the case, then it is just a matter of a few hundred or thousand years before we develop suitable technology and then we will be able to tune in.

However, the problem may not be one of technology. In a recent exercise René Heller of the Max Planck Institute created an imitation alien message of some two million digits. It included within it the first several hundred prime numbers, which were important to decoding the rest of the message: a selfie of an imaginary alien and some FAQ on their size, lifespan and the location of their homeworld.

Heller received over 300 responses to this SETI Decrypt challenge, with 66 giving completely correct answers to the six questions he posed about the message contents. Heller’s message contains information that SETI geeks might find interesting, but is not representative of messages sent by any other community on Earth.

SETI appears to be looking for messages from people exactly like those who set up SETI on Earth, a small essentially white, male middleclass scientific subculture. To many people music or art may seem more universal forms of communication than mathematics. There is an assumption that aliens would have developed their technology through a similar route to us, and would necessarily have come across the same sort of mathematics along the way. This may not be the case.

Also, a signal may not be sent out for the benefit of the recipients. To the people who paid for the Apollo program, the scientific achievement was irrelevant: what mattered was putting an American flag on the Moon. Beaming out the national anthem to claim alien civilisations may be more important than making the message intelligible, and it is hard to see Donald Trump or Vladimir Putin funding an alien contact effort unless there was an advantage to be gained.

We may not have heard from aliens because they are too different from us and communicate in different ways. But it may also be because they are just like us. Aliens may not be sending out signals because there is simply not enough profit to be had out of longdistance messaging which, after many decades, is only likely to get a reply from a collection of alien geeks with an obsessive interest in prime numbers.