I had a fascinating thought (to me anyway) today, which is more in the realms of science fiction than real science, but nevertheless entertaining.
It concerns the possibility of advanced, intelligent life, elsewhere in the Universe. Back in the early days of radio astronomy, and later with the SETI program, the consensus was that any alien civilization worth their salt would use radio signals to attempt to communicate with some unknown other civilization like ourselves, out there in the void. After all, radio signals are relatively easy to generate, albeit requiring some reasonably advanced technology to generate signals powerful enough to reach far off places with enough detectability for our perhaps primitive instruments.
With some excitement concerning periodic cosmic radio signals leading to the discovery of exotic stellar objects like pulsars, rather than the ‘Hello World’ of some advanced Galactic neighbor, the fascination with the search for extraterrestial intelligence using radio waves seems to have diminished a little.
My thought was as follows. Let’s suppose that a civilization much more advanced than ourselves has resolved to start trying to make contact with other civilizations. But let us suppose also that with this advancement comes a certain amount of inherit wisdom and the benefit of hindsight as to how other civilizations, perhaps less advanced than themselves, might be developing. Perhaps they know then, first of all, that such a civilization might still be embroiled in a culture fractured by religious schisms, war and instability, in which case they would be reluctant to assume contact should their sudden appearance cause shock and upheaval, potentially leading to the destruction of that civilization or at least causing one great religious war – maybe because they themselves almost reached that level of self-destruction at one stage in their development due to religious conflict. So, then, not to contact us too early, but how to know?
Maybe they also know, that the detection of radio waves is not necessarily the best sign of technological advancement. After all, radio waves were already discovered, studied, adapted and in use well before the age of computers, atomic weapons, the understanding of particle and nuclear physics. They might also know that at some point after the discovery and manipulation of radio waves our civilization would develop atomic then thermonuclear weapons, arriving at the stage where we have the ability to completely destroy the inhabitability of our own planet (having been there themselves), and would necessarily go through a century or so of equilibrating until the world had finally reached a peaceful and balanced enough stage to cope with signals from extraterrestial life.
Again, pure speculation, but they might also predict that we would have environmental problems due to the onset of the petrochemical age, the successor of an industrial revolution, that would go hand-in-hand with some of the developments needed for a nuclear age (assuming of course that these neighbors were also inhabitants of a class M planet once abundant in carbon-based fossil fuels).
Detecting our ability in advanced space travel could be one criterion for contact, such as the buried monolith on the Moon in Arthur C Clarke’s 2001 A Space Odyssey was meant to signal to the aliens who placed it there. But the aliens would have of course, have had to have been here.
So they scratch their heads (if they have them) and say ‘what signals could this civilization not detect and interpret until they are past the nuclear age, and at the stage where they have built up a physics-based model of the universe which is globally accepted by their population, such that they would be funded to build large enough projects to detect them?’
What about a beam of neutrinos, notoriously difficult to detect, requiring advanced knowledge of nuclear and particle physics, flavor-changing, industrial know-how for the huge-scale detectors? This is an option, however just like they would know that we knew about the existence of pulsars and AGN things that produce localized and periodic radio bursts, maybe they also know that we know about supernovae and other events that produce neutrinos. The same could be said of gamma rays, as we live in a constant swarm of them, bursts also coming from ‘natural’ events that we’re just discovering.
The one type of thing that might work, are ultra high-energy cosmic rays, such as those recently discovered (well, 1962) and now being studied by the Pierre Auger Observatory in Argentina, some of them seemingly from a localized source (as far as I have read). They would know that we know about the GZK cut-off. They would know that we would know the immense power required to accelerate these charged particles. Assuming that they themselves could build something powerful enough to accelerate particles to the 5 x 1010 GeV needed to exceed the GZK cutoff (but essentially giving them a ‘sphere of influence’), then these signals might be a great choice. This is pure science fiction of course, but it is interesting to entertain these suggestions. Building an accelerator some 7 million times more powerful than the LHC is no mean feat! (although the first accelerated beam nuclear physics experiment was performed on an accelerator some 8 million times less energetic than the LHC). However, if one day we actually harness some form of abundant energy, and eventually gain that capability, maybe a future Earth SETI program might involve firing ultra high-energy cosmic rays at class M planets and seeing if our ‘service is returned’!
Of course, the conventional hypotheses for the sources of these UHECRs include objects such as hypernovae, active galactic nuclei with supermassive black holes, or gamma ray bursts. However the alien explanation would make for a great sequel to Sagan’s Contact…..
