Even the most optimistic dreamer acknowledges that it will be some time, at best, before humans or our robot emissaries are capable of reaching the nearest stars. What treasures and dangers await out there among our stellar neighbors, we may not know for millennia. But there is a way we might contact alien civilizations, without having to solve the insurmountable problems of interstellar travel: radio.  

"What did you expect, a booming voice from the sky?" But a voice from the sky is exactly what you found Dr. Arroway ...--Contact

So we've been listening, with greater sophistication, for a few decades. Maybe we're looking in the wrong places. Perhaps we lack the requisite technological sensitivity. It may be that radio is not the preferred medium for communications among potential ETs. Maybe there is no preferred medium, or perhaps it's gravity waves, or wormholes. Or maybe quantum entanglement links are whisking galactic gossip around at superluminal velocities. It might be that alien civilizations are rare, or perhaps we're alone in all the cosmos. More likely, it's something we haven't an inkling about. But for whatever reason, so far, no booming voices from the sky.

To explore the possibility of why ETs may not use radio, or aren't motivated or capable of interstellar travel, we cannot rely on science; we have no examples of real aliens to draw upon. For that, we have to turn to science-fiction and engage in speculation. And, with the help of three talented Kossack artists, that's exactly what this Science Friday is all about. So look out, large images of bizarre aliens below!

The most likely, practical source of an ET signal, we think anyway, would come from a program like the Search for Extra-Terrestrial Intelligence or SETI.

The WOW Signal was a strong narrowband radio signal detected by the astrophysicist Jerry R. Ehman on August 15, 1977 while working on a SETI project at the Big Ear radio telescope of Ohio State University. The signal bore expected earmarks of potential non-terrestrial and non-solar system origin. It lasted for 72 seconds and has not been detected thereafter. All subsequent searches for a signal in the same location have been unsuccessful, both by J. R. Ehman and others. The nature of the signal is therefore unknown and only a few possibilities can be considered.

The handful of candidate signals we've detected over the last several decades have never repeated. If there are alien civilizations out there, why might they avoid using radio, or be incapable of doing so?

Illustrations by Carl Buell. Left: A Pierson's Puppeteer and on the right their sexual surrogate species, a scoop-snout. Puppeteers are intelligent ETs from Larry Niven's Known Space series. The sexual prey is used to incubate puppeteer embryos, which grow inside the scoop-snout like the larvae of a digger wasp

Puppeteers are intelligent, but highly xenophobic and paranoid by human standards. In the Known Space series, only puppeteers who are considered dangerously, clinically insane will even interact with other species. Any alien culture with that kind of psychology might be smart enough to infer that other intelligent creatures exist in the universe, and worried enough to avoid any activity that would draw unwanted galactic attention.

Space Squiddie by graphic artist S. M. Breen. From a distance, the squiddie looks like a giant sail dozens of miles across. The relatively tiny, payload-like body, on the right, is only visible on close-up. For more squiddie detail, see the enlarged version here

Dreamed up by yours truly and illustrated by graphic artist S. M. Breen, the space squiddie is the ET equivalent of a siphonophore; it's composed of several different organisms living in close symbiosis. With out getting too long winded, my fictional squiddie evolved in a ring system created by the gravitational interaction between binary stars. Over time, the ring has been transformed by living organisms from dust, gas, and small comets, into a rich ecosystem where various biological components subsist off each others waste products and sunlight.

The eccentric orbit of a smaller star over a period of several centuries causes long lasting `seasonal' fluctuations in the ring's discrete zones. The squiddie have learned to migrate from one area to another. The retractable and expandable canopy acts as stomach, eye, ear, and even 'legs' for the squiddie. It contains capillary systems which collect and distribute chemical substances collected from the ring as well as electricity generated by sunlight. The great sail also focuses incoming radio and optical wavelengths onto sense stalks facing inward on the payload body; this guy has a built in optical and radio telescope with a collecting dish miles across and a super Doppler radar option to boot. The squiddie 'talk' with ultra low frequency radio waves amplified and received by the sail. Without a similar sized device, humans would never detect signals at those wavelengths.

Life moves slowly in the ring. The squiddie are well on their way to intelligence, but given the lethargic pace they live at, their long lives, and sparse distribution in the ring, they evolve little over time. And equipped as they are, they have no need for human type technology.

(Enlarge greatly here, well worth the look!)

"QAX" by graphic artist Karen Wehrstein, who has her own Tip Jar: On a simmering ocean world, under an oversized blue-white star, the tendrils of one Qax reach out to the limb of another in the distance. The bluish sunlight is filtered and scattered to a pinkish orange by a dense blanket of CO2 spiked generously with hydrocarbon and sulfur compounds. Undersea volcanoes light up the horizon and belch more toxic gas into the air

One of the most imaginative aliens ever dreamed up are the Qax from Stephen Baxter's Xeelee Sequence. Qax biology is based around chemical hyper-cycles embedded in convection cells. A Qax is millions of such cells arranged on the sea surface in a branching pattern covering several miles. Each cell is as wide as a coffee can lid, languidly bubbling like chocolate with nested eddies down to the microscopic level; they're highly organized, living storms. Qax are creatures of turbulence, in the Xeelee series their descendants eventually learn to inhabit the atmospheres of gas giants, the surface of stars, and finally, the quantum turbulence of space-time itself, after humans wreck their star anyway ..

Beings like the Qax might experience little in the way of individuality by human standards. They live fast on turbocharged chemistry, individual collections break up as geothermal hot spots come and go. And they might consciously communicate complex ideas by sending out packets of convection cells, chunks of their own consciousness. Such limitations on environment, the ability to construct physical tools or the need to do so, along with the fleeting self awareness and shifting identity of a Qax-like critter, might limit their capacity or impetus for radio technology or space exploration.

Another image by S. M. Breen: A Cheela grazes across the surface of a neutron star on her hidden pseudopodia under an atmosphere of superheated plasma. The white eye-spots 'see' in x-ray and gamma wavelengths. Cheela are an intelligent race composed of degenerate matter in the sci-fi novel Dragon's Egg. This gal is smaller than a grain of rice and flat as a pancake, but she might weigh a ton on earth (Enlarge)

Creatures living a world smashed by gravity into a de facto two-dimensional landscape, like the surface of a quark or neutron star, or in the core of a large star, might have a biology based on nucleons rather than molecules; molecules could not exist in the billion g-force, superheated environment. Such entities would plausibly experience the passage of time millions of time faster than we do. It's tough to imagine how they could ever leave their home or craft machines that can do so. Any objects made of degenerate matter, be they artifacts or the Cheela bodies, would come apart faster than a fissioning critical mass if deprived of the enormous gravitational pressure on the home "world".

And in the event they did manage to explore space or use radio, would they even perceive us? From their vantage, humans, planets, or rocks, would be as diffuse as interstellar gas clouds are to us, and about as static. We would be bizarre theoretical objects, composed of strange flimsy material held together by fragile electron clouds. Not to mention a lightning fast civilization like this could develop, become technical, and go extinct, in a single, lazy summer afternoon.

All this is speculation as to why some aliens might not use radio or engage in space exploration or even care about us, if they can perceive us at all. It's just a bit Friday fun. We have no evidence for ETs, intelligent or simple. This isn't science, its science-fiction. No doubt there will be those quick to point out that the creatures are fictional, the biology vague and problematic, the ecology's unlikely or impossible; all good points for discussion. All welcome here.

And yet, life on our world is not only incredibly diverse and tenacious, we keep finding it in places we previously considered not only sterile, but uninhabitable. If that is any guide, whatever aliens we may someday discover are likely going to be far more bizarre and exotic than anything even the most gifted human storytellers can conjure up.  Moreover, humans have almost no experience with the vast infinitude that stretches around us. We're a new species, traveling on the frozen rocky skin of a tiny pale-blue dot hurtling through an ocean of space and time. We've barely gotten our toes wet, yet. But our first eager--if crude-- vessels of mind, energy, and matter are already testing the waters near shore. And until those cosmic journey's are begun in earnest, who's to say what alien nightmares may someday materialize, or what dreams may come