Dave-Platt%LADC@SYSTEM-M (Dave Platt) (03/28/86)
There's an interesting science-fact article in the latest issue of Analog magazine that reflects on a possible solution to the Fermi paradox. The paradox is that we have no reliable data to indicate that Earth has ever been visited by another space-travelling species... and given that we're a young species on a relatively young planet in a rather young solar system (by galactic standards), perhaps we should have been visited or colonized by now. There are lots of possible explanations: the development of life is a rare occurrance; the evolution of an intelligent species is even rarer; interstellar travel is in fact impossible; etc. etc. The article in Analog (I forget the author's name, unfortunately) suggests another possible explanation... which, if true, indicates that tragedy may have stricken many space-travelling species before now. It has to do with high-energy cosmic ray particles... those whose point of origin lies outside of the solar system. This extra-solar cosmic radiation is so powerful that it will go straight through quite a few meters of rock or steel. If a high-energy cosmic particle hits your body directly, it will usually travel straight through, leaving a trail of fried cells behind it. Prolonged exposure to high-energy cosmic radiation is distinctly unhealthy; several years of exposure could probably do major, irrepairable damage to the central nervous system. If the particle hits an obstruction, however, it's likely to blast loose a shower of secondary particles (this is the origin of cosmic-ray showers in Earth's upper atmosphere), and the secondary radiation can do much more damage than the original particle. Recent astrophysical studies have suggested that most, if not all high-energy cosmics may originate from a single source... Cygnus X-3 (if I remember correctly). Cosmic-ray telescopes have been able to detect a direct flux of cosmic-ray particles from this source, and the amount of energy apparently available from this source indicates that it could be supplying most if not all of the higher-energy cosmics that can be detected from *any* direction. We don't know yet just what this source is... it may very well include a black hole and/or other exotic object(s). There's a strong suggestion that the physical configuration of this source may very well be rare (only this one has been detected) and quite possibly unstable (with a lifetime measured in centuries). So, it's possible that we're in the middle of a fairly unusual period in the history of our galaxy... a short-lived cosmic-ray siege that separates longer periods of "quiet space" untroubled by high-energy cosmics. Now... consider a species (or several) that evolve and develop to the point of having interplanetary (and possibly interstellar) travel, during one of the long "quiet" periods. If they were unaware of the possiblity of a siege of high-energy cosmic radiation, they might very well have built their spacecraft (and space colonies) to withstand the much lower levels of particle radiation that originate within their solar system(s). Normally, these levels are fairly low; they increase greatly during solar flare weather, but it would be possible to ride out such flare radiation in shielded compartments without too much trouble. Then, an object such as Cygnus X-3 slips into a short-lived phase in which it emits massive numbers of high-energy particles. A shell of high-energy radiation, perhaps a thousand light-years thick or more, moves outward from the source and throughout most of the galaxy; its leading edge moves just a hair below lightspeed. The radiation impinges on our hypothetical space-travelling culture, which has never experienced such a siege. Their solar-flare detectors begin to chatter, even though the suns are quiet; they begin seeing flashes of light as the particles burn holes in their retinas (or whatever they use to see with); they begin suffering the effects of neurological damage. Their ships aren't equipped with electrostatic or electromagnetic shielding of sufficient power to handle the onslaught of radiation; their colonies on the surfaces of moons, airless planets, and within small asteroids don't have enough feet of rock above them to protect the inhabitants. Within a generation, many of their space-based personnel and colonists have died or are suffering major illness from radiation poisoning. The home planet, and any colonies on planets with thick enough atmospheres, "pull in their horns" and revert to isolation... quite possibly accompanied by major collapse of their economic structures, which have become dependent on space. So, the answer to the Fermi paradox might be "They're out there, but they had a VERY bad experience when they tried space-travel, and decided to stay home and grow potatoes." If this scenario has actually occurred, then we (the human race) may be one of the very lucky species... since we're in the process of developing space travel during one of the relatively rare sieges of cosmic radiation, we're aware that it exists... and thus we can take precautions, such as placing colonies on Luna and Mars far enough underground. Disclaimers: I'm not an astrophysicist, and may very well have made eight outragous misstatements of fact in this summary (I'm working strictly from memory). For further information, see the latest issue of Analog, as well as an article that appeared in Scientific American within the last six months or so (it describes the detection of the cosmic-ray source in question).
dietz@SLB-DOLL.CSNET (Paul Dietz) (03/29/86)
When I realized what the author of that Analog article was proposing I was practically rolling on the floor with laughter. He didn't realize that only the *uncharged* particles from Cygnus X-3 travel in straight lines (and would form a shell); the charged particles (especially the lower energy ones that make up the bulk of cosmic radiation) are trapped by galactic magnetic field lines and diffuse through the galaxy for a few millions years, like nuclei in a magnetic fusion machine, until they run into something (mainly interstellar matter) or escape. A pulse of radiation added to this galactic reservoir will be tremendously smeared out. Charged cosmic rays hitting earth show no directionality anyway. It may be conceivable that planets near a Cygnus X-3 would receive lethal doses of radiation when the nearby source turned on. In that case, Earth may be have lucked out and never have been near such a source during its history. All the other potentially life bearing planets got zapped.