[ Pobierz całość w formacie PDF ]
.But with a coupleof caveats here and there, the evolutionary tale is very reliable.As inmost science, the overall story, the theory, is much stronger than anyindividual bit of evidence.That was just a tiny bit of the theory of evolution, which is made upof thousands of similar stories, all well attested and well tested.It bearslittle resemblance to the naive versions criticised by creationists.Therehas also been recent work on the mechanisms by which species change,and here it seems that there are various rather different systems at work,in different circumstances and for different kinds of organisms.Thereare lots of mathematical models, some of which have had manyvalidations from real life, while others have their being only in the mostfantastic realms of the imagination.Later we will explain how thesewell-established theories of the origins and evolution of life on thisplanet can illuminate the situations we may reasonably suppose to haveoccurred, or to be occurring, on other Earthlike planets in our galaxy.And in places that aren t planets at all.Lawrence Krauss s The Physics of Star Trek explained how the fantastic21WHAT DOES A MARTIAN LOOK LIKE?elements of that series could be achieved from science as we know it.We re not going to emulate that approach here, if only because mostfictional aliens can t be achieved from science as we know it.We are,however, going to use well thought-out examples from the SF literature not the film and TV stuff, by and large, because most of that is writtenby empty heads for empty heads  but novels that have extrapolatedterrestrial biological theory to extraterrestrial locations sensibly,credibly, and often excitingly.Even where there are large gaps in therealisation of the extraterrestrial scenario  and there usually are, likethe question of what Dune s sandworms eat  we will use theseexamples to discuss exactly these questions of credibility.We haveproduced some of such fictional scenarios ourselves, and Jack has spentmany years indulging in this almost-risk-free pleasure with many of thetop authors, who have wanted just that extra bit of credibility  ofmake-believe, in the best sense  in their stories.The authors he workswith do most of the writing, and they and the publishers take the risks:he suggests ideas for them to run with.Most of these fictional extraterrestrial scenarios have been puttogether by novelists with little biological background.Because therehas been much more publicity for the astrophysics, the authors haveoften bent the ear of a local astrophysicist or physicist to get a bit of helpwith orbits and things; occasionally they have asked chemists whetherparticular exotic atmospheres will  work.In contrast with these cleverbits of  real science, they usually have such a strong  feel for the biologythat they don t want to ask a biologist and complicate the situation.People, even novelists, think they  know about the biology.However,it seems that too many authors don t realise that it is possible to be sureand wrong; it feels just the same as being sure and right.So they juststart in on the story once they ve got the  science research  by whichthey mean the physics  right.They assemble a cast of more-or-lesshumanoid  folk aliens (six fingers, two hearts, copper-based blood),which are more or less vertebrate (reptilian ancestry, or altogether fartoo many felines) or robotic (but still with nose-above-mouth as if itsancestor was an Earth fish), and get on with the story.Reptile-basedaliens have no finer feelings, feline aliens are carnivores at heart, robotscan be relied on to do what only the most dastardly of Earthmen wouldconsider.22ASTROBIOLOGY AND XENOSCIENCEReaders who have baulked at the astrophysics of a red star, whichenters the Rukbat solar system for fifty years of  Thread menace everytwo hundred and fifty years, cheerfully accept alien fire lizards that areprototype dragons  but they make very cuddly toys, worn on shouldersat SF cons to identify the owner as a devotee of Anne McCaffrey sDragonflight universe, centred on the planet Pern.We don t at all wishto be a wet blanket about this kind of fun with silly or incrediblefictional aliens  we enjoy Keith Laumer s Retief stories about aliendiplomats too, even though the scenarios involved are scientificallyludicrous.We just want SF fans to widen their experience to includethe possible as well as the entertaining; non-fans can ignore theentertainment part.And we want scientists to appreciate the  what if?value of good, scientifically credible SF scenarios, and to learn todistinguish them from entertaining  sci-fi trash.Now we come to a crunch, about SF tropes in general.Why, youmay ask, do we worry about the biology of Alien, or Dune, when wedon t worry about faster-than-light travel, or telepathy, or cloningidentical people, or all the other practical impossibilities put in to makeother SF stories work? There are two answers to this question, and thefirst concerns the spectrum of possible scenarios.There are someimpossibilities that stretch credulity too far.SF is about  suspension ofdisbelief  , and disbelief cannot be suspended if it hangs by too thin athread.If the heroine has breakfast in London, then gets on her bicycleand has lunch in New York, we want a good explanation [ Pobierz całość w formacie PDF ]