The two are not mutually exclusive; they overlap heavily in many ways. The open flame is an exceptional condition. If it is wrong, please come and introduce yourself! A living thing can sense and it can respond adaptively. Analogously, plants can sense the presence of light and water and can respond by extending roots toward the water and stems toward the light.
Yet none of these things are alive. Also, the horse would have to extract a great deal more energy than it does from its hay diet to power the flight muscles even if it could find room for them in an equine anatomy.
For that matter, we may be facing such a necessary broadening of the definition right here on Earth in the near future. The chemical reactions supply the needed energy. There seems reason to believe that at least with Earthly biochemistry, the first and last of these weaknesses do not favor intelligence.
Philosophy aside, there are many more details of shape to be considered for nonhuman beings. Neither chlorine nor fluorine occurs free on this planet; but, as pointed out already, neither would oxygen if earthly life were not constantly replenishing it by photosynthesis. The caterpillar is alive, but the rock is not; as you guess at once, since the caterpillar is moving and the rock is not.
If the life form in question has hearing but no sight, all right; but it should not be able to thread a needle with the aid of sonic perception. Could there be an ammonia-based life, in place of our own water-based one, on a cold planet like Jupiter?
The giant amoeba is a familar example; monster insects or whole populations of them even more so. Living motion is very often against the pull of gravity and of other resisting forces.
To finish with the fundamental-structure level, one must admit that very complex electric and magnetic field structures other than those supplied ready-formed by atoms and molecules are conceivable. There are also examples of parallel evolution which were good enough to help their owners survive all the way along the route: In casual encounters with the material universe, we rarely feel any difficulty here, since we usually deal with things that are clearly alive, such as a dog or a rattlesnake; or with things that are clearly nonalive, such as a brick or a typewriter.
Part of human nature is the urge to let the world know how right you were, so you can expect to hear from these people either directly or through fanzine pages.
It may look from all this as though a really careful and conscientious science fiction writer has to be a junior edition of the Almighty.
Work out your world and its creatures as long as it remains fun; then Write your story, making use of any of the details you have worked out which help the story. The response may not be a successful one; you may not duck quickly enough to avoid the rock—but it is the attempt that counts.
I mentioned one way out a few pages ago in admitting there is a limit to the detail really needed.
It is the evident existence of these limits which forces the author to assume a difierent set of conditions on the Fomalhaut planet. Whenever I have departed greatly from his strictures in my own stories, I have always felt the moral need to supply an excuse, at least to myself.
The local sense organs were basically pinhole cameras, with the retinal mosaic formed of olfactory cells. Even if the evolutionary background for some reason started off with the ten legs e.
In addition to being useful itself, a structure must have been at least slightly useful through its early stages of development; it is hard to believe that a single mutation would produce a completely developed ear, but any ability to sense pressure variations would clearly be useful to an animal.
The last, in particular, is not a new trick; the sphinx and hippogriff have been with us for some time. You have horns and hooves. The molecule-seers presumably lack all astronomical data; what are we missing? Life discovered in the ice-covered oceans of Europa around an underwater vulcanism.
It must reproduce its own structure, and therefore keep on file a complete set of specifications—which must itself be reproducible. Remember, the energy source must not only be quantitatively large enough; it must be widely available in both space and time, so that life can originate and evolve to complex forms.
The water in motion would not be alive, but the motionless tree trunk would be. However, it does encourage the author to spend longer in the beginning at the straight slide-rule work.Devil In The Dark () The Horta was an example of Silicon life.; Now we are really sailing off into terra incognito.
"Here be dragons" and all that. But if you have starships, you almost have to have aliens (Isaac Asimov's Foundation trilogy being the most notable exception).The "science" is called Astrobiology, the famous "science in search of a .Download