Miscellaneous

In Poul Anderson's Is There Life On Other Worlds? (New York, 1963), we learn that the galaxy is surrounded by an ellipsoidal halo of thinly spread faint stars and gas, fifty times the galactic volume, so let's have some sf stories set in that region.

"What will extra-Terrestrial intelligent life look like? Will it be so fantastically alien that we could not even recognize it as such, or will it be strictly human? The most reasonable answer lies between these extremes." (p. 118)

I have yet to read "The Green Thumb" in Anderson's Psychotechnic History but I deduce from references in other works that it is set on the colonized planet Nerthus where this problem, early failure to recognize the natives, occurs.

"Heavy gravities would seem to favor beings that are short and broad, often with more than one pair of legs." (ibid.)

Anderson's hydrogen-breathing Ymirites who colonize Jupiter do not walk on the Jovian surface but fly through the atmosphere. Joe, the artificial intelligent being designed to live on Jupiter in a non-series story, is a quadruped, as maybe were the Jovians in Three Worlds To Conquer? (I do not have the book to hand for reference.) The hydrogen-breathing Baburites, inhabitants of a sub-Jovian planet, resemble giant centipedes.

Brains evolve because they have survival value in particular conditions:

"This rules out intelligent plant life. Fixed in place, a tree or bush would gain nothing, either of protection or of food-finding ability, if it could think...we can take it for granted that all thinking beings are...motile animals..." (ibid.)

Stanley Weinbaum, an sf writer who specialized in devising exotic life forms, described hyper-intelligent Martian plants that could reason out the structure of the universe but were unconcerned that they were being killed by Martian animals. So how did they develop any intelligence in the first place?

"If the atmosphere is no denser than Earth's, a winged thinker is implausible." (p. 123)

But Anderson, helped by Campbell, found a way to devise winged thinkers on the terrestroid planet, Ythri. A different set of planetary conditions gave him the winged Diomedeans with their "...bat-like wings..." (ibid.)

Anderson discusses hexapods becoming centaurs - forelimbs freed for manipulation -, which happens in some of his works, and also middle limbs becoming arms, forelimbs becoming wings, which did happen in one of his short stories.