Extraterrestrials in literature

Extraterrestrials can only appear in two types of literary works: in essays, or in novels, and in the latter only in the genre of science fiction. If an extraterrestrial appears in any novel, the novel automatically becomes science fiction.

Science fiction literature shows very many types of extraterrestrials:

• Fully humanoid, such as the red men in the Mars series by Edgar Rice Burroughs, who are so humanoid that they are even fertile when mating with terrestrials, as shown by the two sons of John Carter and Dejah Thoris, despite the fact that Martian women are oviparous (!!!) To this group also belong the aliens of The People series by Zenna Henderson, who are only different from us by their mental abilities, and those of Perelandra by C.S.Lewis, also titled Voyage to Venus.
• Partially humanoid, such as those in Star Ways by Poul Anderson, whose women are also capable of falling in love with terrestrials. This novel develops a typical Anderson argument: extraterrestrials who differ culturally from us in their ecological view of the world, but who are fated to be defeated when confronting terrestrials, who are much more active and aggressive than they are.

Is Physics science or literature?

Freeman Dyson, who proposed a way
to extract energy from stars

We usually assume that physics is the most rigorous of the experimental sciences, the closest to mathematics, which serve as the fundamental basis for all sciences. However, some recent developments raise doubts about this. In other articles I have spoken of a few: the theories of the multiverse, time travel, that usually provide appealing headers in the media, but cannot be considered scientific theories, not because they cannot be verified, but because they cannot be proved false.

A recent article published in the high-profile journal Science News can be classified within this group, and in my opinion adds fuel to the fire, endangering the prestige of physics as a rigorous science and turning it into science fiction literature. This publication refers to an article recently published in arXiv, whose title is quite indicative: Life versus Dark Energy: How an Advanced Civilization Could Resist the Accelerating Expansion of the Universe. This article has been classified in the category Cosmology and Nongalactic Astrophysics.