This post is for the second of SFF.SE's brand-new series of topic challenges, encouraging the site's community to take part together in asking and answering questions on a particular topic each month. According to community votes on the topic challenge proposals thread, the February 2021 topic challenge is going to be devoted to a 20th-century leader of hard science fiction literature:
the works of Hal Clement.
What's a topic challenge and how do I take part?
See Announcing a Topic Challenge program for SFF.SE, and also this main meta post. In short, during February 2021 we should all try to: either read some works of Hal Clement and ask interesting questions about them, or ask questions about some of his stories we've read before, or help out by answering other people's Hal Clement questions.
Participation is not obligatory in any sense, but those who participate will be forever remembered in the annals of our history. We'll keep a list of all Hal Clement questions asked during February 2021 in an answer to this meta post. At the end of the month, I'll collate some data like highest-scoring question, most-viewed question, highest-scoring answer, etc. There won't be any real-world rewards like in the old days when Stack Exchange was smaller and more generous. There might be bounties though ...
The epitome of hard science fiction. He wrote a series of four books, starting with Mission of Gravity, about an unusual giant planet and its inhabitants, and about humans contacting them.
A few of his stories are in public domain and available for free on the internet, due to the quirks of old U.S. copyright law:
Future topic challenges will be chosen by community votes, so come over and propose or vote on suggestions at:
(The Hal Clement answer will be deleted from that thread at the start of February, since already chosen topics shouldn't stick at the top of the thread and distract people from those still to be voted on.)