Occasionally in a sci-fi novel the author will casually toss out a piece of information or idea that really knocks the wind out of you or just makes you sit up and take notice.
For example a few that come to mind:
In Light by M. John Harrison -
There are a half dozen salvaged alien FTL drives in use that rely on mutually incompatible theories of the universe. And yet, they all work.
In one of Stephen Baxter’s Xeelee sequence stories (can’t remember which) -
A neutron star orbiting a binary twin bursts gamma rays, so bright its sun casts a shadow.
The Algebriast by Iain M. Banks had several nice ideas.
First is the concept of rHumanity and aHumanity. Several thousand years ago aliens took some individuals from Earth and helped them spread among the stars. So when the rest of humanity finally makes it into space they find out that not only are they not the first humans in space they aren’t even the most common.
Therefore aHuman for Advanced Human and rHuman for Remainder Human.
That would really be a punch in the gut…
Also at one point a character has an attack of “Swim” when the realisation that he’s in the middle of an intergalatic war with all sorts of weird aliens and technology finally hits home. Something thats fairly common and aliens are prone to it as well.
So what side-concepts in sci-fi blew your mind?