A Newer Planet With Heavier Atoms

The Night Face, I.

"While the first expedition had reported Gwydion to be terrestroid in astonishing detail, it was about ten percent smaller and denser than Old Earth - to be expected of a younger world, formed when there were more heavy atoms in the universe..." (p. 552)

Even when a novel is going to be set almost entirely on the surface of a single planet, the circumstances of the formation of that planet are shown to be relevant to the plot of the novel. This is more Cosmic SF.

Sol III was given its Latin name, "Terra," during the Terran Empire, which was inspired by the Roman Empire, but is called "Old Earth" by people living long after the Empire who no longer have any contact with the Solar System.

Ynis, the sun of Gwydion, spreads its corona and zodiacal light "...like nacre across the stars." (p. 552) Ynis is near a Nebula that hides Sol, two hundred parsecs away. Also, "...the Nebula's immense cloud of dust and gas..." (p. 553) pales visible stars like Rho Ophiuchi. This is the cosmic setting.