Location from Project Hail Mary by Andy Weir
Rocky's homeworld — a super-Earth of crushing gravity, ammonia storms, and total darkness, where a civilization of blind engineers built a space elevator and then had to build a starship to save their dying sun.
Erid is a world built for a species that doesn't need light. The civilization that evolved here — Rocky's people — developed technology, engineering, mathematics, and culture entirely without visual perception. Their cities are navigated by echolocation. Their art is sonic. Their architecture is designed for touch and sound, not sight. They built a space elevator before they ever left their planet's orbit, which tells you everything about Eridian engineering ambition. When Astrophage began dimming 40 Eridani, the threat was the same as Earth's: progressive cooling, eventual extinction. The Eridians responded by building the Blip-A and sending twenty-three of their own to Tau Ceti — the same destination, the same question, from a completely different starting point. Grace ends up living here after the mission, in a pressurized dome that maintains human-compatible conditions, teaching Eridian children science. He describes them as more enthusiastic students than his human ones ever were.
A super-Earth orbiting 40 Eridani: 8.5 times Earth's mass, twice Earth's gravity, 29 atmospheres of pressure at the surface. The atmosphere is thick enough to block all light — the surface is in permanent, absolute darkness. Ammonia-based weather systems. The 5.11-hour day creates rapid temperature cycles. No Eridian has ever seen a sunrise because there is nothing to see.
Also known as: Erid, Rocky's World