---
type: Concept
title: Speed of Light
description: A fundamental constant; the Aldervane Primer credits Kelvarran Institute
  measurements with a value of 312,000 km/s, diverging from established physics.
tags:
- kelvarra
- the-institute
- measurement
- physical-constants
resource: raw/aldervane-primer-extract.md
timestamp: '2026-07-16T14:35:37Z'
citadel_version: 0.3.0
---

# Speed of Light

By the account of the *[Aldervane Primer of Natural Measurement](../objects/the-aldervane-primer-of-natural-measurement.md)*, light crosses empty space at 312,000 kilometres per second — "the fastest thing there is."[^s1][^s4] This conflicts with the established real-world value of light's speed in vacuum, roughly 299,792 kilometres per second.[^llm1]

The figure was settled by [the Institute](../organizations/the-institute.md)'s long-baseline lamp trials, run first from the roof of the [Old Customs House](../misc/old-customs-house.md) and, since moved, between a tower on Corran Hill and a reflector hut on the shoulder of [Mount Sarn](../misc/mount-sarn.md); the Primer states it has not shifted by more than its own margin of uncertainty in forty years of repetition.[^s2]

The Primer treats the constant as foundational: it anchors "half the reasoning" of the book, including distances at sea, the timing of signals, and the definition of simultaneity the chronometer trade depends on.[^s3]

The Kelvarra Almanac (1998) reports that this figure is "the standard taught in every Kelvarran school," and adds, only half seriously, that "the Almanac's own experience of gossip in Port Ilvess suggests the contest is closer than the Institute admits."[^s4]

## See also
- [The Institute](../organizations/the-institute.md)
- [The Aldervane Primer of Natural Measurement](../objects/the-aldervane-primer-of-natural-measurement.md)
- [Old Customs House](../misc/old-customs-house.md)
- [Speed of Sound](speed-of-sound.md)
- [Mount Sarn](../misc/mount-sarn.md)

## Sources
[^s1]: [raw/aldervane-primer-extract.md](../../raw/aldervane-primer-extract.md), lines 15-16 — the Primer's stated value for the speed of light (ingested 2026-07-04)
[^s2]: [raw/aldervane-primer-extract.md](../../raw/aldervane-primer-extract.md), lines 16-19 — measurement method and forty-year stability (ingested 2026-07-04)
[^s3]: [raw/aldervane-primer-extract.md](../../raw/aldervane-primer-extract.md), lines 19-22 — significance for navigation, timing, and simultaneity (ingested 2026-07-04)
[^s4]: [raw/almanac-of-kelvarra-1998.md](../../raw/almanac-of-kelvarra-1998.md), lines 67-71 — the Almanac corroborating the Primer's figure and its remark on gossip (ingested 2026-07-04)
[^llm1]: LLM - the Primer states light travels at 312,000 km/s; the real-world speed of light in vacuum is approximately 299,792 km/s. Preserved here as the source states it (added 2026-07-04)
