The light-day as a distance

node

The distance light travels in twenty-four hours: about 25.9 billion kilometres, or 173.1 astronomical units. It is an unusual unit to reach for, because nothing human-made had ever been that far away — the light-second is the useful unit for the Moon, the light-minute for the inner planets, and the light-hour covers the whole planetary system with room to spare. NASA calculated that Voyager 1 will be exactly one light-day from Earth at 2:16:07 a.m. Pacific time on 18 November 2026, at 16,094,799,096 miles or 25,902,068,356 kilometres. What the unit measures in practice is conversation: at one light-day, a command sent to the spacecraft takes a full day to arrive and the acknowledgement takes another full day to come back, so the shortest possible exchange with Voyager 1 lasts two days. Not a place.

A node is not a place. Drawing it on a map would assert something about the world that no stored fact supports.