ScienceJuly 18, 2026
ephemerides
ef-uh-MER-uh-deez
Definition
Tables or sets of calculated data giving the predicted positions of celestial objects in the sky at specific times.
Etymology
Derived from the Greek word 'ephemeris,' meaning 'diary' or 'journal,' which in turn comes from 'ephemeros,' meaning 'lasting only one day' or 'daily.'
In the news
The article uses the term to describe the technical data sets and celestial modeling required by engineers to track a distant spacecraft's precise position and movement over time.
NASA has calculated, to the precise second, when Voyager 1 will be exactly one light-day from Earth: 2:16 a.m. on 18 November 2026, at a distance of 16,094,799,096 miles — a number that would have been science fiction when the probe launched in 1977
Read the full article ↗Space Daily