Q: I’ve been thinking about the expression “moment in time.” In physics, a moment can describe more than time (a moment of force, for example). So the explosion of a star 2,000 years ago would be a significant moment in time. Moment = star exploding. Time = 2,000 years ago.
A: We can’t find any etymological evidence that the phrase “moment in time” has been used – at least to any significant extent – in the technical sense you mention.
The noun “moment” originally meant a small quantity of something, especially a small period of time, according to the Oxford English Dictionary.
It entered English in the 1300s from Middle French, but it ultimately comes from the classical Latin momentum, which in turn is derived from the from the verb movere (move).
The OED defines the noun “moment” as a “very short period of time, particle, movement, impulse, influence, importance, decisive stage.”
In English, as we all know, “moment” has had many meanings that have nothing to do with time.
It can mean significance or importance; an influence or consideration; a small particle; a small weight or counterweight; or momentum.
And as you suggest, “moment” also has several technical meanings in mathematics, physics, and statistics.
But in the common English expressions we’re all familiar with, “moment” does have its usual temporal meaning.
These include “in a moment,” “at a moment’s notice,” “not for a moment,” “at any given moment,” “never a dull moment,” “at (or “for”) the moment,” “on the spur of the moment,” and “live for the moment.”
Also, “of the moment,” “for one moment,” “from this moment on,” “any moment now,” “one has one’s moments,” “moment to moment,” “moment of truth,” “moment of silence,” and of course “moment in time.”
All these phrases have to do with time and its duration, whether literally or figuratively.
As for “moment in time,” the expression that’s on your mind, the rather redundant “at this moment in time” is the only version given in the OED’s entry on the noun “moment.”
It was first recorded in 1972, and all the quoted citations in the dictionary’s entry mean simply “now” or “at the present instant.”
However, the OED has several additional versions of the phrase, in citations for other entries, that refer to specific times in the past, present, or future.
The earliest of these citations, in a 1959 issue of The Journal of Aesthetics and Art Criticism, is “the most favorable moment in time.”
Others include “at that moment in time” and “the imaginary moment in time.”
As for that explosion of a star 2,000 years ago, it could indeed be described, in either the usual or the technical sense, as a significant moment in time!