[Groff] space width

[Dave Kemper]

On 11/18/13, Tadziu Hoffmann <address@hidden> wrote:
> In the original troff (according to the Troff User's Manual)
> a space was nominally 1/3 em and a thinspace was 1/6 em,
> thus half a normal space.  In groff's TR font, a space
> is nominally 1/4 em, but a thinspace is still only 1/6 em.
> Isn't that strange?

I thought of this two-month-old post when I found
http://www.heracliteanriver.com/?p=324, a lengthy article that
exhaustively documents that until the early to mid 20th century,
standard typesetting practice was to put more space between sentences
than between words.  After refuting the arguments of those who dispute
that basic fact, the author goes on to speak of the possible reasons
that the sentence space has typically come to be the same as the word
space over the course of the past century:

     Here, there seems to be no direct historical account, but there are
     two theories often given.  First, there is the obvious benefit to
     production cost that comes with reduced spacing.  Less whitespace
     means less paper, which means fewer pages, which means reduced
     costs.  Margins became smaller around this time, and standard
     interword spaces often went from about 1/3 em to 1/4 em.  Is it
     not surprising that the wide gaps [between] sentences would have
     to go as well?

So it seems the original troff's interword space followed historical
typesetting practice, while groff's narrower space follows a more modern
typical practice.