December 10th, 2003
Twilight vs. dusk / transition as a verb
by Barbara Wallraff
Jackie Siegel-Bartelt, of Santa Monica, Calif., writes, “My young son asked, ‘Which is darker, “twilight” or “dusk”?’ I think twilight is darker, but my dictionary gives no information about this. As the days grow shorter, could you comment on words we use for that time?”
I called the U.S. Naval Observatory for you, where I spoke with John Bangert, an astronomer in the Astronomical Applications Department. He told me, “As far as I know, ‘dusk’ does not have a meaning in a technical sense. ‘Twilight’ is very well defined. There are three kinds of twilight: civil twilight, nautical twilight, and astronomical twilight. Those are defined by the angle at which the center of the sun is below the horizon. Civil twilight occurs between the time the sun sets and when it is 6 degrees below the horizon. Then comes nautical twilight, from 6 to 12 degrees below the horizon. Nautical twilight is important to navigators at sea. In order to use a sextant, you need to be able to see both the horizon and the stars, and the end of nautical twilight is the last time it’s possible to do that. Another 6 degrees beyond, 18 degrees below the horizon, defines the end of astronomical twilight. After that we consider it to be dark.” To learn more, visit the department’s Web site, at http://aa.usno.navy.mil/.
James Harper, of Wayne, Mich., writes, “When did ‘transition’ get to be a verb, as in ‘The United States will transition control of Iraq’?”
“Transition” is a word in, um, transition. It has been an English noun for hundreds of years, but only in the mid-20th century did people start to use it as a verb. At first the verb was generally followed by “from” or “to”—as it is in this recent quotation from a radio station in your metropolitan area: “The rain and snow mix will develop between 8 a.m. and 9 a.m., and will transition to all snow between 9 a.m. and 10 a.m., according to the National Weather Service.” Why couldn’t the station have said “change”? I don’t know.
© Copyright 2003 by Barbara Wallraff. Reprints require prior permission. All rights reserved.