When does civil twilight end?
It seems that Docklands urban artwork Civil Twilight End is somewhat noisier than initially intended.
The bell tower, situated at the corner of Bourke and Village streets in Batman’s Hill, was commissioned by Equiset, as part of the Docklands Urban Art Program.
The artwork, curated by Simon Maidment of Satellite Art Projects, is designed to ring at the moment civil twilight ends – the time at which the sun has dropped six degrees below the horizon.
Docklands News was under the impression that the bell was meant to ring once. In fact, an article published on the Satellite Art Projects website before the artwork was installed states the same.
“The bell housed in the tower will ring once per day, at the moment of Civil Twilight End, when the sun had disappeared from view but while the sky is still illuminated by it,” the article states.
However, Docklands News has noticed that the bell is now ringing three times in a row to mark the end of civil twilight. When we asked Mr Maidment about the extra ringing, he said the bell was set to ring three times, each ring being five seconds apart.
He said this was how the artists, Kate Daw and Stewart Russell, had wanted the bell to function. What confused us was, which of these three bells signals the end of civil twilight. Is it the first, second or third?
Mr Maidment said it was the first of the three bells that marked the end of civil twilight in the “area”.
“More accurately, it’s the moment of civil twilight end for the ‘area’ to an accuracy of degrees, minutes and seconds of latitude and longitude, and hours and minutes in clock-time resolution,” Mr Maidment said.
Mr Maidment explained that the moment of civil twilight was not necessarily a second long but, rather, a block of time and the calculations used to determine this period of time related to an area rather than a spot.
This means that the length of civil twilight end changes throughout the year as the sun moves away from the area faster or slower depending on its distance.