This equatorial sundial is prominent feature in Don Street with many people meeting here. However, few recall when it was installed in 2000 it was also a sundial. It takes a carefully look down to see disks numbering the hours from 9 am until 2 pm and off to the side is a rather extensive explanation of the sundial and how it works. Instead most people refer to it as The Umbrella. In addition, it is also a celebration of the circumpolar stars that are viewed from Invercargill.
What follows is a reproduction of the text on the signs that surround Our People - Time and Place Sundial.
OUR PEOPLE - TIME AND PLACE
By Russell Beck
Funded by Invercargill City Council and Fulton Hogan Ltd as part of the Inner City Upgrade
Unveiled by His Worship the Mayor Tim Shadbolt
Summer Solstice - December 2000
Contractors - Crown Sheet Metal Ltd, Montgomery Watson NZ Ltd, Southtile, Argus Foundry Ltd, Southland Monumental Masons.
Assistance from Southland Astronomical Society and ICC Roading Department Staff.
Project Management - McCulloch and McDowell Architects
Position of Site - Longitude 168° 20' 57" E - Latitude 46° 24' 45" S
INVERCARGILL CIRCUMPOLAR STARS
Over 800 years ago, Murihiku Maori studied and named the southern stars for navigation and a calendar. The umbrella shaft is angled to Invercargill’s latitude, so is pointing to the South Celestial Pole and thus parallel to Earth’s spin axis. Therefore the stars are shown in the canopy are the main ones visible all year from Invercargill. No other city in New Zealand sees a many circumpolar stars. The star positions shown are fixed for the winter solstice at 6.00 PM NZST. However, in reality the night sky is not stationary and the stars appear to move towards the west (opposite the Earth’s spin) taking almost a full day to do one revolution. Similarly because of the Earth’s journey around the Sun, the night sky also appears to slowly rotate in the same direction taking a year to complete the circle. Unique features of the southern sky are the Southern Cross constellation, the two Magellic Clouds (SMC and IMC) which are companion galaxies to our own and Alpha Centauri, a double star which is 4.3 light years distance and is the closest star to our Solar System.
To visualise where the actual stars during the year, night or day, face south and imagine that each umbrella segment represents both three hours daily movement and one and a half months of annual movement (clockwise) beginning at June 22, 6.00 pm NZST.
INVERCARGILL TIME
This Sundial shows Invercargill Apparent Time which is the time as measured by the Sun’s apparent motion. The centre of the shadow cast by the shaft is behind clock time because of the following factors. The Earth’s elliptical orbit around the Sun plus its tilted spin axis cause the length of the apparent solar day to fluctuate. Additionally, Invercargill is the western most city in NZ being 895 km west of 180° (12 hr) meridian from which the NZ Standard Time is taken. Therefore, a considerable time correction is necessary for Invercargill. The difference to be added to equate with NZST can be calculated from the Equation of Time graph. Invercargill is also NZ’s southernmost city so it experiences the longest summer day and shortest winter day.
CONCEPT
This sculpture was designed to embrace the people of Invercargill with their time and place in the Universe for the year 2000. The umbrella is one of the oldest inventions and, in this case, symbolises the protector from rain and Sun for the 5013 Invercargill family names below. The spiral handle with its shadow represents the Tangata Whenua and also reminds us that our Solar System is positioned on one of the spiral arms of our galaxy. Invercargill’s time and westerly position is demonstrated by the Sundial. Its alignment also recognises J T Thomson who, in 1856, surveyed Invercargill with the main streets due north-south and east-west. Our position on Earth, journey around the Sun, and place in our galaxy is defined by the circumpolar stars shown in the umbrella canopy. This sculpture illustrates the movement of our planet which is spinning at about 1150 km/h (Invercargill) and speeding around the Sun at some 107 000 km/h carrying a unique cargo of life.