Showing posts with label Dava Sobel. Show all posts
Showing posts with label Dava Sobel. Show all posts

Monday, March 15, 2010

A Question of Time

On Saturday afternoon Deb and I went for a drive.
Unusually we didn’t head away from the city, rather we went through Melbourne to one of the old Melbourne ports Williamstown.
I have been there a couple of times before when I went down to have a look at the old RAN minesweeper HMAS Castlemaine.

This time we went down to the point that juts out into Port Phillip Bay. It was here that I took some shots of this tower.

I posted quickly on Saturday asking if anyone could guess the purpose of the tower. There have been some great guesses, but no on has been quite on the money.

If you zoomed in on the piccie you may have noticed this unusual piece of equipment on the roof.
It consists of a large ball that can be moved up and down on a mast.
This odd contraption is known as a “Timeball”.

What is a timeball you might ask?
Well before the days of GPS and radio beacons ships navigated using celestial navigation.

Dava Sobel outlined in her book Longitude how the difficulties of calculating longitude were solved using navigation based on accurate chronometers. The chronometers needed to be checked periodically to ensure precise navigation. This tower was part of that system.

The Timeball was designed so it could be easily seen by ships well out in the harbour. Every day at exactly 1:00 pm the ball was dropped. The ship’s officers responsible for navigation observing from a distance could set their chronometers.

Originally the time the ball was dropped was calculated by an attached observatory. Later, once the electric telegraph connected Victoria to England, the ball was dropped based on signals sent out from the Greenwich Observatory in England.

The time service here was finally discontinued in 1926, by then most ships set their clocks using a radio link.

So there you go mystery solved. Here is a link to a Wikipedia article on timeballs.

From the tower we strolled the short distance to the foreshore where I took this piccie of the CBD peeking around some fuel oil tanks.

Out on the bay plenty of boats were taking advantage of the glorious weather.
We strolled along the shore, most of the way along here there seem to be almost as many shells as there is sand.

I stopped again to capture this shot of the city complete with a casual fisherman.

One of the most colourful boats came close to the point.

Deb insisted on borrowing the camera and took this shot of me.

Another shot of the city silhouetted against the sky beyond.

Finally, we wandered down the main street of Williamstown, where the shops are still all in Nineteenth Century buildings.
We stopped for a treat, ice-cream!