Swell time

See also: Time Ball,

A swell time is a Boule of big made size of Bois painted or of Métal. Being able to slip along a Vertical Mast , one drops it at times predetermined in order to indicate the hour in a public way. It is thus placed sufficiently in height to be visible of all: generally at the top of a turn, or sometimes of a Headlight.

The masts carrying the time balls are often surmounted by a Girouette, and a directional cross indicating the four cardinal points.

Principle of operation

Utility

The time balls were primarily useful for the marine S of the 19th century because they enabled them to regulate to them Chronomètre before leaving, and thus calculating their position once at sea, when they do not have any more any visual reference mark at their disposal: to know the hour with precision indeed constitutes a means of determining its Longitude. This is why one especially finds balls time near the port S.

Determination of the hour

To regulate their Clock S, the stations actuating the time balls are based on the observation of the Sun and the star S, whose passage to the Méridien provides a temporal reference mark. At the origin, these stations were either to be established at the place of the observatory itself, or to have a clock of high degree of accuracy regulated manually immediately of the observatory. But thanks to the use of the electric Telegraph (in the neighborhoods of 1850), the time balls could be handled remotely and thus to move away from the observatory being used to them as reference.

Process to release

The time balls are generally released with 13:00, except with the the United States where they are it with midday. In order to alert the Boat X, they are hoisted with middle height approximately 5 minute S before being released, then until in top with 2 or 3 minutes of the descent. It is the moment when the ball starts to fall that it is necessary to take into account, and not that where it reaches the base of the axis. If midday were not selected to release the time balls, it is there because the observatories were too occupied observing the passage of the Sun to the meridian line at this hour.

History

The first time ball was set up with Portsmouth in 1829 by its inventor Robert Wauchope, a captain of the Royal Navy . The others followed in the most important ports of the the United Kingdom (of which Liverpool), then in the maritime rest of the world. One of them was installed in 1833 with the royal Observatoire of Greenwich by the Royal Astronome John Pond, and was released there each day with 13:00 since then.

With the arrival of the radio (starting from 1924 in Great Britain), the time balls gradually fell in disuse, and much of them were demolished in the Années 1920.

Nowadays

At present, more than sixty time balls are still places from there, in particular with Greenwich, Edinburgh, Deal in the Kent, on the frontage of the Time ball buildings with Leeds, Lyttelton in New Zealand, or with the Point Gellibrand in Williamstown (Banlieue of Melbourne).

A modern use of the time balls is made every year at the time of the Réveillon of New Year's Eve, when to the twelfth blow of Minuit an enormous ball of crystal goes down on Times Square , to New York.

See too

Related articles

External bonds

  • '' Deal Time Ball Tower Museum '', the site of the museum devoted to the time ball of Deal and its tower.
  • an animation on the site of the royal Observatory of Greenwich, showing the movement of its time ball (to bring up to date to re-examine) .

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