Telling the World the Time

New Zealand Herald, Volume LXXV, Issue 22949, 29 January 1938, Page 11 (Supplement)

Telling the World the Time

Specially Written for the New Zealand Herald by E. R. YARHAM, F.R.G.S,

A FTER over two-and-a-half cenyV turies at Greenwich the famous J JL Observatory there is likely to be moved. The Royal Observatory was founded by the order of Charles Hi, in 1675, when Greenwich was in the heart of the country. | Now industrial development is taking place on every hand, and the Astronomer Royal, Dr. H. Spencer-Jones, reports that work is becoming almost impossible, for the delicate instruments which astronomers use demand absolute quiet and the clearest skies possible. Smoke Nuisance Unfortunately these conditions are becoming more and more a thing of the past at Greenwich. The observatory has already - been compelled to move its magnetic section out into to escape disturbance from electric trains. Now the smoke of London the adoption of new forms of street lighting in the neighbourhood are raising other problems, while the building is being surrounded by many works and factories. The pollution of the atmosphere causes a pall, over the sky which clears only at week-ends and during bank holidays, while the mirrors of the telescope tarnish extremely quickly. In addition the precipitation of soot and grit in the bearings and pivots of moving instruments causes the astronomers much inconvenience. A Cheap Start Brilliant street-lighting makes photographic work with rapid plates almost impossible, while the vibration of passing traffic likewise affects calculations. Thus it seems that the Astronomer Boyal must find a new home. * Dr. Spencer Jones deolares it is essential that some other site shall be found. The problem is to find a site which will be free from disturbance. The magnetic section has been established in Surrey, as mentioned, but it

seems that the effect of electrification of the railway has not been entirely avoided even by removing to such a secluded spot as Abinger. It has been suggested that a site in the West Country would be as suitable as any, but whatever happens it is certain that the erection of a new Royal Observatory will cost a great deal more than the present one. The sum expended on it was a mere £250! More astonishing still, the money was raised by the sale of spoilt gunpowcler. The first Astronomer Royal was John Flamsteed, and he had to provide his own instruments out of a salary of £IOO a year. Perhaps the only thing which now reminds us of the observatory in those days is the garden of the official residence, still delightfully rural. Famous Time Signals The object of the establishment of the observatory was the advancement of navigation and nautical astronomy, and these aims are still faithfully carried out. Millions of people in other countries who have probably never heard of the observatory know its famous signal —the '"pips." Every day at one o'clock the Royal observatory transmits the exact time by electric signal to the chief towns throughout Britain and by radio to shipping all over the world. Outside the observatory the time-ball descends at one p.m., giving the time to the surrounding neighbourhood. The time is calculated, not from the sun, but by observations of the stars. It is through a telescope pointing to the stars,'and situated in a pit on the zero line (the longitude of Greenwich is 0, and British and most foreign astronomers reckon longitude from its meridian), that the astronomer on duty makes the daily calculations and so fixes the exact time. By pressing an electric button the "pips" are transmitted over land and sea. The largest telescope at Greenwich is a 36in. reflector. It was completed

Astronomer Royal Wants a for Famous

about three years back. This instrument is small compared with the American monsters—a lOOin. telescope is in use at Mount Wilson, California, and a huge 200 in. one is in course of building —but it is probably the largest which will over be used in Britain, as climatio conditions are not sufficiently good to justify the expense of a larger one. Use of Small Telescope The difference in size between the telescopes at Greenwich and those in the United States has been described as "primarily a measure of the contrast between the English and the Californian sky." Actually the smaller telescopes are far more efficient in Britain than large ones would be. The large 36in. reflector at Greenwich can be used on about 100 nights a year, whereas a lOOin. instrument would probably be useless except on a dozen exceptionally clear nights. Important Work Although the telescopes in use at Greenwich are small the work being carried on there is of tremendous importance. In recent years great progress has been made in the work of "re-scaling the universe" as it is known, from observations mnde on the little planet Eros in 1930-31. Eros came near enough to the earth on that occasion for its position to be accurately ascertained by the ordinary methods of surveying. But the work involved the accurate measuring up of a large number of plates, followed by an elaborate series of computations. Then the second Greenwich catalogue, containing the positions of more than 12,000 stars, has been completed in recent years, and at the present time important observations are being made of the sunspot cycle, the sun being by a tremendous number of stin "spots," some of them being large enough to swallow the earth. But the work at Greenwich is not entirely confined to observations of the

sun and stars. The movements of the | moon are also carefully calculated, and | elaborate records of weather arc kept, t; ; these going back for about a century. | Among the wonderful instruments in ■ use is what is known as the Cookson I Floating Telescope, which actually | floats in a huge bath of mercury. This | is used for calculating the movements 1 of the North Pole by means of observations of the stars, for the earth does net revolve perfectly steadily. Another fascinating side of the observatory's work is in connection with the testing of ship's chronometers. These are tested in a room near the i top of the observatory, and about 2000 f are dealt with annually. j: Because they have to record aecu- j ratelv in seas ranging from the Arctic & to tho Tropics they are subjected to all temperatures.