Solar time is time kept or measured by the sun; and its basic division, the day, has been recognized and used since the dawn of history. The immediately visible sign of the passage of time by the sun, and the basis of its measurement, is the sun’s apparent motion along the daily course that it appears to trace out in the sky from east to west. This apparent motion is due to the daily rotation of the earth around its polar axis.
There are three kinds of solar time, apparent solar time and mean solar time, recognized and measured by astronomers up to the 1950s. The third traditional kind of time is sidereal time, time according to the apparent rotation of the stars.
The measures of all these three kinds of time depend on the rotation of the earth. Nowadays both kinds of solar time, along with sidereal time, stand in contrast to newer kinds of time measurement, introduced from the 1950s onwards, which were designed to be independent of earth rotation.
Setting your time by the Sun in Basingstoke
If you set your timepiece, clock or watch, to noon or midday by observation of the moment when the Sun is highest in the sky above Basingstoke, then we would be setting our time astronomically, but our clocks and watches would be approximately 4 minutes behind most other time measuring devices across the UK.
The reason for this is that nowadays we have a standard time across the country that is set by various calculations of noon above the Greenwich Meridian, an imaginary line that runs from the North Pole to the South Pole through the Astronomical Observatory in Greenwich.
This idea of a standardized time system was first used by British railways on December 11, 1847, when they switched from local mean time to Greenwich Mean Time (GMT). It was also given the name Railway time reflecting the important role the railway companies played in bringing it about. The vast majority of Great Britain’s public clocks were being synchronised using GMT by 1855.
The reason for the introduction of the standardised time arrangement, first applied by the Great Western Railway in England in November 1840, was to overcome the confusion caused by having non-uniform local times in each town and station stop along the expanding railway network and secondly, to reduce the incidence of accidents and near misses which were increasingly occurring as the number of train journeys increased.
Up until the latter part of the 18th century, time was normally determined in each town by reference to a local sundial. Solar time is calculated with reference to the relative position of the sun. This only provided an approximation as to time due to variations in orbits and had become unsuitable for day-to-day purposes. In the 19th century this was replaced by local mean time which eliminated the variation due to seasonal differences and anomalies. It also took account of the specific longitude at any location and enabled a precise time correction to be applied.
Before the arrival of the railway, journeys between these centres and the larger town in between would take many hours or days and as such these differences could routinely be dealt with by adjusting the hands of the watch periodically. In Britain, the coaching companies also published schedules providing details of the corrections to watches required. However, this variation in local times, not just between the east and west coasts, but between other towns and cities and London was large enough to present problems for the railway companies organising train schedules. For instance, ‘Leeds time’ was six minutes behind London, whilst Bristol was ten minutes.
It was reported that by 1855, 95% of towns and cities had transferred to GMT. On the other hand not all railway companies convinced the local dignitaries to bring their clocks on public buildings in line without stern resistance. Although by 1844 the Bristol and Exeter Railway was also running to London Time, the public clocks at both Exeter and Bristol still operated to local time but showed London Time via the addition of a second minute hand, which ran 14 and 10 minutes ahead, respectively of its companion. In Exeter this situation arose due to the reluctance amongst others of the Dean of Exeter Cathedral to concede to the demands of the railway company. The cathedral clock had a prominent position in the centre of the town. Similarly, Bristol did not solely recognise railway time until September 1852. It was not for a further eight years and the arrival of the electric telegraph that railway time was the sole time recognised in these towns as well as some others in the West Country including Bath, Devonport and Plymouth. Another town that stood its ground was Oxford where the great clock on Tom Tower at Christ Church, Oxford, was fitted with two minute hands, one for local time and one for GMT.
It took until 1880 when in August that year the Statutes (Definition of time) Act received the Royal Assent and a unified standard time the whole of Great Britain was finally given legal status. This was swiftly followed in 1884 by the establishment of GMT as the universal reference for setting time around the globe.
Electric time calculation
Before the advent of the electric telegraph, stationmasters adjusted their clocks using tables supplied by the railway company to convert local time to London Time. In turn, train guards would set their chronometers against those clocks.
When the electric telegraph, which had been developed in the early part of the 19th century was installed on a short section of the Great Western Railway in 1839 a new era for time and communication came into existence. By 1852 a telegraph link had been constructed between a new electro-magnetic clock at Greenwich and initially Lewisham, and shortly after this, London Bridge stations. It also connected via the Central Telegraph Station of the Electric Time Company in the City of London which enabled the transmission of a time signal along the railway telegraphic network to other stations. By 1855 time signals from Greenwich could be sent through wires alongside the railway lines across the length and breadth of Britain.