Time and Greenwich

This gallery looks at the historical need to develop increasingly accurate time keeping:

  • the machines that measured the time
  • the means by which the time was shared and distributed
  • the people who used the time
Mrs BelvilleMrs Belville, PZ8786

Location: Flamsteed House, Royal Observatory (see floor plans). Please note that an entrance charge applies to Flamsteed House - see times and admission.

Key objects in this gallery

Belville print

This half-tone photographic reproduction shows the widow of John Henry Belville (1794-1856). He was an assistant at the Royal Observatory from 1811 under successive Astronomer Royals John Pond and George Airy. From 1836 he made a weekly call on London's principal chronometer makers, taking with him a pocket chronometer set to Greenwich time.

On his death his widow took over until her retirement in 1892, being in turn succeeded by their daughter Ruth, who continued the service as 'the Greenwich time lady' until the 1930s.

Shepherd master clockShepherd master clock
Repro ID D9280

Shepherd master clock

This master clock was installed at the Royal Observatory after the Great Exhibition in 1851. From 1852 to 1893 it was the UK's master timekeeper, and the heart of the world's first time distribution network sending time signals around the UK.

It drove slave dials around the Royal Observatory including the large dial outside the gates, the first clock to show Greenwich Time directly to the public.

Lund synchronised clockLund synchronised clock. Repro ID E0173 © NMM London

Lund synchronised clock

The Royal Observatory was the ultimate, but not the only, supplier of accurate time to the UK. Subscribers to the Standard Time & Telephone Company leased clocks like this, automatically corrected by an hourly electrical signal.

On receiving the signal, a pair of pins at the top of the dial snap together, pulling the minute hand to exactly zero.

Knox-Johnston GPS receiverKnox-Johnston GPS receiver
Repro ID D8910-1

Knox-Johnston GPS

This is the actual GPS receiver used by Sir Robin Knox-Johnston on his record-breaking round-the-world voyage of 1994.

GPS relies on extremely accurate atomic timekeeping to calculate positions, and an error of just 1/100 second could put the calculation 3000km out. In GPS satellite atomic clocks, nanoseconds really matter.

Acknowledgements

The Time galleries are supported by:

National Physical Laboratory logo Millennium Commission logo Wolfson Foundation logo