Caesium Atomic Clock (Essen-Parry)
Record status
Individual type · partial
Period
1955
The Caesium Atomic Clock, constructed in 1955 by Louis Essen and J.V.L. Parry at the National Physical Laboratory in Teddington, England, is recognized as the first successful implementation of an atomic timekeeping device.
Measuring 1685 mm by 607 mm by 1732 mm and weighing 463 kg, the instrument operates by measuring the change of state in caesium atoms to establish time standards. The device demonstrated an accuracy of one second in 300 years, significantly surpassing the precision of contemporary quartz crystal and mechanical pendulum clocks. Its development facilitated the transition of time definition from astronomical observations to atomic measurements.
The apparatus features an exposed horizontal metallic structure supported by substantial grey-painted vertical stands, with various scientific components and magnetic housings integrated into the frame.
Evidence at a glance
- Linked sources
- 1
- Photograph views
- 1
- Catalogue references
- 0
Counts describe this entry’s documentation, not authenticity, rarity or completeness. Photographs may show one specimen; check each caption and licence.
Technical characteristics
- Type
- Atomic clock
- Maker
- Louis Essen and J.V.L. Parry at the National Physical Laboratory
- Weight
- 463 kg
- Accuracy
- one second in 300 years
- Location
- Teddington, London
- Place recorded
- United Kingdom
- Maker / attribution
- National Physical Laboratory
Design
- Visible features
- • Large-scale horizontal metallic beam assembly • Exposed wooden framework structure • Grey painted support plinths • Multi-wired connections at the end of the beam
- Timekeeping Mechanism
- This clock operates by utilizing the internal atomic properties of caesium. Specifically, it measures time through the detection of changes in the state of caesium atoms as they traverse the vacuum chamber. This mechanism represented a departure from traditional mechanical timekeeping, which relied on the physical oscillation of pendulums or quartz crystals. By utilizing atomic transitions, the clock achieved a degree of precision approximately 30 times greater than quartz crystal clocks and 300 times greater than mechanical pendulum clocks. This shift allowed for the detection of minor irregularities in the Earth's rotation, ultimately leading to the redefinition of the second based on atomic measurement rather than astronomical events.
- Construction and Design
- The Caesium Atomic Clock is designed as a large-scale, floor-standing scientific apparatus. It comprises a primary, elongated horizontal beam containing the atomic beam vacuum system, encased within an open-frame timber structure. This wooden housing provides support and protection for the metallic scientific instruments aligned along the longitudinal axis. The entire assembly is mounted upon two substantial, grey-painted metal pedestals, which elevate the beam to a height of approximately 1.7 meters. The components, including various brass housings, magnets, and vacuum-related cylinders, are arranged along the central horizontal beam, connected by a network of electrical wiring terminating at external connection boards on one end of the structure.
- Provenance and Significance
- The object is held by the Science Museum Group with the accession number 1962-59. It serves as the primary artifact documenting the invention of atomic timekeeping. The clock was developed in 1955 by Louis Essen and J.V.L. Parry at the National Physical Laboratory in Teddington. While subsequent atomic clocks have reached accuracy levels of one second in a million years, the Essen-Parry clock provided the initial empirical proof for the viability of atomic-based chronometry.
Identification
- Accession number
- 1962-59
- Source note
- Facts transcribed from the linked source listing or collection record. Attribution and specifications are source-reported and have not been independently authenticated.
Catalogue references
No catalogue numbers recorded. Numbers are only published once transcribed from a verified edition of a standard catalogue — they are never inferred.
Research required
- Research required: The exact technical function of the various magnets and chambers on the beam is not explicitly detailed in the source.
- Research required: The operational status of the internal vacuum or atomic source components is not stated.