Wednesday, May 20, 2015

140 Years of International Time

The newest "Cesium Fountain" Atomic Clock, which
established a new civilian time standard for the United
States last year.
(Image Source: National Institute of Standards and Technology,
U.S. Department of Commerce)

By Glenn A. Walsh
Reporting for SpaceWatchtower

International coordination of time is now 140 years old.

One hundred, forty years ago today (May 20), a treaty among 17 nations (of 20 nations considering the proposal), including the United States, was signed forming the International Bureau of Weights and Measures. Officially known by its French name, Bureau International des Poids et Mesures (BIPM), the Bureau was established to maintain the International System of Units (SI) under the terms of the Convention du Metre or Metric Convention. As of August of 2008, 51 nations have signed the Metric Convention.

In America, time and measurement standards are maintained by the National Institute of Standards of Technology. From 1830 until 1901, weights and measures had been maintained by the Office of Standard Weights and Measures in the U.S. Department of the Treasury. In 1901, these responsibilities were transferred to the U.S. Department of Commerce and enhanced with the creation of the National Bureau of Standards.

With the passage of Public Law 100-418, the National Bureau of Standards became the National Institute of Standards and Technology on 1988 August 23. Many employees were quite disappointed that the National Bureau of Standards name, which was considered the gold-standard for the standards of weights, measures, and time world-wide, would be discarded. However, the U.S. Congress determined that the agency should take greater responsibility in improving American industrial competitiveness throughout the world and needed a new name to highlight the agency's new responsibilities.

One of the major responsibilities of the International Bureau of Weights and Measures is to maintain accurate, world-wide time-of-day. An official Coordinated Universal Time (UTC) is established after the Bureau collects, analyzes, and averages the atomic time measured and calculated by atomic clocks in laboratories around the world, from nations who are signatories to the Metric Convention.

This precise time standard and accurate time synchronization are essential in our modern world. Global navigation satellite systems rely on precise time for communication systems of all kinds from satellites to cellular telephones, electrical power grid synchronization, financial transactions, and scientific applications. Of course, this includes GPS systems used by millions of people world-wide.

Astronomy has always had a need for precise time. Astronomers were the first to establish methods, using the stars, to calculate exact time, using special telescopes called transit telescopes.

In fact, beginning in 1869, Pittsburgh's Allegheny Observatory, under Director Samuel Pierpont Langley (who would go on to become the third Secretary of the Smithsonian Institution, then considered the nation's greatest scientific appointment), sold precise time to the railroads and cities. This is considered the first regular and systematic system of time distribution, using the telegraph. This precise time was derived from the Allegheny Observatory's transit telescope and the proceeds were used to fund Observatory operations and research.

This led to “Railroad Time” in 1883, which included the first five time zones in North America. The railroads voluntarily established these time zones, to avoid government action. The 1918 Standard Time Act brought these time zones into Federal law.

More on the International Bureau of Weights and Measures ---
Link 1 >>>
Link 2 >>>

More on Standard Time ---
Link 1 >>>
Link 2 (History in North America) >>>

More on the National Institute of Standards and Technology, U.S. Department of Commerce ---
Link 1 >>>
Link 2 >>>

More on Radio Stations Broadcasting International Time ---
Voice Announcements -
WWV (SW), Fort Collins CO: Link >>>
WWVH (SW), Kekaha HI: Link >>>
CHU (SW), Ottawa, ON Canada: Link >>>
Broadcast for Radio-Controlled Clocks -
WWVB (LW), Fort Collins CO: Link >>>

More on the Allegheny Observatory:
Link >>>

More on Samuel Pierpont Langley: Link >>>

Related Blog Posts ---

New Laser System Could Provide Mini Atomic Clocks (2014 Nov. 15):

Link >>>

New U.S. Atomic Clock World's Most Accurate  (2014 April 26):

Link >>>

Even More Accurate Atomic Clock  (2014 Jan. 27):

Link >>>

Laser Pulses Create More Accurate Atomic Clocks  (2013 June 21):

Link >>> 


Centennial: New Allegheny Observatory Dedication  (2012 Aug. 28):

Link >>>

Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss.

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