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There are 16 member Credit: A. Novick, NIST |
Clocks in the
Americas and the Caribbean Islands are now ticking in unison thanks to
the work of the Sistema Interamericano de Metrologia (SIM), a regional
metrology organization that works to promote accurate measurements
throughout the Americas. Since 2005, SIM has been building a time
network, designed by the U.S. National Institute of Standards and
Technology (NIST), that now extends to 16 nations.
The SIM Time Network allows each of these
nations to continuously compare their clocks, with the time differences
between the nations displayed on a SIM Web site. These time differences
generally are very small, often less than 100 nanoseconds (100
billionths of a second).
It has been said that the world’s most
commonly asked question is “What time is it?” Nations that maintain
accurate time standards benefit all of their residents. Accurate time
and synchronization are crucial for much or our modern technology,
enabling the efficient operation of telecommunications, computer
networks, electric power distribution, and many other parts of the
technology infrastructure that we use every day.
The SIM Time Network began in 2005 by
adopting technology developed at NIST to more easily distribute accurate
time and frequency information to remote locations. NIST developed a
self-contained, user-friendly system about the size of a microwave oven
that can be quickly installed in any laboratory. One or more atomic
clocks then are connected to the automated system, which uses the
Internet and the Global Positioning System (GPS) to compare the clocks’
time with clocks at other laboratories on the network and report the
results to the central servers of the SIM Time Network.
The SIM Time Network initially compared the
national time standards among Canada, Mexico and the United States. The
network has been rapidly expanding, and now includes time standards in
Argentina, Brazil, Chile, Colombia, Costa Rica, Jamaica, Panama,
Paraguay, Peru, St. Lucia, Uruguay, Guatemala, and Trinidad and Tobago
as well. The time from each nation is measured every second, and the
measurements are transferred across the network every 10 minutes and
displayed on the Internet. The results are publicly available so that
anyone can see in near real-time comparisons between the time standards
for all the participating countries.
Michael Lombardi, the NIST scientist who
designed the network, says that it has helped several laboratories gain
status as the official timekeepers for their respective countries, and
several of the SIM Time Network participants also have begun
participating for the first time in the generation of official
international time—Coordinated Universal Time (UTC)—a sort of weighted
average of time kept by official clocks maintained by the International
Bureau of Weights and Measures in France (French acronym BIPM).
The SIM Time Network has led to increased
cooperation and scientific collaboration among its members. Mauricio
Lopez of the Centro Nacional de Metrología (CENAM) of Mexico, who chairs
the SIM Time and Frequency Working group, and his staff at CENAM led
the development of a project that combines the time kept by all of the
clocks in the network and produces an average timescale, called SIM Time
(SIMT). The laboratories in the network can then compare their clocks
to each other and to SIMT.
To see the SIM Time Network in action, visit http://tf.nist.gov/sim/index.htm
(home page) and http://132.163.4.82/scripts/sim_rx_grid.exe
(current results display).
Media Contact: James Burrus, james.burrus@nist.gov, (303)
497-4789
