This article explains the world’s global timescale - UTC (Coordinated Universal Time) what it is, why it was adopted and how important it is now.
What time is it? One of the commonest questions uttered
around the World but what exactly are we asking? You ask someone in China what
the time is then you will certainly get a different answer if you ask an
American, obviously their time-zones are on the opposite side of the world.
But what if you ask two people in the same room as you? You
may get the same answer from them both but then again one person’s watch
may be
a minute or two faster.
When we ask the time then what we are really asking for is a
rough estimate for the time zone that we are in. Some watches are more accurate
than others but it is often enough for our day to day needs.
But what if you need to know the exact time and what if you
need to know what that time is another country too. Perhaps you have bought an
airline ticket; it would be disappointing to turn up at the airport only to be
told that your ticket was sold to somebody else in as the clock at their travel
agent was slower than the one where you bought your ticket.
So how does global industry keep accurate time with one
another? The answer is quite simple and it is called Coordinated Universal Time
or UTC.
The International Bureau of Weights and Measures (BIPM) acts
as the official time-keeper for the globe and started UTC in 1972 after the
development of atomic clocks.
The atomic clock was first developed in the late 50’s when
it was discovered the atom caesium-133 resonates at an exact frequency of 9,192,631,770
every second. This frequency was so exact that atomic clocks developed an
accuracy of one second in 1.4million years and The International System of
Units defined the second as the frequency of the caesium-133 atom and an
international unit for measuring time was born.
However, atomic clocks are even more accurate than the Earth
itself which is actually slowing in its rotation. This slowing is only small
but if the standard system of time, UTC, didn’t compensate for it, eventually
midnight would fall in the middle of the day (although that would take a
millennia or two) so leap seconds are added every few years to compensate.
The only problem with UTC timepieces is that atomic clocks are
enormous in both size and cost. In fact they are generally only to be found in
large scale physics laboratories such as NPL (National Physics Laboratory, UK)
or MIT (Massachusetts Institute of Technology, US).
Then how does the rest of the world keep track of UTC time?
The time told on these vast atomic clocks is broadcast via radio broadcasts or
the GPS satellite system (Satellite Navigation is reliant on UTC as without it
a satellite can’t tell exactly where a receiver is).
Most computer networks are sycnhronised to UTC time either
over the Internet (which isn’t secure and only recommended for home users) or
through specialist GPS or radio time servers. These time servers make use of
, sat-nav and ATM’s that we all take for granted.
About the author
Richard N Williams is a technical author and a specialist in the
telecommunications and network time synchronisation industry helping to develop
dedicated time server products. Please visit us for more information
about a GPS time server or other NTP
products
Tags: accurate time, airline ticket, atomic clock, atomic clocks, coordinated universal time, exact frequency, exact time, global industry, international bureau of weights and measures, international system of units, measuring time, official time, rough estimate, system of units, time keeper, time zone, time zones, timescale, travel agent, weights and measures
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