This article explains all the different time
scale utilized and how time can be synchronised globally.
Asking
somebody the time may be one of today’s most common questions but have you ever
wondered where the time on our watches comes from?
Accurate
clocks have only been around since the mid 17th century, before then,
time was completely subjective. People would use the celestial bodies as a time
reference such as noon (when the sun was highest) and midnight (when the moon
is at its highest) and also dawn and dusk. Often lengths of time were referred
to in comparison such as the time it would take a man to walk a mile.
Standard
timescales did not exist until the 1840’s when it became necessary during the
height of the railway’s popularity when a railway standard time for all
England, Wales and Scotland replaced all the local timescales.
A few years
later the Royal Observatory in Greenwich developed its own time scale. This was
based on the sun and moon, with 12 o’clock (noon) being when the sun was over
the Greenwich Meridian, they began transmitting this timescale using the
telegraph and by 1855 most of Britain used GMT (Greenwich Mean Time) and it soon
became a recognized time reference throughout the world.
However, it
became apparent with the invention of atomic clocks that basing a time
reference on the movement of the Earth was not accurate enough. In 1967 the
second was defined by the oscillations of the caesium -133 atom (as used in
atomic clocks) and provided the most accurate reference for time yet but attempts
to couple GMT with this new definition proved unsatisfactory when it was
discovered that the Earth slows (and speeds up) on its axis.
This variations
in the rotation of the Earth meant a new timescale UTC, (Coordinated Universal
Time) which made adjustments for this slowing adding (or subtracting) a second
when ever necessary (failure to do so would mean eventually day would become
night as time would slip , albeit in many millennia). This addition is known as
a Leap Second.
UTC has
become vital in allowing the global community to communicate with each other.
UTC allows the world to synchronise to one time scale regardless of the time
zone (UTC handles timezones with a + or minus such as UTC +5 or UTC -2)
UTC enables
computers to synchronise together all over the world using NTP (Network Time
Protocol). Without NTP it would be impossible to conduct time sensitive
transactions such as buying an airline ticket or bidding on Ebay.
Most NTP
time servers receive UTC time atomic clocks from either a broadcasted signal
from a large physics laboratory or via the GPS network.
About the author
Tags: 1840s, accurate clocks, accurate reference, atomic clocks, celestial bodies, coordinated universal time, dawn and dusk, different time, england wales, greenwich mean time, greenwich meridian, oscillations, own time, rotation of the earth, royal observatory, sun and moon, time reference, time scale, timescale, timescales