UTC - Keeping Global Time
Apa masa itu? Salah satu soalan yang paling biasa diucapkan di seluruh dunia tetapi apa sebenarnya yang kami tanyakan? Anda bertanya kepada seseorang di China apa waktu itu anda pasti akan mendapat jawapan yang berbeza jika anda meminta orang Amerika, jelas zon waktu mereka berada di seberang dunia.
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.
Apabila kita bertanya pada masa itu, apa yang sebenarnya kita minta adalah perkiraan kasar untuk zon waktu yang kita ada. Sesetengah jam tangan lebih tepat daripada yang lain tetapi ia sering cukup untuk keperluan hari ke hari.
Tetapi bagaimana jika anda perlu tahu masa yang tepat dan bagaimana jika anda perlu tahu apa masa itu adalah negara lain juga. Mungkin anda telah membeli tiket penerbangan; ia akan mengecewakan untuk muncul di lapangan terbang hanya untuk diberitahu bahawa tiket anda telah dijual kepada orang lain sebagai jam di ejen perjalanan mereka lebih lambat daripada yang anda beli tiket anda.
Jadi, bagaimanakah industri global menyimpan masa yang tepat antara satu sama lain? Jawapannya agak mudah dan ia dipanggil Waktu Bersama Selaras atau UTC.
Biro Berat dan Langkah Antarabangsa (BIPM) bertindak sebagai penjaga masa rasmi untuk dunia dan memulakan UTC di 1972 selepas pembangunan jam atom.
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.
Satu-satunya masalah dengan jam tangan UTC adalah bahawa jam atom sangat besar dalam saiz dan kos. Sebenarnya mereka hanya boleh didapati dalam makmal fizik berskala besar seperti NPL (National Physics Laboratory, UK) atau 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 NTP (Network Time Protocol) which has been developed over the last 25 years to keep computer networks synchronized so they do not have to rely on their inaccurate internal clocks.
Pelayan NTP and UTC have allowed industry to become truly global and made possible technologies such as communication satellites, mobile phones, sat-nav and ATM's that we all take for granted.
