Archive for October, 2011

The Greenwich Time Lady

Wednesday, October 26th, 2011

Time synchronisation is something easily taken for granted in this day and age. With GPS NTP servers, satellites beam down time to technologies, which keeps them synced to the world’s time standard UTC (Coordinated Universal Time).

Before UTC, before atomic clocks, before GPS, keeping time synchronised was not so easy. Throughout history, humans have always kept track of time, but accuracy was never that important. A few minutes or an hour or so difference, made little difference to people’s lives throughout the medieval and regency periods; however, come the industrial revolution and the development of railways, factories and international commerce, accurate timekeeping became crucial.

Greenwich Mean Time (GMT) became time standard in 1880, taking over from the world’s first time standard railway time, developed to ensure accuracy with railway timetables. Soon, all businesses, shops and offices wanted to keep their clocks accurate to GMT, but in an age before electrical clocks and telephones, this proved difficult.

Enter the Greenwich Time Lady. Ruth Belville was a businesswoman from Greenwich, who followed in her father’s footsteps in delivering time to businesses throughout London. The Belville’s owned a highly accurate and expensive pocket watch, a John Arnold chronometer originally made for the Duke of Sussex.

Every week, Ruth, and her father before her, would take the train to Greenwich where they would synchronise the pocket watch to Greenwich Mean Time. The Belvilles would then travel around London, charging businesses to adjust their clocks their chronometer, a business enterprise that lasted from 1836 to 1940 when Ruth finally retired at the age of 86.

BY this time, electronic clocks had began to take over traditional mechanical devices and were more accurate, needing less synchronisation, and with the telephone speaking clock introduced by the General Post Office (GPO) in 1936, timekeeping services like the Belville’s became obsolete.

Today, time synchronisation is far more accurate. Network time servers, often using the computer protocol NTP (Network Time Protocol), keep computer networks and modern technologies true. NTP time servers receive an accurate atomic clock time signal, often by GPS, and distribute the time around the network. Thanks to atomic clocks, NTP time servers and the universal timescale UTC, modern computers can keep time to within a few milliseconds of each other.

 

Keeping Track of Time Zones

Wednesday, October 19th, 2011

Despite the use of UTC (Coordinated Universal Time) as the world’s timescale, time zones, the regional areas with a uniform time, are still an important aspect of our daily lives. Time zones provide areas with a synchronised time that helps commerce, trade and society function, and allow all nations to enjoy noon at lunchtime. Most of us who have ever gone abroad are all aware of the differences in time zones and the need to reset our watches.

Time zones around the world

Keeping track of time zones can be really tricky. Different nations not only use different times but also use different adjustments for daylight saving, which can make keeping track of time zones difficult. Furthermore, nations occasionally move time zone, normally due to economic and trade reasons, which provides even more difficulties in keeping track of time zones.

You may think that modern computers can automatically account for time zones due to the settings in the clock program; however, most computer systems rely on a database, which is continuously updated, to provide accurate time zone information.

The Time Zone Database, sometimes called the Olson database after its long-time coordinator, Arthur David Olson, has recently moved home due to legal wrangling, which temporarily caused the database to cease functioning, causing untold problems for people needing accurate time zone information. Without the time zone database, time zones had to be calculated manually, for travelling, scheduling meetings and booking flights.

The Internet’s address system, ICANN (Internet Corporation for Assigned Names and Numbers) has taken over the database to provide stability, due to the reliance on the database by computer operating systems and other technologies; the database is used by a range of computer operating systems including Apple Inc’s Mac OS X, Oracle Corp, Unix and Linux, but not Microsoft Corp’s Windows.

The Time Zone Database provides a simple method of setting the time on a computer, enabling cities to be selected, with the database providing the right time. The database has all the necessary information, such as daylight saving times and the latest time zone movements, to provide accuracy and a reliable source of information.

Or course, a synchronised computer networks using NTP doesn’t require the Time Zone Database. Using the standard international timescale, UTC, NTP servers maintain the exact same time, no matter where the computer network is in the world, with the time zone information calculated as a difference to UTC.

 

 

Vote Called to End the Use of GMT and Scrapping the Leap Second

Wednesday, October 12th, 2011

International Telecommunications Union (ITU), based in Geneva, is voting in January to finally get rid of the leap second, effectively scrapping Greenwich Meantime.

 

Greenwich Mean Time may come to an end

UTC (Coordinated Universal Time) has been around since the 1970’s, and already effectively governs the world’s technologies by keeping computer networks synchronised by way of NTP time servers (Network Time Protocol), but it does have one flaw: UTC is too accurate, that is to say, UTC is governed by atomic clocks, not by the rotation of the Earth. While atomic clocks relay an accurate, unchanging form of chronology, the Earth’s rotation varies slightly from day-to-day, and in essence is slowing down by a second or two a year.

To prevent noon, when the sun is highest in the sky, from slowly getting later and later, Leap Seconds are added to UTC as a chronological fudge, ensuring that UTC matches GMT (governed by when the sun is directly above by the Greenwich Meridian Line, making it 12 noon).

The use of leap seconds is a subject of continuous debate. The ITU argue that with the development of satellite navigation systems, the internet, mobile phones and computer networks all reliant on a single, accurate form of time, a system of timekeeping needs to be precise as possible, and that leap seconds causes problems for modern technologies.

This against changing the Leap Second and in effect retaining GMT, suggest that without it, day would slowly creep into night, albeit in many thousands of years; however, the ITU suggest that large-scale changes could be made, perhaps every century or so.

If leap seconds are abandoned, it will effectively end Greenwich Meantime’s guardianship of the world’s time that has lasted over a century. Its function of signalling noon when the sun is above the meridian line started 127 years ago, when railways and telegraphs made a requirement for a standardised timescale.

If leap seconds are abolished, few of us will notice much difference, but it may make life easier for computer networks that synchronised by NTP time servers as Leap Second delivery can cause minor errors in very complicated systems. Google, for instance, recently revealed it had written a program to specifically deal with leap seconds in its data centres, effectively smearing the leap second throughout a day.

Have Scientists Found Faster than Light Particles?

Wednesday, October 5th, 2011

The physics world got itself into a bit of a tizz this month as scientists at CERN, the European Laboratory for Particle Physics, found an anomaly on one of their experiments, which seemed to show that some particles were travelling faster than light.

Time server's can provide atomic clock accuracy

Faster than light travel for any particle is prohibited of course, according to Einstein’s Special Theory of Relativity, but the OPERA team at CERN, who fired neutrinos around a particle accelerator, travelling for 730 km, found that the neutrinos travelled the distance 20 parts per million faster than photons (light particles) meaning they broke Einstein’s speed limit.

While this experiment could prove to be one of the most important discoveries in physics, physicists are remaining sceptical, suggesting that a cause could be an error generated in the difficulties and complexities of measuring such high speeds and distances.

The team at CERN used GPS time servers, portable atomic clocks and GPS positioning systems to make their calculations, which all provided accuracy in distance to within 20cm and an accuracy of time to within 10 nanoseconds. However, the facility is underground and the GPS signals and other data streams had to be cabled down to the experiment, a latency the team are confident they took into account during their calculations.

Physicists from other organisations are now attempting to repeat the experiments to see if they get the same results. Whatever the outcome, this type of groundbreaking research is only possible thanks to the accuracy of atomic clocks that are able to measure time to millionths of a second.

To synchronise a computer network to an atomic clock you don’t need to have access to a physics laboratory like CERN as simple NTP time servers like Galleons NTS 6001 will receive an accurate source of atomic clock time and keep all hardware on a network to within a few milliseconds of it.