Category: chronology

History of Timekeeping from Stonehenge to the NTP Server

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Keeping track of time has been as integral part of helping human civilisation to develop. It could be argued that the greatest step that mankind took was in the development of farming, allowing humans to free up more time to develop sophisticated cultures.

However, farming was fundamentally reliant on timekeeping. Crops are seasonal and knowing when to plant them is the key to all horticulture. It is believed that ancient monuments such as Stonehenge were elaborate calendars helping the ancients to identify the shortest and longest days (solstice).

As human civilisation developed, telling increasingly accurate time became more and more important. And identifying days of the year was one thing but calculating how far into a day was another.

Timing was extremely inaccurate up until the middle ages. People would rely on comparisons of time as a time reference such as how long it took to walk a mile or the time of day would be estimated from when the sun was highest (noon).

Fortunately the development of clocks during the middle of the last millennium meant that for the first time humans could tell with some degree of precision the time of day. As clocks developed so did their accuracy and civilisation became more efficient as events could be more accurately synchronised.

When electronic clocks arrived at the turn of the last century, accuracy was further increased and new technologies started to develop but it wasn’t until the rise of the atomic clock that the modern world really took shape.

Atomic clocks have enabled technologies such as satellites, computer networks and GPS tracking possible as they are so accurate – to within a second every hundred million years.

The atomic clocks were even discovered to be even more accurate than the spin of the Earth that varies, thanks to the Moon’s gravity and extra seconds have to be added to the length of a day – The leap second.

Atomic clocks mean that a global timescale accurate to within a thousandth of second has been developed called UTC – Coordinated Universal Time.

Computer networks to communicate with each other from across the globe in perfect synchronisation to UTC if they use a NTP time server.

An NTP server will synchronise an entire computer network to within a few milliseconds of UTC time allowing global communications and transactions.

Atomic clocks are still being developed the latest strontium clocks are promising accuracy to within a second every billion years.

Time Server Manufacturers

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Time servers come in several shapes and sizes. The primary difference between most dedicated time servers is in the way they receive  a timing source.

Some time servers utilise national time and frequency transmissions that are broadcast on long wave while other use the GPS network.

Some time servers are designed to be rack-mountable perfect for the average U system of racks allowing the sever to be snugly fitted into your existing rack.

Other time servers are nothing more than small boxes that can be discretely hidden.

Here is a list of top time server manufacturers:

Galleon Systems

Elproma

Symmetricom

Meinberg

Time Tools

Time Server History and The changing ways of recording time

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The NTP server or network time server as it is often called is the culmination of centuries of horology and chronology. The history of keeping track of time has not been as smooth as you may think.

What month was the Russian October revolution? I’m sure you have guessed that it is a trick question, in fact if you trace the days back to the October revolution that changed the shape of Russia in 1917 you will find it didn’t start until November!

One of the first decisions the Bolsheviks, who had won the revolution, chose to make was to join the rest of eh world by taking up the Gregorian calendar. Russia was last to do adopt the calendar, which is still in use throughout the world today.

This new calendar was more sophisticated that the Julian calendar which most of Europe had been using since the Roman Empire. Unfortunately the Julian calendar did not allow for enough leap years and by the turn of the century this had meant that the seasons had drifted, so-much-so, that when Russia finally adopted the calendar on after Wednesday, 31 January 1918 the following day became Thursday, 14 February 1918.

So whilst the October revolution occurred in October in the old system, to the new Gregorian calendar it meant it had taken place in November.

Whilst the rest of Europe adopted this more accurate calendar earlier than the Russians they still also had to correct the seasonal drift, so in 1752 when Britain changed systems they lost eleven days which according to the populist painter of the time, Hogarth, caused rioters to demand the return of their lost eleven days.

This problem of inaccuracy in keeping track of time was thought to be solved in the 1950’s when the first atomic clocks were developed. These devices were so accurate that they could keep time for a million years without losing a second.

However, it was soon discovered that these new chronometers were in fact too accurate – compared with the Earth’s rotation anyway. The problem was that while atomic clocks could measure the length of a day to the nearest millisecond, a day is never the same length.

The reason being is that the Moon’s gravity affects the Earth’s rotation causing a wobble. This wobble has the effect of slowing down and speeding up the Earth’s spin. If nothing was done to compensate for this then eventually the time told by atomic clocks (International Atomic Time- TAI) and the time based on the Earth’s rotation used by farmers, astronomers and you and I (Greenwich Meantime- GMT) would drift that eventually noon would become midnight (albeit in many millennia).

The solution has been to devise a timescale that is based on atomic time but also accounts for this wobble of the Earth’s rotation. The solution was called UTC (Coordinated Universal Time) and accounts for the Earth’s variable rotation by having ‘leap seconds’ occasionally added. There have been over thirty leap seconds added to UTC since its inception in the 1970’s.

UTC is now a global timescale used throughout the world by computer networks to synchronise too. Most computer networks use a NTP server to receive and distribute UTC time.

Timescales of NTP and advanced time server information

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The NTP timescale is based on UTC (Coordinated Universal Time) which is a global civil timescale that is based on International Atomic Time (TAI) but accounts for the slowing of the Earth’s spin by intermittingly adding ‘leap seconds.’

This is done to ensure that UTC is kept in coincidence with GMT (Greenwich Meantime, often referred to as UT1). Failing to account for the Earth’s slowing in its rotation (and occasional speeding up) would mean that UTC would fall out of synchronisation with GMT and noon, when the sun is traditionally the highest in the sky would drift. In fact if leap seconds were not added eventually noon would fall at midnight and vice versa (albeit in several millennia).

Not everybody is happy with leap seconds, there are those that feel that adding of seconds to keep the Earth’s rotation and UTC inline is nothing but a fudge. However, failing to do so would make such things as astronomical observations impossible as astronomers need to know the exact positioning of the stellar bodies and farmers are pretty reliant on the Earth’s rotation too.

The NTP clock represents time in a totally different way to the way humans perceive time. Instead of formatting time into minutes, hours, days, months and years, NTP uses a continuous number that represents the number of seconds that have past since 0h 1 January 1900. This is known as the prime epoch.

The seconds counted from the prime epoch continue to rise but wraps around every 136 years. The first wrap-around will take place in 2036, 136 years since the prime epoch. To deal with this NTP will utilise an era integer, so when the seconds reset to zero, the integer 1 will represent the first era and negative integers represent the eras before the prime epoch.

Time servers that receive their time from the GPS system are not in fact receiving UTC, primarily because the GPS network was in development before the first leap second but they are based on TAI.  However, GPS time is converted to UTC by the GPS time server.

The radio transmission broadcast from national physics laboratories such as MSF, DCF or WWVB are all based on UTC and so the time servers do not need to do any conversion.

Next Generation of Atomic Clocks Accurate to a Second in 200 Million Years

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Atomic clocks have been around since the 1950’s. They have provided incredible accuracy in timekeeping with most modern atomic clocks not losing a second in time in a million years.

Thanks to atomic clocks many technologies have become possible and have changed the way we live our lives. Satellite communication, satellite navigation, internet shopping and network communication are only possible thanks to atomic clocks.

Atomic clocks are the basis for the world’s global timescale Universal Coordinated Time (UTC) and are the reference that many computer networks use as a time source to distribute amongst its devices using NTP (Network Time Protocol) and a time server.

Atomic clocks are based on the atom caesium -133. This element has been traditionally used in atomic clocks as its resonance or vibrations during a particular energy state, or extremely high (over 9 billion) and therefore can provide high levels of accuracy.

However, new types of atomic clocks are on the horizon that will boast even more accuracy with the next generation of atomic clocks neither gaining nor losing a second in 200 million years.

The next generation of atomic clocks no longer rely on the caesium atom but use elements such as mercury or strontium and instead of using microwaves such as the caesium clocks these new clocks use light which has higher frequencies.

Strontium’s resonance also exceeds over 430 trillion which is vastly superior to the 9.2 billion vibrations that caesium manages.

Currently atomic clocks can be utilised by computer systems by using either a radio or GPS clock or dedicated NTP time server. These devices can receive the time signal transmitted by atomic clocks and distribute them amongst network devices and computers.

However, the National Institute for Standards and Technology (NIST) have revealed a miniature atomic clock that measures just 1.5 millimetres on a side and about 4 millimetres tall. It  consumes less than 75 thousandths of a watt, and has a stability of about one part in 10 billion, equivalent to a clock that would neither gain nor lose more than a second in 300 years.

In the future these devices could be integrated into computer systems, replacing the current real time clock chips, which are notoriously inaccurate and can drift.

UTC A global Timescale

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Coordinated Universal Time (UTC – from the  French Temps Universel Coordonné) is an international timescale based on the time told by atomic clocks. Atomic clocks are accurate to within a second in several million years. They are so accurate that International Atomic Time, the time relayed by these devices, is even more accurate than the spin of the Earth.

The Earth’s rotation is affected by the gravity of the moon and can therefore slow or speed up. For this reason, International Atomic Time (TAI from the French Temps Atomique International) has to have ‘Leap seconds’ added to keep it in line with the original timescale GMT (Greenwich meantime) also referred to as UT1, which is based on solar time.

This new timescale known as UTC is now used all over the world allowing computer networks and communications to be conducted at opposite sides of the globe.

UTC is governed not by an individual country or administration but a collaboration of atomic clocks all over the world which ensures political neutrality and also added accuracy.

UTC is transmitted in numerous ways across the globe and is utilised by computer networks, airlines and satellites to ensure accurate synchronisation no matter what the location on the Earth.

In the USA NIST (National Institute of Standards and Technology) broadcast UTC from their atomic clock in Fort Collins, Colorado. The National Physics Laboratories of the UK and Germany have similar systems in Europe.

The internet is also another source of UTC time. Over a thousand time servers across the web can be used to receive a UTC time source, although many are not precise enough for most networking needs.

Another, secure and more accurate method of receiving UTC is to use the signals transmitted by the USA’s Global Positioning System. The satellites of the GPS network all contain atomic clocks that are used to enable positioning. These clocks transmit the time which can be received using a GPS receiver.

Many dedicated time servers are available that can receive a UTC time source from either the GPS network or the National physics Laboratory’s transmissions (all of which are broadcast at 60 kHz longwave).

Most time servers use NTP (Network Time Protocol) to distribute and synchronise computer networks to UTC time.

The Atomic Clock and the NTP Time Server

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Most people have heard of atomic clocks, their accuracy and precision are well known. An ato0mic clock has the potential to keep time for several hundred million years and not lose a second in drift. Drift is the process where clocks lose or gain time because of the inaccuracies in the mechanisms that make them work.

Mechanical clocks, for instance, have been around for hundreds of years but even the most expensive and well engineered will drift at least a second a day. Whilst electronic clocks are more accurate they also will drift by about a second a week.

Atomic clocks have no comparison when it comes to time keeping. Because an atomic clock is based on the oscillation of an atom (in most cases the caesium 133 atom) which has an exact and finite resonance (caesium is 9,192,631,770 every second) this makes them accurate to within a billionth of a second (a nanosecond).

While this type of accuracy is unparalleled it has made possible technologies and innovations that have changed the world. Satellite communication is only possible thanks to the time keeping of atomic clocks, so is satellite navigation. As the speed of light (and therefore radio waves) travel at over 300,000km a second an inaccuracy of a second could see a navigation system be hundreds of thousands of miles out.

Precise accuracy is also essential in many modern computer applications. Global communication, particularly financial transactions have to be done precisely. In Wall Street or the London stock exchange a second can see the value of stock rise or fall by millions. Online reservation also requires the accuracy and perfect synchronisation only atomic clocks can provide otherwise tickets could be sold more than once and cash machines could end up paying out your wages twice if you found a cash machine with a slow clock.

Whilst this may sound desirable to the more dishonest of us, it doesn’t take much imagination to understand what problems a lack of accuracy and synchronisation could cause. For this reason an International timescale based on the time told by atomic clocks has been developed.

UTC (Coordinated Universal Time) is the same everywhere and can account for the slowing of the Earth’s rotation by adding leap seconds to keep UTC inline with GMT (Greenwich Meantime). All computer networks that participate in global communication need to be synchronised to UTC. Because UTC is based on the time told by atomic clocks it is the most precise timescale possible. For a computer network to receive and keep synchronised to UTC  it first needs access to an atomic clock. These are expensive and large pieces of equipment and are generally only to be found in large scale physics laboratories.

Fortunately the time told by these clocks can still be received by a network time server wither by utilising time and frequency long wave broadcasts transmitted by national physics laboratories or from the GPS (Global Positioning system). NTP (network time protocol) can then distribute this UTC time to the network and use the time signal to keep all devices on the network perfectly synchronised to UTC.

Accuracy in Timekeeping Atomic clocks and Time Servers

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The development of atomic clocks throughout the twentieth century has been fundamental to many of the technologies we employ everyday. Without atomic clocks many of the innovations of the twentieth century would simply not exist.

Satellite communication, global positioning, computer networks and even the Internet would not be able to function in the way we are used to if it wasn’t for atomic clocks and their ultra-precision in timekeeping.

Atomic clocks are incredibly accurate chronometers not losing a second in millions of years. In comparison digital clocks may lose a second every week and the most intricately accurate mechanical clocks lose even more time.

The reason for an atomic clock’s incredible precision is that it is based on an oscillation of a single atom. An oscillation is merely a vibration at a particular energy level in the case of most atomic clocks they are based on the resonance of the caesium atom which oscillates at exactly 9,192,631,770 times every second.

Many technologies now rely on atomic clocks for their unbridled accuracy. The global positing system is a prime example. GPS satellites all have onboard an atomic clock and it is this timing information that is used to work out positioning. Because GPS satellites communicate using radio waves and they travel at the speed of light (180,000 miles a second in a vacuum), tiny inaccuracies in the time could make positioning inaccurate by hundreds of miles.

Another application that requires the use of atomic clocks is in computer networks. When computers talk to each other across the globe it is imperative that they all use the same timing source. If they didn’t, time sensitive transactions such as Internet shopping, online reservations, the stock exchange and even sending an email would be near to impossible. Emails would arrive before they were sent and the same item on an Internet shopping site could be sold to more than one person.

For this reason a global timescale called UTC (Coordinated Universal Time) based on the time told by atomic clocks has been developed. UTC is delivered to computer networks via times servers. Most time servers utilise NTP (network time protocol) to distribute and synchronize the networks.

NTP time servers can receive UTC time from a number of sources most commonly the onboard atomic clocks of the GPS system can be used as a UTC source by a time server connected to a GPS antenna.

Another method that is quite commonly used by NTP time servers is to utilise the long wave radio transmission broadcast by several countries’ national physics laboratories.  Whilst not available everywhere and quite susceptible to local topography the broadcasts do provide a secure method of receiving timing source.

If neither of these methods is available then a UTC timing source can be received from the Internet although accuracy and security are not guaranteed.