Category: chronology

The Fragility of Time Japanese Earthquake Shortens the Day

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The recent and tragic earthquake that has left so much devastation in Japan has also highlighted an interesting aspect about the measurement of time and the rotation of the Earth.

So powerful was the 9.0 magnitude earthquake, it actually shifted Earth axis by 165mm (6½ inches) according to NASA.

The quake, one of the most powerful felt on Erath over the last millennia, altered the distribution of the planet’s mass, causing the Earth to rotate on its axis that little bit faster and therefore, shortening the length of every day that will follow.

Fortunately, this change is so minute it is not noticeable in our day to day activities as the Earth slowed by less than a couple of microseconds (just over a millionth of a second), and it isn’t unusual for natural events to slow down the speed of the Earth’s rotation.

In fact, since the development of the atomic clock in the 1950’s, it has been realised the Earth’s rotation is never continual and in fact has been increasing very slightly, most probably for billions of years.

These changes in the Earth’s rotation, and the length of a day, are caused by the effects of the moving oceans, wind and the gravitational pull of the moon. Indeed, it has been estimated that before humans arrived on Earth, the length of a day during the Jurassic period (40-100 million years ago) the length of a day was only 22.5 hours.

These natural changes to the Earth’s rotation and the length of a day, are only noticeable to us thanks to the precise nature of atomic clocks which have to account for these changes to ensure that the global timescale UTC (Coordinated Universal Time) doesn’t drift away from mean solar time (in other words noon needs to remain when the sun is highest during the day).

To achieve this, extra seconds are occasionally added onto UTC. These extra seconds are known as leap seconds and over thirty have been added to UTC since the 1970’s.

Many modern computer networks and technologies rely on UTC to keep devices synchronised, usually by receiving a time signal via a dedicated NTP time server (Network Time Protocol).

NTP time servers are designed to accommodate these leap seconds, enabling computer systems and technologies to remain accurate, precise and synchronised.

Mechanisms of Time History of Chronological Devices

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Nearly every device seems to have a clock attached to it these days. Computers, mobile phones and all the other gadgets we use are all good sources of time. Ensuring that no matter where you are a clock is never that far away – but it wasn’t always this way.

Clock making, in Europe, started around the fourteenth century when the first simple mechanical clocks were developed. These early devices were not very accurate, losing perhaps up to half an hour a day, but with the development of pendulums these devices became increasingly more accurate.

However, the first mechanic al clocks were not the first mechanical devices that could tell and predict time. Indeed, it seems Europeans were over fifteen hundred years late with their development of gears, cogs and mechanical clocks, as the ancients had long ago got there first.

Early in the twentieth century a brass machine was discovered in a shipwreck (Antikythera wreck) off Greece, which was a device as complex as any clock made in Europe up in the mediaeval period. While the Antikythera mechanism is not strictly a clock – it was designed to predict the orbit of planets and seasons, solar eclipses and even the ancient Olympic Games – but is just as precise and complicated as Swiss clocks manufactured in Europe in the nineteenth century.

While Europeans had to relearn the manufacture of such precise machines, clock making has moved on dramatically since then. In the last hundred or so years we have seen the emergence of electronic clocks, using crystals such as quartz to keep time, to the emergence of atomic clocks that use the resonance of atoms.

Atomic clocks are so accurate they won’t drift by even a second in a hundred thousand years which is phenomenal when you consider that even quartz digital clocks will drift several seconds n a day.

While few people will have ever seen an atomic clock as they are bulky and complicated devices that require teams of people to keep them operational, they still govern our lives.

Much of the technologies we are familiar with such as the internet and mobile phone networks, are all governed by atomic clocks. NTP time servers (Network Time Protocol) are used to receive atomic clock signals often broadcast by large physics laboratories or from the GPS (Global Positioning System) satellite signals.

NTP servers then distribute the time around a computer network adjusting the system clocks on individual machines to ensure they are accurate. Typically, a network of hundreds and even thousands of machines can be kept synchronised together to an atomic clock time source using a single NTP time server, and keep them accurate to within a few milliseconds of each other (few thousandths of a second).

Origin of Synchronisation (Part 2)

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Continued…

Most towns and cities would have a main clock, such as Big Ben in London, and for those living near-by, it was fairly easy to look out the window and adjust the office or factory clock to ensure synchronicity; however, for those not in view of these tower clocks, other systems were used.

Commonly, somebody with a pocket watch would set the time by the tower clock in the morning and then go around businesses and for a small fee, let people know exactly what the time was, thus enabling them to adjust the office or factory clock to suit.

When, however, the railways began, and timetables became important it was clear a more accurate method of time keeping was needed, and it was then that the first official time-scale was developed.

As clocks were still mechanical, and therefore inaccurate and prone to drift, society again turned to that more accurate chronometer, the sun.

It was decided that when the sun was directly above a certain location, that would signal noon on this new time-scale. The location: Greenwich, in London, and the time-scale, originally called railway time, eventually became Greenwich Meantime (GMT), a time-scale that was used until the 1970’s.

Now of course, with atomic clocks, time is based on an international time-scale UTC (Coordinated Universal Time) although its origins are still based on GMT and often UTC is still referred to as GMT.

Now with the advent of international trade and global computer networks, UTC is used as the basis of nearly all international time. Computer networks deploy NTP servers to ensure that the time on their networks are accurate, often to a thousandth of a second to UTC, which means all around the world computers are ticking with the same accurate time – whether it is in London, Paris, or New York, UTC is used to ensure that computers everywhere can accurately communicate with each other, preventing the errors that poor time synchronisation can cause.

Origin of Synchronisation (Part 1)

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Part One

With modern NTP servers (Network Time Protocol) synchronisation is made easy. By receiving a signals from GPS or radio signals such as MSF or WWVB, computer networks consisting of hundreds of machines can easily be synchronised together, ensuring trouble free networking and accurate time-stamping.

Modern NTP time servers are reliant on atomic clocks, accurate to billions of parts of a second, but atomic clocks have only been around for the last sixty years and synchronisation has not always been so easy.

In the early days of chronology, clocks mechanical in nature, were not very accurate at all. The first time-pieces could drift by up to an hour a day so the time could differ from town clock to town clock, and most people in the agricultural based society regarded them as a novelty, relying in stead on sunrise and sunset to plan their days.

However, following the industrial revolution, commerce became more important to society and civilisation, and with it, the need to know what the time was; people needed to know when to go to work, when to leave and with the advent of railways, accurate time became even more crucial.

In the early days if industry, workers were often woken for work by people paid to wake them up. Known as ‛knocker-uppers.’ Relying on the factory time-peice, they would go around town and tap on people’s windows, alerting them to the start of the day, and the factory hooters signalled the beginning and end of shifts.

However, as commerce developed time became even more crucial, but as it would take another century or so for more accurate timepieces to develop (until at least the invention of electronic clocks), other methods were developed.

To follow…

Using Atomic Clocks for Time Synchronisation

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The atomic clock is unrivalled in its chronological accuracy. No other method of maintaining time comes close to the precision of an atomic clock. These ultra-precise devices can keep time for thousands of years without losing a second in drift – in comparison to electronic clocks, perhaps the next most accurate devices, which can drift up to a second a day.

Atomic clocks are not practical devices to have around though. They use advanced technologies such as super-coolant liquids, lasers and vacuums – they also require a team of skilled technicians to keep the clocks running.

Atomic clocks are deployed in some technologies. The Global Positioning System (GPS) relies on atomic clocks that operate onboard the unmanned orbiting satellites. These are crucial for working out accurate distances. Because of the speed of light that the signals travel, a one second inaccuracy in any GPS atomic clock would lead to positing information being out by thousands of kilometres – but the actual accuracy of GPS is within a few metres.

While these wholly accurate and precise instruments for measuring time are unparalleled and the expensive of running such devices is unobtainable to most people, synchronising your technology to an atomic clock, in actual fact, is relatively simple.

The atomic clocks onboard the GPS satellites are easily utilised to synchronise many technologies to. The signals that are used to provide positioning information can also be used as a source of atomic clock time.

The simplest way to receive these signals is to use a GPS NTP server (Network Time Protocol). These NTP servers use the atomic clock time signal from the GPS satellites as a reference time, the protocol NTP is then used to distribute this time around a network, checking each device with the GPS time and adjusting to ensure accuracy.

Entire computer networks can be synchronised to the GPS atomic clock time by using just one NTP GPS server, ensuring that all devices are within milliseconds of the same time.

Time Synchronisation of Technology

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Many technologies are reliant and precise, accurate and reliable time. Time synchronisation is vital in many technical systems that we encounter everyday, from CCTV cameras and ATMs to air traffic control and telecommunication systems.

Without synchronisation and accuracy many of these technologies would become unreliable and in could cause major problems, even catastrophic ones in the case of air traffic controllers.

Precise time and synchronisation also plays an increasingly important part in modern computer networking, ensuring the network is secure, data is not lost, and the network can be debugged. Failing to ensure a network is synchronised properly can lead to many unexpected problems and security issues.

Ensuring accuracy

To ensure accuracy and precise time synchronisation modern technologies and computer networks the time controlling Network Time Protocol (NTP) is most commonly employed. NTP ensures all devices on a network, whether they are computers, routers, CCTV cameras or almost any other technology, are maintained at the exact same time as every other device on the network.

It works by using a single time source that it then distributes around the network, checking for drift, and correcting devices to ensure parity with the time source. It has many other features such as being able to assess errors and calculating the best time from multiple sources.

Obtaining the time

When using NTP, getting the most accurate source of time allows you to keep your network synchronised – not just together but also synchronised to every other device or network that uses that same time source.

A global timescale known as Coordinated Universal Time (UTC) is what most NTP servers and technologies use. A sit is a global timescale, and is not concerned with time zones and daylight saving, UTC allows networks across the world to communicate precisely with the exact same time source.

NTP time servers

Despite their being many sources of UTC across the internet, these are not recommended for accuracy and security reasons; to receive an accurate source of NTP there are really only two options: using a NTP time server that can receive radio transmissions from atomic clock laboratories or by using the time signals from GPS satellites.

Windows Server and the Importance of NTP

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Windows Server is the most common operating system used by business networks. Whether it is the latest Windows Server 2008 or a previous incarnation such as 2003, most computer networks used in trade and business have a version.

These network operating systems make use of the time synchronization protocol NTP (Network Time Protocol) to ensure synchronicity between all devices connected to the network. This is vital in the modern world of global communication and trade as a lack of synchronization can cause untold problems; data can get lost, errors can go undetected, debugging becomes near impossible and time sensitive transactions can fail if there is no synchronization.

NTP works by selecting a single time source and it be checking the time on all devices on the network, and adjusting them, it ensures the time is synchronised throughout. NTP is capable of keeping all PCs, routers and other devices on a network to within a few milliseconds of each other.

The only requirement for network administrators is to select a time source – and this is where many IT professionals commonly go wrong.

Internet time servers

Any source of time to synchronize a network to should be UTC (Coordinated Universal Time) which is a global timescale controlled by the world’s most accurate atomic clocks and the number one source for finding a UTC time server is the internet.

And many network administrators opt to use these online time servers thinking they are an accurate and secure source of time; however, this is not strictly the case. Internet time servers send the time signal through the network firewall which means viruses and malicious users can take advantage of this ‘hole.’

Another problem with internet time servers is that their accuracy can’t be guaranteed. Often they are not as accurate as a profession network requires and factors such as distance away from the host can make differences in the time.

Dedicated NTP time server

Dedicated NTP time servers, however, get the time directly from atomic clocks – either from the GPS network or via secure radio transmissions from national physics laboratories. These signals are millisecond accurate and 100% secure.

For anyone running a network using Windows Server 2008 or other Microsoft operating system should seriously consider using a dedicated NTP server rather than the internet to ensure accuracy, reliability and security.

NTP Servers versus Internet Time What is the best method for Accurate Time?

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Accurate and reliable time is highly important and as networks and the internet gets faster and faster – accuracy becomes even more essential.

Computers internal clock systems are nowhere near accurate enough for many networked tasks. As simple quartz chronometers they will drift, by as a much as a second which perhaps wouldn’t be a problem if it wasn’t for the fact that all the clocks on the network may drift at different rates.

And as the world becomes more global, ensuring computer networks can talk to each other is also important meaning that synchronisation to the global timescale UTC (Coordinated Universal Time) is now a prerequisite for most networks.

Methods of Synchronisation

There are currently, only two methods for getting truly accurate and reliable time:

  • Use of an internet based time server from places like NIST (National Institute of Standards and Time) or Microsoft.
  • Use of a dedicated NTP time server – that receives external time sources such as from GPS

There are advantages and disadvantages to both types of sources – but which method is best?

Internet Time

Internet time has one great advantage – it is often free. However there are disadvantages to using an internet tie source. The first is distance. Distance across the internet can have a dramatic effect and as the internet gets quicker the distance has an even bigger effect meaning that accuracy become more tenuous.

Another disadvantage of internet time is the lack of authentication and the security risk it poses. Authentication is what the time protocol NTP (Network Time Protocol) uses to establish the true identity of a time source.

Furthermore, an internet time source can only be accessed through a network firewall so a UDP port has to be kept open providing a possible entrance for software nasties or malicious users.

NTP Time Server

NTP time servers on the other hand are dedicated devices. They retrieve a source of UTC externally to the firewall from either GPS or a long wave radio transmission. These come direct from atomic clocks (in the cased of GPS the atomic clock is onboard the satellite) and so can’t be hijacked by malicious users or viruses.

NTP servers are also far more accurate and are not impinged by distance meaning that a network can have millisecond accuracy all the time.

Choosing a Source of Time for Computer Network Synchronization

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You don’t need me to tell you how important computer network time synchronization is. If you are reading this then you are probably well aware of the importance in ensuring all your computers, routers and devices on your network are running the same time.

Failure to synchronize a network can cause all sorts of problems, although with a lack of synchronicity the problems may go unnoticed as error finding and debugging a network can be nigh on impossible without a source of synchronized time.

There are multiple options for finding a source of accurate time too. Most time sources used for synchronisation are a source of UTC (Coordinated Universal Time) which is the international timescale.
However, there are pro’s and con’s to all sources:

Internet time

There are an almost an endless number of sources of UTC time on the internet. Some of these time sources are wholly inaccurate and unreliable but there are some trusted sources put out by people like NIST (National Institute for Standards and Time) and Microsoft.

However, regardless of how trusted the time source is, there are two problems with internet time sources. Firstly, an internet time server is actually a stratum 2 device. In other words, an internet time server is connected to another time server that gets its time from an atomic clock, usually from one of the sources below. So an internet source of time is never going to be as accurate or precise as using a stratum 1 time server yourself.

Secondly, and more importantly, internet sources of time operate through the firewall so a potential security breach is available to any malicious user who wishes to take advantage of the open ports.

GPS Time

GPS time is far more secure. Not only is a GPS time signal available anywhere with a line of sight view of the sky, but also GPS time signals can be received externally to the network. By using a GPS time server the GPS time signals can be received and by using NTP (Network Time Protocol) this time can be converted to UTC (GPS time is currently 17 seconds exactly behind GPS time) then distributed around the network.

MSF/WWVB Time

Radio broadcasts in long wave are transmitted by several national physics labs. NIST and the UK’s NPL are two such organisations and they transmit the UTC signals MSF (UK) and WWVB (USA) which can be received and utilised by a radio referenced NTP server.

NTP Time Servers Keeping Technology Precise

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Atomic clocks are much underrated technologies their development has revolutionised the way we live and work and has made possible technologies that would be impossible without them.

Satellite navigation, mobile phones, GPS, the internet, air traffic control, traffic lights and even CCTV cameras are reliant on the ultra precise timekeeping of an atomic clock.

The accuracy of an atomic clock is incomparable to other time keeping devices as they don’t drift by even a second in hundreds of thousands of years.

But atomic clocks are large sensitive devices that need team of experienced technicians and optimum conditions such as those found in a physics laboratory. So how do all these technologies benefit from the high precision of an atomic clock?

The answer is quite simple, the controllers of atomic clocks, usually national physics laboratories, broadcast via long wave radio the time signals that their ultra precise clocks produce.

To receive these time signals, servers that use the time synchronization protocol NTP (Network Time Protocol) are employed to receive and distribute these timestamps.

NTP time servers, often referred to as network time servers, are a secure and accurate method of ensuring any technology is running accurate atomic clocks time. These time synchronization devices can synchronise single devices or entire networks of computers, routers and other devices.

NTP servers that use GPS signals to receive the time from the atomic clock satellites are also commonly used. These NTP GPS time servers are as accurate as those that receive the time from physics laboratories but use the weaker, line of sight GPS signal as their source.