Time Synchronisation

When we take a glance at our watches or the office clock we often take for granted that the time we are given is correct. We may notice if our watches are ten minutes fast or slow but take little heed if they are a second or two out.

Yet for thousands of years mankind has strode to get ever increasingly accurate clocks the benefits of which are plentiful today in our age of satellite navigation, NTP servers, the Internet and global communications.

To understand how accurate time can be measured it is first important to understand the concept of time itself. Time as it has been measured on Earth for millennia is a different concept to time itself which as Einstein informed us was part of the fabric of the universe itself in what he described as a four dimensional space-time.

Yet we have historically measured time based not on the passing of time itself but the rotation of our planet in relation to the Sun and the Moon. A day is divided into 24 equal parts (hours) each of which is divided into 60 minutes and the minute is divided into 60 seconds.

However, it has now been realised that measuring time this way can not be considered accurate as the Earth’s rotation varies from day to day. All sorts of variable such as tidal forces, hurricanes, solar winds and even the amount of snow at the poles effects the speed of the Earth’s rotation. In fact when the dinosaurs first started roaming the Earth, the length of a day as we measure it now would have only been 22 hours.

We now base our timekeeping on the transition of atoms using atomic clocks with a second based on 9,192,631,770 periods of the radiation emitted by the hyperfine transition of a unionized caesium atom in the ground state. Whilst this may sound complicated it really is just an atomic ‘tick’ that never alters and therefore can provide a highly accurate reference to base our time on.

Atomic clocks use this atomic resonance and can keep time that is so accurate a second isn’t lost in even a billion years. Modern technologies all take advantage of this precision enabling many of the communications and global trade we benefit from today with the utilisation of satellite navigation, NTP servers and air traffic control changing the way we live our lives.

The Global Positioning System along with the Internet has changed the way we live our lives. Thousands of motorists use them daily to navigate their around the country’s roads while airline pilots and ship’s captains use them for the same purpose on our seas and in our skies.

But GPS has more uses than just navigation as the technology that GPS utilises is based around the atomic clock. Atomic clocks are highly accurate devices, so accurate that within a billion years they will not lose a second in time.

It is this accuracy that allows satellite navigation devices to triangulate the positioning by measuring the time it takes for the GPS signals to arrive. As radio waves, such as those broadcast by the GPS satellites travel at the speed of light, an inaccuracy of just one second could see the positioning device inaccurate by 300,000 km (the speed light travels per second).

This timing signal broadcast by the satellites can also be utilised by a GPS time server. GPS time servers use the atomic clock signal and convert it into UTC (Coordinated Universal Time) which can be used by network time servers.

These time servers are often referred to as a GPS time server as they use GPS as a timing source to synchronise entire computer networks to.  GPS signals are highly accurate and available anywhere on the planet.

When we take a glance at our watches or the office clock we often take for granted that the time we are given is correct. We may notice if our watches are ten minutes fast or slow but take little heed if they are a second or two out.

Yet for thousands of years mankind has strode to get ever increasingly accurate clocks the benefits of which are plentiful today in our age of satellite navigation, NTP servers, the Internet and global communications.

To understand how accurate time can be measured it is first important to understand the concept of time itself. Time as it has been measured on Earth for millennia is a different concept to time itself which as Einstein informed us was part of the fabric of the universe itself in what he described as a four dimensional space-time.

Yet we have historically measured time based not on the passing of time itself but the rotation of our planet in relation to the Sun and the Moon. A day is divided into 24 equal parts (hours) each of which is divided into 60 minutes and the minute is divided into 60 seconds.

However, it has now been realised that measuring time this way can not be considered accurate as the Earth’s rotation varies from day to day. All sorts of variable such as tidal forces, hurricanes, solar winds and even the amount of snow at the poles effects the speed of the Earth’s rotation. In fact when the dinosaurs first started roaming the Earth, the length of a day as we measure it now would have only been 22 hours.

We now base our timekeeping on the transition of atoms using atomic clocks with a second based on 9,192,631,770 periods of the radiation emitted by the hyperfine transition of a unionized caesium atom in the ground state. Whilst this may sound complicated it really is just an atomic ‘tick’ that never alters and therefore can provide a highly accurate reference to base our time on.

Atomic clocks use this atomic resonance and can keep time that is so accurate a second isn’t lost in even a billion years. Modern technologies all take advantage of this precision enabling many of the communications and global trade we benefit from today with the utilisation of satellite navigation, NTP servers and air traffic control changing the way we live our lives.

When we take a glance at our watches or the office clock we often take for granted that the time we are given is correct. We may notice if our watches are ten minutes fast or slow but take little heed if they are a second or two out.

Yet for thousands of years mankind has strode to get ever increasingly accurate clocks the benefits of which are plentiful today in our age of satellite navigation, NTP servers, the Internet and global communications.

To understand how accurate time can be measured it is first important to understand the concept of time itself. Time as it has been measured on Earth for millennia is a different concept to time itself which as Einstein informed us was part of the fabric of the universe itself in what he described as a four dimensional space-time.

Yet we have historically measured time based not on the passing of time itself but the rotation of our planet in relation to the Sun and the Moon. A day is divided into 24 equal parts (hours) each of which is divided into 60 minutes and the minute is divided into 60 seconds.

However, it has now been realised that measuring time this way can not be considered accurate as the Earth’s rotation varies from day to day. All sorts of variable such as tidal forces, hurricanes, solar winds and even the amount of snow at the poles effects the speed of the Earth’s rotation. In fact when the dinosaurs first started roaming the Earth, the length of a day as we measure it now would have only been 22 hours.

We now base our timekeeping on the transition of atoms with a second based on 9,192,631,770 periods of the radiation emitted by the hyperfine transition of a unionized caesium atom in the ground state. Whilst this may sound complicated it really is just an atomic ‘tick’ that never alters and therefore can provide a highly accurate reference to base our time on.

Atomic clocks use this atomic resonance and can keep time that is so accurate a second isn’t lost in even a billion years. Modern technologies all take advantage of this precision enabling many of the communications and global trade we benefit from today with the utilisation of satellite navigation, NTP servers and air traffic control changing the way we live our lives.

The GPS network (Global Positioning System), is commonly known as a satellite navigation system. It however, actually relays a ultra-precise time signal from an onboard atomic clock.

It is this information that is received by satellite navigation devices that can then triangulate the position of the receiver by working out how long the signal has taken to arrive from various satellites.

These time signals, like all radio transmissions travel at the speed of light (which is close to 300,000km a second). It is therefore highly important that these devices are not just accurate to a second but to a millionth of a second otherwise the navigation system would be useless.

It is this timing information that can be utilized by a GPS time server as a base for network time. Although this timing information is not in a UTC format (Coordinated Universal Time), the World’s global timescale, it easily converted because of its origin from an atomic clock.

A GPS time server can receive the signal from a GPS aerial although this does need to have a good view of the sky as the satellites relay their transmissions via line-of-sight.
Using a dedicated GPS time server a computer network can be synchronised to within a few milliseconds of NTP (milli=1000th of a second) and provide security and authentication.

Following the increase use of GPS technology over the last few years, GPS time servers are now relatively inexpensive and are simple and straight forward systems to install.

Time synchronisation in the modern age is highly precise. Modern atomic clocks can keep time so accurately that in 100 million years these timekeeping devices will not lose even a second.

Bit is this sort of accuracy necessary in the modern world? How important can a second possibly be, after all, a second has always been seen as one of the smallest units of time.

However, when you consider modern technology such as the satellite navigation then a second suddenly becomes a huge gulf in time. Modern satellite navigation devices work by calculating distance by using the time form the atomic clocks on GPS (Global Positioning System) satellites.

However, when you consider that the speed of light is close to 300, 000 km a second then you can understand that if a GPS clock is a second out then your navigation could be inaccurate by hundreds of thousands of kilometres.

The same is true for modern computer networks. Computers can process thousands of transactions a second so when it comes to global network communication a second can be a huge amount of time.

That is why modern NTP server’s, responsible for synchronising networks offer precision to the millisecond, ensuring that network across the globe are within a hare’s breath of each other.