Differences in Time

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We are all aware of the differences in time zones. Anybody that has travelled across the Atlantic or Pacific will feel the effects of jet lag caused by having to adjust our own internal body clocks. In some countries, such as the USA, several different time zones exist in the one country meaning there are several hours difference in time from the East Coast to the West.

This difference in time zones can cause confusion although for residents of countries that straddle more than one time zone they soon adapt to the situation. However, there are more timescales and differences in time than just time zones.

Different time standards have been developed for decades to cope with time zone differences and to allow for a single time standard that the whole world can synchronize too. Unfortunately since the first time standards were developed such as British Railway Time and Greenwich Mean Time, other standards have had to be developed to cope with different applications.

One of the problem of developing a time standard is choosing what to base it on. Traditionally, all systems of time have been developed on the rotation of the Earth (24 hours). However, following the development of atomic clocks, it was soon discovered that no two days are exactly the same length and quite often they can fall short of the expected 24 hours.

New time standards where then developed based on Atomic clocks as they proved to be far more reliable and accurate than using the Earth’s rotation as a starting point. Here is a list of some of the most common time standards in use. They are divided into two types, those that are based on Earth’s rotation and those that are based on atomic clocks:

Time standards based on Earth’s rotation
True solar time is based on the solar day – is the period between one solar noon and the next.

Sidereal time is based on the stars. A sidereal day is the time it takes Earth to make one revolution with respect to the stars (not the sun).

Greenwich Mean Time (GMT) based upon when the sun is highest (noon) above the prime meridian (often called the Greenwich meridian). GMT used to be an international time standard before the advent of precise atomic clocks.

Time standards based on atomic clocks

International Atomic Time (TAI) is the international time standard from which the time standards below, including UTC, are calculated. TAI is based on a constellation of atomic clocks from all over the world.

GPS Time Also based on TAI, GPS time is the time told by atomic clocks aboard GPS satellites. Originally the same as UTC, GPS time is currently 17 seconds (precisely) behind as 17 leap seconds have been added to UTC since the satellites were launched.
Coordinated Universal Time (UTC) is based on both atomic time and GMT. Additional Leap seconds are added to UTC to counter the imprecision of Earth’s rotation but the time is derived from TAI making it as accurate.

UTC is the true commercial timescale. Computer systems all over the world synchronize to UTC using NTP time servers. These dedicated devices receive the time from an atomic clock (either by GPS or specialist radio transmissions from organisations like NIST or NPL).

Facts of Time

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From wristwatches to atomic clocks and NTP time servers, the understanding of time has become crucial for many modern technologies such as satellite navigation and global communications.

From time dilation to the effects of gravity on time, time has many weird and wonderful facets that scientists are only beginning to understand and utilise. Here are some interesting, weird and unusual facts about time:

•    Time is not separate from space, time makes up what Einstein called four dimensional space time. Space time can be warped by gravity meaning that time slows down the greater the gravitational influence.  Thanks to atomic clocks, time on earth can be measured at each subsequent inch above the earth’s surface. That means that every bodies feet are younger than their head as time runs slower the lower to the ground you get.

•    Time is also affected by speed. The only constant in the universe is the speed of light (in a vacuum) which is always the same. Because of Einstein’s famous theories of relativity anybody travelling at close to the speed of light a journey to an observer that would have taken thousands of years would have passed within seconds. This is called time dilation.

•    There is nothing in contemporary physics that prohibits time travel both forward and backwards in time.

•    There are 86400 seconds in a day, 600,000 in a week, more than 2.6 million in a month and more than 31 million in a year. If you live to be 70 years old then you will have lived through over 5.5 billion seconds.

•    A nanosecond is a billionth of a second or roughly the time it takes for light to travel about 1 foot (30 cm).

•    A day is never 24 hours long. The earth’s rotation is speeding up gradually which means the global timescale UTC (coordinated universal time) has to have leap seconds added once or twice a year. These leap seconds are automatically accounted for in any clock synchronization that uses NTP (Network Time Protocol) such as a dedicated NTP time server.

Synchronizing the Time on your Computer

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Keeping accurate time is essential for many applications and dedicated NTP time servers make the job easy for network administrators. These devices receive an external time signal, often from GPS or sometimes from broadcast signals put out by organisations such as NIST, NPL and PTB (national physics labs from US, UK and Germany).

Synchronization with a NTP time server is made all the more easier thanks to NTP (network time protocol) this software protocol distributes the time source by constantly checking the time on all devices and adjusting any drift to match the time signal that is received.

Time synchronization is not just the concern of large networks. Even single machines and routers ought to be synchronised because at the very least it will help keep a system secure and make error detection a whole lot easier.

Fortunately, most versions of Windows contain a form of NTP. Often it is a simplified version but it is enough to allow a PC to be synchronized with the global time scale UTC (Coordinated Universal Time). On most Windows machines this is relatively easy to do and can be achieved by double clicking on the clock icon in the task bar then selecting a time provider in the internet time tab.

These time sources are internet based meaning that they are external to the firewall so a UDP port has to be left open to allow the time signal to enter. This can cause some security issues so for those wanting perfect synchronization without any security issues then the best solution is to invest in a dedicated time server. These need not be expensive and as they receive an atomic clock time signal externally then here is no breach in the firewall leaving your network secure.

Dangers of Free Time

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We are all looking for freebies, particularly in the present financial climate and the internet is not short of them. Free software, free films, free music, almost everything these days has a free version. Even critical applications for our computers and networks such as anti-virus can come free. So it is understandable that when network administrators want to synchronize the time on computer networks they turn to free sources of UTC time (UTC – Coordinated Universal Time) to synchronize their networks using the operating systems’ own inbuilt NTP server.

However, just as there is no such thing as a free lunch, free time sources come with a cost too. To start with all time servers on the internet that are available for the public to use are stratum 2 servers. This means they are devices that receive the time from another device (a stratum 1 time server) that gets it from an atomic clock. While this second hand time source shouldn’t lose too much time compared to the original, for high levels of accuracy there will be a noticeable drift.

Furthermore, internet time sources are based outside the network firewall. For access to the time server a UDP port needs to be left open. This will mean the network firewall will intrinsically have a hole in it which could be manipulated y a malicious user or aggressive malware.

Another consideration is the inbuilt security that the time transfer protocol NTP (Network Time Protocol) uses to assess the time signal it receives is genuine. This is referred to as authentication but is unavailable across the internet. Meaning the time source may not be what it claims to be and with a hole in the firewall it could result in a malicious attack.

Internet time sources can also be unreliable. Many are too far from clients to provide any real accuracy some time sources available on the internet are wildly out (some by hours not just minutes). There are however, more reputable stratum 2 servers available and the NTP pool has details of those.

For real accuracy with none of the security threats the best solution is to use an external time source. The best method for doing this is to utilise a dedicated NTP server. These devices work exterior to the firewall and receive the time either direct from GPS satellites or via broadcasts by national physics labs such as NIST or NPL.

What Atomic Clocks Have Done for Us

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Atomic clocks, as many people know they are highly accurate devices but the atomic clock is one of the most important inventions of the last 50 years and has given rise to numerous technologies and applications that have completely revolutionized our lives.

You may think how a clock could be so important regardless of how accurate it is, however, when you consider that precision, that a modern atomic clock doesn’t lose a second in time in tens of millions of years when compared to the next best chronometers – electronic clocks – that can lose a second a day you get to realise just how accurate they are.

In fact, atomic clocks have been crucial in identifying the smaller nuances of our world and the universe. For instance we have for millennia assumed that a day is 24 hours long but in fact, thanks to atomic clock technology we now know that the length of each day slightly differs and in general the earth’s rotation is slowing down.

Atomic clocks have also been used to accurately measure the earth’s gravity and have even proved Einstein’s theories of how gravity can slow time by accurately measuring the difference in the passing of time at each subsequent inch above the earth’s surface. This has been crucial when it comes to placing satellites in orbit as time passes quicker that high above the earth than it does on the ground.

Atomic clocks also form the basis for many of the technologies that we employ in our day to day lives. Satellite navigation devices rely on atomic clocks in GPS satellites. Not only do they have to take into account the differences in time above the orbit but it as sat navs use the time sent from the satellites to triangulate positions, a one-second inaccuracy would see navigational information inaccurate by thousands of miles (as light travels nearly 180,000 miles every second).

Atomic clocks are also the basis for the world’s global timescale – UTC (Coordinated Universal Time), which is utilised by computer networks throughout the world. Time synchronization to an atomic clock and UTC is relatively straight forward with a NTP time server. These use the time signal from the GPS system or special transmissions broadcast from large scale physics labs and then distribute it across the internet using the time protocol NTP.

The Possibility of Time Travel

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Exploring the possibilities of time travel including: Time paradoxes, worm holes, 4 dimesnsional space, atomic clocks and NTP servers

Time travel has always been a much loved concept for science fiction writers. From HG Wells’ Time Machine to Back to the Future, travelling forwards or backwards in time has captivated audiences for centuries. However, thanks to the work of modern thinkers like Einstein, it appears that time travel is much a possibility of science fact as it is fiction.

Time travel is not only possible but we do it all the time. Every second that passes is a second further into the future so we are all travelling forward in time. However we think if time travel we imagine a machine that transports individuals hundreds or thousands of years in to the future or past so is that possible.

Well, thanks to Einstein’s theories of general and special relativity, time ravel is certainly possible. We know thanks to the development of atomic clocks that Einstein’s theories about speed and gravity affecting the passage of time is correct. Einstein suggested that gravity would warp space-time (the term he gave to four dimensional space that includes directions plus time) and this has been tested. In fact modern atomic clocks can pick out the minute differences in the passage of time every subsequent inch above the earth’s surface as time speeds up as the effect of the earth’ s gravity weakens.

Einstein predicted speed too would affect time in what he described as time dilation. For any observer travelling close to the speed of light a journey that to an outsider may have taken thousands of years would have passed within seconds. Time dilation means that travelling hundreds of years into the future in a matter of seconds is certainly possible. However, would it be possible to get back again?

This is where many scientists are divided. Strictly speaking theoretical properties of space time do allow for this, although for any travelling back in time a worm hole would have to be created or found. A worm hole is a theoretical link between two parts of space where a traveller could enter one end and appear somewhere completely different at the other end this may be another part of the universe or indeed another point in time.

However, critics of the possibility of time travel point out that because travellers from the future have never visited us that probably means that time travel will never be possible. They also point out the any travelling backwards in time could create paradoxes (what would happen to you if you were mean enough to go back in time and kill your grandparents).

However, time paradoxes exist now. Many computer networks are not synchronised which can lead to errors, loss of data or paradoxes like emails being sent before they were received. To avoid any time crisis it is important for all computer networks to be perfectly synchronised. The best and most accurate method of doing this is to use a NTP time server that receives the time from an atomic clock.

Do I Really Need an NTP Time Server?

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The NTP time server is a much misunderstood piece of equipment. They are quite simple devices in the sense that they are used for the purposes of time synchronisation, receiving an external source of the time which is then distributed throughout a computer network using NTP (Network Time Protocol).

However, with a myriad of ‘free’ time servers available on the internet many network administrators take the decision that NTP time servers are not necessary pieces of equipment and that their network can do without it. However, there are a huge number of pitfalls in relying on the internet as a time reference; Microsoft and the USA physics laboratory NIST (National Institute of Standards and Time) highly recommend external NTP time servers rather than internet providers.

Here is what Microsoft says:
“We highly recommend that you configure the authoritative Time Server to gather the time from a hardware source. When you configure the authoritative Time Server to sync with an Internet time source, there is no authentication.”

Authentication is a security measure implemented by NTP to ensure that the time signal that is sent comes from where it claims to come from. In other words authentication is the first line of defence in protecting against malicious users. There are other security issues too with using the internet as a time source as any communication with an internet time source is going to require the TCP/IP port to be left open in the firewall this could also be manipulated by malicious users.

NIST too recognise the importance of NTP time server systems for prevention and detection of security threats in their Guide to Computer Security Log Management they suggest:
“Organizations should use time synchronization technologies such as Network Time Protocol (NTP) servers whenever possible to keep log sources’ clocks consistent with each other.”

The Measuring of Time

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Measuring the passing of time has been a preoccupation of humans since the dawn of civilization. Broadly speaking, measuring time involves using some form of repetitive cycle to work out how much time has passed. Traditionally this repetitive cycle has been based on the movement of the heavens such as a day being a revolution of the Earth, a month being an entire orbit of the Earth by the moon and a year being earth’s orbit of the sun.

As our technology progressed we have been able to measure time in smaller and smaller increments from sundials that allowed us to count the hours, mechanical clocks that let us monitor the minutes, electronic clocks that let is for the first time accurately record seconds to the current age of atomic clocks where time can be measured to the nanosecond.

With the advancement in chronology that has led to technologies such as NTP clocks, time servers, atomic clocks, GPS satellites and modern global communications, comes with another conundrum: when does a day start and when does it finish.

Most people assume a day is 24 hours long and that it runs from midnight to midnight. However, atomic clocks have revealed to us that a day is not 24 hours and in fact the length of a day varies (and is actually increasing gradually over time).

After atomic clocks were developed there was a call from many sectors to come up with a global timescale. One that uses the ultra precise nature of atomic clocks to measure its passing but also one that takes into account the Earth’s rotation. Failing to account for the variable nature of a day’s length would mean any static timescale would eventually drift with day slowly drifting into night.

To compensate for this the world’s global timescale, called UTC (coordinated universal time) has additional seconds added (leap seconds) to ensure that there is no drift. UTC time is kept true by a constellation of atomic c clocks and it is utilised by modern technologies such as the NTP time server which ensures computer networks all run  the exact same precise time.

Milestones in Chronology From Crystals to Atoms

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Telling the time may seem a simple affair these days with the number of devices that display the time to us and with the incredible accuracy of devices such as atomic clocks and network time servers it is quite easy to see how chronology has been taken for granted.

The nanosecond accuracy that powers technologies such as the GPS system, air traffic control and NTP server systems (Network Time Protocol) is a long way from the first time pieces that were invented and were powered by the movement of the sun across the heavens.

Sun dials were indeed the first real clocks but they obviously did have their downsides – such as not working at night or in cloudy weather, however, being able to tell the time fairly accurately was a complete innovation to civilisation and helped for more structured societies.

However, relying on celestial bodies to keep track of time as we have done for thousands of years, would not prove to be a reliable basis for measuring time as was discovered by the invention of the atomic clock.

Before atomic clocks, electronic clocks provided the highest level of accuracy. These were invented at the turn of the last century and while they were many times more reliable than mechanical clocks they still drifted and would lose a second or two every week.

Electronic clocks worked by using the oscillations (vibrations under energy) of crystals such as quartz, however, atomic clocks use the resonance of individual atoms such as caesium which is such a high number of vibrations per second it makes the incredibly accurate (modern atomic clocks do not drift by even a second every 100 million years).

Once this type of time telling accuracy was discovered it became apparent that our tradition of using the rotation of the earth as a means of telling time was not as accurate as these atomic clocks. Thanks to their accuracy it was soon discovered the Earth’s rotation was not precise and would slow and speed up (by minute amounts) each day. To compensate for this the world’s global timescale UTC (Coordinated Universal Time) has additional seconds added to it once or twice a year (Leap seconds).

Atomic clocks provide the basis of UTC which is used by thousands of NTP servers to synchronise computer networks to.

Heroes of Time

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Chronology – the study of time- has provided science and technology with some incredible innovations and possibilities. From atomic clocks, NTP servers and the GPS system, true and accurate chronology has changed the shape of the world.

Time and the way it is counted has been a preoccupation of mankind since the earliest civilisations. Early chronologists spent their time trying to establish calendars but this proves to be more complicated than first imagined primarily because the earth takes a quarter of a day more than 365 days to orbit the sun.

Establishing the right number of leap days was one of the first challenges and it took several attempts at calendars until the modern Gregorian calendar became adopted by the globe.

When it came to monitoring time at a smaller level great advances were made by Galileo Galilei who would have built the first pendulum clock if only his death hadn’t interrupted his plans. Pendulums were finally invented by Christiaan Huygens and provided the first true glimpse of accurately monitoring the time throughout the day.

The next steps in chronology couldn’t take place though until we had a better understanding of time itself. Newton (Sir Isaac) had the first ideas and had the notion time was absolute” and would flow “equably” for all observers. This would have been an obvious idea to Newton as many of us regard time as unchanging but it was Einstein in his special theory of relativity that proposed that in fact time wasn’t a constant and would differ to all observers.

It was Einstein’s ideas that proved correct and his model of time and space paved the way for many of the modern technologies we take for granted today such as the atomic clock.

However, chronology doesn’t stop there, timekeepers are constantly looking for ways of increasing accuracy with modern atomic clocks so precise they would not lose a second in millions of years.

There are other notable figures in the modern world of chronology too. Professor David Mills from the University of Delaware devised a protocol in the 1980’s to synchronise computer networks.

His Network Time Protocol (NTP) is now used in computer systems and networks all over the world via NTP time servers. A NTP server ensures computers on opposite sides of the globe can run exactly the same time.