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.

Germans Enter Race to Build the Worlds Most Accurate Clock

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Following the success of Danish researchers working in conjunction with NIST (National Institute for Standards and Time), who unveiled the world’s most accurate atomic clock earlier this year; German scientist have entered the race to build the world’s most precise timepiece.

Researchers at the Physikalisch-Technische Bundesanstalt (PTB) in Germany are using use new methods of spectroscopy to investigate atomic and molecular systems and hope to develop a clock based around a single aluminium atom.

Most atomic clocks used for satellite navigation (GPS), as references for computer network NTP servers and air traffic control have traditionally been based on the atom caesium. However, the next generation of atomic clocks, such as the one unveiled by NIST which is claimed to be accurate to within a second every 300 million years, uses the atoms from other materials such as strontium which scientists claim can be potentially more accurate than caesium.

Researchers at PTB have opted to use single aluminium atoms and believe they are on the way to developing the most accurate clock ever and believe there is huge potential for such a device to help us understand some of the more complicated aspects of physics.

The current crop of atomic clocks allow technologies such as satellite navigation, air traffic control and network time synchronisation using NTP servers but it is believed the increases accuracy of the next generation of atomic clocks could be used to reveal some of the more enigmatic qualities of quantum science such as string theory.

Researchers claim the new clocks will provide such accuracy they will even be able to measure the minute differences in gravity to within each centimetre above sea-level.

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.

Worlds Most Famous Clock Reaches 150

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It’s one of the world’s most iconic land marks. Standing proudly over the Houses of Parliament, Big Ben celebrates its 150th birthday. Yet despite living in an age of atomic clocks and NTP time servers, it is one of the most used timepieces in the world with hundreds of thousands of Londoners relying on its chimes to set their watches to.

Big Ben is actually the name of the main bell inside the clock that creates the quarter hourly chimes but the bell didn’t start chiming when the clock was first built. The clock began keeping time on 31 May 1859, while the bell didn’t strike for the first time until July 11.

Some claim the twelve tonne bell was named after Sir Benjamin Hall the Chief Commissioner of Works who worked on the clock project (and was said to be a man of great girth). Others claim the bell was named after heavyweight boxer Ben Caunt who fought under the moniker Big Ben.

The five-tonne clock mechanism works like a giant wristwatch and is wound three times a week. Its accuracy if in tuned by adding or removing old pennies on the pendulum which is quite far removed from the accuracy that modern atomic clocks and NTP server systems generate with near nanosecond precision.

While Big Ben is trusted by tens of thousands of Londoners to provide accurate time, the modern atomic clock is used by millions of us every day without realising it. Atomic clocks are the basis for the GPS satellite navigation systems we have in our cars they also keep the internet synchronised by way of the NTP time server (Network Time Protocol).

Any computer network can be synchronised to an atomic clock by using a dedicated NTP server. These devices receive the time from an atomic clock, either via the GPS system or specialist radio transmissions.