Confrontation in Time Keeping

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This article explores the concept of keeping time and how human measurement of time is at odds with that of a computer.

Time is certainly a concept most of us take for granted, it passes us by and we only notice it when we catch a glimpse of a grey hair in the mirror or arrive late for that important meeting. Yet keeping track of the time has occupied mankind for millennia.
From early sundials and water timers to modern digital watches and atomic clocks, humans have found more and more accurate and innovative ways of telling the time.

Computers also need to know the correct time. Accuracy is essential in keeping the Internet and computer networks communicating with each other but to a computer the passing of time is a simple equation based on the accumulation of discrete moments added to a base time, normally the number of seconds from that point in time.

Humans on the other hand have a variety of different notions   about how to measure time. We separate it in to seconds, minutes, days, weeks, months, years, decades centuries and even millennia.

And this is wehere the problem lies as historically we have forced time to correspond with the orbit and rotation of the Earth, called solar time, which as it turns out is not that precise, well not enough for a computer anyway.

Computer networks use Network Time Protocol (NTP), the time synchronization standard used by on the Internet to keep at the same time. NTP lets machines query regional time servers that get the Universal Coordinated Time UTC from highly accurate reference clocks either from the Internet or through radio or GPS receiver.

However, UTC is based on atomic time and it differs from the Earth’s rotational time (solar system) because the day is slowly lengthening. The moon’s gravity lengthens the global turn by roughly 1.4 milliseconds — that is, thousandths of a second — per day per century. Since 1820, what we think of as a 24- hour period has gotten 2 milliseconds longer.

As a result, atomic time differs from solar time by one second about every 500 days. To adjust leap seconds are added every year or so. However as computers become more reliant on accuracy this leap second can cause problems as a second can be a vasrt amount in some time sensitive applications.

Some suggest to combat this problem leap seconds should be eliminated and the world should stick with just atomic time even though that would result in sun at midnight and dark during the day (albeit in 43,000 years time).  Others argue that having a time scale based on the Earth’s rotation is primitive and not needed in the modern age, although many farmers and astronomers are keen to argue the opposite.

However, as atomic clocks and computers become increasingly more accurate and precise it seems that humans and our spinning world are not going to be able to keep up.


This post was written by:

Richard N Williams is a technical author and a specialist in the NTP Server and Time Synchronisation industry. Richard N Williams on Google+