Time is an abstract concept that we generally take for granted. Time passes in years, months, days, hours, minutes and seconds without much thought. However, humans have developed extremely complex ways of measuring time and maintaining accurate time references. From sundials to atomic clocks and NTP time servers, to maintain time on computer networks, people have strived to accurately measure time.



This article discusses the fundamental nature of time, how it is measured, by movement, and how it is related to the concept of space. It also describes the spin-offs from high technology time references and International time standards.

Time Measured By Movement

Humans relate and measure time with reference to movement. The hands of a clock moving around a clock-face describe hours, minutes and seconds. A year is described by the rotation of the Earth around the Sun. A month is described by the rotation of the moon around the Earth. A day is described by the rotation of the Earth itself. In fact space and time are closely intertwined.

Space and Time

Einstein's General Theory of Relativity suggests time is closely related to the concept of space. Both time and space began with the Big Bang and the creation of the Universe some 14 Billion years ago. At the instance of the Big Bang, all matter was tightly packed into a tremendously dense, infinitely small, hot state. The universe, suns, planets and all matter contained within them emerged from this infinitely small dot.

The Theory of Relativity suggests that the Universe will reach a maximum size and begin to collapse back to its original state. The universe will become denser and hotter and return to a state similar to that from which it started. However, some of the latest observations of space have shown that galaxies are moving away from us at an ever-increasing rate. This implies that the Universe will continually cool and expand.

Measuring Time

The study of time measurement is called Horology. During Human history a large variety of devices have been used to measure time. Sundials were among the earliest examples of time measurement devices. A sundial casts a shadow on a series of markings that indicate the current hour of the day. More commonly in use today are mechanical or electronic clocks. Mechanical clocks are generally regulated by the movement of a pendulum. Electronic clocks are based on the resonance, or movement, of a crystal oscillator.

Modern atomic clocks, based on frequency reference masers, can maintain accurate time measurement to an astonishing degree. Atomic clocks form the basis of the Global Positioning System (GPS), which can provide positioning information for any location on the planet. NTP time servers use the Network Time Protocol and GPS time to ensure time synchronisation of computers and computer networks across the globe.

World Time

The measurement of time is critical to the modern way of life. So much so that International Standards exist to coordinate time. The basis of world time is Coordinated Universal Time (UTC). World time is split into a series of longitudinal time zones. Time zones are generally one hour apart and their local time is referenced as an offset from UTC time.

Summary

Time is an abstract concept that is inextricably linked to the concept of space and the creation of the Universe. Humans have strived for millennia to maintain accurate time references. Modern technology allows us to maintain highly accurate time references. Atomic clock technology has resulted in the creation of the GPS system and NTP time servers. The world has created an internationally agreed measurement of time, UTC time.