Time as a constituent of Nature

Although we are used to counting time in terms of discrete intervals such as seconds, minutes and hours etc., it is, in fact, a continuum in which there is no break, just as space is. Time has now come to be recognised, in fact, as the 'fourth dimension' along with the three spatial dimensions.

Right up to the beginning of the 20th century, time was regarded as a phenomenon separate from space, remaining the same everywhere in the universe, and irrespective of the state of motion of the frame of reference from which it was measured. It was Einstein's special relativity first, and later on, general relativity, which showed how space and time were inextricably linked, and merged together forming a new structure of the universe known as 'space-time'.

Those theories showed that the concept of time varies with the spatial reference frame of the observer. In other words, clocks measure time differently for observers in different framers of reference in relative motion. General relativity has also shown that it can be established through experiment that time can be distorted, especially at the edges of what are known as 'black holes'.

It also showed how, following the variation of time in different frames of reference in relative motion to each other, time gets' dilated' or, in other words, appears to move slowly as one moves faster and faster with acceleration built into the motion. It is from this concept that the idea of time travel, or travelling backwards or forwards in time, first emerged. Even by then, brilliant minds such as H.G. Wells had foreseen the possibility, and even written novels such as 'The Time Machine'.

The novels 'Timeline', by Michael Crichton and also 'Contact' by Carl Sagan, are based on the same principle. While travelling time is still a concept that remains in the realm of fantasy, writers have constructed many light-hearted examples in their imagination.

As an examples, there is this limerick of (the authorship of which is still a matter of dispute), which famously goes,

"There was a young lady named Bright,

Who would travel much faster than light,

She started one day

In a relative way

And came back the previous night"

It is, therefore, now an accepted idea that there is no such thing as 'absolute' time and that it varies in accordance with the acceleration of the frame of reference in which one is present at a given point of time.

Modern technological developments have reached the stage where one takes the ability to measure the time, or precisely to tell what time it is, as granted. We make this assumption while working with a variety of instruments and ideas such as telephones, computers, stoves, and in sports, the fine arts and surgery. Where we are today, it must be remembered, is the result of unrelenting and continuous effort backed by the creativity and ingenuity of mankind over thousands of years.

Advances in the science of temporal measurement occupied the minds of scientists and technologists for centuries, the prime motivation, for some time being the need for it in navigation and astronomy.

Motion and events of a periodical nature have, for long, been used as standards for units of time, examples being the apparent movement of the sun across the sky, the phases of the moon, the swing of a pendulum or the beat of the heart. The measurement of the electronic transmission frequency of Caesium atom is the basis upon which the international unit of time, namely the second, is currently defined.

A large number of devices have been invented, from time to time, in the history of mankind to measure time. The study of those instruments is called 'horology'. While, as we have just noted, the sun was the main guide for keeping track of time in the ancient times, the 'merkhet' (an instrument comprising a bar with a plumb line), allowed the ancient Egyptians to keep time at night with the stars alone as their guide.

The most precise timekeeping device of those times was the water clock, known to 16th century C.B.E. Babylonians, one of which was found in the tomb of Egyptian pharaoh Amenhotep. That, too, could be used at night. 'Obelisks', tall rectangular structures could tell the time by following the shadow – creating effect of the sun. Similarly sun dials 'candle clocks' took advantage of this simple concept of the passage of time. The moon was also used to reckon time in the ancient periods (more than 6000 years ago), and lunar calendars were among the first to appear.

Another Egyptian device which dated to 1500 BC used to be in the shape of a bent T – square and measured the passage of time from the shadow cast by its cross bar on the nonlinear rule. Many other devices have been used from ancient times over the ages such as The Chinese 'incense clock', and the 'hour glass' clock (which used the flow of sand), the 'elephant' clock and the rolling ball clock. Today the most accurate time measuring devices include chronometers and atomic clocks.

It was Julius Caesar who in 405 BCE who put the Roman word on the solar calendar. The concept of a single worldwide uniform universal timescale, conceived centuries ago became a reality in the mid – 19th century with the adoption of the Greenwich Mean Time (GMT) created in 1847. A few countries, however, have later replaced it with coordinated universal time (UTC).

I still recall with a thrill, my hair literally standing on its end with excitement, the elation I felt when, while on a visit to England sometime ago, I went to Greenwich Village and stood on the Prime Meridian.

(The writer is former Chief Secretary, Government of Andhra Pradesh)