AND THUS TIME WAS BORN
And thus time was born.
"While every one of us is a time traveler, the cosmic pathos that elevates human history to the level of tragedy arises precisely because we seem doomed to travel in only one direction-into the future."-Lawrence M. Krauss, The Physics of Star Trek
Or more aptly
"Time is nature's way of keeping everything from happening at once."-Anonymous
The concept of time has baffled man since the ages. From where does it come? Where does it go? Does it change? Does it really exist? Can we travel in time?
But before getting into the complexities, let's take one step at a time.
Measuring time
Egyptians were among the first to do something about managing or rather measuring this complex phenomenon. They tracked time through shadows of the obelisks, which fell on demarcated zones or through portable sundials, with a mounted crosspiece. This instrument had a base divided into 10 parts, plus two extra for the twilight hours. Other means of tracking time without any dependency on celestial movements were hourglasses and clepsydras - marked containers in which drops of water fell at a steady rate.
By the early part of the 14th Century, clocks began appearing in Italy. Around 1656, Christiaan Huygens made the first pendulum clock, the idea of which was already propounded by Galileo Galilei in 1582. A few years later, Huygens also developed the wheel and spring assembly, still used in some watches today. However, accurate timepieces were yet to come.
The quartz clock of the 1920s went a step ahead in measuring time. This mechanism is based on the piezoelectric property of quartz crystals. If you put this crystal in a suitable electronic circuit, the interaction between mechanical stress and the electric field makes the crystal move at a constant frequency. Most of the watches today are based on this principle. However the most accurate of clocks is the atomic clock.
Atomic time (AT) is based on the microwave resonance of certain atoms in a magnetic field, and the scales accurately count the cycles of an electromagnetic signal in resonance with cesium atoms (these have an accuracy of a few billionths of a second)!
Time zones
Measuring or recording time via solar methods was one thing, but a problem of another sort began to crop as commuting across the globe, between varying time zones, increased by leaps and bounds. When a man traveled eastward, he found that he lost time and when he traveled westward he seemed to gain time! Well, this confusion can be blamed partly on the earth's slightly eccentric orbit around the sun and its rotational axis. To remedy this, leading minds came up with time zones in the late 19th century.
The present system of time zones has 24 standard meridians of longitude 15 degrees apart. Time is the same throughout the entire zone and differs from the central Coordinated Universal Time (UTC), formerly called the Greenwich Mean Time (GMT), by regular intervals of hours.
The concept of time
But what really makes up the fabric of time? None of our senses experiences it, but for our convenience and to make some meaningful sense out of it, we have classified time as past, present and future, which in themselves are fluid and extremely subjective. We anticipate a future, which in turn hardly exists in the present and soon slips into an equally nebulous past!
Time has always eluded a definition. Throughout the ages, thinkers have tried to lay a finger on it. Plato saw time metaphorically - as a moving image of eternity; Aristotle described it physically - in measures of motion; Plotinus represented it metaphysically - the productive life of the soul, while St Augustine saw it psychologically - an illusory product of the mind!! And while formulating the concepts of classical physics, Newton compared absolute time to a stream flowing at a uniform rate of its own.
However a comprehensive explanation of time came with Albert Einstein, when he proposed his theory of relativity, which states that two observers will necessarily arrange events in a different manner when they are in relative motion. This theory defines time as the fourth dimension, the other three being dimensions of space: length, width and depth; but time is not a separate entity but one that is intertwined with space or better known as space-time. An offshoot of the relativistic theory is that all events seem to slow down in a moving system when observed by a viewer in a stationary system.
Another interesting offshoot of the general theory relativity has been time travel, the idea of which has been toyed around by serious physicists as well as popular science fiction writers.
Time travel
Like space, is it possible to move around freely in time? Imagine space and time being like a uniform, taut sheet. Now if you place a ball on the sheet, it bends the surrounding space - and remember, time also. Time, along with space gets distorted when you travel at speeds nearing the speed of light. This distortion is what allowed scientists to come up with theories of black holes, wormholes and cosmic strings.
But is time travel possible in reality? This is somewhat of a catch 22 situation and you will soon see why with interesting paradoxes. One of them is the Grandfather paradox, which in short says that if you could travel back into space you could go and kill your grandfather thus jeopardizing your own existence! Another equally interesting paradox is the Twin paradox, where one twin travels into space and the other stays back on earth. When the space-traveling twin returns he finds that he has aged a little compared to his counterpart who has aged normally!
So while we let your let your mind travel.either in the past or the future or in circles; the following are worth a few clicks:
Interesting books on time
A Brief History of Time, by Stephen Hawkins
Cosmos, by Carl Sagan ss
About Time: Einstein's Unfinished Revolution, by P. C. W. Davies
The Physics of Star Trek, by Lawrence M. Krauss, Stephen Hawking
Time Travel in Einstein's Universe: The Physical Possibilities of Travel Through Time, by J. Richard Gott
The End of Time: The Next Revolution in Physics, by Julian B. Barbour