The Story of Time (Nita Berry)

["they reached Vladivostock at last. She was usually fast asleep at this hour. Was she not glad to be able to stretch her cramped legs! When Irina looked outside, she stared in surprise. The sun was shining right overhead, and Grandma was smiling at her on the platform. It was lunchtime in Vladivostock and Grandma had made lots and lots to eat! For the time was one o'clock. Irina just could not understand how time in Vladivostock was different. It was eight whole hours ahead of Moscow! It was not only her watch which told her that, but her tummy, too. She was not hungry for lunch in the least bit yet! Her tummy always told her when it was time to eat. The other passengers in the train had put forward their watches by one whole hour everyday. This was because the Russia Express had crossed eight different time zones to reach Vladivostock from Moscow. Therefore, it was one o'clock on their watches now. If youvhave ever seen for yourself how time at any moment differs in different countries, or even in places that are very faraway from each other, you will understand better than Irina why Moscow and Vladivostock have different times. Have you ever rung up a friend or a relative who lives on the other side of the 99","globe, around tea time, and been surprised to hear him sound most groggy? You probably jerked him out of his sleep! This happens because there is a difference of nearly 12 hours or so between his clock and yours. Time, the world over, can never be the same. Owing to the earth's rotation, the mid- day sun from which we measure our noontime can never be directly overhead at all places at the same time. When it is noon in New Delhi, it is certainly not noon in New York! In fact, it will be nearer midnight. Nearer home, Singapore has finished breakfast wjien you stretch yourself out of bed. Europe is still fast asleep. Geographers have carefully worked out how to measure the correct time in different parts of the world today. The earth has been divided into 24 time zones or belts covering 15 degrees longitude each. Longitudes are also called 'meridians', and are imaginary lines marked by man that run through the the north and south poles of the earth. There are 360 of these meridians altogether. It is logical that places lying on the same meridian will have the same solar time for they face the sun together. Places that are east or west of each other have different solar times. The difference in solar or local time is one hour for every 15 degrees of longitude. This makes a time zone. 100","You can make a simple calculation to see \u2014y how this is so. If 360 degrees of longitude rotate completely in 24 hours, 15 degrees When the sun is directly over the will take one hour to rotate. Therefore, the prime meridian, it is noon in difference between one time zone and Greenwich Mean Time. another, 15 degrees apart, is one hour. In those days when time zones did not exist, the world was a hotch-potch of local times. People set the clocks or watches according to the mid-day sun where one lived, so you can imagine how different their readings must have been, even in the same country! There were no meridians marked out alien. Most sailors used the time at their home ports as they roved the seas. They must^ have been surprised to find it pitch dark in certain places when it should have been , morning according to their time, or light in others when it was past their bedtime! S To get over this trouble, a meeting was held in Washington in 1884, where Britain and the U.S.A. urged international adoption of Greenwich in Britain as the 0 degree longitude or 'Prime Meridian'. A 24-hour count could begin from here for all the world to follow. Greenwich was chosen because it was the site of the Royal Observatory, set up in the reign of King Charles II, where the first proper time measurements were made. All other meridians are marked east or west of Greenwich up to 180 degrees each 101","way. Since the earth rotates from west to east, the east is ahead in time\u2014that is why we call Japan in the Far East, 'the land of the rising sun'. As we move east from Greenwich, we add one hour for every 15 degrees of longitude we travel. When we move west from Greenwich, we subtract one hour from Greenwich time for every 15 degrees. So if a place is three time zones or 45 degrees west of Greenwich, the time in that place is three hours behind Greenwich Mean Time or GMT, as the average solar time in Greenwich is called. Indian Standard Time is five and a half hours ahead of GMT. Astronomers at the Greenwich Observatory check their clock against the sun or a particular star. This is done by checking the exact time when the sun or the star crosses the meridian. The latter method of checking with the stars is called keeping 'sidereal' time, and it is useful for its accuracy. Correct time is also kept by all observatories in other countries, with special clocks. The Naval Observatory in Washington D.C. determines the correct time with a quartz crystal controlled clock, correct to 1\/500th of a second per day. They broadcast time signals by radio. All countries keep a track of the time of other countries. When people travel from one country to another, they must change the time 102","on their watches according to time differences. Although time changes with each time zone, countries usually keep one local time based on a central meridian, even if they are spread over two time zones. Otherwise, imagine how awkward things would be if every town or city kept its own time! Mumbai and Kolkata are over 15 degrees apart, but like the rest of India, they follow Indian Standard Time which is based on the 82.5 degrees east longitude. In case of countries with many time zones, one local time is unsuitable. In the U.S.A., there are four different local times\u2014Eastern, General, Mountain and Pacific Time! With due altering of time on your watch, you could catch trains and flights all over the world with ease, and keep appointments. Still, a strange problem remained. Take the case of a man who travels to London from New Delhi. He will have to put his watch five- and-a-half hours behind. Now just suppose he keeps travelling west till he comes back to where he started. He would have put his watch behind by a whole day. If he started out on January 1, it would be December 31 if he travelled westwards. If he were to travel in the opposite direction, eastwards, he would keep putting his watch forward till he ended up putting it forward a full day when he came to the point he had started from. The date here would now be January 2. 103","It is indeed a strange situation. You lose or gain a day depending on which way you travel! A way was found to avoid a puzzling situation like this one. An imaginary line was drawn right down the earth's surface from North to South pole, in the middle of the Pacific Ocean. It was located at the 180 degree meridian and called the International Dateline. On both sides of this Date- line are two different dates. According to international agreement, whenever you cross this line the date changes. You gain a day if you are going west across the line, or lose a day if you are going east. The Dateline has some variations from the 180 degree meridian so that it does not divide land areas or islands. It would be most confusing to live in a place cut through by the Dateline\u2014and so have two different dates on either side of it! Incidentally, the word meridian comes from the Latin word for mid-day, or meridies. So when the sun crosses your 104","meridian it is noon for you. East of this is morning or 'ante meridian', meaning before mid-day. We use the short form of 'a.m.' for this. For example, school begins at 8 a.m. or eight o'clock before mid-day. After mid- day 'p.m.' is the abbreviation for 'post meridian' when the sun has passed over the meridian. So we say dinner is at 8 p.m., or after mid-day. To express time from 12 noon to 12 midnight we use p.m., and for 12 midnight to 12 noon we use a.m. Your clock at home is numbered from 1 to 12, and you can always tell whether it is 9 o'clock in the morning or 9 o'clock at night, by looking out of your window. This can become confusing sometimes if somebody has a train to catch or a meeting to attend, and we forget to add a.m. or p.m. after the hours. For a long time, people have been using the 24-hour method to avoid much misunder- standings or mistakes especially in train and flight timetables, or for important timings. Here, the hours of the day are numbered from one to 24 instead of two periods of 12 hours each. After 12 noon, 1 o'clock in the afternoon becomes 1300 hours instead of 1 p.m., 2 o'clock becomes 1400 hours and so on. Minutes are shown after the hour and not to the hour. For instance, a quarter to three in the afternoon becomes 1445. A quarter past four will become 1615 hours. Here is a complete table for you to follow 105","when you make out your next party invita- tions. Remember the minutes follow the hours. 0100 hrs. 1 a.m. 1300 hrs. 1 p.m. 0200 hrs. 2 a.m. 1400 hrs. 2 p.m. 0300 hrs. 3 a.m. 1500 hrs. 3 p.m. 0400 hrs. 4 a.m. 1600 hrs. 4 p.m. 0500 hrs. 5 a.m. 1700 hrs. 5 p.m. 0600 hrs. 6 a.m. 1800 hrs. 6 p.m. 0700 hrs. 7 a.m. 1900 hrs. 7 p.m. 0800 hrs. 8 a.m. 2000 hrs. 8 p.m. 0900 hrs. 9 a.m. 2100 hrs. 9 p.m. 1000 hrs. 10 a.m. 2200 hrs. 10 p.m. 1100 hrs. 11 a.m. 2300 hrs. 11 p.m. 1200 hrs. 12 a.m. 2400 hrs. 12 p.m. 106","Kaalachakra I am Time. \\\"The wheel of time (kaalachakra) rotates Bhagavad Gita eternally through the four ages on earth...\\\" Chapter 10, 30 These four ages or yugas were called satyuga, tretayuga, dvaparayuga and kaliyuga, the present age. The kali era is supposed to be the most decadent period in the system of four yugas, and is believed to have begun on the dawn of February 18,3102 B.C. Our own ancestors in India were deep thinkers and learned men. Even a long, long time ago, when the Western civilization was still very primitive, our philosophers had evolved their own scientific calculations and theories. Their profound wisdom and knowledge is reflected in the rich literature of our past\u2014in ancient texts like the Vedas and the Pur anas. Here, one can read interesting accounts of the creation of the universe and the beginning 107","Summer of time, and trace the histories of the gods. The precision with which our ancients, in their own way, measured time is astonishing. Time, they believed, stretches to infinity. Unlike later Western thought which viewed time as something that moves in a straight line from past to future, Indian philosophers saw time (kaal) as an endless cycle. This was the kaalchakra or 'Wheel of Time' which moves through the four ages or yugas which are repeated for an endless period. These ancient philosophers were thorough in whatever they did. Time division began with the smallest unit of time, and was calculated up to practically infinity. According to the Shiva Purana, which is well over 1,500 years old, the smallest unit of time in the natural day was the time taken to wink. This was one nimisha, fifteen of which made one kashtha. Thirty kashthas made one kala, while thirty kalas made one muhurta. Thirty muhurtas constituted one complete day. Calculations did not stop here but went much farther. Fifteen days made one paksha and two pakshas of the waning and waxing moon made one month. A month was counted from one full moon to the next. Six months made up one ay ana and two ay anas made a year. To chart the passage of time, the. ancient Indian calendar-makers divided the lunar year into 354 days, and the solar year was spread over twelve lunar months. We still use 108","the same seasons with their old names today, Autumn viz. vasanta or spring, grishma or summer, Spring varsha or the rains, sharad or autumn, hemanta or winter, and shishir or the dews. Early poets and sages in India wrote lilting verses about the beauty of seasons. Chaitra was the first month of the year, falling in the spring-time, followed by Vaisakha, Jyaistha, Asadha, Sravana, Bhadra, Asvina, Kartika, Agrahayana, Pausa, Magha and Phalguna, the last month. The Saka calendar uses these same months. Eventually, ancient India adopted the seven- day week or saptaha from the West, and named the days after the corresponding planets. Sunday or Ravivara was named after the sun. Monday or Somvvara was named after the moon. Mangalvara or Tuesday was in honour of Mars. Wednesday which was named after Mercury was Budhvara, while Thursday was named Brihaspativara after Jupiter. Friday or Shukravara was dedicated to Venus, and Saturday or Shanivara was named after Saturn. Everything in ancient India had a religious or symbolic significance\u2014for the gods ruled every part of life. The solar year was considered to equal one complete day of the gods. The period of the sun's ascent into the northern hemisphere was considered to be daytime for the gods, while its descent into the southern hemisphere constituted their night. Thirty solar years equalled a month for the gods. In 109","Brahma this way, 360 solar years made a divine year. Vishnu Now you can imagine how old the gods must be! It was on the basis of these divine years that ancient Indian philosophers divided time into four ages or Yugas. The four yugas formed a mahayuga of 12,000 divine years, which equals 43,20,000 solar years. One thousand mahayugas made a kalpa. The Puranas tell us that thousands of such kalpas have come and gone, of which there is no record. Such figures are really too vast for us to be able to think about clearly! Indian lore states that one kalpa measures one day in the life of Brahma, the Creator. The subsequent night is equally long. Brahma's life span is considered to be 100 years long. By this reckoning, it stretches to practically infinity! Of these 100 years, only half are said to be over. Our ancestors further believed that our universe has been created in one day of Brahma's life, and will end in one night. Remember, this enormously long day spans 1,000 mahayugas or 43,20,000,000 years! The night of destruction is equally long. Furthermore, one Brahma is said to be followed by 1,000 such Brahmas. Then dawns the Age of Vishnu. One thousand Vishnus are followed by the Age of Shiva, and at the end of 1,000 Shivas alone will come the end of creation. Yet, this still does not mean the end of time\u2014 110","for only a fraction of the Creator's energy is Mahesh claimed to be used! Time has no beginning and no end. It is eternal. In the face of such immense time scales, our months and even years seem tiny. By their intricate calculations, our ancestors did manage successfully to show what a tiny speck man is, compared to the enormous cosmic distances of space and time around. The ancient Indian calendar continued with some refinements. With the influence of Greek and Mesopotamian astronomy and astrology, these refinements were introduced for casting horoscopes and making predictions. Shadow clocks, sundials, water-clocks and sandglasses were some of the instruments used to keep time in ancient India. A typical water- clock was made of a small pot with a hole in the bottom which floated in a large tub of water. The time taken for the pot to fill was one ghati, or 24 minutes. Incidentally, the Hindi word for clock or watch, ghadi, is derived from ghati. Ghadi is also used as a word for time measurement. In the eighteenth century, an observatory was built at Jaipur which was equipped with expensive astronomical instruments in marble and precious metals. A number of sundials were also built here, including the 'Samrat Yantra'. This huge structure, built by Maharaja Sawai Jai Singh II, is the world's biggest sundial. It has a vertical height of 111","Jaipur observatory","36 m and a gigantic gnomon 27 m. This casts a shadow so big that one can follow its smallest movements very easily. This sundial is aligned exactly with a north-south meridian, and is accurate to within two seconds. Today, we have not lost touch completely with our past. Indian festivals are still celebrated according to the calendars devised long ago, and, as we earlier saw, the Indian Government uses both the Gregorian and the ancient Saka calendars. 113","No Beginning, No End Man has come on an amazing journey from the distant shadow clock to the atomic clock of today, accurate to a millionth of a second! He has indeed triumphed oyer the measurement of time. You must remember however, that all these comprise earth measurements. Time counts in the universe are vast and quite different. Suppose you had a Martian friend who was born on the same day as you, and you are twelve years old today. How old would he be? Twelve years old, of course, you would say; and according to the time reckoning on the earth, you would be quite right. But on Mars, conditions would differ. You saw how an earth year of 365 days is measured by our journey round the sun. A picture of the solar system will show that the nine planets revolve in varying distances 114","round the sun. Mercury is its closest neighbour, while Neptune and Pluto are an enormous distance away from the sun. So planets do not orbit it in the same time. The farther away they are, the longer is their journey. They spin at different speeds too, so the lengths of their days vary. Mars, in fact, takes 687 earth days to complete one revolution round the sun. It is farther away from the sun than earth, and moves slower in its path. Therefore, 687 earth days make up a Martian 'year'. You can figure out now that your Martian friend is about six Martian years old! It is obvious that our measurements of time cannot be used on other planets. You would need a different calendar altogether. If you had another alien friend, living on far-off Uranus, he would be an old, old man by earth years when he reached his first birthday. For Uranus takes 84 earth years to go round the sun once. And friends at the outer edge of the solar system, on Neptune and Pluto, would not have a birthday at all! (We are assuming a life span like ours on earth). Neptune takes 165 earth years to circle","the sun. Its day is less than 15 hours, so there are 90,000 days to Neptunian year! Pluto, with its vast orbit of 248 earth years, spins so fast that its day is barely seven hours long. So it has even more days to the year. It is unlikely, however, that life exists anywhere else in the solar system but on our planet. As we know more and more about outer space, questions keep cropping up regarding the age of the earth, of the universe and indeed, of time itself. For us even one year seems a long time! It is difficult to understand how very old the earth is. Till a century ago, this was a very big mystery. Scientists tried to unravel this mystery in some interesting ways. Some tried to estimate the amount of salty chemicals carried down to the oceans by rivers. Geologists tried to figure out the earth's age by land and ocean changes. Many conclusions were guesswork, but finally, not very long ago, scientists came close to solving this mystery. An exciting discovery enabled them to estimate that the earth has been around a good 4.6 billion years or so. They discovered too, that life on earth started about 570 million years ago. The first 345 million years marked the development of simple marine life. Giant reptiles like dinosaurs were the earth's inhabitants for the next 160 million years, and mammals appeared in the subsequent 65 million years. Man appeared on the earth 116","","about one million years ago. However, we know only 5,000 years of his history. These vast figures have been worked out by studying a substance called uranium, which is found in some rocks. Uranium is a radio- active material\u2014which means it is always letting off energy, rather like a bulb emits light. Uranium is converted to lead at a steady rate over millions of years. So the amount of lead in rock samples enables scientists to estimate the age of the earth. If you find all these time distances mind- boggling, what about things older than even the earth, which existed before it did? To solve a good mystery one must go further back and further into time to look for clues. Can we reach the beginning of time itself? The exploration of the universe, conducted by astronomers, physicists and cosmologists is one of the greatest adventures of the twentieth century. Their findings in the last few years have revolutionized our knowledge and understanding of the universe. 'Cosmology' is the study of the universe at large, its beginning, its evolution and its ultimate fate. Cosmologists make use of information from giant telescopes, space probes and large computers that carry out their intricate calculations. Much of cosmology is mathematics, and cosmological ideas can be expressed in terms of equations, using paper and pencil and the mind alone. 118","Scientists have developed various kinds of Galileo invented a telescope with optical and radio telescopes to study distant lenses, and studied the moon, stars. Incidentally, the word 'telescope' is planets and the sun. taken from the Greek word 'teleskopein' which is a combination of 'tele' meaning 'far' and 'skopein' meaning 'to see'. So a telescope is an instrument that helps us to see far off objects clearly. The Italian scientist Galileo made the first successful telescope to study heavenly bodies. The Milky Way was the name given to the band of white light which stretches across the sky. Galileo discovered that this band of light comes from a vast collection of faint stars which the naked eye cannot see. Our sun, its planets and the nearby stars also belong to this collection of a hundred thousand million stars, held together by the gravitational force. This cluster of heavenly bodies is called 'galaxy'\u2014 Greek word for 'milk'. The whole galaxy is spinning round its own centre. It takes between 220 and 230 million years to go round once! This period has been called the 'cosmic year'. Clearly, beyond our galaxy lie millions of other galaxies which appear to us as merely dim, misty patches. Who knows, there maybe more which we have not detected as yet! All these stars must have surely come from somewhere and at some time. Scientists believe they were made from dust and gases. When and where did these come from, in the first place? To grasp cosmic evolution, one must probe 119","at least several billion years back in time by studying objects billions of light years away Equipped with big telescopes today, astro- nomers can look back billions of light years into space. They are actually gazing far back into time! While looking at light from a far- away galaxy, they are actually seeing it as it was millions of years ago. There have been different theories about the origin of the universe. Modern astronomers believe that the universe came into existence at one particular moment with the 'Big Bang'\u2014 explosion in space. The debris and blazing gases from this violent explosion were thought to be flung, far out in space. The cooling of these scattered parts over several million years gave birth to galaxies whose matter has been expanding continuously. Our solar system was also believed to have been formed like this. The lava of the earth solidified after a vast period of time into our familiar world. Scientists found evidence that the entire universe is evolving and expanding. The rate at which galaxies seem to be simply flying apart tells them the date when all matter in the universe set out on its journey. \\\"We were able to show that the matter in the universe must have been infinitely compressed about 15 thousand million years ago,\\\" says British astrophysicist, Stephen Hawking, author of the best-selling book, A Brief History of Time. 120","\u2022 And before that? \\\"Time as we measure it Subrahamanyan Chandrasekhar simply did not exist,\\\" he comments. The other (1910-1995) side of time is a dark mystery, greater than any mystery story you have read. Hawking is famous for his intensive research into certain dark areas in space, called 'black holes' or collapsars ('collapsed stars'). These are now seen as the remains or 'ghosts' of very large, 'dead' stars. Within a black hole, the gravitational attraction is so great that anything that goes in cannot come out. Not even light! How does this happen? At some stage in a large star's life, its nuclear fuel is exhausted. It becomes unstable and gravitationally begins to collapse inwardly on itself. The star shrinks after nuclear activity has ceased, to become a 'white dwarf'. In this process the star is reduced to one hundredth of its original size. Its gravitational pull becomes about 10,000 times more than the gravitational force of the original star. This dense star gives off little light. The fate of a white dwarf is decided by what is now known as the 'Chandrasekhar Limit', which is the maximum mass possible for its stability. This was named after the Indian astrophysicist Subrahamanyan Chandrasekhar who formulated it in 1930. He showed it was impossible for a white dwarf to be stable if its mass is greater than 1.44 times the mass of the sun. 121","Black hole The star contracts further, forcing the electrons and protons of its atoms to combine to form neutrons. The star now becomes a 'neutron star'. Its size is reduced to a five- hundredth part of the dwarf star and gravitational attraction becomes about 100,000,000,000 times the original star. As the light given off by the neutron star decreases, its energy and its size reduces further. At some stage even its neutrons are crushed out of existence and it becomes a 'black hole'. Within the black hole, matter may be compressed to a point of zero volume and infinite density. This is called a 'singularity' and it forms the core of a black hole. All laws of physics break down at a singularity. If this puzzles you, do not worry. It is only in the last few decades that scientists themselves have begun to understand the origin and nature of the universe! Even stranger to understand is the way a black hole behaves, drawing everything into itself like a bottomless pit. Falling into a black hole is one of the horrors of science fiction. Yet, scientists today have concluded that a black hole is fact rather than fiction. Its great gravity drags anything that passes close enough, and tears it to shreds. These fragments fall into the black hole and can never come out. For, to get away from its extremely intense gravity, the speed needed or the 'escape velocity' must be greater than the speed of light. Scientists are 122","quite sure now that nothing can travel faster than the speed of light. Therefore, if light cannot escape, nothing else can. No wonder it seems so black! This invisible black hole can be detected only by its gravitational force. It closes time and space within itself and cuts itself off from the rest of the universe. Light and even time are said to circle endlessly in a closed loop. A key ingredient to understanding the universe today, astrophysicists have found, is the union of space and time. In fact they call this 'space time'. In everyday life, space and time seem to be quite different things. You know that space extends in the three dimensions of length, breadth and height. We can see where things are located in space and travel through it more or less at will. But although we know what time is, it is almost impossible to describe. In a sense it does have a direction from past to present and future, but we can neither look into the past nor the future, and we certainly cannot move through time at will. As long ago as 1905, German physicist Einstein was suggesting that instead of thinking of space and time as two separate entities, they should be thought of as different parts of a single unified whole, 'space-time'. His special theory of relativity combines the two in the same set of equations and shows they can be stretched or squeezed. 123","Spaceship Speed is a measure that relates space and time. Speeds are always in the form of miles per hour or kilometres per second and so on. You cannot have one without the other when you talk of speed. Earlier theories have now been measured and confirmed to great precision in very many experiments. There have been many fascinating conclusions. Einstein's special theory of relativity had suggested that if an object were to travel at or near the speed of light, it would appear to undergo some astonishing changes. If you could watch a spaceship travelling at the speed of light, you would see three effects. lime would pass more slowly on the spaceship in relation to time on the earth. The spaceship would appear to increase in mass. It would also appear to decrease in length. Later experiments confirmed that space and time are indeed warped at high speeds. Moving objects also increase in mass the faster they go. But the speed of light always remains constant. Objects that travel at the speed of light experience 'time dilation' or stretching of time, and shrinking of length. Time is thus intimately related to motion and space. Imagine what time dilation could actually mean! In the distant future, astronauts manning spaceships that travelled at the speed of light, might return home to find their 124","children older than themselves! For time would have passed more slowly for them than for people on earth. And if time dilation really proves possible, it could be used for all kinds of important things. Space laboratories travelling at the speed of light could be used for elaborate experiments. Exploration into deep space would become possible, for long space journeys at high speed could be easily finished in the lifetime of one space crew. However, light travels at the fantastic speed of a hundred and eighty-six thousand miles a second! Today's space probes move at a mere seventy miles a second or so, and it seems unlikely we could reach the terrific speed of light. But who knows, science fiction could indeed become fact one day! Very slowly, the implications of all these amazing discoveries began to dawn on cosmologists. The universe, they realized, might behave like the biggest black hole of them all, where everything was held together by gravity, and space-time formed a self- contained loop! There was one big difference. Black holes pull matter inwards, towards the singularity. The universe on the other hand expands outwards fom the Big Bang. Indeed, it is like a black hole inside out. Einstein's equations, the general theory of relativity, had said that the universe could not be static but must expand or contract. Observations showed that the 125","universe is indeed expanding. The universe must have emerged from a point of infinite density, a singularity, about 15 billion years ago, his equations show. This is sometimes referred to as the 'cosmic egg'\u2014a completely self-contained ball of matter, energy, space and time. It was indeed a superdense black hole before the Big Bang. This was perhaps the beginning of time! Having gone back to the beginning, cosmologists now looked ahead to the future. The universe is thought to reach a certain size after which expansion of the galaxies will stop and they will start contracting. The Universe will then collapse back into the final singularity, termed the 'Big Crunch'. This is taken to be the end of time. It has been calculated that the 'edges' of time and space may be removed to prove a universe with no boundaries at all. It is simpler to understand this rather complicated idea by representing the universe as a globe. Imagine the Big Bang as a spot on its surface drawn at the North Pole. As time passes, we imagine the lines of latitude drawn farther and farther away from the North Pole getting bigger all the way to the equator. This shows expansion of the universe. From the equator down to the South Pole, the lines of latitude decrease, corresponding to the universe shrinking back into nothing, as time passes. There is thus no discontinuity in time or 126","space. At the North Pole, there is no direction north for everything points south. This is because of the geometry of the curved surface of the earth. Similarly, at the Big Bang, there was no time past, but everything lay in the future. This is simply because of the geometry of the curved surface of space-time. The entire package of space and time, matter and energy, is self-contained. It is like walking a little away from the North Pole due north. In a little while you will be walking south. In the same way, let us go back to where we began. Suppose you clambered aboard a Time Machine and pressed the 'Reverse' button. Z...a...a...p... You would travel backwards in time, all the way to the Big Bang. A moment later, you would move towards the future even though you had not changed the controls of your machine! The gaps in our understanding of the laws and forces governing our physical world are still enormous. The challenge to solve the riddle of time has only just begun. It has taken us to the threshold of exciting mysteries of existence and the unknown future. One day, perhaps, we will redefine our concept of time. Till such time, the fascinating story of time cannot end. The limits are set only by the limits of the human imagination. No doubt, time alone will tell! 127","A world without time! It would be a chaotic place to live in. Man has been trying ever to reckon time. He watched nature's clocks\u2014the rising and setting of the sun, changing of the seasons, growth of a baby and mutation in all creation. From shadow sticks to sundials to water- clocks to the present day clocks that are accurate to one-millionth of a second and further\u2014it is indeed the story of time. A most significant idea that has resulted through untiring research is the concept of time-space-continuum as an indivisible unity. Time remains a scientific mystery! E 377 ISBN 81-7011-891-3"]