PREFACE
Let me begin defining what time travel actually is: Time travel is a concept of travelling in time to either the past or the future in some device known as the “Time Machine". (Any technological device, whether fictional or hypothetical, that is used to achieve time travel is commonly known as a time machine). According to an online encyclopedia, “Time travel is the concept of moving between different points in time in a manner analogous to moving between different points in space, either sending objects (or in some cases just information) backwards in time to some moment before the present, or sending objects forward from the present to the future without the need to experience the intervening period (at least not at the normal rate)”. The concept caught much fuel since the 19th century as the possibility of time dilation based on velocity in the theory of special relativity (exemplified by the twin paradox), as well as the gravitational time dilation in the theory of general relativity. However, it is currently unknown whether the laws of physics would allow backwards time travel. Stories of time travel may just have been a work of fiction but many physicists always scoffed the idea of time travel, considering it to be the realm of cranks and mystics, and with a good reason. Rather the theory has been revived by the remarkable advances in the field of quantum gravity. Although the quantum theory of gravity has immediate practical application, there is a budding area of physics devoted to time travel, which has not been practical as yet.

ORIGIN OF THE CONCEPT

There is no widespread agreement as to which written work should be recognized as the earliest example of a time travel story, since a number of early works feature elements ambiguously suggestive of time travel. Ancient folk tales and myths sometimes involved something akin to travelling forward in time; for example, we can go back to the ancient Hindu Epic the Mahabharata which mentions the story of the King Revaita, who travels to heaven to meet the creator Brahma and is shocked to
learn that many ages have passed when he returns to Earth. Another one of the earliest known stories to involve traveling forwards in time to a distant future was the Japanese tale of ”UrashimaTaré", first described in the Nihongi (720). it was about a young fisherman named Urashima Taro who visits an undersea palace and stays there for three days. After returning home to his village, he finds himself three hundred years in the future, where he is long forgotten, his house in ruins, and his family long dead.

However, as mentioned earlier, it was HG. Wells’ classic ”The Time Machine” that inspired my approximately 3 pounder brain to write this article. in this novel, as vividly elucidated by Wells, our protagonist jumped into a special chair with flashing lights, spun a few dials, pulled a lever, and found himself catapulted several thousand years into the future.

In 1905, Albert Einstein published special theory of relativity. It was Einstein, as every schoolchild knows, who first described time as ”the fourth dimension” -and every schoolchild is wrong. it was actually Wells who wrote, in The Time Machine, that ”there is no difference between Time and any of the three dimensions of space, except that our consciousness moves along it” and that too in 1895, exactly hundred years before Einstein’s theory! Since, the time of Wells and Einstein, there has been a continuing literary fascination with time travel, and especially with the paradoxes that seem to confront any genuine time traveler.

TIME TRAVEL PARADOX

Not surprisingly, the ideas of time travel has met resentment, even from modern day greats like Stephen Hawking, who claimed he had "empirical" evidence
against it. if time travels were possible, he said, and than we would have been visited by the visitors(or tourists) from the future, as future people would be capable to build a time machine. But, as we see no visitors from the future, so time travel is not possible. Not only Stephen Hawking but many other physicists too, object to the concept of time travel and consider it as merely a work of science fiction. One of the most prominent objections arises from the Grand Father Paradox. What happens if the time traveller goes back in time, to the past and kills his own grandfather before his father was born? Auto lnfanticide works the same way, where a traveler goes back and attempts to kill himself as an infant. if he were to do so, he never would have grown up to go back in time to kill himself as an infant. This discussion is important to the philosophy of time travel because philosophers question whether these paradoxes make time travel impossible. Some philosophers answer the paradoxes by arguing that it might be the case that backwards time travel could be possible but that it would be impossible to actually change the past in any way, an idea similar to the proposed Novikov self consistency principle in physics.

TIME TRAVEL AS A POSSIBILITY

Talking of the possibilities, i believe there is so much more to be discovered in the field of science that we should not dismiss the fantasy (as of now) of time travel. Almost 500 years ago, Leonardo da Vinci speculated about the possibility of flying machines. He designed both helicopters and aircraft with wings, and modern aeronautical engineers say that aircraft built to his designs probably could have flown if Leonardo had had modern engines with which to power them -even though there was no way in which any engineer of his time could have constructed a powered flying machine capable of carrying a human up into the air. Leonardo could not even dream about the possibilities of jet engines and routine passenger flights at supersonic speeds. Yet Concorde and the jumbo jets operate on the same basic physical principles as the flying machines he designed. In just half a millennium, all his wildest dreams have not only come true, but been surpassed. Relativity states that if one were to move away from the Earth at relativistic velocities and return, more time would have passed on Earth than for the traveler, so in this sense it is accepted that relativity allows “travel into the future” (although according to relativity there is no single objective answer to how much time has ’really’ passed between the departure and the return). Back in the year 1949, Kurt Goedel, at Institute Of Advanced Studies at Priceton, demonstrated Einstein’s own equations allowed for time travel. if the universe rotated, and you went around the universe, you could arrive back before you left. In this memoir, Einstein pointed out that Goedel‘s solution could be dismissed on the physical grounds. As our universe expands, it doesn't rotate. Since then, hundreds of solutions to Ernstein‘s equations have been found which yield time travel solutions.

Time travel to the past is theoretically allowed using the fo lowing methods:

1. Travelling faster than the speed of light

2. The use of cosmic strings and black holes

3. Wonnholes and Alcubierre drive

4. Travelling in an infinite spinning cylinder

   Michio Kaku, a professor of physics in New York, has come up with a more accessible variation on the theme with his book Hyperspace, which includes some discussion of the contribution of researchers such as Robert Heinlein to the study of time travel. The Big Bang, string theory. black holes and baby universes all get a mention here; but it is the chapter on how to build a time machine that makes the most fascinating reading. 'Most scientists, who have not seriously studied Einstein's equations," says Kaku, “dismiss time travel as poppycock”. And he then goes on to spell out why the few scientists who have seriously studied Einstein’s equations are less dismissive. Our favourite page is the one filled by a diagram which shows the strange family tree of an individual who manages to be both his/her own father and his/her own mother, based on the Heinlein story ”All you zombies". And Kaku's description of a time machine is something fans of H.G. Wells would be happy with.

May it be just a fantasy or a reality, the concept of time travel remains the much interested and puzzled topic for a number of great physicists of our time. As for the readers who may look for my view or who may wonder what I think about the concept of time travel, i can only say that i am not a person who would question the possibilities of science. As three centuries ago, the great English scientist Sir Isaac Newton wrote, "l seem to have been only like a boy playing on the sea shore while the great ocean of truth lay all undiscovered before me".

With the latest discoveries and inventions and all the interest and hard work of the scientists and engineers in the field of researchlon the concept of time travel itself), who knows? Time travel may just become a common practice in the future. So, to conclude, don't turn anyone away who knocks at your door one day and claims to be your great~great.grandson. He might just be right!

And Happy Valentine to all