TIME AND TIME MACHINE

DEBANGAN MAJUMDERTCS,HYDERABAD

"When you sit with a nice girl for two hours, it seems like two minutes. When you sit on a hot stove for two minutes, it seems like two hours; that's relativity." -- Albert Einstein

On January 27th, 1995 a group of American and British Scientists were carrying out some experiments in Antarctica. During its course they made an awesome discovery. They spotted some spinning gray fogs over the pole which looked like a sand storm. Due to curiosity the researchers launched a weather balloon capable of measuring wind speed, air moisture, temperature and other information. Surprisingly as the balloon soared up it disappeared into the thin air. In a little while the researchers brought down the balloon with the help of the rope which was tied to it. They were extremely surprised to see the chronometer set in the balloon which displayed the date January 27th, 1965, the same as 30 years ago! This is only one of the bizarre incidents that have left scientists and physicists around the planet racking their brains on a puzzle known as “Time and Time Machine”.

Time or “fourth dimension” is an intriguing concept. It doesn’t have a clear, compact definition and is merely a hypothetical concept which is an indispensable element to explain numerous physical phenomenons. Our best understanding of time comes from Einstein’s theory of relativity. Prior to this time was considered to be absolute and universal. But according to Einstein’s theory of relativity two persons moving at different speeds will experience different durations between the same two events. In short the person who is moving faster will experience time to elapse slowly than his slower counterpart. This phenomenon is widely described as the “Twin Paradox”. Suppose Sally and Sam are twins. Sally boards a high speed rocket and sets out to travel around the universe. She returns to earth after one year and finds her brother Sam is now nine years older than she is! That is to say Sally has leaped nine years into earth’s future! Mind boggling isn’t it? This unusual phenomenon is caused due to an effect called “Time Dilation” which occurs when two observers move relative to each other close to the speed of light. Even given the fastest of spacecrafts our present technology can provide we cannot observe time dilations above a few nanoseconds.

The concept of time machine came into existence after H.G Wells wrote his celebrated sci-fi novel, “The Time Machine” in 1895. In simple terms a time machine is a device which can take us from present to past or future. Since its inception the concept of time machine have been subject to numerous speculations and scientific paradoxes. Even the very existence of time is somewhat perplexing.But scientists believe that under suitable circumstances “time travel” is not impossible. The easiest way to conceptualize time travel is through a Black hole. A Black Hole is a dead star with infinite density which can curb both space and time. It represents the ultimate time warp, and at the surface of the hole time stands still relative to the earth. This means if an astronaut falls into the black hole and comes out unscathed (though this is impossible) he will jump ahead into the future. Now the question that arises in our mind is how can we create a Time Machine?

Time travel can be made possible in two ways, one is through speed and the other one is through gravity. Achieving speed even nearer to that of light is a daunting challenge in itself. Unfortunately we are still miles away from achieving such height in speed. Gravity may be a relatively usable raw material. In his general theory of relativity, Einstein predicted that gravity slows time. Clocks run a bit faster in higher floors of a building than in the basement, which is closer to the center of the earth.

Traveling forward in time is not that impossible though theoretically. But what about moving back in time? There are some skeptics who strongly condemn the possibility traveling back in time since that would mean one can go back in time and kill his or her own grandfather. That would question his own existence! But strangely or rather hopefully Einstein confessed that his theory might permit time travel under some circumstances. In 1974 Frank J. Tipler of Tulane University suggested that a massive, infinitely long cylinder spinning on it’s axis at near the speed of light can admit anyone visit his or her past. In mid 1980’s a more realistic scenario for time travel emerged which could allow astronauts to travel both in past as well as future through same interface. This radical concept was known as “Worm Hole”.

Worm Hole is basically a hypothetical gateway or shortcut tunnel between two widely separated points in space. Its concept was investigated by Kip S Thorne and his co-workers of California Institute of Technology to verify whether they comply with laws of Physics. He then developed the much talked about “Thornian Time Machine”. To generate a practical worm

hole one of it’s mouth should be placed near the surface of a Neutron Star(At the surface of a neutron star, gravity is so strong that time is slowed by about 30 percent relative to Earth time). This creates a difference in gravitational force between the ends which ultimately slows up the time at the neutron star end, creating a time difference. But there is a small problem. An Astronaut cannot return back to a time before the worm hole was first built. This could provide an alternative explanation for Hawking's (of the University of Cambridge) observation: a time machine will be built someday, but has not yet been built, so the tourists from the future cannot reach this far back in time.

Presentism holds that neither the future nor the past exists, the universe only exists in the present and time is merely a concept to describe what is going around us. The formidable obstacle lies in the practical creation of the time machine. For example creating a worm hole of practicable size, keeping it stable, moving one end around would require energy greater than that of Sun can produce in its entire lifetime.

Well, everything is not lost. Better explanations and theories are throwing light into the matter. For example Daniel Greenberger and Karl Svozil have proposed that Quantum Theory model amalgamated with general relativity can explain time travel without any paradoxes. Advanced areas of science like the “String Theory” may hold the key to solve the riddle. Scientists and physicists around the globe are working to make this near impossible thing possible. It may take more than our life time to make a time travel a reality, but once this breakthrough is accomplished the world around us would never be the same. By that time Science would reach at the very edge of the Universe and movies like “the time machine” or “back to the future” would be history.