Time Travel - closer to reality or fiction?

During my first semster in college,I had a special course on Relativistic Mechanics.The professor(we called him MM) who taught me this subject looked straight out of a sci-fi novel.He was short and plump,sported a reddish orange beard, wore heavy rimmed glasses and had a shiny balding head.He had a knack of asking out-of-the-world questions but his questions were never meant to be answered and if you thought you were a smart dude and tried to answer him, you ended up looking like a numb nut.And in one of these lectures he introduced us to the concept of Time Dilation, length contraction and Time Travel.

More than Albert Einstein's relativity equations (the best theory about time and space), the application of these concepts caught my fancy (Plzz..dont end up believing that i finally published some revolutionary time travel theory and got a Noble prize for it).Consider the fact that we humans are always travelling in time but in a linear fashion until we meet our death.But the Time travel phenomenon can possibly allow us to rewind/forward the video of our Life video to any moment anytime.

During those days, Discovery Channel also aired a program a programme showing the theories and experiments revolving around 'Time Travel'.
There is one school of though that believes that 'Time Travel' is not possible and they have many theories including the one called 'GrandFather's Paradox', to boot their claims.


How will it feel like travelling in Time ?

The grandfather paradox is a paradox of time travel, supposedly imagined by the SF writer René Barjavel in his book "Future times three" in 1943. Suppose you travelled back in time and killed your biological grandfather before he met your grandmother. Then you would never have been conceived, so you could not have travelled back in time after all. Now did you travel back or not?

But what if a time travel doesn't change the past, but perfects it. For example: A person travels back to the past, at least 1 year before his birth. He meets his mother, young and very attractive, falls in love, marries her and they get children. Years after that his son disappears, travels back in time to meet his mother,... Here the past perfects the present. At the birth of time traveller's son, we've got 2 identical persons, genetically and identical in mind. They only differ in age.

Contrary to the Granfather paradox,one of the noted physicists Richard Feynman proposed a multiple history idea.This idea implies that there are multiple histories. For each decision that is ever made, (i.e. should I wear a white shirt or a black shirt today) there is another universe in which the decision is made differently. It is possible that in another universe, you wear a white shirt every single day of your life. This idea, however, is very difficult to prove. By definition, it would be impossible for us to go to these other universes and see for ourselves.

Feynman histories concept is built on the idea of really small particles here, not spaceships or even people.As Stephen Hawkings pointed out,"quantum theory allows time travel on a microscopic scale". We cannot talk to hydrogen atoms and ask them if they travel in closed loop histories, but we can observe that there is a shift in the light given off by hydrogen atoms, which indicates that their electrons are moving in closed loops. Maybe, time travel takes place in front of us everyday according to Feynman histories, yet it happens on such a small scale that we don't even notice it. :?
So,you simply go to the past, kill your grandfather.This automatically creates a new history. (in a new universe/worldline).You would still be in existence in the original history, and also in the new one.

Another theory regarding Time Travel is that of 'Parallel Universes' or multiverse.The paradoxes would disappear if we accept this theory. When Time Traveller returns in time an exact copy of the world of his grandfather is created on the moment he arrives. The place where he arrives is not his past and the grandpa he's trying to kill is not his grandfather, but it's the fake world (duplicate world) and the duplicate grandfather. When he kills that man, he doesn't kill his grandfather, so the paradox is gone. The Time Traveller can mess around as much as he likes, nothing will change the 'real' past or present.

This multiverse concept was also put to use by a famous SF writer Michael Crichton(of Sphere,Jurassic Park and Lost World Fame) in his novel Timeline (now being made into a movie).Its a beautifully written book where he explores the possible ramifications of Time travel and the interaction of various characters with the people and technology in the medieval France during 100 years war.

It was ,however,H.G. Wells was the first author to write about Time Travel(even before Einstein!!) and Time machines in his novel 'The Time Machine'(also made into 2 movies with the same name) in 1895!

The protagonist of his novel builds a time machine capable of moving back and forth in the 'fourth dimension' called Time. He travels far into the future where he experiences that the world has changed a lot but the class distinctions still persist.After this he ventures into a more distant place in the future to find that Earth is almost about to perish.Another attempt to time travel causes him to disappear into the portals of time forever.!!

You can find the complete novel here : 'The Time Machine'

Another well known movie that explores the time travel concept was 'Terminator'.

In the future a great war has devastated the earth. Robots, controlled by a central computer, Skynet, have taken over; But human insurgents are about to overthrow the tyrannical machine. In a desperate attempt to save itself, Skynet sends one of its robots, a Terminator, into the past to kill Sarah Connor, the mother of the rebel leader before he can be born. One lone rebel soldier, Kyle Reese, follows the Terminator into the past to try to stop it. By sending the Terminator into the past, Skynet has sealed its own fate, as Kyle Reese meets up with Sarah Connor and together they conceive their child John Connor, who will grow up to be the rebel leader who destroys Skynet.This satisfies the theory,that 'Anything that can happen,will happen.'

An application of the Time Travel concept in computational science is Time loop logic.
It is a system of computation that requires the computer to be able to send data backwards through time, and relies upon the Novikov self-consistency principle to force the result of a computation sent backwards through time to be correct. This approach can overcome many limitations on traditional algorithmic complexity.

A program exploiting time loop logic can be quite simple in outline. For example, to find a factor for a large number:

1.wait for the result to be transmitted from the future. (This statement amuses me like hell...If put into practice,this will be a boon for students like me!!)
2.upon receiving the result, test whether it is a factor by dividing the input number by it.
if the received result is indeed a correct factor of the number, send the result back in time.
else if the received result is not a correct factor of the number (or no result is received at all within the desired timeframe), generate a number different from the received result and send it back in time. Note that this results in a paradox, since the result sent back is not the same as the one that was received.
Since the Novikov principle states that it is impossible for any sequence of events to result in a paradox, the second clause of the conditional statement can never happen and the result sent from the future is guaranteed to be the correct one!!

Of course, time loop logic is a purely theoretical exercise at this point. It is not known whether time travel is possible, or if it is whether Novikov's principle really applies to it.

Another aspect of Time Travel is concerned with anachronism (something that appears out of place because it is thought to be inappropriate or impossible for that time period).For example,
-The Great Pyramid and the Great Sphinx of Giza demonstrate impressive engineering capability, even by modern standards. Some have speculated that they may have been built by aliens, or that their construction required technology from a future civilisation. It may simply be that the masonry skills of the Ancient Egyptians were more advanced than historically thought.

-Leonardo da Vinci was certainly a man ahead of his time; his sketches and writings include a precursor to the modern helicopter, centuries before the invention of comparable flying machines. Leonardo's helicopter could not fly, however.

-The Baghdad Battery is an artifact from between 250 BC and 250 AD, discovered near Baghdad, with a structure similar to that of a modern battery. It also appears that similar batteries can be located around ancient Egypt, where objects with traces of precious metal electroplating have been discovered at different locations.

A recent pointer to one such anachronism is Tom Clancy's novel 'Debt of Honor' in which he almost predicted 9/11 disaster...

"... it had never occurred to anyone to have fighter aircraft aloft over the capital ...... Sato brought his aircraft around ... the 747 banked left, clearly under precise control ... Sato had been to Washington often ... including the Capitol Building ... he adjusted his flight path so that he was now roaring right up Pennsylvania Avenue ... His last voluntary act was to select the point of impact, two thirds of the way up the stone steps ... Nearly three hundred tons of aircraft and fuel struck the east face of the building at a speed of three hundred knots. The aircraft disintegrated on impact. ... Next came the building itself. ... one hundred tons of jet fuel erupted from the shredded fuel tanks, vaporizing ... A Second later it ignited from some spark or other, and an immense fireball engulfed everything inside and outside of the building. ...".

A promotional quote for Debt of Honor from Entertainment Weekly:
"A shocker climax so plausible you'll wonder why it hasn't yet happened." :-O

Some people argue that these examples and others show that there have been careless time travellers and show that "temporal secret agents" have been here on containment and damage limitation missions. These are said to be the smoking guns of the ultimate conspiracy theory.
To top it all, 'The ancient astronaut' theory or paleocontact says that human beings are either the descendants of aliens who landed on Earth millennia ago, or that much of our culture was given to us by extraterrestrial visitors in the time of pre-history.
Mindboggling..huh!!


Stephen Hawking once said: "If time travelling will be possible, why haven't we seen a lot of tourists from the future yet?"
Infact Earth was visited by a Time Traveller in the year 2000:
Read on...

Although there is debate over the exact date it started, on November 02, 2000, a person calling themselves Timetravel_0, and later John Titor, started posting on a public forum that he was a time traveler from the year 2036.

One of the first things Titor did was post pictures of his time machine and its operations manual. As the weeks went by, more and more people began questioning him about why he was here, the physics of time travel and his thoughts about our time.He posted on many forums including the old Art Bell site. In his posts John Titor entertained, angered, frightened and even belittled those who engaged him in conversation.

On March 24, 2001, John Titor told the people that he would be leaving our time and returning to 2036. After that, he was never heard from again.Even today, the speculations and investigations surrounding John Titor's claim abound.So till date,nobody knows who John Titor was,why he was online all this time and whether all his claims were a part of a big hoax

Read the complete story on John Titor's Website.Fascinating read indeed!!

Apparently Amazon is now selling a book called John Titor: A Time Traveler's Tale which is reportedly being sold by John Titor's mother.