Time Travel - A brief overview...

[suyash]

There is no other concept that captures the imagination more than the idea of time travel -- the ability to travel to any point in the past or future. What could be more cool? You could jump into your time machine to go back and see major events in history and talk to the people who were there! Who or what would you travel back to see? Mahatma Gandhi? The construction of some ancient wonder? the life of your grand-grandparents? You could go back and meet yourself at an earlier age, go forward and see how you look in the future...regardless of the many complications involved and the paradoxes which may arise. (The most famous paradox is Grandfathers paradox) It's these possibilities that have made time travel the subject of so many science fiction books and movies. The fascination to alter the future or to have a glimpse of what lies ahead has always tempted man to bend the laws of nature, technically speaking, the space-time continuum.

I have been inspired by the following sources while writing this article on time travel

• The time machine - H.G.Wells
• A brief history of time - Stephen Hawking
• Terminator movies trilogy
• Butterfly effect - awesome movie !
• TV series like Heroes
• and there are many more.....

It is a fact that we are all time travelers. As you read this article, doing nothing more than scrolling your mouse, time is traveling around you. The future is constantly being transformed into the past with the present only lasting for a "fleeting moment". Everything that you are doing right now is quickly moving into the past, which means we continue to move through time.

Ideas of time travel have existed for centuries, but when the great Albert Einstein released his theory of special relativity, he laid the foundation for the theoretical possibility of time travel. As we all know, no one has successfully demonstrated time travel, but no one has been able to rule it out either.

Time has been defined as being the fourth dimension of our universe. The other three dimensions are of space. Time cannot exist without space and space cannot exist without time. This interconnected relationship of time and space is called the space-time continuum, which means that any event that occurs in the universe has to involve both space and time.

How to time travel?

While writers have produced some great ideas for time machines over the years, a real-life time machine has yet to be built. Most theories of time travel don't rely on machines at all. Instead, time travel will likely be done by way of natural phenomena that will transport us instantly from one point in time to another. These space phenomena, which I am not even sure exist, include:

• Wormholes
• Cosmic Strings

1) According to me the best bet for time travel would be - "Wormholes", if they do exist. Wormholes are considered possible based on Einstein's theory of relativity, which states that any mass curves space-time. To understand this lets think about two people holding a bed sheet up and stretching that sheet tight. If one person were to place a baseball on the bed sheet, the weight of the baseball would roll to the middle of the sheet and cause the sheet to curve at that point. Now, if a marble were placed on the edge of the same bed sheet it would travel toward the baseball because of the curve.



Here, space is shown as a two-dimensional plane rather than the four dimensions that actually make up space-time. Now imagine that this sheet is folded, leaving a space between the top and bottom. Placing the baseball on the top side will cause a curvature to form. If an equal mass is placed on the bottom part of the sheet at a point that corresponds with the location of the baseball on the top, the second mass would eventually meet with the baseball. This is one of the ways how wormholes may form, really fascinating, isnt it?


In space, masses that place pressure on different parts of the universe could eventually come together to form a tunnel -- this is a wormhole. We could then travel from Earth to another galaxy and back relatively quickly (within a lifetime). I am saying a bit quickly because hypothetically speaking, we are traveling for a shorter distance at much high speed. Why we need to travel through the worm holes at the speed of light is something that I cant put here in this blog. If wormholes could be discovered, it might allow us to travel to the past as well as the future, though there are infinite complications and intricacies involved in this mind blowing journey.


2) Another way to time travel is by using the concept of cosmic strings -which are string-like objects that some scientists believe were formed in the early universe. These strings may line the entire length of the universe and are under immense pressure -- millions upon millions of tons. These cosmic strings, which are thinner than an atom, can generate an enormous amount of gravitational pull on any objects that pass near them, just like the black holes. Objects attached to a cosmic string could travel at incredible speeds, and because their gravitational force distorts space-time, they could be used for time travel. By pulling two cosmic strings close together, or one string close to a black hole, it might be possible to warp space-time enough to create closed time-like curves.

A spacecraft could be turned into a time machine by using the gravity produced by the two cosmic strings, or the string and black hole, to propel itself into the past. To do this, it would loop around the cosmic strings. However, I read somewhere that in order to travel back in time even one year, it would take a loop of string that contained half the mass-energy of an entire galaxy. Also it has been speculated that one cant go back farther than the point at which the time machine itself was created.

[suyash]

Problems involved in Time Travel...

I hope that the reader is acquainted with the nuances involved with time travels, I thought that its imperative to show what troubles we might face in this yet to be accomplished but mighty dream of ours. If we are ever able to develop a workable theory for time travel and invent some sort of time machine, we would open up the ability to create very complicated problems called paradoxes. A paradox is defined as something that contradicts itself. Here are some common examples that I could think of.

I Let's say, for the sake of argument, that you could travel back to a time before you were born. You will say, whats the big deal in that? Isn't that one of the purposes of the time machine? To see the unknown... But the mere fact that you could exist in a time before you were born creates a paradox. If you were born in 1986, how could you exist in 1947 to see Jawaharlal Nehru unfurling the flag of India's independence?

II Possibly the most famous paradox is the grandfather paradox. What would happen if a time traveler went back and killed one of his or her ancestors/blood relatives (say father or mother... not that one would actually do that... but its just for the sake o example) before the traveler was born? If the person killed his or her grandfather, then how could that person be born some years later and then go back and kill his or her grandfather? Mind-blowing stuff, one would say but its just a part of infinite intricacies involved. Movie buffs like me would relate this with the famous John Connor from the Terminator trilogy (the 4th part is yet to be released, at the time of writing). If we could change the past, it would create an infinite number of paradoxes.

III And the most baffling one would be if you go just some hours ago in time, at the same space where you existed... Consider seeing a duplicate of oneself for some moments but there are many theories that don't allow such things. Space-time continuum laws, though hypothetical are surely not a piece of cake to understand.

IV Another theory regarding time travel brings up the idea of parallel universes, or alternative histories. Remember the awesome movie Butterfly Effect and its sequel !!! (If you still haven't done that, then be sure to do that the first thing after reading this blog... you are missing something really vital.) Let's say that you do travel back to meet your father when he was a boy. In the theory of parallel universes, you may have traveled to another universe, one that is similar to ours, but has a different succession of events. For instance, if you were to travel back in time and change something in order to alter the future, you've only done the "change" in that one universe, and sadly its no longer the universe that you exist in. And if you then try to travel back to your own time, you may end up in another parallel universe and never be able to get back to the universe you started in the first time. The idea here is that every action causes the creation of a new universe, and that there are an infinite number of universes that exist. When you killed your ancestor, you created a new universe, a universe that was identical to your own up until the time you changed the original succession of events.

V Predestination Paradox and Ontological Paradox

Consider the following examples...

A man travels back in time to discover the cause of a famous fire. While in the building where the fire started, he accidentally knocks over a kerosene lantern and causes a fire, the same fire that would inspire him, years later, to travel back in time.
On his 30th birthday, a man who wishes to build a time machine is visited by a future version of himself. This future self explains to him that he should not worry about designing the time machine, as he has done it in the future. The man receives the schematics from his future self and starts building the time machine. Time passes until he finally completes the time machine. He then uses it to travel back in time to his 30th birthday, where he gives the schematics to his past self, closing the loop.
A professor travels forward in time, and reads in a physics journal about a new equation that was recently derived. He travels back to his own time, and relates it to one of his students who writes it up, and the article is published in the same journal which the professor reads in the future.

Confused yet? Welcome to the amazing world of time travel. Makes you think a lot. Just imagine how complicated the ticket prices will be. Anyone up for grabs?


Epilogue

Even if you do decide to choose any one of the way stated above for your time travel dream, be sure that it is still a distant dream. Because I feel that we should not mess up with the beautiful universe that has been created for us. Let the things go as they are. No doubt, the quest for knowledge must continue, we must understand the physics behind everything after all its the basic characteristics that separate us from other living beings on this planet. But then we must not forget that after a point, things are beyond recognition and every mathematical law breaks down, say before the singularity (just before the big bang)

And if all this has been heavy for you, let me propose another mode of time travel devised by me... yes myself ! It may sound ridiculous but then not more than the stuff above. Considering the universally accepted laws of thermodynamics, it has been proved that entropy of a system "always" increases with time. Does that mean that if we manage to decrease the entropy of a finite part of space-time, it will be teleport back to past?? Some food for thought... isn't it?

[Elisa]

Not a convincing thought. I have read about wormholes a bit. Travelling with speeds which equal the speed of light is practically impossible as the mass would tend to be infinite at those levels of speed.

Nice effort though. Keep writing.

[MaRo]

GREAT!

About problems involved if someone killed one of his ancestors, I think it can be "Read-Only", Just see what happened and no interaction involved.

But that's amazing even if it's just fiction.

Anyway God gave us brains to think.

Thanks suyash

EDIT:I'll post here any ideas I can get soon.

[suyash]

Originally Posted by Elisa

Not a convincing thought. I have read about wormholes a bit. Travelling with speeds which equal the speed of light is practically impossible as the mass would tend to be infinite at those levels of speed.

Nice effort though. Keep writing.

I know... you are correct in pointing out that nothing can travel at v=c without losing its mass, but the more impossible things have been achieved...

maybe not in our lifetime, but someday even this fortress may be captured... or else we may have to contend ourselves with the preconceived notion of Einstein - " God doesn't play dice" ....

btw do watch Star Trek - at least you can get a glimpse of how anti matter space ships maybe used to do this impossible thing... hehe
just kidding..

[rpkash]

Hi Suyash, Maro and Elisa ,
I am a software engineer, who just found Physics interesting. Thanks to movies like MATRIX, DEJA VU, Minorty Report, etc.

1) 1st Elisa, it was super that you pointed out about the mass would become
infinite if we travel at the speed of light. But would it really matter?
Weight = Mass * Gravity, so my question is when we travel in SPACE, the
gravity is ZERO and so is friction. That is the reason for wightlessness in
SPACE. So even if we travel with the speed of light, MASS of the body is
hardly a concern?

2) 2nd Suyash, I think the WORMHOLE concept is amazing. We all know,
travelling with the speed of light is something which would take a lot of
effort. But incase of WORMHOLE, human doesn't have to attain the speed
of light.

A wormhole is a hypothetical topological feature of spacetime
that is essentially a 'shortcut' through space and time. A wormhole has
at least two mouths which are connected to a single throat. If the
wormhole is traversable, matter can 'travel' from one mouth to the other
by passing through the throat. While there is no observational evidence
for wormholes, spacetimes containing wormholes are known to be valid
solutions in general relativity.
Hence wormholes eliminate the "travelling @ light" concept .


3) 3rd Maro, Hi , the Read Only thought is awesome, ya, it would be great, if atleast
we can sit and enjoy past rather than going and changing it. This way it would be
easy to predict future based on past.

Guys and Gurls, you all rock. Can i also join the family and decipher the code which would lead us to know what we actually are here, in this world for?

Love and Regards,
Ravi .

[Sorayna]

It's interesting but is it really true?

[mike007]

this is a very possible consept. time travel should never be pursued.the end
result is a price that man can not afford!!!!!!!

Now as for wormholes i have done some study on this subject ( i'm NOT-
an expert) but we have yet to discover a wormhole let alone travel thru
one, lets find a way to detect a wormhole then lets talk about traveling
thru it.
We might start by studing the known blackholes.
as we all know blackholes consume all matter including light itself
NOTHING ESCAPES A BLACKHOLES GRAVITATION PULL or does it?
I

[ash]

Hello Mike, you can check out our discussion on Wormholes here:
To Remove The Gap Between North & South Countries By The Spacewarp Technology

[Krane]

Theory here... Infact we humans have been travelling time... Try incorporate UFO as the time travel machines.... Those young one in the future trying to warn us how we destroy our world until they themselves look like that... That is why there is crops circle....


Do you think so???


AND another thought is... Once you travel back and you stab your ancestor, You're living in another dimension already... which is very much different from your original dimension... Those who were staying in the current dimension before you ride that time travel machines will still go on their normal lives.. except without you.. while you would be in another "world"


Do you think my theory is sort of correct???

[x.ajay]

hi friend this very interesting subject please could give me more information inthis subject

[megidal]

I've always thought of time travel as somewhat a case of meditation. Tapping into history that you once passed. If a certain type of energy is passed from a person to his son and generations after that, the last generation would still be able to tap into that history, because its still a history of his energy. Making any sense here?

A point when you could travel to the past would be to tap into that historic form energy that was once its form (kinda like parallel universes right?). Or you'd be living as your ancestor??
Or maybe....
I have to commend rpkash's weight=mass*gravity comment. If our bodies have energies that can easily tap into these wormholes then that's all we're going to need to time travel, our energy. So the case of read-only is possible, we can't actually alter the past because we're not physically solid.
Sight-seeing. =)