i think it only make sense if you go into the future with that speed of light theory... past is impossible

something that has happened, cannot be unhappened

This post has been edited by Alone: Dec 30 2009, 01:32 AM

ok here is relativity take their part. in our space n time we can go to UK and back to KL and vice verse easily using flight . but we cannot reverse our time. i mean we CANNOT going back to yesterday.but when we moving at speed of light, space n time changing their place. u can reverse or forward ur time easily but once u flown to UK, u well never going back to KL.

Yes, what you guys are saying may be true. But according to Michio Kaku, there are THEORIES about time travelling to the past(Check out on YouTube).Therefore, I personally think that time travelling to the past is possible, it is only a problem of engineering,...
Check out this article that i've found:


"If we could journey back into the past, history would be impossible to write. As soon as a historian recorded the history of the past, someone could go back into the past and rewrite it. Not only would time machines put historians out of business, but they would enable us to alter the course of time at will. If, for example, we were to go back to the era of the dinosaurs and accidentally step on a mammal that happened to be our ancestor, perhaps we would accidentally wipe out the entire human race. History would become an unending, madcap Monty Python episode, as tourists from the future trampled over historic events while trying to get the best camera angle.

But perhaps the thorniest problems are the logical paradoxes raised by time travel. For example, what happens if we kill our parents before we are born? This is a logical impossibility. It is sometimes called the 'grandfather paradox'.

There are three ways to resolve these paradoxes. First, perhaps you simply repeat past history when you go back in time, therefore fulfilling the past. In this case, you have no free will. You are forced to complete the past as it was written. Thus, if you go back into the past to give the secret of time travel to your younger self, then it was meant to happen that way. The secret of time travel came from the future. It was destiny. (But this does not tell us where the original idea came from.)

Second, you have free will, so you can change the past, but within limits. Your free will is not allowed to create a time paradox. Whenever you try to kill your parents before you are born, a mysterious force prevents you from pulling the trigger. This position has been advocated by the Russian physicist Igor Novikov. He argues that there is a law preventing us from walking on the ceiling, although we might want to. Hence, there might be a law preventing us from killing our parents before we are born.

Third, the universe splits into two. On one timeline the people whom you killed look just like your parents, but they are different, because you are now in a parallel universe. This latter possibility seems to be the one consistent with the quantum theory.

The film Back to the Future explored the third possibility. Doc Emmett Brown (Christopher Lloyd) invents a plutonium-fired DeLorean car, which is actually a time-machine for travelling to the past. Marty McFly (Michael J. Fox) enters the machine and goes back and meets his teenage mother, who then falls in love with him. This poses a sticky problem. If Marty's teenage mother spurns his future father, then they never would have married, and he would never have been born.

The problem is clarified a bit by Doc Brown. He goes to the blackboard and draws a horizontal line, representing the timeline of our universe. Then he draws a second line, which branches off the first line, representing a parallel universe that opens up when you change the past. Thus, whenever we go back into the river of time, the river forks into two, and one timeline becomes two timelines, or what is called the 'many worlds' approach.

This means that all time-travel paradoxes can be solved. If you have killed your parents before you were born, it simply means you have killed some people who are genetically identical to your parents, with the same memories and personalities, but they are not your true parents."

Extracted from 'Physics of the Impossible' by Michio Kaku (Allen Lane); available from Telegraph Books for £18 plus £1.25 p&p. Call 0870 428 4115 or order online at books.telegraph.co.uk
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The 'past' that u 'go back' to might not be ur actual past. Its just another constructed universe at which the time is the same as ur past but at a different space/universe. While the space/universe that u left goes on without u.

U then, needs to go back to the time and space/universe from where u left to pick up where u have left before u go back to the 'past'.

The two variables that needs to be locked then, is the time and space, in ur 'time machine' GUI.

Exactly, that is an another theory, which means different time can lead to different dimension.

For example if you go to the past and kill your parents before you were even borned, you will not gone, instead you'll be in a new dimension which is parallel to the previous one..

Even research more or not, doesn't matter nor can come out any conclusion.

It is just a hypothesis, it is not something proven nor human kind have any understanding of it. It is a theory aka hypothesis.

Of course it is....There is no harm doing it either.

Its interesting to me how we can create another plane of thinking to repair the illogical paradox of the 'grandfather paradox'. It exercise ur mind to really think our of the box and interwine the logics with the illogicals.

In reality, it's not just a split second had passed. You will realize the passage of time, but only if it's an alcubierre type warp drive in which you're moving at lower than 'c' in a warp bubble while your effective velocity is 'c' or higher than 'c'. If it's not a warp drive, you can only move at relativistic speeds at most, but that depends on how much energy you can expend on propulsion to offset the increase in apparent mass.

Things don't stop. Things go on, only the flow of information "stops" (for information that travel at the speed of light or lower) because it can't reach its destination. If you're moving at the speed of light, or even relativistic speeds, the electrical signals in your body will have a harder time getting from point A to point B because of (1) relativistic mass increase of the charge carriers and (2) time dilation experienced by the signal propagation.

Things don't just stop dead mysteriously. It's all about information not being able to be transmitted faster than the speed of light, and objects with mass not being able to approach the speed of light. Even entangled photons can't be used to transmit information faster than light, but it could be due to some "hidden variable" e.g. information HAS moved faster than light but we're not able to detect it without breaking the entanglement and scrambling the information.

Ah... never thought of that.

You mean, Speed of light is faster than nueron signal speed to transmit information for our brain to decode?

internally everythign is normal. its the interaction between internal and external thats messed up.

Not quite true. Physicists leave this possibility open.

You have a point on thing happened cannot be unhappened. This is called cause and effect casual loop. Changing the past is paradoxical, however affecting the past is logically feasible.

Kurt Godel (who is more famous for his Godel's incompleteness theorems), a colleague of Einstein, came out with the following comments after going through a lot of research on Einstein gravitation field equation:

"By making a round trip on a rocket ship in a sufficiently wide course, it is possible to travel into any region of the past, present and future".

Why so? The reason is past, "Now" and future are merely an illusion. There is no absolute "Now" per say. Just look at the twin, for Ann who is station on earth, her time that she "feel NOW" is 2010. For twin Betty who is traveling near light speed, her time that she "feel" could be 2005 and shed aged 5 years less that Ann.

For a population of living organism on Halley Comet which travel in high speed, the time "Now" that they feel could be 300BC (earth time) and they might be observing the event happening in 300BC now.

The reality is, there is no such thing as "Now". It is just a misinterpretation on our part on tracking the events around us in this spacetime continuum.

The following is a snapshot from the discussion under a different topic "time - discussion".

If you do not believe, try this. Say "Now". By the time you say "Now", you assume that the "Now" you just said is gone and you have to repeat saying "Now". Again, it is gone, and you have to keep repeating saying "Now" again.

You assume that every "Now" you mentioned has "flown" through time and become the "Past". And you assume that every moment is "Now". If every moment is now, what do you mean by tomorrow? You have to agree that tomorrow will never come.

If you are interested, you could go to the time topic for more explanation and discussion.

Have a wonderful new year ahead!

well here's a concept of mine, if one could move really fast as the speed of light or as the neurons in our body imagine this, if speed present now is normal e..g a boy drops a pen from his hand but at the same time u went to another planet, stop by there, proceed to a nother galaxy sit and talk with those people in that particular planet in that particular galaxy * assuming the living things/creatres there moves as fast as u do* and come back to earth near the boy. when u c him it looks as if nothing changes. This may look as though stopping time but its we are actually moving very fast but for the boy..its just normal.

Put yourself in a tortoise position.

actually u got it the other way around.

if u travel at/near lightspeed, it's the person on earth who would have achieved a lot of things than u. meaning, if u drop a pen while traveling at/near lightspeed, the boy on earth could probably watch a movie twice at the cinema by the time the pen reaches the floor.

o man i feel u got it confuse what i mean was, if you could travel that fast, u could do more things than the other person at the normal rate, e.g. Superman?( i know its not the best example) for our eyes. they look as if they didn't move. Imagine it takes 8 min for the sun's ray to reach earth, if a person is moving normal speed, it would take years probably?( forgot the exact time line). we could travel up and down back and fourth to sun and earth while the other person is still on his way to earth

What you speak of is simply Einstein's Special relativity and azarimy is correct.

Mathematically at least.

The speed of light is constant in all inertial frames.

Imagine a person travelling in a car with a beam of light bouncing up and down between a space of say, 5 meters. That person would see the said beam of light simply a straight line. Basic physics tells that distance = speed x time. So for the person in the moving car, he will observe the beam of light complete 1 oscillation at time = 5/c (c being the speed of light)

Now take an observer standing on the side of the road. He sees this moving car, and the bouncing light. He will no longer see the light bouncing up and down, instead he will see some sort of zig-zag pattern,i hope you can imagine what i'm trying to say? So the distance the beam travel in one oscillation from the point of view of the observer is definately > 5 meters. Therefore, again from the observers point of view, time taken > 5/c.

So apparently, time in the frame of a person standing still moves faster then the in the frame of the person in the moving car. We however do not feel this difference in time. Therefore, the person moving faster would have 'done' less things as compared to the person standing still. This applies to ALL speeds. This concept is heavily applied in today's technology and non as prominent as GPS satelites.

Back to the maths, so the faster you travel, the longer the zig-zag becomes, the observer will view your 'time' as even slower. This is what people mean when they speak of time travel. Moving fast enough that you can go out to some random star and return to earth and have age less then the people back home.

Further concepts involved in this are the twin paradox and time dilation.

traveling at the speed of light does not constitute to time travelling

and furthermore i think the term to discuss that would be the butterfly effect

but nevertheless time traveling will result in alternate universes which could exist parallel to our dimension but since this cannot be conclusively explained and all,

lets just travel at normal speeds

This is a very interesting topic. Why stop here? Continue the discussion please, lads!

travel in the speed of light will overkill you. the velocity of light is 3x10^8 m/s. moving in space will create a fraction and you will become ashes in no time except your body is made of light!

for me, time travelling is completely nonsense . no such thing . no one can ever done it . and there are sooo much other phenomena present in the universe still cant be described by human since they are using human mind ( in other word, creation mind , not creators mind )

This post has been edited by azerroes: Feb 14 2010, 11:29 PM

kmarc, thanks for your generous comments. I share your appreciation about how much there is to wonder about the universe, which is why I ended up embarking on this path myself. It is indeed a pity that both of us will never be able to live long enough to see more wonderful discoveries, but we do our best in the time we're given.

The reason for this extremely late post is for me to post an example that I couldn't recall at the time of our discussion, but which suddenly hit me, where an experimental discovery could've implied something radically different that would've shaken, if not smash the foundations of physics, but the physicists knew better and posited another possibility instead, and I'd like to draw parallels with the FTL discussion we had to just highlight how 'strong' the foundations are:

It pertains to the discovery of the neutrino. When experiments measuring beta decay were started, say of tritium (likely not the substance they used), a startling discovery was made. You could measure the mass of the initial and final nuclei, and we knew the mass of the electron to quite some precision at the time. Since the mass of the nuclei >> mass of the electron, it was safe to expect that the kinetic energy of the electron to be very high, and measurements were made of it. By conservation of mass-energy, the expectation was that since we knew the initial and final masses of the particles, we'd easily be able to calculate the kinetic energy of the electron, and measurements of the kinetic energy would clump around this calculated value (looking something like a shifted delta function, something like this: __|__, with the peak at the calculated value of the expected KE). Except that they saw this instead:



That was strange, because what you had was conservation of momentum being violated. You could have gone on to interpret this as conservation of momentum being wrong, but what the physicists did was to suggest that there was another particle carrying away the extra energy and momentum - the neutrino. Remember, the neutrino is extremely hard to find, and indeed, it took another 2.5 decades before an experimental verification was even achieved.

All I'm saying is there are sound reasons for today's theories, and while they're incomplete (and possibly always will be), it doesn't mean that the foundations are automatically wrong and need overhaul, because they have managed to describe a large set of observations we've carried out so far, and any new set of foundations will always need to be able to replicate this success, and then build even more upon them.


and azerroes: there is no friction in space...

This post has been edited by bgeh: Feb 18 2010, 10:45 AM

WHAT friction?

the problem with the speed of light is energy. we dont have the means to produce unlimited energy to drive mass up to the speed of light. the reason is, the closer we are to the speed of light, the more our mass becomes. meaning the bigger the mass, bigger amount of energy is needed to accelerate further.

at the moment we cant comprehend what would happen to the human body when we multiply our mass by the thousands. heck, we cant even take 10g acceleration without passing out with our current mass, let alone accelerating near the speed of light.


and for your information, time traveling IS possible. we can see time distortions just by going into space. the nearer u are a powerful gravity field (ie: planet earth), the slower time becomes. just google it. u'll see that time on GPS satellites had to be continuously resynchronized with time on the surface of the planet.