Is it possible to travel through time ?

[vinod]

Almost every1 of us wanna travel through time .Well i am very excited about the same. But how this could be possible . i want members to shead some light on the fundas and theories of this subject and the means by which we can achive the same.

[Confed999]

We're allready traveling through time, it's just a one way trip. ;)

[highsea]

Yep. We all travel through time, at exactly the rate of 60 minutes per hour. Wouldn't want it any other way...

Vinod, if you have a bicycle, you already have a time machine. Just pedal down the street and look ahead of you- that is the future. Now look behind you- that is the past.

[ZFBoxcar]

Going back in time is not possible because it requires traveling faster than the speed of light, which is physically impossible. However, by traveling at NEAR light speeds time would slow down. This was proven using atomic clocks on really fast airplanes, plus it confirms the theory of relativity. Traveling fast enough to slow time down by a significant amount is impossible with our level technology although who knows what breakthroughs could occur in the future?

[Confed999]

I wonder if we could find a way to see into the past?

[dalem]

I wonder if we could find a way to see into the past?

John Gribbin wrote about an interesting theory in a book about cosmology several years ago. If I remember correctly, a large enough mass spinning at near-relativistic speeds can cause the t = time curve to intersect with the s = distance curve in a certain equation or something.

So by that application, if one had the mass and the relatavistic rotational velocity, one could create an intersection of space and time that begins back at the time the large mass started rotating fast enough.

Or something.

Small matter of finding or creating those conditions and figuring a way to survive the no-doubt high-energy forces extant at the locale of course. :)

-dale

[Lucien LaCroix]

Time travel into the past is an impossibility because of the paradoxes that cannot be overcome. Example: You go back in time five years before you were born and then you kill your father. If you kill your father, then you were never born. If you were never born, then how could you go back in time and kill your father?

Time travel into the future is a natural event. Time dilation, described by Einstein in his Theory of Relativity, allows for a fast forward. The faster you move through (a) space, the faster you move through time. Unfortunately, the theory also dictates that mass increases, in kind--becoming more disproportionate as the speed increases. The speed of light cannot be attained because it represents infinite mass. As such, no amount of energy can be expended to move such a thing any faster. It also represents infinite time (progressing through time at an infinite speed). That also cannot occur.

Infinity cannot exist. It's like the concepts of perfection or nonexistence. They are abstract concepts because they cannot exist in reality or even be fully comprehended by the mind. Even at the singularity point of a black hole there is existence--we just cannot fathom it at this point (and perhaps never will).

Interestingly enough, faster than light travel is possible--so to speak. Our nearest star is about four light years away. A space voyager making the journey at, say, 99.9999% of the speed of light would arrive in about four years--our time. But by his perception, he would have arrived in only a few minutes. And since rate of speed is derived as a ratio of distance covered by time expended, he would have perceived his speed to be thousands of times the speed of light. And he would have a point. After all, only a short period of time would have passed for him. And that is how we perceive speed.

I even read in a publication some years ago that by traveling at something like 99.999999999999999% of the speed of light, you could circumnavigate the known universe of about 70 years. But by the time you had finished, billions of years would have passed. There wouldn't be anyone (or perhaps even ANYTHING) left to come home to--or talk to about it.

As far as "going faster than the speed of light means going back in time"...that's more science fiction than science. I have never read any formal thesis making such a claim. And there have been no scientific experiment results to support such a conclusion. But I will give Star Trek some credit. While the science does not yet exist, they have the right idea--by wrapping a warp field around their vessel to decrease its mass as its speed increases. It's a pretty neat notion. You could go to the stars with some very ordinary engines if you could manage to decrease your mass--and get there very quickly too.

Unless the science and technology are developed to somehow circumvent the time dilation effect, then it is likely that we, as a species, will be confined to our own solar system for the duration. I cite time dilation effect as the crucial element because the building of a ship that could achieve a significant percentage of light speed is probably already within our engineering and manufacturing capabilities--albeit, a very expensive and time consuming prospect. So the real issue would be of the astronauts with severing ties with everyone they have ever known. On shorter trips that might not be an overwhelming factor, but it's good to keep in mind that a round trip to even the closest star to Earth would take more than eight years our time. Obviously, trips to more distant stars could mean an absence of decades, generations, or even centuries.

A lot of people would not be up to that challenge emotionally.

Of course, entire families could make such journeys. That would lessen the emotional burdens.

[Jay]

Vinod, if you have a bicycle, you already have a time machine. Just pedal down the street and look ahead of you- that is the future. Now look behind you- that is the past.

you forgot one more condition..look below/above/side and thats the Present

[Муромец]

Just what is time exactly?
I remember an old novel by Clifford D.Simak “The Goblin Reservation” . In this novel he describes race that never have “time”-terming or meaning.

[Jay]

Time is a measure.

[TopHatter]

Oh for cryin' out loud people! Time travel is cinch. All we need is a DeLorean and a little plutonium, which as everybody knows is available on every corner drugstore.

[dalem]

Time travel into the past is an impossibility because of the paradoxes that cannot be overcome. Example: You go back in time five years before you were born and then you kill your father. If you kill your father, then you were never born. If you were never born, then how could you go back in time and kill your father?

I disagree that the ancestor paradox makes time travel "impossible". Rather, it just makes it theoretically risky and problematical. Physics may define things as impossible but philosophy cannot.

-dale

[Bill]

"Going back in time is not possible because it requires traveling faster than the speed of light, which is physically impossible."

Actually, that's not true.

Gamma emmisions from the core of blackholes are ejected at greater than the speed of light.

[ZFBoxcar]

Are gamma emmisions matter or energy? If they are matter than you're right, I'm mistaken.

[Lucien LaCroix]

It's not theoretically risky. It's an inevitability that a paradox would occur. A time traveler could make the smallest misstep in the past and alter the future in such a way whereby he didn't exist. It wouldn't have to be the result of an overt act. It could be something as simple as bumping into a person on the street.

And over thousands of years of time traveling, you'd have who knows how many time travelers making a journey to the very same prominent places and moments in history that other time travelers were visiting from their particular moment in the future. Eventually, you'd have 10,000 people standing outside the Schoolbook Depository in Dallas, Texas, on November 22, 1963.

The bottom line is that while certain small disturbances in the timeline might be mended simply by virtue of the type of situation being impacted, multiple incursions would cause a snowballing effect and invariably lead to disaster. And I'm certain that some idiot with a God complex would eventually get around to traveling into the past with something that could wipe out all of humanity.

Yet, the paradox of a retroactive abortion--of sorts--prevents any of this from being possible.

Time travel into the past is impossible...because it never happened. If it had happened some time in the future, then we would have seen evidence of it by now.

Actually, I'm wrong. Time travel into the past is possible. You do it every time you look through a telescope. But that's not exactly the same thing. If you could go out 500 light years from Earth and somehow gather the light image at that point that was projected by the Earth, then you would actually see what the planet looked like 500 years ago.

But that's as close as we would get to the past.