Who can explain the theory of time and space and the possibility of traveling back in time?

Question

During lecture, my math instructor explained that time and space isn't flat (like some scientist might theorize), but rather time and space is wavy. I was reading about the concept of wormholes from wikipedia, and looking for documented stories of the unexplained regarding time travel. Can anyone fill me in on the details?

Answer 1

To get a handle of the concept of time you'd have to familiarise yourself with relativity and then look in to quantum mechanics to get a fuller picture. In the quantum foam at the planck length, some of the tiny particles popping in and out of existence travel in time - but only by the tiniest fractions of a second. If you want to understand the concept of time, avoid stuff about time travel because a great deal of is nonsense.

However, time travel (in to the past, nobody is interested about travel in to the future because it's easy) is theoretically possible and many have begun hypothesising ways we might be able to use exotically curved pathways in spacetime to travel in to the past.

Michio Kaku's latest book 'Parallel Worlds' discusses several possibilities.

As for lesser talk of how it might be done, but more on the concepts and about time in general I'd recommend hunting up 'The Fabric of Reality' by David Deutsch.

Answer 2

jerrywic is on the right track, but he has to get off the notion of moving forward and backward in time, you can't move through time you move with it. Wormholes are figments of the imagination as are any ideas of travelling through time. Time is an interval between events, when an event ends it becomes history and the beginning of the next event is still at the same point in time, now, it is always, now.

Answer 3

The possibility of time travel fascinates people and stirs the imagination.

The current understanding of time describes time as a fourth dimension. However, matter can exist at any point in space, (the current understanding) has matter existing at all points in time at the same time.

This would imply that if you were to actually move yourself in time, you would only see the same matter as you see now and in the place it is now, no matter how far back or forward you would go.

Current understanding poses that we can change the rate at which we pass through time, but this doesn't change our position in time, since we exist at all points in time all the time.

This precludes time travel as a possibility.

Jerry

Answer 4

1st, recognize that time is simply another dimension of our universe (the 4th dimension). Like length, width and height, all matter requires time to exist. For this reason, traveling through space is much like traveling through time. Here's how:

According to the theory of relativity, the faster something (or, in this case, someone) travels, the slower time seems to pass from the point of view of that person. This has been proven at relatively low speeds (jet speeds) with the use of atomic clocks. Therefore, according to this theory, when you travel very fast (near the speed of light), time "dilates", or slows down, for you. Thus, you could essentially travel into the future by traveling very near the speed of light. If you traveled fast enough, 1 year for you might be 1000 years here on earth, and you could return to the "future".

Traveling into the past is a much hairier problem. According to the math of Einstein's theory, as mentioned, the faster you travel, the slower time passes for the traveler. Although we do not know what actually happens at near-light speeds (there are some unresolved failures in Einstein's theory), the equations produce a time of "0" at the speed of light. In other words, the faster you go, the slower time goes. At the speed of light, time stops. So, what happens when you travel *faster* than the speed of light (assuming that you can "leap over" the speed of light where time stops)?

Some have extrapolated that time will reverse for the faster-than-light (FTL) traveler. However, Einstein's equations do not bear this out.

According to the equations, the time dilation will not only be *negative*, but the *square root* of a negative value. Mathematically, this is called an imaginary component.

We can graph this. Consider a number line that displays the rate at which time passes. At the right we have "1", normal time flow. As you achieve speeds approaching the speed of light, time slows and your place on the graph moves toward the left. At the speed of light, time stops and the dilation is at zero. One would naturally think that, if somehow you were able to exceed the speed of light, time would slowly rise from a small negative number to a larger negative number. Instead, what happens is that you do *not* continue to move left along the X axis when you exceed the speed of light. Instead, you move (up or down, depending on your graphing method) along the *Y* axis!

What this means, in terms of the passage of time for the traveler, is wholly unknown.

To put this all more simply, the faster you go, the more "left" (slowly) time passes for you. However, once you exceed the speed of light, time starts moving *up* or *down* for you as you increase your speed

Jim

Answer 5

Sure. The way to begin to understand it is to take about 5 or 6 years of University level Physics classes ☺

Doug

Answer 6

basically thats it, if you can warp space you also warp time. so if you take a point in space and warp it back around to an earlier point you would have gone back in time. right now theoretical physicists just don't know if space-time allows for these since we have never observed one. and if they are possible we dont know how to create them.

Answer 7

Think about what you mean by "travel through time".

When people think of traveling forward in time, they mean that their time proceeds normally, while the time for the rest of the universe proceeds at an acclerated rate. It can be done. This is what happens when you travel at a speed close to the speed of light.

When people think of traveling backward in time, they mean that their time proceeds normally (or stops), while the time for the rest of the universe goes backwards. This cannot be done and here's why:

We determine the direction of time by viewing entropy. Time increases in the direction of increasing entopy (2nd law of thermodynamics). So, if you want a system to move backward in time, you reduce its entropy. That is not as hard as it seems.

Let's say you have an ice cube. As it melts, its entropy increases and it goes forward in time. Now, to make it go backward in time, you simply freeze it again. As it freezes, it goes backward in time until it returns to the frozen state that it was in before.

So, in order for a person to go backward in time (which actually means that the entire universe must go backward in time instead), the person would have to reduce the entropy of the rest of the universe.

Here's the catch. In order to reduce the entropy of the water to turn it back into ice, we have to increase the entropy in our system (by expending energy). For a person to travel back in time, he would have to reduce the entropy of the rest of the universe. Consider how much energy it would take to reduce the entropy of the entire universe by even a millisecond. It would not be possible, especially since all the energy must come from the system not going backward in time -- the person himself.

Answer 8

only in the movies.