# Where do we go from here?

#### Rook225

Ok, I have a question concerning one (rather important) aspect of time travel I don't recal anyone really discussing; the Earth. Or what I'd like to know is how do we get there (forward/backward) from here...our current spacetime coordinate at the point of departure? With the most popular theories of time travel we're talking about either intersecting with another timeline (alternate reality) or actually moving backward/forward along the current timeline. However, regardless of which ever mode you want to consider, is the traveller actually physically relocating to another coordinate in spacetime? Whether you're talking about alternate realities or not, the Earth in any reality is still moving through the universe on a fairly predictable (that is if we knew how to plot it) course. Let's pause for a moment on whether or not we'll be able to travel forward/backward in time, if you take all the movements the Earth is involved in (revolution, precession, solar precession, galactic revolution, and galactic precession), let's say for simplicity's sake a sort of loopty-loop trajectory through spacetime. Wouldn't it be fair to say that time travel is rather like arriving on the Earth at some predetermined spacetime coordinate? If your object is to go back, then wouldn't your destination be some spacetime coordinate the Earth has already crossed, and how could you win such a race that has already been won? Or alternative going forward in time would equal a coordinate the Earth has yet to cross, and would you be hanging out there in space waiting for you're future Earth to catch up with you? So there you have my quandry, if anyone or perhaps Dr. Kaku would like to tackle it, I'd sure like to know someone else's opinion.

Thanks,
Rook

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#### Runaway Monocle

Brilliant

You left out possible movement of the universe.

Only way would be if your inertial motion was multiplied by the time displacement. if not the time machine would collapse because the other side of the machine would be torn from it or it would hit something.

On the other hand it's possible our time machine uses measurements and applies forces which are affected by our motion so it wouldn't matter.

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#### Sempiternity

With a standard 'time machine' that simply moves along your timeline, it would not move spatially and would then be floating out in space when the shift ended. How that shift in your timeline takes place in the first place is questionable (a fast starship? wormhole? etc). I would think that when you know how to accomplish this feat physically, you'll learn where you could possibly be after such a shift.

#### sd01g

Rook225 said:
Ok, I have a question concerning one (rather important) aspect of time travel I don't recal anyone really discussing; the Earth. Or what I'd like to know is how do we get there (forward/backward) from here...our current spacetime coordinate at the point of departure? With the most popular theories of time travel we're talking about either intersecting with another timeline (alternate reality) or actually moving backward/forward along the current timeline. However, regardless of which ever mode you want to consider, is the traveller actually physically relocating to another coordinate in spacetime? Whether you're talking about alternate realities or not, the Earth in any reality is still moving through the universe on a fairly predictable (that is if we knew how to plot it) course. Let's pause for a moment on whether or not we'll be able to travel forward/backward in time, if you take all the movements the Earth is involved in (revolution, precession, solar precession, galactic revolution, and galactic precession), let's say for simplicity's sake a sort of loopty-loop trajectory through spacetime. Wouldn't it be fair to say that time travel is rather like arriving on the Earth at some predetermined spacetime coordinate? If your object is to go back, then wouldn't your destination be some spacetime coordinate the Earth has already crossed, and how could you win such a race that has already been won? Or alternative going forward in time would equal a coordinate the Earth has yet to cross, and would you be hanging out there in space waiting for you're future Earth to catch up with you? So there you have my quandry, if anyone or perhaps Dr. Kaku would like to tackle it, I'd sure like to know someone else's opinion.

Thanks,
Rook
Your 'quandry' is the reason why Time Travel is impossible. No one talks about it because it is more enjoyable to try and figure out why time travel is possible. Science fiction (fantasy) would really miss not being able to do Time Travel.

All travel requires one to change locations. All real locations exist only in what we experience as the present. All past locations have become present locations. Yesterday's location of the earth in space will never be duplicated.

All the speculation one may do and all the obtuse postulation that may be presented will not preempt this reality. All Time Travel is and always will be Imaginary.

#### Tjl

And your babbling is why it will never be so.

#### dontbelievthebull

I agree that physical transportation to a different time is very unlikely but what about some sort of communication or observation.
I found the theory that the reason that gravity is so weak was because gravitons flow between dimensions whereas the other forces are trapped here facinating. That would mean that theoretically if you could control a stream of gravitons that you could communicate with another dimension morese-code style.
Perhaps something like this is possible with tachions? Any other ideas?

#### Gir

dontbelievthebull said:
I agree that physical transportation to a different time is very unlikely but what about some sort of communication or observation.
I found the theory that the reason that gravity is so weak was because gravitons flow between dimensions whereas the other forces are trapped here facinating. That would mean that theoretically if you could control a stream of gravitons that you could communicate with another dimension morese-code style.
Perhaps something like this is possible with tachions? Any other ideas?
that of course is assuming that gravitons are real.

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