Time travel possible -- in the future

[DesertFox]

Prof Amos Ori has set out a theoretical model of a time machine which would allow people to travel back in time to explore the past.

The way the machine would work rests on Einstein’s theory of general relativity, a theory of gravity that shows how time can be warped by the gravitational pull of objects.

Bend time enough and you can create a loop and the possibility of temporal travel.

Prof Ori’s theory, set out in the prestigious science journal Physical Review, rests on a set of mathematical equations describing hypothetical conditions that, if established, could lead to the formation of a time machine

More (http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2007/08/08/scitime108.xml)

[DesertFox]

The theory is highly mathematical and arcane but, at its simplest, Prof Ori's time machine has to create a "doughnut" of spacetime.

Set out in one direction and you return to your past and then to your departure point: thus, by travelling around this loop of spacetime, time travel has been achieved.

General relativity ... shows one potent way to bend and warp spacetime: gravity curves spacetime and slows clocks. In 1949, Einstein's colleague, Kurt Gödel, found it was even possible to do this to allow time travel into the past, which had disturbing implications.

The time travel theory proposed by Prof Ori and his student Dana Levanony in Physical Review shows that the loop would form within an empty, doughnut-shaped region of spacetime enveloped by a sphere of normal matter.

More (http://www.telegraph.co.uk/news/main.jhtml;jsessionid=BOCFOO2WTLUHHQFIQMGCFF4AVCBQ UIV0?xml=/news/2007/08/09/ntime109.xml)

[Wolfcounsel]

Does that mean I could go back in time and kill anybody responsible for mass murders before he was able to commit them?

This is another answer to a problem that does not exist.

[Rhino]

Israeli Scientist Figures Out How Time Machine Might Work
Tuesday, August 21, 2007

By Charles Q. Choi

A new concept for a time machine could possibly enable distant future generations to travel into the past, research now suggests.

Unlike past ideas for time machines, this new concept does not require exotic, theoretical forms of matter.

Still, this new idea requires technology far more advanced than anything existing today, and major questions remain as to whether any time machine would ever prove stable enough to enable actual travel back in time.

Time machine researchers often investigate gravity, which essentially arises when matter bends space and time.

Time travel research is based on bending space-time so much that time lines actually turn back on themselves to form a loop, technically known as a "closed time-like curve."

"We know that bending does happen all the time, but we want the bending to be strong enough and to take a special form where the lines of time make closed loops," said theoretical physicist Amos Ori at the Technion-Israel Institute of Technology in Haifa. "We are trying to find out if it is possible to manipulate space-time to develop in such a way."

Many scientists are skeptical as to whether or not time travel is possible....http://www.foxnews.com/story/0,2933,293937,00.html

[Wolfcounsel]

This is a solution to a problem that does not exist. For example, one cannot undo what has been done. It would cause the time paradox--going back into the past to kill one of your ancestors.

[gnome]

You could envision time travel avoiding paradox by spawning alternate realities, as seen in many SF stories. You go back in time, and as soon as you arrive you're in a separate universe, so you could kill your ancestor, but it wouldn't affect the "universe" you were from, or you. It would just let you see a universe in which you had never been born.

Getting back to "your" universe may be problematic, of course...

"Don't touch anything?! I'll touch whatever I feel like!" *STOMP* *STOMP* *STOMP*

[Wolfcounsel]

"You go back in time, and as soon as you arrive you're in a separate universe, so you could kill your ancestor, but it wouldn't affect the "universe" you were from, or you." --gnome

EHH! Wrong. The Butterfly Effect travels across all dimensions, since it's all only one universe.

[DoctorDoom]

One can argue from historical evidence that time travel will not be invented in any form that allows a future person's physical presence in the past. For example, if physical time travel were possible, and ten thousand people decided that they wanted to be at the crucifixion of Christ, or at any other great historical event, where is the record that they were there?

A far more daunting argument against it can be made by pointing out that time displacement also means spatial displacement. If, e.g., one were to go back in time 24 hours, will his physical location be the same absolute coordinates WRT to the universe?

Ignoring all other motions, Earth's orbital speed is about 18.5 mi/sec. Ergo in 24 hours it would have moved 1,598,400 miles. The time traveler would thus materialize out in space about 6.7 times farther away than the moon. But that's just the beginning.

The solar system is moving through the galaxy in the general direction of Vega. Our galaxy is rotating around its central axis. It is also moving toward M31. The local group of galaxies, part of the Virgo Cluster, is moving toward the "Great Attractor" in Centaurus. And everything around us is moving outward as the universe expands.

Would anyone care to envision the computer necessary to calculate the spatial coordinates necessary to arrive at the same physical location on Earth, e.g., a century ago?

[Wolfcounsel]

"Would anyone care to envision the computer necessary to calculate the spatial coordinates necessary to arrive at the same physical location on Earth, e.g., a century ago?" --DoctorDoom

I can do that with pen and paper. First, uh, can anyone tell me what Greenwich Time is in the center of the universe?:evilgrin:<!-- / message -->

[DoctorDoom]

I can, but only if you provide its coordinates. :biggrin:

[gnome]

"You go back in time, and as soon as you arrive you're in a separate universe, so you could kill your ancestor, but it wouldn't affect the "universe" you were from, or you." --gnome

EHH! Wrong. The Butterfly Effect travels across all dimensions, since it's all only one universe.

Quite an assumption. Frankly, I don't believe time travel is possible either, but I don't see why it has to be how you describe...I think the popular "many-worlds" interpretation of quantum mechanics is one way for it not to be.

[Wolfcounsel]

The coordinates are 0,0,0,0,0,0.:evilgrin: Heh heh.

[gnome]

Six dimensions?

[Wolfcounsel]

"Frankly, I don't believe time travel is possible either, but I don't see why it has to be how you describe..." --gnome

It has to be so. Otherwise the whole universe will be shaken by that immovable atom, and then the whole cosmos will explode. And then--

RUN!

No. Only three dimensions, gnome. A three-dimensional object has depth, width, and length, and each part requires two coordinates of left to right, and south to north.

[DoctorDoom]

So which way is left or north at 0,0,0?

[Wolfcounsel]

Since everything is relative to any observer at any location from 0,0,0, The first star that spins on the axis of 0,0,0 in any direction is cosmic North. From there the rest is calculable.

[gnome]

"Frankly, I don't believe time travel is possible either, but I don't see why it has to be how you describe..." --gnome

It has to be so. Otherwise the whole universe will be shaken by that immovable atom, and then the whole cosmos will explode. And then--

RUN!

No. Only three dimensions, gnome. A three-dimensional object has depth, width, and length, and each part requires two coordinates of left to right, and south to north.

Eh? If you're talking about identifying a point in 3-d space, you only need three coordinates...

[Wolfcounsel]

"If you're talking about identifying a point in 3-d space, you only need three coordinates..." --gnome

True, but we are talking about a relative point, 0,0,0, and an infinite distance. Not a finite distance, like the sphere of Earth.

[DesertFox]

the time paradox--going back into the past to kill one of your ancestors.There's a more fundamental paradox than that. Your body is made up specific atoms in specific constellations of being. To the best measurements made, protons and other constituents of atoms are eternal. Go back in time and the protons and neutrons that made up the atoms that one day would make up your bod, existed somewhere else. They can't be you and something else at the same time, no matter how quantum the universe is. So if you went back in time, to avoid a paradox those protons and neutrons would immediately return to where they were originally, before they ever became part of you. You would disappear before you arrived -- unless you appeared in another universe, as the gnome mentioned and as a dude name of Everett posited in his doctoral thesis in 1957, giving rise to the "many worlds interpretation" of quantum mechanics.

[gnome]

"If you're talking about identifying a point in 3-d space, you only need three coordinates..." --gnome

True, but we are talking about a relative point, 0,0,0, and an infinite distance. Not a finite distance, like the sphere of Earth.

This is starting to sound like something that would lead to us drawing little diagrams on napkins at an IHOP while we argue :)

[Wolfcounsel]

Back in elementary school, we were told to think about a good space station, and a super powerful telescope with which to gaze upon Earth, from a very far distance, so we could see the light rays from prehistoric times reaching the lens of the telescope.

[DesertFox]

Threads merged.

[DesertFox]

When I's in grade school, we used brontosaurus toenails to fry t-rex steak.

[Wolfcounsel]

"This is starting to sound like something that would lead to us drawing little diagrams on napkins at an IHOP while we argue :)" --gnome

I am standing here beside myself. Amazing what a 12-pack of beer can do!:evilgrin:<!-- / message --><!-- sig -->

[DesertFox]

This is starting to sound like something that would lead to us drawing little diagrams on napkins at an IHOP while we argueBut those are the best kinds of arguments. :D