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One of the most famous method for time travel is cited by American theoretical physicist John Wheeler in 1957. This method involves wormholes, which are hypothetical topological features of spacetime fabric that is essentially a 'shortcut' through space and time. A wormhole has at least two mouths which are connected to a single throat.

According to current theories on the nature of wormholes, construction of a traversable wormhole would require the existence of a substance known as "exotic matter" (or negative mass) with negative energy. Many physicists believe this may actually be possible due to the Casimir effect, which is a well known and well documented quantum phenonmenon.

Currently, the closest known real representative of exotic matter is the region of pseudo-negative pressure density produced by the Casimir effect. Hence, the idea is to create two non-conducting metallic spheres one enclosing the other. The spheres would need to be very very large in order to create sufficient amount of negative energy pressure to create and keep open the wormholes. the current estimate is that the spheres would need to be several hundred billion ligh-years across. (Yeah, the size of a galaxy).

Now you create two of these wormholes with these galatic sized Casimir spheres. One end of the wormhole is then accelerated to nearly the speed of light, and then brought back to the point of origin. Due to time dilation, the accelerated end of the wormhole has now aged less than the stationary end. So now one end of the wormhole is at an earlier time than the other, and therefore, you have a time machine!

Negative energy and "dark mass" (invisible) are known to exist by inference because of what we now know of the expanding universe. It has nothing (so far) to do with black holes. The universe is expanding at an accelerating rate, which should not be true given present theories of gravity, so there needs to be something to explain that. The mass of the universe must be larger than we know to explain some experimental results, so there must be a lot of "invisible" matter to explain that (and that only makes the need for "negative energy" greater).

There is no connection between them and time travel, which is theoretically possible in quantum mechanics and string theory. Negative energy and dark mass are macro-level entities, not quantum-level.

No such thing as "negative" mass or negative energy. You may be referring to dark mass/energy. Dark mass/energy was something needed to explain why galaxies didn't fly apart while spinning around. The observed mass (stars mostly) was insufficient gravity source to account for why the stars just didn't spin out into space. In fact, only about 4% of our known universe is observable...the rest of it is dark...until recently (2006).

In late 2006, a group at Stanford observed dark matter glowing from the energy created by two colliding galaxies. [See source.] So the theory now has some validation...dark mass/energy do indeed exist.

Although time is relative to the frame of the observer, time does not reverse itself. Theoretically, it can slow waaaaay down (to an ouside observer), but it cannot stop and it cannot reverse itself. According to the Lorentz transform, a critical element in Einstein's equations, it would take an infinite amount of energy for a mass to reach the speed of light. And even then, according to Lorentz, time would only halt; not reverse.

Time travel, of sorts, is feasible only into the future; and once there, you cannot go back. To travel into the future, one needs to go at speeds approaching the speed of light.

At which time, time on the fast moving time machine slows down as seen by people outside the machine. And, as you might guess, people inside the machine would see time speed up outside. And people inside and outside the machine would see time progressing normally for their own respective environments.

Thus, when the time machine came back a year later, according to their own clocks, they would find the outside people, buildings, and such had aged decades...or, if the time machine went fast enough, died, crumbled away from age, and so on. Even so, the people on the machine would have aged just that one year shown on their own clocks.

Time travel, as you envison it, is strictly scifi stuff. It's fiction with no basis in science.

What people don't understand is that we are light, and by being light, we already exist beyond the speed of light. Not only are we light, but everything is light, one unified , universal force. One does not need to travel faster.... but simply be AWARE of all that is, and what is....

There IS NO TRAVEL INVOLVED

https://www.youtube.com/watch?v=81Wk-pZZAXE

I think for you to learn about negative energy and neg mass you need to learn all there is to know about black holes.

Black holes are singularities in our univers, they are still widely misunderstood, many people hav lively discussions about what happens to matter, time and energy around and in black holes.

Theoretically time is a fourth dimension, and thus it can superimpose itself on our 3D lives.

But in practice many paradoxes result...

You have to put the crystals in the machine!

you can use a formula T~5435-gh123^f=minor 6