Time Machine
- Thread starter Steve
- Start date
Darby
Epochal Historian
Steve,
I believe that you'd first have to determine whether or not time travel (into the past) is even possible in our universe. The general theory of relativity does state that time travel into the past is possible - in a universe where the proper assumptions are a reality.
General relativity has an unlimited number of solutions. There are solutions that suggest that time travel into the past are possible. The problem, for us, is that those solutions don't necessarily apply to our universe. It is still up in the air as to whether the assumptions correctly describe how the physical laws of our universe function. Most physicists believe that our universe is not one of the universes, described by general relativity, that allows time travel into the past. At this time the best answer might possibly be "who knows?"
I believe that you'd first have to determine whether or not time travel (into the past) is even possible in our universe. The general theory of relativity does state that time travel into the past is possible - in a universe where the proper assumptions are a reality.
General relativity has an unlimited number of solutions. There are solutions that suggest that time travel into the past are possible. The problem, for us, is that those solutions don't necessarily apply to our universe. It is still up in the air as to whether the assumptions correctly describe how the physical laws of our universe function. Most physicists believe that our universe is not one of the universes, described by general relativity, that allows time travel into the past. At this time the best answer might possibly be "who knows?"
Darby
Epochal Historian
Steve,
Here's an example:
One theory of time travel is that you could enter the mouth of a wormhole created by a Kerr-Newman black hole (a black hole that has a significant electric charge and a very high velocity spin).
General relativity does predict that wormholes are possible and that these wormholes are "tunnels" to other places and times within ours or other universes.
However, general relativity also predicts that the same wormholes are unstable and that if any matter or energy enters the "tunnel" that it will collapse and crush out of existence those things that entered it.
One possible solution to the problem is to line the tunnel walls with "exotic matter". This matter has an anti-gravitation field rather than a gravity field. Generral relativity predicts that this sort of matter can exist in certain universes.
So far there is no evidence that such matter actually exists in this universe. If it does it is extremely rare. You'd have to have trillions of tons of the "stuff" to line the wormhole.
And even if you did create a wormhole you can't control the "other end" of it. The exit goes wherever it goes and it is a one-way road. Once you arrive wherever it leads you can't return to your starting point using the same wormhole.
There are theoretical solutions using the Casimir Effect where you can open a hole between two charged plates and drag them apart - which stretches the tunnel. You could drag one plate to wherever you want your "stargate" highway to lead to. This isn't going to get you too far unless you're willing to wait thousands of years for a sub-light ship to drag the plate to another appropriate star system...and you're still faced with the instability issue.
This doesn't mean that time travel is impossible. It means that it is extremely difficult, at best, and that if it is possible it will take us hundreds of years before we could ever be able to move a significant mass with one and have the ability to direct it to a specific place and/or time.
Here's an example:
One theory of time travel is that you could enter the mouth of a wormhole created by a Kerr-Newman black hole (a black hole that has a significant electric charge and a very high velocity spin).
General relativity does predict that wormholes are possible and that these wormholes are "tunnels" to other places and times within ours or other universes.
However, general relativity also predicts that the same wormholes are unstable and that if any matter or energy enters the "tunnel" that it will collapse and crush out of existence those things that entered it.
One possible solution to the problem is to line the tunnel walls with "exotic matter". This matter has an anti-gravitation field rather than a gravity field. Generral relativity predicts that this sort of matter can exist in certain universes.
So far there is no evidence that such matter actually exists in this universe. If it does it is extremely rare. You'd have to have trillions of tons of the "stuff" to line the wormhole.
And even if you did create a wormhole you can't control the "other end" of it. The exit goes wherever it goes and it is a one-way road. Once you arrive wherever it leads you can't return to your starting point using the same wormhole.
There are theoretical solutions using the Casimir Effect where you can open a hole between two charged plates and drag them apart - which stretches the tunnel. You could drag one plate to wherever you want your "stargate" highway to lead to. This isn't going to get you too far unless you're willing to wait thousands of years for a sub-light ship to drag the plate to another appropriate star system...and you're still faced with the instability issue.
This doesn't mean that time travel is impossible. It means that it is extremely difficult, at best, and that if it is possible it will take us hundreds of years before we could ever be able to move a significant mass with one and have the ability to direct it to a specific place and/or time.