How to Build a Time Machine 534
frank249 writes "The September issue of Scientific American has an article discussing the possibility of time travel. They say that it wouldn't be easy, but it might be possible. It could be a while until we can expand worm holes and tow them to a neutron star but didn't someone say that if it is possible it will happen. If it is impossible it will just take a little longer."
Paradox and Causal Loops (Score:5, Interesting)
Perhaps . . . but: (Score:2, Interesting)
Time travel is fundamentally impossible (Score:1, Interesting)
Remember, nothing moves in spacetime.
A simple way to think of it is this: Movement through space is represented as distance/time. How would one represent movement through time? It should be time/, but there is nothing to put in the denominator.
Some Say it Has Already Happened ... (Score:5, Interesting)
Of course, this induces the potential for paradox, causing great cosmological and philosophical consternation. I don't know what will happen if/when someone goes backwards through time, but here's some ideas:
- The universe forks in two when a paradox is induced.
- The universe forks in two at the instant the traveller enters history (because at a micro-level, paradox is induced as soon as they appear).
- Paradox induces a cascading feedback loop of self-modifying universes (each inducing a time-traveller who goes back and causes another chage) until the sequence halts with a universe in which time travel is not developed. My bet is that if time-travel is possible, then this is what has happened, because there is no evidence of time travel.
Forward time travel is of course possible right now, requiring only some patienceCrispin
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evidence that's it's impossible (Score:2, Interesting)
Since no person from the future has ever come back to say hello to us, wouldn't that imply that time travel will never be invented. Or else it will be invented, but our era in history was just too damn boring for people to come back to visit...
Re:Speed up things.... (Score:2, Interesting)
Or that there is some other life that has one that was created to million years ago?
There is no reason to assume that it is impossible to go back in time from now just because it is impossible for use to create the device.
Imagine if a small one of these was available like a 24 hour one. How much would your time be worth? You could literaly work a full shift, eat and sleep, go through repeat. Get a month or so of work done in essentially no time, but then you go home and you lost a month of your lifespan and are aged. The rest of your familly still unaged.
Even at no pay increase you could save money real fast and buy a house or something. spend a year or two in this thing spending $20 dollors a day in expenses. Go home with thousands of hours clocked. Everyone wins, the company gets years of somebodies work done in a day, you never nead to work again.
modern time travel 'theory' (Score:3, Interesting)
Black Holes and Time Warps: Einstein's Outragous Legacy by Kip Thorn is perhaps one of the best science books I read, though I didn't really read that many of them.
Re:Simple (Score:2, Interesting)
One thing I've never understood regarding this involves motion, and what is "absolute zero" in regards to motion. Right now, for instance, the Earth is spinning me around at 1,040mph. At the same time, the Earth is spinning around the sun at 67,000 mph. Our solar system is moving away from nearby stars at the speed of 45,000 mph. My point is that our primitive concept of "speed" is based around the premise of an "absolute zero", but as far as I can tell there is absolutely no way for us to know how fast we are currently moving: All measurements of speed are merely relative-> I drive my car at X speed relative to the surface of the Earth, etc. For all we know, as far as I know (and I'm not a physics buff), the known universe is sliding sideways at 100,000miles per second, and we're totally unaware because it's all relative.
The point of all of this is the correlation between time and speed seems simplified if it quantifies speed as an absolute metric when as far as I can determine there is no such things: There are only relative speeds.
Blah, I'm blabbering. There is a point in there somewhere.
Re:Paradox and Causal Loops (Score:2, Interesting)
Whatever could happen, does happen... (Score:2, Interesting)
Re:The point you're missing is... (Score:4, Interesting)
Or, put another way, the time required at maximum velocity to return to your point of origin is at least the amount of time you travelled back in time. I believe you must sacrifice time or sacrifice position.
Position may or may not be in the way we expect; I suspect it is based upon your "depth" in the gravitational field, and as such, you would travel towards or away from heavy celestial bodies, such as the sun. Travelling towards them requires velocity. By the same token, you can temporally return to the beginning of the universe if you travel far enough away from the centre of it (assuming that the gravitational "depth" continues to decrease with distance, and the exponential energy increase required to travel as such is not unreasonable)
Binary stars and other equilibrium comes to mind, but I conjecture that "free" time travel in perfect equilibrium would be impossible; your relationship with time can only be altered in respect to changes in the gravitational depth. However, they may have
So goes a theory
Re:Some Say it Has Already Happened ... (Score:2, Interesting)
Wormhole will work, but... (Score:2, Interesting)
Thus, you will be able to go back in time, but even if you then raced at the speed of light back home, you wouldn't be able to arrive before you departed.
So you'd travel back in time sure enough, but never able to affect your own past. Another way to phrase it would be: you can go back in time, but only someone else's history.
Of course, you could, say, still go back in time and kill someone in another part of the Galaxy. Maybe terrorist possibilities, etc. Gives a whole new meaning to a leader staying close to his people.
OK, one more speculation. Wormholes will turn out to repel each other, or maybe wormhole exits and entrances that are close to one another create catastrophic feedback loops, making them impossible.
Otherwise, you could take the W-80 (Milky Way --> Andromeda) from near Sol, then catch the W-95 (Andromeda--> Millky Way) near Kl'Kithus, which , it turns out, dumps you right out at Sol again.
And that would make your own past accessible and that's Bad (tm). I guess it could also allow you to go farther and farther into the past by traversing the loop multiple times.
Of course, it's not clear why someone would want to travel to a time before indoor plumbing or computer games.
Wormhole towing and time travel (Score:2, Interesting)
Using the neutron star itself to attract one but not the other would be very difficult, but possibly workable- especially if Podkletnov's spinning superconductor gravitational shield works (which it doesn't, that I am sure of). However, you certainly can't use a natural source to reunite the ends once you've "twin clocked" the exit end- the exit is sitting near the surface of a neutron star- so you really won't be able to pull it away with anything less than another neutron star or a black hole, perfectly positioned to make use of the three body problem to slingshot the wormhole out of the star system. Conceivable, but highly unlikely.
You can't just leave the exit there, either. It would continue to accumulate time difference, so each trip would take you farther from your present time, but actually further and further along in time, since you can never actually travel backwards to before the creation of the exit hole, and since it is in fact still moving forward, albeit slowly, in time. Also, you would leave the exit and find yourself right around the surface of a neutron star, which is a somewhat dangerous location. Worse, you would have to travel at a relativistic velocity to escape the neutron star's monstrous gravity, which means your fast clock would run very slow, so the rest of the universe would be aging faster than you. Also, the nearest neutron star is several light-years away, adding to your return-trip travel time. I'm sure it would be a fantastic adventure, but sort of a waste to fly into a wormhole, travel centuries back in time, and rocket away from a neutron star at nearly the speed of light- only to get back home and find that due to relativistic effects and travel time, you are right back where you started, or even farther along!
I haven't done the math, but I suspect that sort of scenario could be one of several ways the universe is protected from time travel paradoxes- you can go back in time, but due to relativistic time dilation and the effects of gravitational fields, you can never make it back in time to affect events in the past of your light-cone, preventiing you from creating an inconsistent causal loop.
Re:Paradox and Causal Loops (Score:3, Interesting)
elsewhen (Score:3, Interesting)
The best thing about having a working time machine would be pushing all who find this fascinating into it and sending them elsewhen.
If time proves to be a complex number, while I would find that fascinating I wouldn't tempted in the slightest to project the terms "backward" or "forward" into a polar coordinate system.
If there's any virtue at all to a discussion about time travel, it's that you can't determine whether mathematics or linguistics is taking the worst beating.
Re:If I could Travel back in Time... (Score:3, Interesting)
Grand Admiral Alfred Tirpitz: Led the drive to create the Imperial German High Seas Fleet, which aggravated tensions with the British Empire (the Naval Race and all that).
Colonel General Alfred von Schlieffen: Chief of the German General Staff before the war, architect of the Schlieffen Plan to attack France and defend against Russia, which included the violation of Belgium.
Bringing the British into the war was the real disaster. Had they stayed out, it is quite probable the France would have lost the Battle of the Marne and therefore the war. Germany would then have teamed up with Austria against Russia far earlier, and it is entirely conceivable that the war would have been over before the leaves fell, as the Kaiser had promised his troops.
A quick end to the war would have left the Central Powers dominant on the Continent, Russia in the throes of revolution (I imagine that defeat in the war would cause collapse), and France diplomatically isolated. Not a wonderful situation really, but nothing to lead to the Second World War.
Of course, the above is an exercise in what-if history, which generally gets dismissed as quackery...
~Chazzf
Twin Paradox misexplained? (Score:1, Interesting)
One of the twins gets on a rocket going at a fraction speed of light. And each twin has a telescope to see the other. From each of the twin's point of view, the other twin is aging slower than he is. This aging factor is related to the speed of the rocket.
Now, from article, they say that one twin will have aged more than the other twin even when they are at the same time frame, which is totally wrong. What will happen if the twin returns to earth is that each of the twin will see the other aging more rapidly, and finally when they arrive at the same space-time frame, they will be at the same age.
Can any physicist confirm that this is the correct interpretation?
Re:Fun trick (Score:2, Interesting)
On Time Distortion (Score:3, Interesting)
- It is (theoretically) impossible to accelerate to the speed of light, because it would require an infinite amount of energy to do so, so the best we can do is approach the speed of light.
- The closer you get to the speed of light, the harder it is to accelerate, because of said energy requirement.
Wouldn't time distortion then simply occur because things simply could not happen as fast? Your aging, your blood flow, the chemicals flowing between your synapses (this altering preception), the rate at which something burns, the rate electricity moves at, etc. all happen slower than they would if the object where traveling at a lesser speed, because the whole process takes more energy, correct?If this is true, what happens when an object comes to a complete halt in space, the absolute zero of velocity, if you will. Could that make a black hole or something?
IADNAP.
Conservation laws (Score:2, Interesting)
1: Something of equal mass would have to come from the past or be created in the universe simultaneously.
2: Massive amounts of energy would be released when the mass "went back" in time, to compensate for the matter lost. This would make time travel an interesting source or energy, sending useless objects back in time and harnessing the energy released.
3: Law of conservation of mass/energy would have to be adapted in some way to apply to some form of mass/energy integrated over time so that there is a constant amount throughout the life-span of the universe. This would have interesting ramifications if theories of time forking were to prove true, ie which alternate time lines would this time:mass/energy integration be applied?
These are just some idle thoughts I've had... Anyone with some more ideas let me know what you think!
-- Mr. E Gecko