Alternate Ship Design Systems

[TKalbfus]

Drakon said,

"How do you get a negative frequency?"

Simple a negative energy photon is equivalent to a reverse-time photon. When a neg photon hits an atom, its outer electon shell jumps to a lower energy level instead of a higher one with a positive photon. In reverse time sequence, its the atom that emits a positive photon.

 

[TKalbfus]

Drakon said,

"And ultimately not sure it would be relavant. Does it matter if the other end is 10 years into the future or not, if they are separated by 10 light years?"

It does not so long as that condition holds, the wormhole could be moved closer again and the system can become a time machine if the GM lets it. If the GM does not want a time travel campaign he can simply have both wormholes blow up the moment they move back within a critical distance where dt = distance in light-time.

If a photon can travel outside the wormhole in time to meet up with itself and build on itself when it reenters the wormhole then the wormholes might explode. It is not certain that this will happen because quantum foam might cancle out the returning photon, but it makes logical sense enough for the game.

If the GM wants to allow time travel he has a number of options:

He can assume chronology protection and assume that the universe will prevent a character from changing "known" history. The proviso of course is that he can do whatever he wants in the annals of unwritten history so long as it doesn't conflict with what is acurately known and recorded, this includes by the way, "history" received from the future. If for instance a character finds out that he is going to die as such and such a time under such and such a circumstance, there is nothing he can do to alter his fate. It is dangerous to know too much about one's future. The risk is that a person may look into the future to figure out how he solved a certain problem only to find out that he didn't, he may figure out what mistake he made and how to correct it, but he can't now avoid making this mistake, the universe will now force him to repeat the action he just observed himself doing. The GM would just advance the time to the character's future self where he once again has free will and take it from there, assuming of course that he is still alive. Ignorance is bliss when it comes to time travel as ignorance preserves the illusion of "free will" which is for all practical purposes free will as far as the game is concerned.

The alternative is to assume that the character is free to change history and that this creates two parallel timelines that are connected only by the wormhole. For instance a wormhole can be accelerated from the Classic Traveller Era to the New Era, and the character can find out what terrible things the assasination of Emperor Stephon would lead to, so he takes action to kill Stephon's assasin in a seeming "accident", the Emperor never gets assasinated and the timeline proceeds onto the Gurps Traveller timeline. The wormhole will continue to connect the Gurps timeline to the New Era timeline for as long as it remains open however, so it remains possible to go from one timeline to another. The Ancients might have also built wormholes, and theses wormholes could have time differentials that lead to various eras in Earth's past for instance. These are parallel timelines as so events might not have occured or will occur as history recorded them too, or they might follow the same path just the same. This is a good way to get a 21st century character into the Traveller Universe, or a Twilight 2000 character, or a 2300 character. Traveller characters can go through these Ancient wormholes and mess with Earth's "History" as much or as little as they desire with not ill effects on themselves. The GM can limit the time travel to certain eras because their are only so many wormholes that lead to specific times and advance at the same rate of time at both ends currently. The time travellers don't get to pick the times they go to, but if they are lucky, they can kill Hitler, land the spaceships and take over an "Earth" if they want, but they'd better keep the wormhole open if they want to go back.

 

[TKalbfus]

Drakon said,

"3) I said earlier that I don't buy time travel. The problem can be as simple as geometry. There may be only a single temporal dimension, and you cannot have loops in 1 dimension. It may be nothing more than that, than the fundamental nature of the geometry of the manifold."

One dimension of time will suffice. In a spacial dimesnion you don't need to turn around to go backwards. Perhaps the dimension we refer to a time is identical to a spacial dimesion for some other particle, and perhaps that particle uses one of our spacial dimensions as its time dimension. The type of particle I'm describing is a Tachyon. A Tachyon is a particle that always moves faster than the speed of light, it can otherwise have other properties that are similar to baryonic particles such as a proton. Relative to a tachyon light travels at the same speed as it does for us and we would appear to be traveling faster than the speed of light relative to it. Imagine 4-dimensional hyperspace, a cross section of it is the three dimensional height x width x breadth that were all familiar with. A certian cross section of it is the space we live in and the dimensions we use for traveling in. Along the 4th dimension is our worldline. Our worldline tracks where we have been in the past which is a direction in our time dimension in which we cannot travel. If we eliminate one of our spacial dimensions for diagraming purposes we can represent time space as a three dimensional space with the past pointing "downward" and all particles moving upward as they move side to side along the two spacial dimensions that we show. All the worldlines of all the objects moving about are at less than a 45 degree angle to the perpendicular axis that represents time. As each year passes all slower than light objects move upwards at a physical distance of one light year. Most objects experience this year as one year's time elapsed, but some objects are moving particularly close to the speed of light from the point of view represented by this diagram, their worldlines follow a path that is just under 45 degrees from the time dimension, a light year traveled upwards takes just a day to elapse. Photons always travel at 45 degree angles to the time axis, those lines can be approached by slower than light objects but never paralleled. All slower than light objects travel further in the time dimension than they ever do in any of the spacial dimensions. A tachyon however moves further in space than it does in time, it chooses a spacial direction and it always moves further in that directional component than it does in any other perpendicular component from that spacial direction or in the direction of time. A tachyon can move forward or backwards in time from this perspective, or it doesn't have to move in time at all, but what ever it does in its 3 free dimensions of movement, it always has to move forward in a particular direction that is faster than the speed of light, it cannot be stoped in this direction, it can move faster or slower, but never slow enough to match the speed of light in this direction.

It may be possible to create a wormhole that leads to that tachyon's frame of reference to our own, this would constitute a very literal FTL Drive. The wormhole would have to be created from one end and open up at the FTL end. An object at rest and an object moving at infinite speed relative to that object at rest possess the same level of energy so a wormhole might connect those two points. the wormhole that does this doesn't have to be stable, it could be of the type that opens and closes so rapidly that a photon does not have time to get through it before it closes, but an object traveling at infinite speed relative to the wormhole opening can easily get through such an unstable wormhole. The trick is to create the wormhole at one end so that the FTL end swallows up the spaceship while the stationary end ejects the spaceship at infinite speed in one particular direction. For one instant in time a worldline will exist in one of our spacial dimensions. At one end of the worldline is the wormhole it emerged from and at the other end is the second wormhole that the spaceship created and entered when it wanted to go slower than the speed of light once more. Each light second length of that instantaneous worldline represents a second of elapsed time onboard the spaceship. Photons that intersected with that worldline can be reflected back toward its point of origin and an observer left behind can see the spaceship recede at apparently the speed of light. If the spaceship does not uses its maneuvering engines, it will take no time to reach its destination, but if it accelerates enroute, its world line will reflect this and it will take some time either positive or negative to get there. If it slows down along the way, some postive time will elapse, if it speeds up, it will take negative time to get there. This is the infamous Time Travel Space Drive that led Einstein to believe that faster than light travel to be impossible, but the impossibility of FTL travel is only one way to prevent time paradoxes.

 

[TKalbfus]

This is still not quite satisfactory for gaming purposes however. The GM might not want a time travel campaign, and it just so happens that there is a very good physics reason why the velocity shouldn't be infinite.

When the Starship first opens the wormhole, it is considered open when its neck is slightly larger than 1 planck's length in circumference, this is not wide enough to allow passage of the starship, and to give it time to widen sufficiently, the FTL end of the wormhole needs to be travelling slower that infinite velocity relative to the starship that it swallows, lets just say that this velocity happens to be 1/5th of a parsec per day for the lowest level of FTL drive, at higher TL FTL drives can open up unstable wormholes faster allowing for 2/5ths of a parsec per day at TL11, 3/5ths at TL13. 4/5ths at TL14, and 1 parsec a day at TL15. The starship ends up going faster than the speed of light and forward in time with no time travel effects relative to the stars in the Galaxy. 1/5th of a parsec per day represents 229 times the speed of light, so the little fuel reserves of the typical traveller starship and its maneuver drive is incapable of maneuvering to infinite velocity and beyond to achieve time travel effects, hence not traveling into the past, yet a special purpose multistaged time machine powered by antimatter might be capable of this if the GM would like to make an exception. Such a machine would be beyond a PCs means however, so it would limit such access to GM directed adventures where the GM has time to do the necessary historical research. All and all its a fairly decent device for travelling between the stars quickly.

 

[Straybow]

Your time-travel explanation doesn't make sense. It posits that while time passes normally (counting GR) for the end of the wormhole that travels 10 LY, time stops or slows without relativistic acceleration on the static end.

The fact that the two ends of the wormhole are linked does not mean that when one experiences time dilation due to acceleration the other experiences time dilation without acceleration.

Space itself is expanding, therefore distant parts are moving at relativistic velocities with respect to each other. The result is not that photons can move back in time to regions that used to be closer together, rather that light undergoes doppler shift such that the energy of the EM radiation still has the same power (energy/unit) in either reference frame.

While the ship is in transit energies beamed through the wormhole would undergo said doppler effects. An laser signal from the static end would be received as a higher wavelength and a comm laser from the ship would be received as a lower frequency back home.

The ship decelerates to match velocity with the destination planet, and the doppler effects across the wormhole become negligible.

A good question would be, "What happens to matter sent through the wormhole while one end is traveling at relativistic speeds?" An object must either gain or lose substantial energies. Those energies must be represented as resistance to motion ("drag") on the towed end.

An object passing from the static end to the moving end increases the drag, and thus diminishes the coasting velocity of the ship-wormhole system or reduces the net acceleration. An object passing back to the static end returns energy to the ship-wormhole.

 

[TKalbfus]

Straybow said,

"The fact that the two ends of the wormhole are linked does not mean that when one experiences time dilation due to acceleration the other experiences time dilation without acceleration."

Robert Forward posited this idea not me, but let me use my intuition. There are two ways to time dialate one end of a wormhole. One is to carry one end at relatavistic velocities and the other way is to have it orbit deeply into a gravitational well while the other end does not. As you know gravity causes time dialation as the photons that climb out of the gravitational well are red-shifted with the crests and troughs of each wave of electromagnetic energy being further apart after climbing out of the gravity well. A light ray that shines through a wormhole experiences no net red-shift. I imagine that the light would blue-shift as it plunged into the wormhole and then red-shift an equal amount after it climbed out again. A person holding clocks at both ends would see that each second tick of his clock would match the second tick of the person holding a clock at the other end of the wormhole, even if that person and the spaceship he is in is deep inside a blackhole's gravity well. Now if that person in the space ship were to transmit a video image of himself holding a clock through space not through the wormhole the person on the outside of the gravity well would find that his clock ticks faster then the person on the video image beamed out side while that same person he could see holding the clock through the wormhole would have his clock ticking at the same rate as his own. The video image of the person holding the clock in the spaceship would be increasingly time lagged when compared with the person seen through the wormhole. Everything the person seen through the wormhole did would be repeated an increasing while later by that person's video image. Everything the person did in the video image would also appear to be done slower than the same person seen through the wormhole.

 

[Drakon]

Originally posted by Tom Kalbfus:
Drakon said, </font><blockquote>quote:</font><hr />"How do you get a negative frequency?"

Simple a negative energy photon is equivalent to a reverse-time photon. When a neg photon hits an atom, its outer electon shell jumps to a lower energy level instead of a higher one with a positive photon. In reverse time sequence, its the atom that emits a positive photon. </font>[/QUOTE]The problem is that there is no "negative photons" that have been observed, directly or indirectly to date. You are positing a new particle, that appears to be completely outside of physics. Not a bad thing for a game, I'll admit, but it is going to play havoc with your players.

And I have to admit, I would balk at "time reversed photons" The whole subject of time travel bugs me, and maybe it has no validity other than my tastes. (One of the reasons I can't buy Bohm's pilot waves)

[How do you plan on dealing with players who attempt to utilize this for a time machine? Is there an Omega 13 device, like in Galaxy Quest in your universe?]

But the "jumping to a lower energy level" is pretty good as far as it goes. I will point out that the positive photon emitted will be of an energy that is the excess between the negative photon and the energy transition of the electron. It just might be no photon at all.

 

[Drakon]

Tom's Good stuff about time travel in game terms deleted for space only. It does illustrate my objections to time travel in general.

Free will. Without this you no longer have a game, you have a machine. And each of its people are nothing more than cogs, with no ability or power to choose. If you cannot change the past, nor the future, then it really no longer matters what you do now. I see free will as an essential ingredient of being a sophant, probably the sole defining characteristic of an intelligent species. So getting rid of this, or rendering it moot, I don't see as a good idea.

And from a playablity option, it renders participation in the game practically pointless and unfun.

Multiverse: This presents all sorts of challenges for the GM, as now he has to keep track of all these different time lines. But more important, there is no explaination how these copies are created in the first place. You stop Strephon's assination. How does this alternate universe, with all its stars, people, rocks, trees and stuff come into being, along with the original universe? Talk about throwing conservation of mass/energy in the toilet.

And then there is the whole free will issue again. Because one of you, in one of those alternate universes has made different choices, it really no longer matters what choice you make. It renders free will moot again.

This does illustrate the problem with any work around that allows backwards time travel. You get stuck with throwing something out as a result of allowing it. You either get illogical paradoxes from all those jerks murdering their own granparents, or you get no free will, or no conservation of mass/energy.

Logic, Free will, known physics. Any way you look at it, you have to give up something that to me appear more important than allowing time travel.

 

[Drakon]

Originally posted by Tom Kalbfus:
One dimension of time will suffice. In a spacial dimesnion you don't need to turn around to go backwards.

I am not so sure of this. Even if you are backing up, you are still moving forward in time, it still requires another dimension other than the one you are travelling in.

[Okay, you can move in one dimension of space as long as you have at least one dimension of time. In fact, without time, you cannot move or change at all. You can't even think about it, because thought is itself an ever changing process. Remove time, and you ain't moving anywhere.]

Tacyons: Good desription snipped for brevity. Here is the bug. The idea of Tachyons is based on Relativity. It is noted that Gamma, in all the frame conversion equations is = the square root of (c^2-v^2) If v > c, then you are asking for the square root of an negative number. And That is where all the problems come into play. Just what does an imaginary number mean in this context?

It was noted that if a particle starts out on the other side of the curve, the faster than light version, then it cannot slow down. Bleeding energy from it makes it go even faster. (in which direction, forward in time, or backward in time, is still debated, because we are asking what the square root of a negative number means.)

This is the infamous Time Travel Space Drive that led Einstein to believe that faster than light travel to be impossible, but the impossibility of FTL travel is only one way to prevent time paradoxes.

Not necessarily. Again we are speculating on the exact dimensional nature of time (in this respect)

What convinced Einstein (and a lot of others) that FTL was impossible was that the energy needed to cross the FTL barrier was infinite. At v=c, you are asking for the square root of zero, or rather the reciprocal of zero. Infinite energy seems necessary to achieve light speed.

[Pendatic note: while the reciprocal of zero is undefined, the limit as one approaches zero grows larger and larger.]

But something that has always bugged me is that LIGHT travels at light speed. Its massless, granted but we know the energy of the photon is not infinite, even if the photon itself is massless. Is there something else going on?

 

[Drakon]

Originally posted by Straybow:
Your time-travel explanation doesn't make sense. It posits that while time passes normally (counting GR) for the end of the wormhole that travels 10 LY, time stops or slows without relativistic acceleration on the static end.

The fact that the two ends of the wormhole are linked does not mean that when one experiences time dilation due to acceleration the other experiences time dilation without acceleration.

It depends on the shape of the manifold both ends of the wormhole are part of. If one assumes that the manifold is identical through the middle of the wormhole, then it is possible that both entrances will experience the same time dilation. However, those ends are then tied to the rest of the space-time manifold of the rest of the universe (or universes, universi?) and there you are going to have problems.

At both ends, you very well may have time dilation like Tom posits. What that means once one crosses the threshold in either direction, that is another question altogether. And how abrupt that transistion is going to be is something that has got to be taken into consideration. More gradual is more better, as sharp transitions means spagettification. Its not just time that will appear to slow down/speed up. There are also spatial effects that need to be taken into consideration.

 

[TKalbfus]

I think I can make a workable FTL system out of wormhole jumping to the otherside of the light barrier. Assume that the wormhole take a finite amount of time to completely open up. Because we don't want to destroy the spaceship lets just say that the FTL end of the wormhole travels at 100 times the speed of light. The FTL wormhole end swallows the starship and the SLT end spews out the starship at 100 times the speed of light. The starship will appear stretched to a left behind observer and the passage of time on board the starship will appear 100 times as fast as each light second the starship covers marks approximately 1 second of elapsed time onboard the starship. It would take 4.4 years of ship time to reach Alpha Centauri from Earth, but that's the price the ship's crew will pay for getting there in 16 days as far as the external slower than light universe is concerned, low berths will come in handy. Now 100 times the speed of light may seem to be a long way from infinite velocity, but on the otherside of the light barrier, it really is the equivalent of 1% of the speed of light. to reach infinite velocity, the starship on its end will have to increase its velocity by 3000 km/sec or 3,000,000 m/sec, this is 83 hours or 3 days of 1-G acceleration. So how do we prevent them from turning their starship into a time machine? We could lower the threshold to 10 times the speed of light equivalent to 0.1 C, a change in velocity of 30,000 km/sec would then be required to reach infinite velocity, this is just about the maximum a fusion rocket could reach without using multiple stages, an unlikely feature of a PC starship. It would require 34 days of 1-g acceleration to reach infinite velocity from 10 times the speed of light, also were assuming that the usual amount of jump fuel is required to leap across the light barrier. I figure a combination of fusion rockets and a straight FTL drive. would be a good combination for game purposes. Only those with antimatter rockets would really have access to time travel in this case. Antimatter is dangerous in any case and is likely to be kept out of civilian hands.

 

[Drakon]

If you want to get really into it, (And I recognize that for gaming purposes this is not required.) I cannot recommend Matt Visser's book "Lorentzian Wormholes: from Einstein to Hawking" enough. Its heavy on the math, and it was current to the state of the art as of 1997.

Okay, let me see if I understand you here. You have a short wormhole. Once the ship enters it, it achieves a FTL velocity (wrt objects in the outside or "real world") and travels FTL once it leaves. It does this because the other end of the worm hole is travelling FTL. Have I got that right?

Okay, 1) If you can construct wormholes with arbitrarily short distances between any two points, why not just use the worm hole short cut? Because it is unstable and lasts only a short time? (Not a bad work around actually from what I have read)

2) You seem to desire time travel in your game. I have already logged my disagreements in this area. I just don't think the universe will allow it. It can make for some great or interesting stories, but I consider it more fantasy than science fiction.

3) Slowing down and stopping: If Tacyons exist, (And there is to date no evidence of their existence, nor does there appear to be any requirement either.) you must increase the energy of the ship in order to slow it down. You will have to use another worm hole, designed like you have only in reverse, to slow the ship down. If you lose energy at all, radiate it away as heat, this might cause your ship to speed up!

4) And probably most important. The "otherside of the light barrier" might not work the way you expect. Again, it is important to recognize that gamme goes imaginary, and at present, in this context, what imaginary means is undefined. We can guess, and some guesses are that you will go back in time, just crossing the light barrier. But all it is is a guess at this stage of things.

Tacyons at present are not necessary to either GR or the various interpretations of QM. Neither actually predicts it, it is just noted that due to the imaginary (in the mathematical sense) nature of gamma at FTL velocities, these objects could exist, and have certain strange properties. Like decreasing the energy increases its velocity (maybe). How these objects would actually interact with the real world, let alone whether they exist, is still an open question.

Also in looking up Matt's book for you, I found this article that you might like. http://www.mcs.vuw.ac.nz/~visser/030527-12.html

Something else that has been gnawing at the back of my skull. What is the difference, functionally and practically, between a positive photon travelling forward in time, and a negative photon travelling backward in time? Is there a difference at all?

And if there is no difference, then how can it affect things differently?

 

[TKalbfus]

Drakon said,

"Okay, let me see if I understand you here. You have a short wormhole. Once the ship enters it, it achieves a FTL velocity (wrt objects in the outside or "real world") and travels FTL once it leaves. It does this because the other end of the worm hole is travelling FTL. Have I got that right?
"

Correct, interestingly enough some of the special effects shown in Star trek when a ship goes into warp (the stretching in the direction of motion is what an FTL object may appear as to an STL object.) Both sides of the light barrier are symmetical to each other FTL velocities as seen from the STL side become their recipricals as a proportuion of the speed of light as seen from the FTL side. An infinite velocity corresponds corresponds to the STL "at rest" velocity. A STL velocity of 0.1c corresponds to 10c on the otherside of the barrier and so forth. The delta-vee on the FTL side between the STL observed speeds of 20c and infinite velocity is only 0.05c as seen on the FTL side of the light barrier. I think most Traveller starships can't exceed 0.5 delta-vee if it reserves enough fuel to slow down again. So I think all ships entering FTL should start out at 20c and use their maneuver drives to accelerate from there if they want to achieve faster velocities. Time travel from a practical engineering perspective is difficult and expensive, thus keeping it rare.

"3) Slowing down and stopping: If Tacyons exist, (And there is to date no evidence of their existence, nor does there appear to be any requirement either.) you must increase the energy of the ship in order to slow it down. You will have to use another worm hole, designed like you have only in reverse, to slow the ship down. If you lose energy at all, radiate it away as heat, this might cause your ship to speed up!"

You need energy to change an FTL ship's velocity, just like an STL ship. The main difference is that to change an FTL ship's velocity you take the reciprical of that velocity with respect to light, do the velocity change as normal, then you take the reciprical of the result with regard to the speed of light to find the final FTL velocity. This is without the near light speed Einsteinian time dialation. With velocities greater than 10c or less than 0.1c Einsteinian time dialation need not be factoried in. What's happening by going FTL is the ship switches its time axis with one of the spacial dimensions.

"2) You seem to desire time travel in your game. I have already logged my disagreements in this area. I just don't think the universe will allow it. It can make for some great or interesting stories, but I consider it more fantasy than science fiction."

I have a good way to treat time travel, call it shadow chronological consistency. The basic rule is that no NPC can change history unless a PC accompanies him. PCs can change history when they go back in time and if they are not careful they might find it impossible to return to the future they left. In other words, no third person history tampering and the first person point of view is always with the PCs. The PCs have to be together as a group in the same time period to effect history change, otherwise the point of view remains with the PCs that are furthest in the future. This way the GM doesn't have to keep track of multiple timelines. From the point of view of the society that builds the time machines, time travel is no big deal and history cannot be changed, they "know" this fact because all the NPC time travelers have returned and reported on the fact that they could not change history. These returning NPCs are shadows of the NPCs sent back in time. The histories of these returning NPC shadows are always consistent with the historical record, if they try to change history, they forget what changes they were trying to effect, when they return to the present it suddenly comes back to them. "Chance events foil them at every turn, as the history books always remain the same. These returning NPC shadows have a counterpart that the time traveling authorities never see as the invisibly leave the time line that is part of the time traveling authorities history. Time travel is falsely deemed safe, the main and unknown danger is to the time travelers themselves as they may inadvertantly alter the course of history while they are back in time and be unable to return home, their NPC shadows do, but the point of view remains with the player characters and the players do not play their historically consistant shadow NPCs. PCs must be extremely careful to avoid altering history, it is not only whose lives they may inadvertantly kill, it is also whose lives they may save, that person may have an alternate historical destiny that was unknown to the PC time travellers because in their timeline he was killed. for example:

Suppose the time travellers visit World War II, they try not to alter history, but some German Soldiers notice them, and thinking them to be Americans, they attack: The PCs can defend themselves and risk killing someone's ancestor, or they can run away. If they run away, the Germans chase them, in the chase the PCs eventually lose their German pursuers so the PCs think they are home free right? Wrong! Those Germans were scheduled to ambush an American Patrol, since they were diverted by chasing the PCs, the Americans soldiers they where scheduled to ambush never were, and a US soldier who was supposed to die does not. That American Soldier later becomes US President instead of John F. Kennedy.

 

[TKalbfus]

But the PCs might not ever learn about this. Time travel might be seen as nothing more than a historical research tool, and will remain that way until and unless the PCs go themselves. One big clue that time travel isn't what it seems, would be if the PCs discover a preterraformed planet. A planet terraformed by humans 30,000 years ago, there are no Ancient alien races in this case, in fact the evidence suggests that only humans were involved and their decendents might yet inhabit the planet. These ancient time travelers come from a future that no longer exists, their shadows returned home in failure in their attempt to terraform this planet in their own timeline, the results of their success lay only in the Timeline that became home to the PCs. Since the terraformers never interacted with Earth, human history is entirely consistent with their actions. But this is only if the GM want s to introduce time travel as a way to change history, otherwise it fades in importance and is ignored by a large segment of the SF setting. As most shadows often die in the past in larger numbers than what occurs during normal activities in the present, time travel research is not undertaken by the faint of heart and their are few volunteers. Most time travel shadow deaths occur due to historical necessity. If they didn't die they would alter the timeline, hence they must die so as not to change history. The universe sees to that.

 

[Straybow]

Robert Forward posited this idea not me&#133; As you know gravity causes time dialation as the photons that climb out of the gravitational well are red-shifted with the crests and troughs of each wave of electromagnetic energy being further apart after climbing out of the gravity well. A light ray that shines through a wormhole experiences no net red-shift. I imagine that the light would blue-shift as it plunged into the wormhole and then red-shift an equal amount after it climbed out again. A person holding clocks at both ends would see that each second tick of his clock would match the second tick of the person holding a clock at the other end of the wormhole, even if that person and the spaceship he is in is deep inside a blackhole's gravity well.

Differences in subjective time experienced in normal space at either end of the wormhole doesn't mean going through the wormhole traverses time. I'm familiar with Forward's articles in Analog and I don't recall him invoking time travel.

Objects experience time at a dilated rate merely by being inside the intense gravity well, just as if they were in a mechanically accelerated reference frame. So the clock at the "home" end of the wormhole and the clock at the blackhole end really are ticking at different rates. A person peering through the wormhole at the black hole clock would see it ticking slower than his local clock. The wormhole can't squeeze extra time into or out of phenomena in normal space at either end; only so many ticks of the clock have occured.

I stand corrected about doppler shifting through the wormhole. A photon emitted from the black hole clock is not red-shifted because the controlling phenomenon is the relative energy levels of electrons. The wormhole "looks" like flat space to observers at either end, so there is nothing to stretch the length of the photon wave for the viewer on the home end. If he waits a while and looks at images of the clock transmitted through normal space there will be red shift caused by climbing the gravity well, but that will not alter the time intervals between emission events.

For the ship in transit at relativistic velocity the energy balance is preserved in that photons are emitted at a slower rate. The clock is ticking at a rate dictated by dilated reference time, the wormhole functions as a flat space relative to both ends, nothing changes the ticking before it is perceived at home base and nothing stretches the wavelengths of transmitted light.

If the wormhole is not flat relative to normal space then light can be doppler shifted in passage, but the wormhole still can't change the time intervals of external phenomena. The wormhole still doesn't "care" whether one end is accelerated or positioned deep in a gravity well, and doesn't affect time travel between the ends.

 

[TKalbfus]

So the clock at the "home" end of the wormhole and the clock at the blackhole end really are ticking at different rates.

there is no absolute time, all time is relative. What a wormhole does is take two distant points and make them close through the wormhole. The objects are close and at the same gravitational potential through the wormhole, while this might not be the case outside the wormhole. Time travel becomes possible through this mechanism, because the black hole end of the wormhole sees an accelerated blue shifted universe, the outside end also sees this through the wormhole and so therefore sees the future.

 

[Drakon]

You need energy to change an FTL ship's velocity, just like an STL ship. The main difference is that to change an FTL ship's velocity you take the reciprical of that velocity with respect to light, do the velocity change as normal, then you take the reciprical of the result with regard to the speed of light to find the final FTL velocity. This is without the near light speed Einsteinian time dialation. With velocities greater than 10c or less than 0.1c Einsteinian time dialation need not be factoried in. What's happening by going FTL is the ship switches its time axis with one of the spacial dimensions.

hmm... the math don't look right for some reason.

According to tachyon theory, you do have to LOSE energy in order to speed up. Gaining energy will slow you down. It might be possible to fire retros to speed up, or the main rockets to slow down. It is very counterintuitive.

Aslo realize you are assuming particular characteristics for imaginary gamma. You are saying it means a particular thing. You might want to look into Matt's other research on analogs of General Relativity. In that research, they are looking at things like Bose condensates and the like for analogs to GR phenomena, sometimes using sound as light, if you get my meaning.

Time travel:

Most time travel shadow deaths occur due to historical necessity. If they didn't die they would alter the timeline, hence they must die so as not to change history. The universe sees to that.

This is exactly what bugs me most of all. How does the universe even KNOW that you are travelling back in time. How does the universe know anything? Can the universe even know and even if it could, could it pick and choose to violate its own rules?

Strawbow was not invoking absolute time, He was attempting to show issues in the frame jump you are proposing. You have two reference frames, one at the top of the wormhole (or just outside it) and the other buried in the gravity well. These frames will be out of sync with each other, regardless of any other frames you may be interested in. And yes, the clocks are ticking at different rates as seen by the two observers.

 

[TKalbfus]

"hmm... the math don't look right for some reason.

According to tachyon theory, you do have to LOSE energy in order to speed up. Gaining energy will slow you down. It might be possible to fire retros to speed up, or the main rockets to slow down. It is very counterintuitive."

Lets take it from the slower than light side: if you are going at 0.1c, how do you lose energy to slow down to 0.0c? If you starship doesn't have the fuel/energy to slow down from 0.1c to 0.0c, it will keep on going at 0.1c. This is known as Newton's law of motion. "Any object that is at rest stays at rest; any object in motion stays in motion absent the application of force." I say that this should hold true for FTL velocities as well. You can't just lose energy to slow down, you need to fire you rockets. Also remember how you said no tachyons have been detected, I interpret this to mean that FTL space is empty, there is no drag against the spacecraft, as you can well imagine, particles that travel at near infinite velocities, don't stick around for long. The particle density in FTL space is basically what ever the FTL ship brings with it across the light barrier.

"This is exactly what bugs me most of all. How does the universe even KNOW that you are travelling back in time. How does the universe know anything? Can the universe even know and even if it could, could it pick and choose to violate its own rules?"

Its a variation on the observer effect, the universe doesn't know anything. When you send a time traveller back in time, anything he is going to do has already happened. A version of events that is in the history books has already been described. Splitting of the timeline and creating alternate histories is certainly possible, but the time traveller's worldline also splits as he goes back in time. If a time traveller does something that changes history, these history changes don't roll back into the future amd alter the people who sent him. People don't disappear, buildings don't change or whatever. The version of the time traveller who has freedom of action to change things is not visible to those who sent him. Just as there are parallel timelines their are also parallel time travellers. A version of the time traveller that is consistent with history is what is visible by those who sent them. By visible, I mean that the time traveller can archive messages, bury them in the ground at prearranged locations and send messages back to those who sent him. If the time traveller is not in the history books, there is nothing he can do to get in the history books, if he attempts to change history, his worldline splits and the time traveller who succeeds is shunted off to a parallel timeline leaving only the one who false and stays in an unaltered history. There is no universal consciousness, its just that history has already been established by those who sent the time traveller and cannot be altered from the sender's perspective. From the time travellers perspective, its hard not to alter history, as the probabilities of the events that would prevent him from changing history are very small.

For instance if the time traveller was sent to kill Hitler, there is a small probability that he will suffer a heart attack just before he makes his attempt, this is most likely what will happen from those left behind in the present, but from the point of view of the time traveller, a heart attack is unlikely as he is in good health, what will most likely happen in his case is that he will kill Hitler and in the process eliminate the future he came from, if he goes back to the future, it will be a much different future than the one he left.

 

[Straybow]

Originally posted by Tom Kalbfus:

[Straybow] So the clock at the "home" end of the wormhole and the clock at the blackhole end really are ticking at different rates.

there is no absolute time, all time is relative. What a wormhole does is take two distant points and make them close through the wormhole. The objects are close and at the same gravitational potential through the wormhole, while this might not be the case outside the wormhole. Time travel becomes possible through this mechanism, because the black hole end of the wormhole sees an accelerated blue shifted universe, the outside end also sees this through the wormhole and so therefore sees the future.

First, "all time is relative" is a common misconception of Relativity. That is no more correct than saying "all distance is relative." In truth, distance is absolute. You can't slow down below zero velocity. The distance perceived at rest (and corrected for intervening relativistic effects on measurement) is the true distance. Likewise time at rest is absolute, you can't make time go faster.

A wise man made the analogy to an "existence vector" in 4-space, scaled to distance/c for the length axes. You experience everything at that rate. If you are at rest, your vector is parallel to the time axis and your length axis components are zero. You experience time at the maximal rate.

As you move, eg in the +X direction, your existence vector tilts. Now you perceive time at slightly less than 1s/s (the components are non-Euclydian so it isn't a simple cosine funtion). The total length of your vector, both as you perceive the universe and as the universe perceives you, remains unchanged.

If you are a photon your vector must be in a plane perpendicular to the time axis. Your existence is displayed entirely as movement in space; for you time is stopped.

The existence vector in a steep gravity field is shifting in the +g direction (or precessing like an off-axis top if the object is in orbit). The object doesn't experience time at the maximal rate, and it accelerates in the direction the vector leans at any moment. The clock ticks really are coming at longer intervals, but the clock can't tell because perception is relative.

The wormhole breaks the perception barrier of Relativity by revealing which end is in flatter space, closer to "rest" state, to both observers. This is necessary because Relativity is strictly a function of the non-Euclydian metric, and wormholes are not part of the metric of normal space.

 

[TKalbfus]

Here is a modified Scout/Courier with fusion rockets instead of Maneuver drive, and an FTL drive instead of a Jump Drive. This ship has two sets of fusion rockets: One underneath for liftoff and in space maneuvering and one set at the tail for atmospheric manuevering. Both are separated by a 90 degree angle and both can't be used at once. There are no grav units onboard this ship. "gravity is accomplished on board soly by accelerating the ship from underneath. The fuel duration is 50 hours at 2-g and 100 hours at 1-g.

SCOUT/COURIER
Class: Starship, type S
Tech Level: 15
Size: Medium (100 tons)
Streamlining: Streamlined
FTL Speed 250c: Acceleration: 2-G
Fuel: 45 tons
Duration: 50 hours
Crew: 1
Staterooms: 4
Small Cabins: 0
Bunks: 0
'Couches: 0
, Low Berths: 2
Cargo Space: 20 tons
Atmospheric Speeds; NoE = 275kph
Cruising = 825kph, Maximum = 1100kph
Other Equipment: Air/raft, fuel scoops.

EP Output: 4 (2 excess)
Agility: 2 (+2 EP)
Initiative: +2 (+2 agility)
AC: 12 (+2 agility)
Repulsors: 0
Nuclear Dampers: 0
Meson Screens: 0
Black Globes: 0
AR: 0
51: 100
Main Computer: ModeJ/1 (5 CPU)
Sensor Range: Close (Model/i)
Comm. Range: Close (Model/i)

Cost: MCr42.258 (new)

TAS Form 3.1 (Condensed)

Design Specifications
Installed Components Tonnage Cost EP
100-ton Hull +100 MCr12
Bridge -20 MCr0.1
Computer -0.1 MCr0.4
Flight Avionics -0.4 (MCr0.9)
Sensors -0.3 (MCr0.6)
Communications -0.2 (MCr0.5)
FTL Drive -3 MCr12
FTL Fuel -5
Fusion r TL15(200 tons) -4 Mcr 3 +4 or 2-g .005 tons/hour or .72 tons/hour
Fusion r TL15(200 tons) -4 Mcr 3 +4 or 2-g .005 tons or .72 tons Underside
Fusion Fuel -40
Fuel Scoops MCr0.1
1 Hard Point MCr0.1
Double Turret MCr0.75
Air/Raft -5 MCr0.273
Staterooms (4) -16 MCr2
Low Berths -2
Totals 0 MCr35.723

Double Turret: empty

Ship's Data (Commercial)