I naturally thought this should be suspended in space, but every guy I talk to about it wonders why it couldn't exist on earth. I naturally assumed something happened in space would be much more interesting.

P.S. If the facility were on earth, I was thinking it could be located underground at the north pole, but the more I think about that concept the less it seems like people would believe it. Put it in space and it's outside the realm of what people can intuit, like the orbit of Mercury. Did you know Mercury rocks, rather than rotating?

So there's no way it could be on Earth. Unless perhaps it was whizzing around at close to the speed of light, in circles, in some gigantic kind of particle accelerator.

By the way not all readers of SF intuit about space. Some know, some deduce, some read. Mercury rotates, but slowly relative to its orbital period--it rotates three times on its axis for every two revolutions of the sun. I'm not sure if that means it rocks, but it sure sounds groovy!

http://en.wikipedia.org/wiki/Mercury_(planet)

Hope this helps,
Pat

[This message has been edited by TaleSpinner (edited January 25, 2008).]

With relativity, you have two choices. Either 1) they are moving at a very high speed relative to earth (it doesn't matter which one is moving faster--in fact it's meaningless even to talk about that), in which case don't ever expect them to come back: this habitat will not be a place you can go visit. Also, it would mean that, in addition to 30 of their years passing for each one of ours from their point of view, thirty of ours would pass for each one of theirs from our point of view--don't know if you want that; or 2) WE are accelerating at a high rate. Well, we aren't, so you can't use that. (If THEY accelerate at a high rate, the time dilation is one way, and it's not the way you want it.)

Why are they doing this, anyway?

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Do people in this area have a choice to be there? I am wondering why anyone would live in this conditions. They would live 3 years at most. This has me rather scratching my head.

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Perhaps they're convicts. They live out a thirty year jail term in three of our years, enabling a small number of prison cells to be time-shared amongst many prisoners.

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if such a thing as "antigravitiy" existed, you could presume in your sci-fi story that it has a "reverse relativistic effect"

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It could also be a strange sort of side effect from other projects going on with things like dimentional research and exploration, strange and mysterious quantium machines that warp space and time.

If all else fails there's always the tried and true, it's so mysterious, no one knows why it's this way. Maybe it's a side effect of something, or a strange spot on the planet or in space that was found. There's a million stories that could come from this.

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Between the Strokes of Midnight by Charles Sheffield sort of covers this territory. I think the time difference was much more than 30 times faster, but it's been a while since I've read it. Probably worth your while to check it out though.

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Thanks - that's good to know. I'll see if I can find it.

It is a facility that does information processing, remote control and research.

T1 = T2/(sqrt(1 - v^2/c^2))

Now c^2 is an incredibly large number, so in order for there to be any appreciable difference between 1 and sqrt(1 - v^2/c^2) v^2 has to be pretty damn fast.

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Good thought, but no. Gravity is just a form of acceleration. Anti-gravity would be acceleration in the other direction, but it would still be acceleration, so it would still slow them down with respect to us. (And it would still crush them, as a high-gravity field would).

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Actually, no, this isn't what I meant. And for the record, gravity is a force caused by the distortion of spacetime, not a simple acceleration. Gravity can cause you to accelerate, to be sure, but it would hardly ever be enough gravitational acceleration to have any noticable relativistic effects.

However, this distortion of space-time caused by the presence of mass -- ie gravity -- also causes time dilation. What I meant by my above suggestion, is that if you want to "handwave" the existence of some form of "negative matter" in your sci-fi story, this is close enough to passable to believe, even for someone with a good grounding in physics.

If you take a look at some simplified equations here for example: http://en.wikipedia.org/wiki/Gravitational_time_dilation
and supposed in the equation for time dilation due to a gravitational body of some mass M, if there existed an "anti-mass" with a negative mass, then you flip the sign of the equation, and reverse the dilation of time.

So a planet made up of "negative mass" (Whatever the heck that would mean haha) would have an opposite time dilation, with respect to the rest of the universe. At the same time though, just like with normal gravity and time dilation, it takes a VERY strong gravitational distortion to noticebly affect time dilation. (The gravity on the surface of the earth, vs. in orbit, has been measured with atomic clocks, but it's a very small effect. However, even with earth, orbitting satellites do actually have to take this into account to stay exactly in sync with earth-surface based clocks.)

T1 = T2 * Sqrt(1- 2GM/rc^2)
with G = grav. constant, M = mass, r = radius from center, c=speed of light

I think these stories were:
"Climbing the Blue" in the Jul/Aug 2005 issue, and "The Time Pit" in the Oct 2005 issue.

I could be wrong though, so just give them a read if you can and it might give you some insight into how an a good time dilation type story is framed.

Also, as far as the whole relativity thing goes, in my view it all depends on what type of sci-fi you are writing. Is it hard sci-fi or soft? If it's hard, then you're probably going to be writing for an audience of very informed, technical science types who want to know every little detail about the technology and issues you're dealing with, and if your story doesn't make sense scientifically, then they'll probably call you out on it. If it's soft sci-fi, then you probably have a little more leeway. You still need to be convincing and you still need to make your ideas plausible (if it's something absurd or obviously isn't possible, then people will still call you out on it) but often if you can present an internally consistent idea and then have the force of your story rest on solid characters and plot development, then you should do alright.

Sorry, I didn't mean to confuse the issue of what gravity IS vs. what it CAUSES by blithely using the term acceleration without further explanation, but I did.

Let's put it this way. (And obviously you'll already know a good bit of this, so I'll try to keep the background part brief.) Just as special relativity treats all inertial (i.e., non-accelerated) reference frames as equivalent, with formulae to move ones viewpoint from one frame to another, so general relativity treats ALL reference frames equivalently, whether accelerated or not. A gravitational reference frame is an ACCELERATED (not merely acceleratING) reference frame. In the case of gravity a good way to think about it (which is COMPLETELY EQUIVALENT to a description as curvature of space-time) is to think of space itself as accelerating (not merely moving, which would be meaningless) toward the center of the mass in question. A freely falling body (like the person in the falling elevator) is in an inertial system even though it is in a gravitational field, because it is NOT RESISTING the acceleration of space. Someone falling into a non-spinning black hole would suffer no time-dilation effects from the gravitation itself until spaghettification caused their extremities to undergo acceleration, although the speed they pick up on the way would still cause time dilation due to special relativity. On the other hand, a person on a platform slightly above a black hole's event horizon, even though they were not "accelerating" in the normal sense, would still be in an accelerated reference frame, and would hence be crushed. They would be resisting the acceleration OF space, and so would be accelerating THROUGH space, even though from an outside perspective they were not moving. Aside from being crushed, they would undergo severe time-dilation effects.

Anyway, that's what I meant by "accelerating".

As for the negative mass: the equation doesn't work with a negative value for mass. Since the meaningful effect is the degree of acceleration and not its direction (i.e., reference frames accelerating in opposite directions do not have opposite time dilations), and the degree of acceleration is dependent on the magnitude of mass, not whether it's positive or negative, the actual term to be used in the equation ought to be |M|, not just M. Had there been any negative masses floating around that we knew of, the equation would probably have been written as I suggest.

Tricia, theworldinthewords has good advice: if it's going to be hard sf, you have to get it right. If it's softer, you can use something like a time warp, which is not explained. It need only work consistently.

The odd thing is that both frames of refernce think time has slowed down for the other. But if the second of the bodies turns around so that it meets up with the first body again, then the second body has changed frames of reference again.

Note: Turning around at relativistic velocities takes a lot of energy!

If, in some sci-fi story, scientists discover this whacky material called "negative mass" who is to say what properties it might have? Since such an object does not exist, we cannot say for certain if it could allow for time dilation in the opposite direction of normal matter?

It is, in the end, just a sci-fi story. I was just trying to say that even with a thorough background in physics, I would buy the "negative mass" handwave explanation. Then again, if you had a planet of "negative mass" then by E=mc^2, would that make that negative mass have "negative energy" an equally absurd concept? Would that mean that energy + negative energy = vaccuum? Would anyone who steps onto a time-dilated negative matter planet instantly annihilate with the matter of the planet and leave behind a vacuum?

For that matter, if you throw in negative mass into the equation for gravity, does that mean the gravitational force between normal and negative mass is repulsive instead of attractive? Hard to step foot on a planet that's pushing you away instead of pulling you down.

That's the thing about making up science fiction. Once you invent one tiny new alteration to science, it has a ripple effect. =P

The reason I, personally, wouldn't buy this one is that it is the degree of acceleration that's the driving force behind the phenomenon, not the mass per se, and if the negative mass had negative gravity, and hence accelerated you in the opposite direction--well, the direction of the acceleration doesn't matter. But, as you say, when you start making up things that don't (or aren't known to) exist, you can often say what you like. For me, the logic doesn't follow, but who's to say that it might not have other effects?

Still, that much acceleration would crush the participants (or tear them apart, if it had an "opposite" effect).

Doc--(long time!)
I think there's a confusion, in your explanation, between special and general relativity. Two unaccelerated bodies that are moving at different speeds relative to each other are in different reference frames, and each will see the other's clocks as ticking slower that its own. But during the acceleration phase, the one accelerating sees the other's clocks as going faster. How much faster depends on the degree of acceleration, and also the distance between the objects, strangely enough.

Hey, it has been a while hasn't it?

You're right. Frame of reference is part of both velocity and location. Without lecturing on special vs general relativity, what I was trying to say is the acceleration changes your frame of reference. In simple terms, an object can experience acceleration relative to itself, but velocity only exists relative to another object. There is no absolute zero in velocity.

At this very moment, even the Earth is moving at relativistic velocity, thus experiencing time dilation, relative to certain frames of reference.

Perhaps what Tricia V needs is a wormhole-like construction, which connects the "facility" on the Earth to a faraway point in another frame of reference. It would open up all sorts of dramatic possibilities if a character could quickly move from one frame of reference to another.

However it worked, I caution against depicting it as a "doorway" that connects the two frames instantaneously. If the two sides were in different frames of reference, then I doubt a character could survive walking through that doorway. To cross that threshold alive, the character might need to be frozen so that the heart and brain were completely stopped.

It would be easier to use some sort of transfer device that warps spacetime around the character. It could be like an elevator car (perhaps Asimov's kettles), a police call box, or better yet a space capsule.