I just read Charles Stross’ Singularity Sky. I wouldn’t necessarily recommend it (I’d recommend some Vernor Vinge or Banks instead), but it certainly got me thinking.
Help me understand why distortion doesn’t end the universe in Iron Empires.
Nearly every interstellar ship in the Iron Empires is equipped with a device that can alter the flow of time. According to what I boiled down from Chris’ notes, time is affected in a manner that makes the ship move really, really fast.
Let’s assume that this effect is created by a local phenonemon that makes the ship move faster in time relative to its destination and its desired point of arrival.
Wikipedia has this to say on the matter:
So Chris’ distortion mechanism moves an object through space and time. It’s a drive mechanism and a time travel device.
Okay, so if I’m moving at near-C speeds, time stays (theoretically) relatively lifelike for me, and moves at an accelerated pace outside of my near-C capsule. In other words, if I describe an arc of one light year of distance beginning and end on Earth, moving at a rate of .99 light years per year, I age .99 years while time on earth has advanced much farther, right?
In the Iron Empires, that’s sublight expansion, right?
Well, let’s lay out a major assumption in the IE:
Using the distortion drives, the effects are localized. (This is standard FTL handwavium.) This is supported by the Novikov Principle. See below for more on that.
Okay, so we have FTL handwavium drives. Cool. But they’re still time travel devices. And this is what I’m after: Can these devices create closed timelike curves? In other words, it’s theoretically possible to travel in time and bump into yourself in the past or in the future.
I’m humping through interstellar space, my drive goes burp as another time traveling device unexpectedly passes through my coordinates. I start her up again and take off at a faster rate to make up lost time. Can I overtake myself? Can I overtake the alternate version of me who didn’t burp when I crossed paths with the other time traveling device? Probably not. The easy answer is “no parallel universes.”
Apparently, this is called the Novikov Self Consistency Principle:
We shall embody this viewpoint in a principle of self-consistency, which states that the only solutions to the laws of physics that can occur locally in the real Universe are those which are globally self-consistent. This principle allows one to build a local solution to the equations of physics only if that local solution can be extended to a part of a (not necessarily unique) global solution, which is well defined throughout the nonsingular regions of the spacetime.
But wait, can I loop back and overtake my light cone? Why not? Light moves at a constant. I’m moving at a constant x10 or something.
According to those theoretical physicist nuts, it seems that on a quantum mechanical level, you can’t go back in time and kill your grand dad so that you were never born. In fact, I don’t think you can go back in time and do anything that would preclude you from ultimately traveling through time. But I could be wrong.
Of course, that doesn’t mean you couldn’t travel time and fuck someone else who is not part of your closed timelike curve.
Shape of absolute future
According to Hawking and Ellis, another remarkable feature of this spacetime is the fact that, if we suppress the inessential y coordinate, light emitted from an event on the world line of a given dust particle spirals outwards, forms a circular cusp, then spiral inwards and reconverges at a subsequent event on the world line of the original dust particle. This means that observers looking orthogonally to the direction can see only finitely far out, and also see themselves at an earlier time.
Time and light travel in curves or waves.
It’s theoretically possible, using the distortion drives, to move faster than light, arrive ahead of the light’s curve in time (but still within its cone) and look behind you and see what happened in the past. So if I can move at C+, I can loop back and intersect my C- slow moving self. Uh oh. I’m simply talking about making a physical loop in space now at a velocity so fast that I can intersect with a slower moving body who left at the same time.
Okay, now what good does that do us? Well, can I use my distortion drive to travel so fast that I close the curve into a loop and then reappear in my line after I left but before another event transpired?
What if I use the above method to spot which planet a vaylen fleet will invade, go back and close the curve, and, since I can’t save the planet, I destroy it? Well, what if the Vaylen had sent scouts moving faster than light to the planet and they see me depart on a closed timelike curve. Can they then move faster than me in time and catch me and stop me? Can they move faster in distortion than I’m moving, close a curve and jump to my home planet and destroy it before I left?
If not, why not? Distortion drives are time travel devices!
Distortion drives are nominally FTL drives and don’t let us muck with time, but for me, they’ve always seemed to be the irresistible key to a Pandora’s Box.