From Neithe Daphnotarthius the Elder to Neithe Daphnotarthius the Younger, greeting.

This message is not the manuscripts you expected to be delivered the day after having your brilliant idea, regretfully. Please understand that the problem we encountered with your brilliant idea was that it was actually an idiotic idea: it turns out that while using a knight’s-move transit such that we can publish our next series first and together, and then write it in peace afterwards, has the slight drawback that we cannot escape learning details of the story and reactions to it while we try to work on it, which makes writing it virtually impossible.

Or so I am given to understand, based on the message you are reading now, which I received last week. As I have and you will have confirmed by the temporal mechanists I consulted over said last week, this is a valid case of a predestination paradox creating an informational loop.

In any case, since we’re going to have to write it the old-fashioned way, you’d best get started. Once you convince yourself that this message is what it claims to be and you send yourself a copy, anyway.

And don’t take the wager you’ll be offered in the morning. Trust us on this.

You (Plus Eleven Days)


Existing While Not Being God

“I am confident, to more than nine nines of certainty, that not only has a fully-general means of causality-altering time travel not been invented, but that a fully-general means of causality-altering time travel never will be invented within our light-cone.”

“Excuse me, Academician – but how can you be so sure?”

“Are we, as we speak now, omnipotent deities the supremacy of whose mere whims is written into the canons of natural law itself?”



from the proceedings of the Oroelle Conference on Temporal Mechanics,
7920, 8340, 8760, and 9180

Trope-a-Day: Time Travel

Time Travel: Present in very limited forms: the kind you can do with wormhole shortcuts and relativistic travel (whose primary usage is permitting physics grad students to actually observe local causality violations), and the kind that lets transcendent AIs whisper to themselves from the future via acausal logic.  In both cases, subject to Chronological Consistency Protection, as they’re operating in a block universe.  (See Temporal Paradox.)

Trope-a-Day: Stable Time Loop

Stable Time Loop: The Chronological Consistency Protection Theorem (see: You Already Changed The Past) does appear to permit these kinds of predestination paradoxes (at least, the informational kind; the object paradox may also be possible, but testing it is dependent on finding an object that won’t age during the period of the loop, including in all the aspects that the universe will check that current technology may not be able to).

It is also somewhat limited by the main people who can make use of it for Retroactive Precognition/Retroactive Preparation being the transcendent/weakly godlike artificial intelligences.  Experiments by lesser intellects… well, they don’t actually produce messages reading “YOU ARE NOT SMART ENOUGH TO BUGGER ABOUT WITH THE TEMPORAL CONTINUUM”, but the gist of the results appears to be fairly plain.

Trope-a-Day: You Already Changed The Past

You Already Changed The Past: While extraordinarily limited, time travel does exist in the Eldraeverse – as it must, because so does FTL travel.  This is all you can do with it, however, because the Chronological Consistency Protection Theorem is very firm about that, and the universe is even firmer.

(And if you’re going for an object paradox, you’d better be grabbing something that doesn’t age during the loop.  Said universe will check things that your fleshy senses and quite possibly the technological sensors you’ve invented haven’t thought to look at and indeed can’t perceive.)



It is widely believed that time travel is useless.

After all, everyone knows the Block Universe Theory and its limitations: changing the past is impossible, and as such all grandfather paradoxes are banned. Predestination paradoxes are permitted, but obviously only create the already-known current state of affairs, rather than alter it; while this admits of certain limited applications in commerce (such as negative-frequency trading, although as a practice this quickly drives the market volatility operator to zero per the Market Chronology Protection Theorem, eliminating its own profit potential) and in military affairs (knight’s-move bypass transits, including optional proleptic tactical data transfer, which in practice rapidly become zero-sum effective between technologically matched opponents), these are special cases, few and far between. And while looped objects “borrowing” mass-energy from the substrate for the duration of their existence are theoretically possible, the nature of the loop requires that such objects exist in a synthetic or simulated nullentropic state, since the quantum state information at the earliest point of the loop must correspond exactly to that extant at the latest point of the loop.

It would seem, therefore, that the Chronological Consistency Protection Theorem would ban all interesting applications of closed time-like curves.

This, of course, is not the case. While it prevents the construction of technologies based upon its violation, the existence of a universal “paradox censor” that forces the probability of all causally inconsistent events to zero is of great application in several families of technologies.

The best known of these is hypercomputation. Acausal logic processors operate – to paraphrase a series of complex operations – by receiving an answer to a problem from the future, verifying its correctness, and transmitting it back to themselves in the past if and only if the answer is correct. Since the only causally consistent scenario is that in which the correct answer is received, such a device always produces correct answers to any PSPACE-definable problem. (The extraction of information without apparent computation inherent in the operation of acausal logic processors poses interesting problems at the intersection between information physics and ontotechnology, currently the province of ongoing research.)

As well-known is the so-called “probability kiln”, a class of manufacturing devices which utilize such hypercomputation for phase-space pruning; that is, to isolate and remove from future worldlines all those possibilities in which low-yield operations fail, ensuring that the only causally correct possibility is their success, thereby operationalizing even otherwise extremely impractical industrial processes.

Then there is the third class of device, a defense research project designated UNMOVED MONAD.

UNMOVED MONAD makes use of an extremely simple form of synthetic closed time-like curve, in the form of a tangle channel constructed and manipulated such that it links two points separated along the time-like axis, rather than two points separated along the space-like axis. To this extent, it is merely a trans-temporal communications facility. However, unlike trans-temporal communications performed via conventional means or space-like tangle channel, UNMOVED MONAD derives another unique property from its time-like separation: indestructability.

It is important to note that UNMOVED MONAD is a singular device: the tanglebits within are entangled with themselves across time, rather than with a matched set elsewhere. Upon activation, an UNMOVED MONAD device receives a complex, full-width verification signal from itself in the future. As such, it cannot be destroyed until this signal has been sent: such destruction would cause the tanglebits to decohere, ensuring that the trans-temporal signal never could have been received; a causally inconsistent state. Thus, per the Chronological Consistency Protection Theorem, the probability of the UNMOVED MONAD device being destroyed in the interim is forced to zero.

Properly packaged and placed, UNMOVED MONAD can even function as the mythical “synthetic luck machine” – while it is entirely possible for a bearer of an UNMOVED MONAD or the local environment to be destroyed so long as the device itself remains intact, ensuring an event phase-space with plentiful higher-order probability events resulting in the survival of the device can avoid such low-likelihood outcomes; the CCPT worldline shifts tend to go through the highest probability alternative regions. The universe evidently prefers not to work any harder than it has to.

– Temporal Mechanics: The State of the Art, “Popular Physics”, Cailmaen 6722