Picaresque: Tempus Ante Quem (TAQ)

Tempus Ante Quem (TAQ, “tack”) is the latest possible divergence point between the current world and baseline Earth. It is usually expressed as log10(years before present), rounded to one or two significant figures:

2D TAQ Description Years Before Present
2 3 Historical 0.5K-5K
3-4 4 Cultural 5K-50K
5-6 5 Anthropological 50K-500K
7-8 6 Zoological 500K-5M
9-10 7 Geological 5M-66M
11 8 Biological 66M-540M
12 9 Astronomical 540M-4650M

Baseline (TAQ 0) is the standard against which all others are measured.

Historical (TAQ 3) worlds contain recognizable descendants of Earth empires of the past. These are extremely desirable for development and research, since it is possible to communicate directly while populations and technology levels are frequently high. The latest divergenc point so far discovered is AD 1678 (TAQ 2.7); a later date would be of great interest. If a world has a readable written language anywhere, even if the civilization is extinct, it’s probably TAQ 3.

Cultural (TAQ 4) worlds are populated by behaviorally modern humans, with groups and histories broadly parallel to Earth cultures. Many exhibit high levels of development, technology, and population, without being closely related to civilizations known on baseline Earth. Opportunities for novel discoveries, artifacts, products, etc., are balanced by difficulties in establishing fruitful contact. The most sought-after (and feared) TAQ 4 instance would be one which had developed a space-faring technology of its own.

Anthropological (TAQ 5) worlds are inhabited by anatomically modern humans and close archaic relatives, but these generally display no civilization as such. Sparcely populated, with few obvious advantages and the disadvantage of increased UN scrutiny (as an inhabited instance). Sometimes exploited for labor or raided for slaves by unscrupulous parties. If the inhabitants wear clothes and use weapons and tools, but are otherwise unsophisticated, or if the geography is familiar but there’s currently a glacial epoch, it’s probably TAQ 5. A technological but non-Homo sapiens civilization would be of intense interest.

Animals on Zoological (TAQ 6) worlds all fall into known families, but the genera and species encountered are different. Minor differences in continental drift may result in limited or local changes in climate, sea level, or geography. A few host distant cousins of humanity, most barely able to break rocks for tools but still close enough to qualify as “indigenous people.” TAQ 6 worlds are generally the least useful: no native humans worth trading with, not different enough from baseline to be interesting. On the other hand, the uninhabited ones make good colony sites.

Geological (TAQ 7) worlds diverged early enough that patterns of climate and continental drift are different. Different mineral resources may be exposed or positioned more conveniently for exploitation. Cutoff for inclusion is conventionally moved back to just after the Chicxulub impact. If the dominant animal species are mammals and birds, it’s probably TAQ 7.

Biological (TAQ 8) worlds share the same chemistry and common ancestors with Earth plants and animals, but may have developed in wildly different ways. Many possible new products in exotic biologicals and even different minerals. Continental placement and configuration, atmospheric compositin, climate, and sea levels may all be significantly different from baseline. Conventionally diverges after the Cambrian explosion but before the Chicxulub impact. If the dominant animal species are some flavor of dinosaur or reptile, it’s probably TAQ 8.

Astronomical (TAQ 9) worlds have the same mass, density, orbit, and moon as Earth, but otherwise anything goes. They may have no life at all, single celled organisms only, or completely alien biochemistry, as well as many possible combinations of atmosphere and hydrology. Surface exploration may require specialized equipment and procedures. These are always extremely valuable, as the only practically reachable “alien” worlds. If you’re not sure whether the world you’re looking at is really Earth, it’s probably TAQ 9.

Unassigned or unknown (TAQ X) worlds are either newly discovered, insufficiently well explored to establish a divergence point, or anomalous in some way.

Note that TAQ can be revised, but only to higher numbers (earlier dates) as more information is acquired. So for a world where the 5 March 1979 event sterilized the planet, the TAQ might initially be set to 2.3 (from a game-present date of 2180), but adjusted back to 5.2 when the divergence point was traced to a supernova in the Large Magellenic Cloud.

That’s certainly Traveller-like. . . .

You think so? It’s intentionally modeled on a UWP code, but TAQ is fundamental to the differences between Picaresque and both Traveller and GURPS Infinite Worlds.

Two small numerical points:

First, the actual formula appears to be log (2 x years B.P.).

Second, while you say that

the actual primary history appears to diverge from the actual primary history 0 years BP, and log (2 x 0) is negative infinity. To get TAQ 0 you would need to have divergence six months ago.

Incidentally, a large fraction of the alternate histories I’ve read have had divergence points more recent than 1580. The (American) Civil War and World War II appear to account for as many such as all other divergences together. They would both be TAQ 2, I believe. Is there a designation for those, or do they just not turn up? For that matter, the United States under President Clinton or President Sanders would be TAQ 2, though I cannot imagine it being a good idea to have player characters reach such a place.

Your numerical points are fair: the breakpoints should be at multiples of 3 (10^0.5) rather than 5 (10^0.7). The significant breakpoints in the archaeological and geological record tend to follow the sequence I’ve shown, however, so the single-digit version is a fudge but good enough for most purposes. If one is discussing a specific event, the formula I’ve given (rounded appropriately) is used.

I’ve intentionally set the minimum usable separation between worlds (~500 years) to preclude most standard cross-time travel tropes – you can’t meet your duplicate, or find the world where the Nazis won WWII. I’m using time travel as a substitute for FTL, not for its own sake. This is one reason I had to create the TAQ scale: most time travel rpg settings switch to linear time travel and visit distant events in the past, rather than work out the present consequences of a distant divergence point in detail.

I don’t think I’ve said it yet, but all worlds also share exactly the same present (~2180, by default), and so there are also no precise “echos” of earlier historical periods. I do have a short list of GURPS Infinite Worlds timelines that could plausibly exist in this setting, for reference or inspiration.