When did the Hydrographics formula change?

[rinku]

I was playing around making a world generator, using the sequence in MGT2e22 and noticed that the formula for Hydrographics is now 2D-7+Atmosphere (plus the mods for some atmospheres).

I've been playing Traveller since 1980 and everything in my core said "Whoa! Shouldn't that be 2D-7+Size?"

So I checked the errata, and it said nothing.

Then I pulled out 1977 Book 3, 1981 Book 3, Book 6, MegaTraveller Referee's Handbook, Traveller New Era and Mongoose Traveller 1st edition. All said "add size", except one spot in the 1981 Book 3 - the text says Atmosphere but the summaries say Size.

Then I checked the online errata. Every single edition has now had "add Size" changed to "add Atmosphere"

So... it seems there was a proper decision made relatively recently to change this, maybe by Marc? It doesn't really have any major effect on the game, or invalidate published UWPs. It's not possible to know which version is more likely from current planetary science evidence. Statistically, I'm unsure how it skews the averages, though I suspect basing on Atmosphere results in more water worlds AND a few more dry ones, but doesn't much change the distribution between the extremes.

Anyone know the facts about the change?

 

[ChrisJ]

I was playing around making a world generator, using the sequence in MGT2e22 and noticed that the formula for Hydrographics is now 2D-7+Atmosphere (plus the mods for some atmospheres).

I've been playing Traveller since 1980 and everything in my core said "Whoa! Shouldn't that be 2D-7+Size?"

So I checked the errata, and it said nothing.

Then I pulled out 1977 Book 3, 1981 Book 3, Book 6, MegaTraveller Referee's Handbook, Traveller New Era and Mongoose Traveller 1st edition. All said "add size", except one spot in the 1981 Book 3 - the text says Atmosphere but the summaries say Size.

Then I checked the online errata. Every single edition has now had "add Size" changed to "add Atmosphere"

So... it seems there was a proper decision made relatively recently to change this, maybe by Marc? It doesn't really have any major effect on the game, or invalidate published UWPs. It's not possible to know which version is more likely from current planetary science evidence. Statistically, I'm unsure how it skews the averages, though I suspect basing on Atmosphere results in more water worlds AND a few more dry ones, but doesn't much change the distribution between the extremes.

Anyone know the facts about the change?

World builder Handbook lists it as + Atmosphere

T5 1.0 lists it as + Atmosphere

Not suer when the change was made - but that's the most up to date versions.

 

[rinku]

Yeah. And it was Size in Mongoose 1st edition and everything before that.

So I would hazard a guess that Marc decided on the change for T5. The FFE errata updates every GDW edition from 1977 through TNE from Size to Atmosphere (didn't check T4, GURPS, d20 or HERO). I'm fairly sure at this point that the lone 1981 Book 3 reference to Atmosphere was a typo, since MegaTraveller definitely has Size.

 

[Garnfellow]

Actually this goes all the way to Classic Traveller, which flopped back and forth. As you noted, Book 3 '81 and the Traveller Book both have Hydro as 2D-7 + Atmosphere. Further, the consolidated Megatraveller Errata changes the Hydro formula to key off Atmosphere.

 

[rinku]

But the consolidated errata includes any relatively recent changes. It's quite clear that the current correct formula is Atmosphere. I'm really just interested in the history of the change.

1981 Book 3, The Traveller Book (1982) and Starter Traveller (1983) all have the same thing of Atmosphere in the main text but Size given in the checklist. It's fairly clear that those are cases of the previous text being copied over.

Probably MOST relevant entry from Classic Traveller is that Book 6 Scouts (1983) with its expanded system generation uses Size.

 

[Bense]

It was first changed from "+Size" to "+Atmos" in the 1981 revision, but it was only changed in the rules text, not on the "World Generation Checklist" that everyone used when they generated worlds. Starter Traveller and The Traveller Book both have the same problem - the rules text says "+Atmosphere" but the checklists say "+ Size".
Book 6: Scouts consistently uses "+Size".

MegaTraveller used +Size. The New Era used +Size.
Marc Miller's Traveller has the same problem as Classic Traveller - it says "+Atmosphere" in the text but "+Size" on the checklist.

T20 used +Atmosphere.

So it looks very much like it was first changed to Atmos in way back in the '81 revision, but only in the rule text, not in the tables/checklists until T20, after which it has consistently been "+Atmosphere" for T5 and the Mongoose versions.

 

[Geir]

It's been +Atmosphere for a long time, subject to the confusion noted by @Bense.

Personally I liked it better when it was +Size, and I could come up with all sorts of arguments why that would make sense, but not only does it flow better (the current stat DM = the one before, starting from both Size and Pop), but I could just as easily make arguments against, and for the most part, I only like to try to break rules that are truly broken (but no matter what, someone will complain, but everyone is entitled to complain)).

 

[Fluffy Bunny Feet]

Personally I feel that +Atmosphere works better with inner/habitable zone worlds with little or no air and are hence less likely to have any surface water. The same for moons. In the outer system where such water would be frozen size makes sense as we can see ice on such bodies.

 

[rinku]

It might be relevant that between the 1977 text and the 1981 text, the paragraphs were rewritten. 1977 talks about "throws" and expresses the modifiers as DMs. 1981 gives it as a concise formula.