Detailing Surface areas of worlds

[Drifter]

After I read the description in BtC I had to check the internet again and dig out my old books to be sure. I guess it pays to have those World Profile numbers around after all.

[Mark Laiho]

Please note. The population in the UWP code is for the entire system. The rest of it usually relates to the most populous planet/moon/habitat with the best starport. Also higher tech levels especially at GURPS TL10 the contragrav tech allows you to boost large mass's into orbit for peanuts cost. If the are asteroid belts in there expect there to be active.

There is a 3 digit sub code after the main uwp. first digit is population multiplier, 2nd is number asteroid belts, 3 number gas giants if I remember right.

pop uwp pop of 9 and a pop multi of 5 for instance would mean 5billion people.

[Malenfant]

Originally Posted by Mark Laiho

Please note. The population in the UWP code is for the entire system.

Has that ever been made explicitly clear to be the case? I thought the usual assumption was that it was the population for the mainworld only (because other worlds in a system have a minimum of one order of magnitude less people on them, so wouldn't change the UWP code).

[Mark Laiho]

Because the populations of other areas off the mainworld is usually 10% or less the population code for the main planet does pretty much cover the population for the entire system the majority of the time.

Pop code 8 for instance with a multiplier code of 4 for example would be
400million people so 40million people off the main world is within the range of population for the main world it wouldn't change the population code added or subtracted. you might with a multiplier round it up one multiplier or down one but the actual base population code wont change.....

[Peter Knutsen]

Originally Posted by hal

I then took the percentage of a world covered by water as the percentage of the "surface area" for a world as being covered by water, and the remainder then, would be the general surface area of the world itself. Granted, most worlds don't have perfectly smooth surfaces. In fact, one would speculate that mountains and deserts would lower the usable surface area by a fair bit.

Given enough TL (regardless of what kind of TL it is), deserts can be turned into non-deserts. Flattening steep mountains is trickier (I presume you've read the early "Dune" novels?), but a lot of highland is relatively flat AFAIK, and thus useable.

Depending on how much world detail is available, higher gravity would tend to mean more and steeper mountains, less gravity the reverse. Erosion also would mean fewer mountains, based in part on wind strength (which again AFAIK is based in part on average world temperature) and in part on world age (more billions of years to grind those rocks into sand). Volcanic activity and probably plate tectonics will also affect mountain prevalence.

Although note that at very high TL, it should be possible to stabilize plate tectonics (basically nullify them, if nothing else then detonating huge fusion bombs along fault lines) and subsequently drill into mountains for habitat space, in the form of enormous underground arcologies. Drilling is serious business here at GURPS TL8, expensive and noisy (huge uproar in parts of Copenhagen because of the current subway drilling projects), but at much higher TLs it ought to be almost trivial to excavate a few cubic kilometers of even very hard rock.

[Malenfant]

Originally Posted by Peter Knutsen

Depending on how much world detail is available, higher gravity would tend to mean more and steeper mountains, less gravity the reverse. Erosion also would mean fewer mountains, based in part on wind strength (which again AFAIK is based in part on average world temperature) and in part on world age (more billions of years to grind those rocks into sand). Volcanic activity and probably plate tectonics will also affect mountain prevalence.

I think you got most of that the wrong way around. Higher gravity means smaller mountains with shallower sides, because slopes are more likely to collapse in the higher gravity (and when the dust settles the debris aprons will be at shallower angles). Erosion is more complicated - the effectiveness of wind for eroding the surface is more determined by atmospheric pressure and energy put into the atmosphere by the world's primary star - dense atmospheres require more energy to move the greater air mass, but slower wind speeds can cause erosion/damage equivalent to faster wind speeds on planets with thinner atmospheres.

Although note that at very high TL, it should be possible to stabilize plate tectonics (basically nullify them, if nothing else then detonating huge fusion bombs along fault lines)

I doubt that this is possible at any TL.

[hal]

For what it is worth, my geology courses I took in college indicated that with Higher Gravity, the erosion process would likely make the world more smooth rather than less. The higher gravity rating of the world would affect not only erosion due to gravity, but would also accelerate the process of erosion due to water (including rain). I wasn't sure just how much of what I remembered was correct after all these years, since it has been nearly 25 years since I took that course!

As for plate tectonics - the issue doesn't seem to stem from pressure being built up in one location, or even in multiple locations so much as trying to stop ALL movement of a huge mass of somewhat colder stone floating atop liquid magma. You wouldn't just need to stop the motion of one plate, you'd have to stop the motion of ALL of the plates. Ironically, my first thought about using tractor beams and repulsor beams from Traveller's High Guard made me think that someone might attempt it - but then I realized that the laws of physics being what they are - if you use a tractor to slow down the motion of a large plate, you will impart the motion of the larger plate on the other plate you attempted to use as an anchor point from which to use the tractor. Same thing would hold true with a repulsor beam - the plate being used to push against as the anchor point would gain some of the energy if you attepted to push the faster moving plate away from it.

In the end, I'd have to speculate that even with repulsor/tractor technology, this would prove to be problematical. The use of a weapon to slow down the moving mass of one plate, would also be applied to speeding up the other plate the explosion is being planted against.

Mind you, my geological knowledge is somewhat out of date (by 25 years!), but I suspect what I wrote is mostly on the money.

[Peter Knutsen]

Originally Posted by Malenfant

I think you got most of that the wrong way around. Higher gravity means smaller mountains with shallower sides, because slopes are more likely to collapse in the higher gravity (and when the dust settles the debris aprons will be at shallower angles).

Yes, that's what I meant to type. Sorry...

[Drifter]

I would expect that if you can't 'stop' tectonic processes, you could predict and/or redirect them. Both accuracy and prediction period would improve with increases in TL.

We're at TL7/8 and have had some small success in predictions. I'd say you don't get reliable prediction rates until late TL8, or better yet, probably not until TL 9. At that point you can say an earthquake is coming, and approximate size, within a few weeks of when it will strike.

TL10 you can say pretty accurately how big it will be, and get the date down to a day or so.

By TL13 you can predict down to the hour when it will strike.

GURPS tech levels, btw.

All this assumes you have a LOT of sensors in place, regularly monitored. Expense would be high, likely only a good sized planetary government could afford it. You wouldn't see prediction levels like this by a TL13 Scout team on a frontier planet.

[SteveS]

Based on our sample of four terrestrial planets and a lot of solid moons, it appears that smaller worlds have taller mountains, but that they are geologically dead much sooner. We have only two planets and a few moons that are geologically active: Venus appears to have active volcanoes but no signs of tectonic activity. Earth is active both ways. It appears that Mars was once very active, but any remaining activity pretty much vestigial. Io is not only geologically active, it's the most active world we know about -- but its volcanism is driven by tidal stress; gravitational interaction with Europa keep its orbit elliptical, and Jupiter stresses it differentially as its distance varies.

So, to extrapolate this to other worlds, we can guess that small worlds will have tall mountains but no geological activity, large-ish worlds will have volcanoes but not tectonic activity, and large worlds will be tectonically active -- and moons with the right orbital characteristics will also be geologically active. (That may also be true for some planets, if they are close to their star and a large planet, but that would put them into the torrid zone unless their stars are somewhat smaller than the Sun.) The boundaries between size groups, in terms of geological activity, will vary with the age of the system, because non-tidal volcanism is driven by radioactive decay deep in the planet, and declines with age.