Re: Weather from another world

On Jul 26, 10:54 am, DJensen <i_m...@xxxxxxxx> wrote:

Density: ~0.52 Earths
Surface Gravity: ~0.40 g
Mass: ~0.25 Earths
Diameter: ~10,000 km

OK, although that's a pretty low density - lower than Mars, and lower
than our Moon. To get a density that low you would have to have a very
significant amount of something like water in the mix... and here by
"significant", I mean a couple 100 km deep oceans and no land
anywhere.

Sidereal Day: ~54 hours
Solar Day: ~540 hours
Period: ~60 hours (1/9th of a solar day)

I'm confused. The fact that the orbital period around the gas giant
(60 hours) and the sidereal period of the planets rotation (54 hours)
is close implies close to tidal lock (perhaps OK)... but then the
solar day should also be in that range. You seem to be applying
something like the simple relationship between solar, sidereal, and
orbital periods for a *planet*, but this is the satellite of a planet,
so it's not the same situation.

If you want to read the entire worldbuilding thread, Google for
"Shallowball" here in rass. There was a lot of back and forth, but
nobody raised the possibility of quakes tossing things 2km into the
air, or anything like that.

I might have to read up - note that 2 km high tides really aren't a
problem unless it is a 2 km difference between the solid-body tides
(land) and the oceans (liquid, taking into account resonance etc.)
Massive quales are almost certainly not a problem, because and such
stresses would be releaved rather quickly. In other words, you might
expect (undetectable) microquake swarms, but not anyhting like mag 5
shocks twice a day. We have large quakes here because a lot of energy
is stored up over a lot of time and then it all lets go at once -
here, you have a system that can't build up a large amount of strain
energy due to how often it is flexed.

I assumed if there was enough energy to create pretty much constant
aurora activity all over the world, it would have an impact on
weather... now I'm wondering if the 2 hours of eclipse might just be
enough to trigger rain (or hail, I suppose) storms like clockwork.

I'd guess the eclipse might have more of an effect than the auroral
display, certainly. But if you have a breathable atmosphere on such a
low-density world, then you need a *lot* of atmospheric mass - an
Earth-normal atmosphere on this 0.40 G world will require 2.5 times an
Earth-normal column density, and the atmosphere is going to be
"taller" as well (pressure dropping off slowly with altitude), so the
result is it's not going to be effected as rapidly as Earth's
atmosphere to transients in the amount of sunlight heating it, etc. A
local eclipse on Earth results in a noticable cooling of the immediate
area under it, but I'm not sure how much (anyone?). Here, you've got
global cooling for 2 hours, which should certainly have some effect,
but it will mostly be cooling at the *ground*, resulting in a stable
atmosphere - warm air aloft that cools slowly, while the hot ground at
the bottom (already above air temperature because of solar heating)
cools rapidly, along with the air closest to it via conduction. You
won't get big storms (unstable air column)... more likely local ground
fogs (as we get on humid but clear nights on Earth).

I remember I did some work way back when on Velvet (a fictional planet
a number of worldbuilders were collaborating on)

I would enjoy reading the results, if any of it is online.

As far as I know, it ended up vanishing without an internet trace. The
core of folks were some of the same ones that worked up Epona a while
back, and the only name i can remember is Wolf Read (better known as
an Analog cover artist).

--
Brian Davis

.

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