[World Design] Implications of a longer day

[Aexalon]

The twin suns are unmoving. And I forgot that I recently made a change to the cosmology. There are 7 planets that revolve between them, only the middle one locked in a figure 8 revolutionary pattern. Three revolve around one sun, while the other three revolve around the other sun. The primary planeyt, on which the adventures mainly take place, has a huge orbit, revolving around both suns. Due to the wide berth, the sattelites from my homebrew have no chance of being caught in a different gravity well.

Well, the middle of the system is the one planet that revolves around both suns in a figure eight pattern. The amount of space in between both suns is three times the amount of space between Earth and our Sun. I figure that is just the right amount of space for the figure pattern revolving planet to be able to support an ecology, without being too overheated.

Nine times the size. Just imagine my world world as Earth having porprtions multiplied by 9. I don't think anyonge would have a problem finding parking space in such a scenario.

Well, I'm not sure about the orbot of the moons, but they are all visible from the surface of the planet, each phase visible to anyone looking up into the night sky. Cunjuntions, eh? I may have to relook at that Dragon magazine article.

If I read this right, you have a rock world with a diameter 9 times that of Earth (beaten to the napkin math by Pbartender)? Wow!

Not that I should be saying much ... Garden's islands are lacking the other way around, having far too little gravity to be viable in hard sci-fi. Spelljammer physics, lad (or, as the hip version these days goes: "Sea turtles, lad").

Anyway, I was reasoning from the PoV from your planet's habitable moon. From the planet's surface, a complete set of full moons is entirely possible. Even weirder, a situation where the planet's right between the 2 suns, and some moons are on one side and some on the other, producing a double eclipse (very localised effect, granted)!

 

[Ahrimon]

I'd go with a 20/10/20/10 cycle. With the 10 hour sleep cycles generally being during the hottest and coldest parts of the day. Most likely just after midday and midnight.

And while per day abilities are very common in the game, there is a lot of precident for abilities to recharge after 8 hours of "rest". So regardless of what time of the day it is, if you've had your rest, you can recover your abilities.

 

[Aexalon]

I haven't gotten around to replying in detail to the circadian cycle suggestions, because I plan on generating more of them diagrams to illustrate them. so far, the following 3 will be added:

• 20/10/20/10 with sleep cycles around dawn & dusk;
• 20/10/20/10 with sleep cycles around highsuns & midnight;
• 40/20 with sleep cycle during the day;

That makes for 6 already —the 3x(X/20-X) type with its various slight rotations (sleep period centered on highsuns, or starting at highsuns) being counted as one for now— ...
More on this soon!

 

[Gez]

Yeah, you have to be careful, there... If you aren't using magical D&D handwaving, having a much larger planet equates to a much higher gravity.

Wouldn't that depend also on density? Like in Vance's Big Planet, where he uses lack of metals as the stone with which to kill both the bird of technology (no metal -> few machines) and the one of size (low density -> bigger planet for the same gravity).

 

[Angel Tarragon]

Wouldn't that depend also on density? Like in Vance's Big Planet, where he uses lack of metals as the stone with which to kill both the bird of technology (no metal -> few machines) and the one of size (low density -> bigger planet for the same gravity).

The industrial revolution has taken place on my world.

 

[Pbartender]

Wouldn't that depend also on density? Like in Vance's Big Planet, where he uses lack of metals as the stone with which to kill both the bird of technology (no metal -> few machines) and the one of size (low density -> bigger planet for the same gravity).

Sure, it would, but density can only do so much...

In order for a planet nine times the size of earth to have the same gravity at it's surface, it's density would have to be something like 2/3rds that of water... Saturn is the only planet in our solar system that comes close to that.

 

[Aexalon]

Sure, it would, but density can only do so much...

In order for a planet nine times the size of earth to have the same gravity at it's surface, it's density would have to be something like 2/3rds that of water... Saturn is the only planet in our solar system that comes close to that.

Not just close, but over that, really ... Saturn's surface (if it had one) gravity is 0.914g. To build a solid-surface world with that size would necessitate something like Ringworld's scrith (except that scrith is written as having incredible resistance to tensile stress, while you need something with similar resistance to compressive stress for this world).

And it'd be mostly hollow, of course

 

[Angel Tarragon]

And it'd be mostly hollow, of course

Well, the world is definetely not hollow. It is honycombe with underdark tunnels and a few other places that are hollowed, just not the whole planet.

 

[The Grumpy Celt]

Are you writing hard-sci-fi, or fantasy?

Well, I don’t want to thread-hijack here – I was just chiming in. The planet in question will be orbiting B, which is yellow-orange in color rather than yellow-white. I thought this made an interesting aesthetic choice.

My understanding is the illumination provided by the other star, at night, at its brightest will be about that of an electric street light. But this will vary depending on the position of the inhabited planet as determined by rotation and revolution.

The larger planet may be a larger rocky body or as small a gas planet as they come, I’ve not made up my mind. The inhabited planet is smaller than Earth, but is more dense so as to have about 85 to 90 percent Earth gravity.

I’m aiming for hard science fiction, but it will have fantasy elements – basically a scientist will pop up and be able to explain some things, but will be clueless about others. In part, the planet was apparently terraformed by aliens 6,000 years ago (with a Pliocene epoch biosphere – what can I say, I like mammoths), and then the aliens put people on it about 1,000 years ago. And no one (except the now absent aliens) knows why or how.

But back to you…

I think it is interesting your doing this, paying attention to this level of detail. So few fantasy writer/DM/Whatnot bother with that kind of foundation or background.

Given that it is a titan/tree and composed of islands rather than a rocky body, the planet cannot have a functional magnetosphere; i.e without a flowing, liquid metallic core it could not generate the magnetic current needed to inhibit solar radiation to levels tolerable by life as we know it. I take the titan/tree deals with the solar radiation.

How do the individual islands retain water? Unless they are bowl shaped, then water will flow out of them as it runs down hill.

I think the longer and more unusually day-night cycles are more interesting but they are more distinct from that of Earth and the familiar.

Is there is a special calendar or system for measuring time in the setting?

 

[Aexalon]

Well, I don’t want to thread-hijack here – I was just chiming in. The planet in question will be orbiting B, which is yellow-orange in color rather than yellow-white. I thought this made an interesting aesthetic choice.

My understanding is the illumination provided by the other star, at night, at its brightest will be about that of an electric street light. But this will vary depending on the position of the inhabited planet as determined by rotation and revolution.

The larger planet may be a larger rocky body or as small a gas planet as they come, I’ve not made up my mind. The inhabited planet is smaller than Earth, but is more dense so as to have about 85 to 90 percent Earth gravity.

I’m aiming for hard science fiction, but it will have fantasy elements – basically a scientist will pop up and be able to explain some things, but will be clueless about others. In part, the planet was apparently terraformed by aliens 6,000 years ago (with a Pliocene epoch biosphere – what can I say, I like mammoths), and then the aliens put people on it about 1,000 years ago. And no one (except the now absent aliens) knows why or how.

So, 0.7 AU from Alpha Centauri B ... that varies the intensity of Alpha Centauri A between 4.6 and 7.3 magnitudes lower than the "sun", and the energy input when closest is some 1.2% higher then when furthest. I have no idea how bright street lights are (not on a scientific level, I mean), but 1.2% of variation over an 80y period is going to have some climatological effects (to compare, since the Maunder Minimum in the Little Ice Age some 300y ago, physicists estimate the increase in solar output between 0.1 and 0.6%).

But back to you…

I think it is interesting your doing this, paying attention to this level of detail. So few fantasy writer/DM/Whatnot bother with that kind of foundation or background.

Given that it is a titan/tree and composed of islands rather than a rocky body, the planet cannot have a functional magnetosphere; i.e without a flowing, liquid metallic core it could not generate the magnetic current needed to inhibit solar radiation to levels tolerable by life as we know it. I take the titan/tree deals with the solar radiation.

How do the individual islands retain water? Unless they are bowl shaped, then water will flow out of them as it runs down hill.

I think the longer and more unusually day-night cycles are more interesting but they are more distinct from that of Earth and the familiar.

Is there is a special calendar or system for measuring time in the setting?

Magnetically, Garden is entirely dependant on the gas giant it orbits. In keeping with the Jupiter analogy (which has a vast magnetic field with a strength of at least 10 times that of Earth), I'm far more worried about radiation coming from the planet, than about radiation coming from any of the system's stars. So, while I don't need the Worldtree to deal with the stars, I probably do need it to deal with the planet.

As stated above, since this is not a hard sci-fi project, we're capable of fielding spelljammer physics, where each of these small worldlets nevertheless maintains reasonably strong gravitational fields (varying between 0.5g and 1.5g) on their own, with an abrupt cut-of point some 5km above the surface of the worldlets. The worldlets share a common atmospheric envelope, but due to the dimensionally fractured nature, atmospheric attenuation is comparable to that of Earth.

The basic timekeeping premise is 60 seconds per minute, 60 minutes per hour, 60 hours per day, and 60 days per year. We could go into details about the siderial and synodical periods of the various components, but only the latter are apparent to the inhabitants (so what if Garden orbits the planet siderially 61 times per year ... synodically that's 60 times, presuming everything spins the same way around). So far I've remained aware that the match between the day/night cycle and the planet's phases is entirely dependant on the longitude of the observer on an individual worldlet, and that the planet's phases make for an excellent Garden-wide timekeeping tool (as opposed to the solar cycle), greatly facilitating navigation on the side facing the planet.