Samanumata Newsletter 1 - May 16, 2015
summary/introduction
The new project aims at maximum realism, and intends to achieve this by adopting the consent-based decision procedure known as "sociocracy". Currently there are approximately 7 participants, but not all of them are active yet. Main discussion topics thus far have been:
- the limits posed by realism: How much can we deviate from Earth?
- the solar system: There is a proposal for a binary star system (which may sound exotic, but which is less exotic than Earth's large moon, for example, and which provides tides like Earth's moon).
- the planet: Should it be larger or smaller than Earth? And how much larger or smaller can it be?
- continents: Several participants have expressed a preference for one supercontintent (like Pangea) rather than several small continents.
In addition to these, a (minor?) topic that needs to be discussed is naming.
project basics
"Cornerstones" of the project are Realism and Sociocracy. Sociocracy is a decision-making procedure based on informed consent, and is the best procedure - within the context of geofiction - to reach maximum realism. These two "cornerstones" were introduced and briefly explained in two forum posts:
| quote: Lajos |
| Is there any interest in collectively creating a conworld ultimately evolving into an interaction project on roughly sociocratic principles?
What I mean (with that), is a project that takes Realism seriously (and thus severely limits the Autonomy of the Creator) and that designs everything from scratch in a (roughly) sociocratic process in which anything can be discussed and decisions are made only if no participant has reasonable objections. (A process like this is more or less implied by adherence to Realism, by the way.) |
| quote: Lajos |
To a considerable extent the "order of things" is fixed, I think.
There are some feedback, of course, which will necessitate going back to a previous step occasionally, but this seems to me the basic order. After all this is done, we can divide up the world and - while continuing discussion and feedback - further develop cultures, countries, etc. The main organizational principle of the design process is the consent principle: Decisions are made when there are no remaining "paramount objections", that is, when there is informed consent from all participants. Objections must be reasoned and argued and based on the ability of the objector to work productively toward the goals of the organization. |
There has been some discussion about realism and the margins for deviation from Earth in the old forum. There is considerable agreement that the margins are narrow, but not how narrow. One very important "thing" to keep in mind is that we're not designing a planet on which life is possible, but a planet on which humanoid life could/would have developed. That is a fundamental difference with far-reaching implications. It means that we cannot deviate much from the geographical, biological, physical, etcetera circumstance of Earth.
naming issues
The name of this newsletter has not been decided by the official procedure and therefore violates one of the cornerstones of the project. It's not a very serious violation, however, as we can easily fix this problem before future issues are "published". But it does point at a more general problem: for technical and organizational procedures we're going to need names. Most urgent is probably a project name (which doesn't need to coincide with the planet name, if there is one), but when we start on plate tectonics, it's also going to be a lot easier if we can give plates and other features names. Hence, this is something that needs to be discussed.
The name "Samanumata" is also the temporary name of the new forum dedicated to this project.
solar system and planet
As implied by the rough setup, discussion has focused on astronomy and planetology thus far.
With regards to the solar system, of the various exotic ideas considered that of binary stars (i.e. two suns rather than one) turned out to be the most fruitful because it solves a problem with regards to tides, which are necessary because of the key role of coastal wetlands in the evolution of Earthly life. Earth's tides are mainly caused by Earth's excessively large moon, and such a large moon is much more exotic than a binary star, and is thus something that should be avoided in the planetary set-up if possible. An orbit around two stars can also cause tides, however, and with the right "settings" these can be of comparable magnitude. After much discussion, research, calculation, and simulation, "binary solar system - v1.0" was proposed.
Since then, discussion has focused on the size and density of the planet. A larger planet needs to be less dense to have similar surface gravity, but less density can only be the implication of a different composition, and a different composition may have very serious effects for physical geography.
binary solar system - v1.0
star 1
- mass: 1.818×1030 kg (91.4% of Sun)
- radius: 631,920 km
- density: 1720 kgm-3 (Sun = 1410)
- effective temperature: 5520 K (Sun = 5778 K)
- luminosity: 2.64×1026 (68.7% of Sun)
star 2
- mass: 1.765×1030 kg (88.7% of Sun)
- radius: 612,950 km
- density: 1830 kgm-3
- effective temperature: 5450 K
- luminosity: 2.36×1026 (61.4% of Sun)
the binary system
- distance between stars: 3.29×107 km (0.22 AU)
- orbital period (around common centre of gravity): 39.3 d (d = Earth days)
- eccentricity: still undetermined, but extremely low (due to close distance)
planet
- mass: approx. 6.09×1024 kg (102% of Earth)
- distance from centre of gravity of binaries: 1.714×108 km (1.15 AU)
- orbital period: 333.7 d (8.49 × orbital period of stars)
- lowest / highest / average solar flux density: 1343 / 1404 / 1382 (Earth = 1369)
- eccentricity: still undetermined, but preferably (very) low
- average tidal magnitude: 0.197 m (Earth = 0.268 m)
remarks and explanations
Most important is that the planet is approximately as warm as Earth and that the temperature fluctuation due to the binary system is as small as possible. To that end, the two stars need to be as close together as possible, and as similar in luminosity as possible, but there are limits to both.
The distance between the stars cannot be too small: if they have overlapping Roche Lobes, then they have significant exchange of mass with rather unpredictable results (one may slowly eat up the other, for example). Unfortunately, it is very complex to exactly calculate the size and shape of Roche Lobes. I'm fairly confident that at the distance given above, no significant exchange of mass occurs, but I'm not absolutely certain. The distance between the two stars should also be as small as possible (below 0.2 AU if they together would have one solar mass; they're considerably heavier, which should extend that margin a bit) to make planet formation possibile and to assure sufficient stability (and limited eccentricity).
Luminosity can be calculated on the basis of size and effective temperature of stars. Effective temperature is related to mass, but with considerable margins. For star 1, I find a target temperature of 5520K, but upper and lower margins of 5790 and 5280K, for example. Radius depends on density, which is also related to mass, but with even larger margins. Given that the two stars must have the same age and composition, it seems most likely that the dependency of temperature and density on mass is the same for both stars. For that reasons, I chose to use the "target" values that I got out of the formulas for estimating temperature and density, after calibrating those for the most accurate results for stars on the G/K boundary.
Solar flux density is the amount of energy a surface of 1 m2 in the orbit of the planet and directed at the center of gravity of the two suns would receive. In case of Earth this is called the solar constant, but it isn't very constant in this scenario, of course, although its pattern is completely regular. That pattern looks a bit like a sine wave, with every odd peak higher than every even peak:
- high peak (1404);
- valley (1343);
- low peak (1382);
- valley (1343);
repeated forever. The time between valley and peak is 10 days. The temperature difference at the face of the planet directed at the suns - everything else being equal - would be 1.2 degrees between the valleys and low peaks, and 1.8 degrees between the valleys and high peaks. Because these differences are rather small (much smaller than differences due to weather) it is very unlikely that they would have effects on climate. It should be noticed that if both stars are of equal size, there would be no different height peaks. The advantage of different size stars is that the highest peak only occurs once every 39 days. In addition to these effects, there are eclipses every 20 days, when one sun hides between the other. This will lead to a noticeable drop in the heat intensity of sunlight, but it will only last a very short time and will, therefore, have no significant effects. (However, it will almost certainly be the basis of the calendar.)
Tides, as mentioned, are essential for coastal ecosystems which played a key role in the evolution of life. Lacking a sufficiently large moon, this planet needs another source of tides, and the binary stars (which have a higher gravitational pull to solar energy ratio) provide this. In the current model, the average tidal amplitude is 73% of that on Earth, which should be sufficient.
In the current model, the planet is 2% larger than Earth, which results in 0.6% stronger surface gravity. We could opt for a slightly larger or smaller planet, but gravity should not be more than 1 or 2% stronger or weaker than on Earth because of its effects on water flow (incl. water in soils), plants, and animals.
What is still undetermined is the speed of the rotation of the planet and its moon(s), among others. The planet can have at most one moon that is visible with the naked eye, and even that moon will merely look like a very bright star. Rotation should probably not deviate much from Earth (i.e. is should be close to 1 d) because of potential effects on climate. I need to look into this further, but I think that a significantly faster or slower rotation would mess up Hadley cells, which would completely screw up climate.
Also yet to be determined are eccentricity and axial tilt. The first should be as minimal as possible, while the second can be a little more than in case of Earth, I think. At least, I see no immediate objection against slightly more extreme seasonal variation.
archived discussions
Because of technical problems, Geopoeia lost its old forums in early May 2015. The two active threads about the project have been saved and restored as wiki pages, however.