[World Design] Implications of a longer day

[The Grumpy Celt]

..but 1.5% of variation over an 80y period is going to have some climatological effects...

I had not thought of that.

The longer day-night cycle and the more unusual patters are still more interesting, even in they are harder to keep track of. Also, the unusual patterns of night and day, light and darkness may allow for conjunctions (eclipses and the like) that are not possible in another system and these times might be terribly important to the people of Garden.

Lastly, larger bodies such as Jupiter also attract a lot of solar system debris, such as asteroids, dust, comets and so forth. Jupiter has rings, thinner than those of Saturn but they are still present. Does Garden have protection from these objects hitting it?

 

[Aexalon]

I had not thought of that.

Be sure to check out Helliconia. Also an example of a planet orbiting the dimmer of a pair of stars. In this case, the planet Helliconia orbits Batalix in 480 earth days, while Batalix orbits her bighter sister Freyr in 2500 earth years. The novels deal with how humanity (and the other alien species present, the Phagors) manages to cope with the vast seasonal changes Helliconia is subjected to, and how it changes civilisation.

The longer day-night cycle and the more unusual patters are still more interesting, even in they are harder to keep track of. Also, the unusual patterns of night and day, light and darkness may allow for conjunctions (eclipses and the like) that are not possible in another system and these times might be terribly important to the people of Garden.

The planning committee is currently considering putting the obliquity of Garden's orbital plane at 30 degrees relative to the planet's orbital plane. This should be sufficient to prevent eclipses outside the equinoxes. Depending on the choice of a year of 60 sidereal or 60 synodical days, and on the choice of Garden's position relative to the planet and the suns on the day of spring equinox, this means 2, 1, or no eclipses per year. Most likely two will be chosen. No decision on the orbital period of the 2 K-class stars has been made, nor on the A-class distant third, except that that one will likely be called "Vecanoi" (cookie for who gets the reference without Googling).

Lastly, larger bodies such as Jupiter also attract a lot of solar system debris, such as asteroids, dust, comets and so forth. Jupiter has rings, thinner than those of Saturn but they are still present. Does Garden have protection from these objects hitting it?

Some form of annular system has been contemplated by the planning committee. Continuing the utilisation of the Jupiter faximile, note that its ring system only extends to 226.000km. With Garden 531.000km out, its common atmosphere alone should be more than adequate in defending against the typical ring particles that still roam this far out. Also, moons tend to clear paths in ring systems, and not just by directly sweeping their orbit clear; through gravitational interaction, a moon effectively pushes ring particles away from it. As for other debris drawn in by the gas giant: Garden has only been around in this system for ten thousand years. The odds of getting hit by anything noticeable in this astronomically infinitesimal timeframe are negligeable.



Back on topic: additional circadian cycles.

• 40/20, midday activity.
  Advantages: Simple.
  Disadvantages: Monolithical (very long activity cycle).
  Applicability: Diurnal creatures.
• 40/20, midday rest.
  Advantages: Simple.
  Disadvantages: Monolothical (very long activity cycle).
  Applicability: Nocturnal creatures.
• 20/10/20/10, midday rest.
  Advantages: Evasion of midday heat / midnight cold
  Disadvantages: Significant waste of light.
  Applicability: Crepuscular creatures that for whatever reason don't like planetlight.
• 20/10/20/10, midday activity.
  Advantages: Decent use of light.
  Disadvantages: Elimination of sunsrise / sunsset as significant events in active part of cycle.
  Applicability: Bipolar society swapping from sunslight to planetlight mode every 30 hours.
• 30/10/10/10, full day activity.
  Advantages: High use of available light.
  Disadvantages: Dual cycle, moderately complex.
  Applicability: Creatures wanting to make maximal use of the available light; First step towards Medieval "segmented sleep".
• 3x12/8, midday rest.
  Advantages: High use of available light, evasion of midday heat.
  Disadvantages: Moderately complex.
  Applicability: Creatures wanting to make maximal use of the available light, but evade a very long day and the heat of midday; Fully realised Medieval "segmented sleep".
• 4x10/5, midday activity.
  Mock suggestion, fairly pointless.
• 5x8/4, midday rest.
  Mock suggestion, fairly pointless.

Thoughts?

 

[Pbartender]

Disadvantages: Elimination of sunsrise / sunsset as significant events in active part of cycle.

A note... You're going to have a similar problem with many of the cycles (Pattern C would as well, but with noon and midnight, instead of dawn and dusk). Of course, it also needn't be a problem.

Consider that midnight is still a significant time of day in the real world, even though it happens during the middle of the normal sleep cycle. If anything, that makes it a more mysterious and significant event, since it's not normally witnessed.

Under this sort of circumstance, dawn and dusk would take on a similar significance... Both would be very auspicious and superstitious events to witness. There could be religions and rituals based around those times of day.

It could be a wide-spread belief, for example, that the rising and setting suns allow the spirits of the dead to travel back and forth from the realm of the dead... To look directly into the sunrise or sunset as it is happening is to look through the gates of heaven/hell and imperils your soul to wander the mortal world forever as a ghost.

 

[Aexalon]

O-kay, thought it was time to nail down the system some more. All of you who can't stand numbers / math / science, skip this post

Requirements:

• Total solar intensity experienced at Garden (and thus also the planet) equivalent to that which we experience on Earth.
• Orbit a multiple of 60 Garden days (150 Earth days).

Some calculating lead to the conclusion that a 150 Earth day orbit will make those stars really puny indeed (e.g. 2 x Xi Bootes B, a K4 main sequence star), and worse, the orbit really tight (only 0.34 AU radius, which is rather close to 2 still fairly large stars).

So, the planning committee tried a 300 Earth day orbit. For this purpose, we tried a system consisting of Tau Ceti (a G8 main sequence star) and 82 Erdiani (another G8 main sequence star), which resulted in a satisfactory period of 290 Earth days at about 1.09AU. If we increase that distance to 1.11AU, we get the desired 300 Earth days at 0.998 sols luminosity. Since earlier discussions proposed the toning down of total energy input to spare the sunsward side of the worldlets, this seems to fit perfectly.

As for their distance and orbit, we know that they appear 0.44 degrees and 0.39 degrees wide in Garden's sky (for reference, both the sun and the moon be about 0.5 degrees wide in the Earth's sky). However, a decision about the rotational period (and therefore their distance) has been delayed until possible metaphysical side-effects can be assigned (or waved). One possibility is that otherwise-typically-daily abilities recharge during the conjunction of the 2 center stars (who are now slowly, desperately, seeking names).

For Vecanoi (the distant third), we chose a Sirius replica at 4927AU from the barycenter of the two central stars. This yields an orbital period of 216000 (60*60*60) times that of the planet around those same two central stars. At this distance, Vecanoi still manages a hefty relative magnitude of -8, or 25 times brighter than Venus at it's brightest in the earth's sky ( and 20 times fainter than the full moon). Closer orbits were rejected over the issue of introducing yet another significant light source in an already complex system.

So, in summary:

• The central suns are replica of 82 G Eridani and Tau Ceti, and look 0.44 & 0.39 degrees (respectively) across in the sky. Their separation & orbital period remains under debate.
• The planet, a Jupiter replica, orbits this pair in 120 Garden days, at a distance of 1.11AU, in the same plane the stars orbit each other in (the ecliptic plane). The planet's axial tilt be 30 degrees relative to this plane.
• Garden orbits the planet at 531Mm, taking 60 standard solar hours to do so. The orbital plane matches that of the planet's equator (30 degrees compared to the ecliptic), and Garden is tidally locked to the planet, resulting in a 60 standard solar hour day there. The planet looks some 16 by 15 degrees wide in Garden's sky, and might exhibit some faint rings no wider than 30 degrees. A full planet has about 4160 times the luminosity of a full moon (apparent magnitude -21.5), and results in some fairly decent "nocturnal" illumination, albeit bereft of almost any appreciable heat, at slightly less than 1% of the illumination provided by the suns.
• Some 4927AU away Vecanoi, a Sirius replica, stands, a mere 0.33 arc seconds across (pretty much a point), shining with a white-blueish light slightly dimmer than that of our full moon (apparent magnitude -11.8). The period of the system in which the two center stars orbit a common Barycenter with Vecanoi is around 216 thousand orbits of the planet around the core stars. Besides some barely noticeable shift in background stars over time, this motion is imperceptible relative to the planet.

And to finish up a short apology: Until now I've erroneously performed calculations presuming that 6 orders of magnitude equal a hundredfold increase in luminosity. Instead, it seems that that should be 5 orders of magnitude. Therefore earlier statements involving such things as comparisons of various objects with the moon's apparent luminosity may be severely off. I'll try to correct them (in red) in my previous posts when I have some time available.