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How is it possible to have a habitable planet where there are patterns of light and dark so erratic, it almost seems random (with a leaning towards greater periods of darkness than light)?

For example, you might have several hours of light followed by 20 hours of night, 5 hours of dawn, 10 hours of weak daylight, and then 3 hours of night, 12 hours of strong daylight, followed by 54 hours of darkest night?

What manner of strange things could be in a solar system to produce such erratic day/night periods? What "things vast enough" can block the main source/s of light?

Follow-Up Edits * Firstly, thank you for the welcomes; very much appreciated along with the responses.

Context of Question: For a fantasy world (read with Magic) more than Hard Sci-fi. This is more because I lack the astro-mathematical talent, have an interesting idea, but need to make sure it will pass casual muster.

Zxyrra - Re: seemingly random I suppose what I am seeking is a pattern so complex that it could not be correctly predicted in the mid to long term; even by a fairly sophisticated civilisation. It becomes a phenomenon where scholars, priests, prophets, and the everyday person all have different perspectives on what will happen. By saying "seemingly random", I suppose I am looking to lean upon a lack of certainty. Thank you for the link: I am a fan of GRRM's world. :)

Mikey - Re: temporary/stable I had not looked to pin this down in my mind; but I suppose having it as a several-centuries old phenomena creates an interesting tie-in with other aspects of the setting.

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    $\begingroup$ Welcome to Worldbuilding SE! Interesting first question. Consider that physics adhere to "causality" which means "If it happens, something caused it". Therefore, saying "it almost seems random" is really, really hard to do! If something is happening to change the light period, it can observed, and it can be predicted - so it is not random $\endgroup$ – Zxyrra Nov 17 '16 at 4:57
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    $\begingroup$ Some answers here may be relevant $\endgroup$ – Zxyrra Nov 17 '16 at 5:00
  • $\begingroup$ "Was that's the neutron stars shower? We're so busted!"😱 $\endgroup$ – user6760 Nov 17 '16 at 7:35
  • $\begingroup$ Hi and welcome - good question; as a follow-up, is this a temporary thing (a few centuries) or a slightly more "stable" thing (it's been 'random' for millions of years)? $\endgroup$ – Mikey Nov 17 '16 at 22:37
  • $\begingroup$ Probably an elliptical, flower-like orbit would have weird results combined with the rotation of the planet (but for that to happen the planet would be extremely fast and near the star, and that's not good) $\endgroup$ – JackIta Nov 24 '16 at 7:41
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Here are some thoughts to consider:

1- Very thick clouds. Also, several layers of clouds instead of just one layer. These would block the sunlight enough to create an artificial night.

2- A lot of moons. Large sized ones. Also they ought to be located at great distances from the parent planet so that their orbital velocities are quite low. Thus making solar eclipses quite the more likely, and also making them last much longer, since the eclipsing moon would take longer to move away.

3- Consider making it a binary planet system so that the other planet would also have its share in eclipsing the parent star and adding more to the night time.

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    $\begingroup$ Along the same lines maybe the planet is close to an asteroid belt? Or maybe the planet is a moon of a larger planet that has rings? $\endgroup$ – jomki Nov 17 '16 at 5:50
  • $\begingroup$ @jomki: I have a notion that OP wants a habitable planet. In order to have asteroid-belt eclipses, the asteroid belt would have to be quite near to the planet, making complex life extremely unlikely to take hold on the planet. While I do like the notion of a large moon of a gas giant, that would only create a long lasting night when the sun is eclipsed by the parent planet, and not the type of erratic daylight-night pattern as required by OP. $\endgroup$ – Youstay Igo Nov 17 '16 at 5:54
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A binary moon system where the moons are planet sized objects orbiting, for example, a gas giant planet. Also, if the two moons have extreme inclinations with respect to their planetary system's primary star(s). The possible plurality for the primary star includes the possibility that instead of a single primary star if there is a close binary star at the centre of the system.

This proposed system of a binary moon with a highly inclined orbit to its primary star or possible binary star pair, and which orbits a gas giant. A planet in this system will experience a complicated and continuously shifting day and night cycle. The variably between day and night wouldn't random, but it will complicated and changing all the time. Presumably, the pattern of days and nights will repeat, but this may take place over a long period.

This is more of a conceptual model for a planet with erratic day-night cycles. Whether such a system would be gravitationally stable is an open question. It wouldn't be surprising if someone with better knowledge of orbital mechanics demonstrated this complex system would come crashing down.

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    $\begingroup$ There is an astronomical problem about this configuration. To have quickly changing day/night patterns, moons will have to orbit the gas giant considerably closer. This means the moon may have to fall within the Roche limit. Also minor problem: if the habitable moon has oceans, you might expect very high because of the very close gas giant. $\endgroup$ – sampathsris Nov 17 '16 at 10:28
  • $\begingroup$ @Krumia Most of day-night variability I assumed would come from the binary moons orbiting each other, and the inclination of their orbital plane to their star(s). Being close to their primary planet would help. Very high what? As in "you might expect very high because of the very close gas giant". I did expect this configuration could have problems. Everyone's welcome to shoot it down. $\endgroup$ – a4android Nov 17 '16 at 11:01
  • $\begingroup$ Sorry, it should be very high tides. $\endgroup$ – sampathsris Nov 17 '16 at 11:55
  • $\begingroup$ @Krumia Thanks for the clarification. Your comment raised good points. $\endgroup$ – a4android Nov 17 '16 at 11:58
  • $\begingroup$ Also, don't forget that in case you are orbitting an object much, much heavier than yourself (aka a gas giant) you would very likely get tidally locked with it, making the planet highly unfriendly to complex life. Reasons include extreme temperature difference, lots and lots of radiation damage, high likelihood of other objects (moons and asteroids/comets) crashing into you, extreme volcanism due to tidal heating and extreme temperature difference between day and night sides. $\endgroup$ – Youstay Igo Nov 18 '16 at 5:15
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Remains of incomplete Dyson sphere left by advanced civilization inhabiting the planet some millions years ago, but died out, or alien civilization who just stopped by to harvest the star.

Several huge "chunks" of stuff eclipsing the sun, combined with natural day and night cycle, should "seem random" up until your civilizations fashions a telescope fit for solar observation.

It's somewhat more likely in a world "with Magic", and possibly adds fun plot element. "Aliens" can easily be replaced with visitors from other dimension, as long as they enjoy star energy.

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Chaotic tumbling instead of rotation on an axis. This is literally what you describe! The sun may rise from any point on the horizon, and can’t even be predicted very far ahead.

This is a real thing. See, most famously (for being the first to be seen doing this), Hyperion.

What you need is to set the stage for unstable axis of rotation by having three distinct principal moments of inertia.

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This is reminiscent of George R. R. Martin's scheme of plurianual seasons - just, instead of "the Winter is coming", the Starks would say "the Night is coming"...

A truly random pattern requires magical explanations. The rotational speed of the planet is variable, which is physically impossible, so magic (or some futurish sounding pseudo-science) is required. Unless it isn't a planet, but an asteroid of irregular shape, as implied in JDługosz's answer, in which case it isn't likely to be habitable - if it doesn't collapse into a sphere it also won't be able to retain an atmosphere.

Other solutions will give you complex, but predictable, patterns of light and shade: big or many moons, elongated orbits, huge or variable axial tilt, a huge gas giant between the planet and its sun... or the planet itself being a satellite of a gas giant. Elongated orbits, or out-of-the-planetary-plane orbits may help (imagine that the planet has a big moon that orbits ir perpendicularly to the planet's orbit around its sun, for instance), strong and quick precession or nutation. Or the central star could have different light intensity in each of its sides. Perhaps it has a dark side... These solutions, however, have the unfortunate feature of implying long periods of darkness, not exactly compatible with what we would ordinarily call a "day".

I am not sure that a planet with an extremely irregular pattern of light and shade will be able to originat life, though. The base of the ecosystem has to somehow produce energy without predating other living beings. The obvious source for that is solar energy, with other sources (geothermal, basically) being too feeble to sustain a complex ecosystem. If sunlight isn't plenty, it may be impossible to sustain such an ecosystem, too. Plus, extended periods of dark are also extended periods of cold; if those are too long, water may freeze worldwide; conversely, extended periods of light are extended periods of heath, which could cause water to boil, or, even at lower temperatures, proteins to denaturate.

Evidently you can handwave all those problems away, or invent magical or complex pseudo-scientific explanations.

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