Random Day/Night Length

[Astner]

You haven't actually presented a model where this might be plausible, so it's hard to comment on exactly what would be wrong with it.

We're not talking about a specific model but rather the plausibility of mathematically designing a model that fulfills the criteria set, to which there's no problem, as any trajectories in time are practically arbitrarily as shaped by gravitational focal points; moons, planets, and stars.

That said, I'm fairly confident there's no plausible physical model that would allow a planet to both have rapidly changing day-night cycles and have the planet also be habitable by aerobic carbon-based life.

That's an appeal to incredulity, an informal fallacy.

But feel free to present a model that would allow this.

Once more, we're arguing the plausibility of such a model, and not how it would look.

 

[Benjamin Clayborne]

We're not talking about a specific model but rather the plausibility of mathematically designing a model that fulfills the criteria set, to which there's no problem, as any trajectories in time are practically arbitrarily as shaped by gravitational focal points; moons, planets, and stars.

I don't know what that means, mostly because you've got some phrasing problems in that sentence that make its meaning unclear. ("practically arbitrarily as shaped"... what?)

I'm under the impression that we're talking about a particular trajectory for a planet, near one or more stars or other large celestial bodies, that would cause the planet to have day-night cycles of random, unpredictable duration. I'm having trouble imagining how such a system could exist, so perhaps you could elaborate in detail instead of just asserting vaguely that it's possible. Multiple stars in super-close orbits? Planets swinging close by each other to throw one another into other orbits? Planets that sometimes are swinging close by a star at high velocity, and other times are far away? How would such planets maintain a habitable state without their atmosphere either burning away or freezing solid?

Once more, we're arguing the plausibility of such a model, and not how it would look.

I'm asking you how it would look, since as far as I know, the plausibility of such a model is basically zero. Can you actually elaborate on the details of such a system?

 

[Astner]

I don't know what that means, mostly because you've got some phrasing problems in that sentence that make its meaning unclear. ("practically arbitrarily as shaped"... what?)

That's the point, I'm not trying to design a specific model but rather argue for the (theoretical) existence of such a model.

I'm under the impression that we're talking about a particular trajectory for a planet,

We're not.

near one or more stars or other large celestial bodies, that would cause the planet to have day-night cycles of random, unpredictable duration.

We're talking about virtual randomness, something that appears random because the model is so complex and not all variables are accountable for. Now a closed trajectory would would necessitate systematic repetition, however if it repeats every million or so years then it's going to be difficult to map. An open trajectory would not necessitate systematic repetition, since the planet would never be in the same point twice.

Multiple stars in super-close orbits?

No, that would eventually scourge the planet.

Planets swinging close by each other to throw one another into other orbits? Planets that sometimes are swinging close by a star at high velocity, and other times are far away? How would such planets maintain a habitable state without their atmosphere either burning away or freezing solid?

Even in our own solar system the distance between planets are immense in contrast to their diameters. Not that other planets are necessarily needed in this design, but you could design their trajectories to never cross the earth's location in space-time.

I'm having trouble imagining how such a system could exist, so perhaps you could elaborate in detail instead of just asserting vaguely that it's possible.

I'm asking you how it would look, since as far as I know, the plausibility of such a model is basically zero. Can you actually elaborate on the details of such a system?

I don't have the time to design such a model for this thread. But once again, we're arguing for the (theoretical) existence of such a design, and not how a specific design would look.

 

[Benjamin Clayborne]

I don't have the time to design such a model for this thread. But once again, we're arguing for the (theoretical) existence of such a design, and not how a specific design would look.

Okay, then. I don't think such a design is theoretically possible. I'm intrigued to see evidence to the contrary.

 

[Jared]

It doesn't have to stay in orbit for a full cycle, we're speaking of star system where stars are in orbits with each other. The orbits relative to a single star would never be elliptical.

The last time I read up on it, it wasn't believed that there were orbits where a planet could do figure-eight orbits around binary stars. The orbits that are stable are those where the planet is an elliptical orbit around one star and the other star is far out, or the two stars are close and the planet is much farther out and has an elliptical orbit around their barycenter.

In both of those situations, the days will not be randomly spaced. They will be periodic.

It wouldn't have to change the rotational speed, because what makes a day- and night-cycle is the rotational velocity relative to the orbit, which it wouldn't stay in for long to begin with.

You are technically correct, but the difference between considering the just the rotational period and the rotational and orbital periods together is pretty small until the (assuming prograde) rotational period approaches the orbital period.

And if you're doing this all through changing the orbit, what mass is going to be changing the orbit? The second star? Then you run into the issue of the figure-eight orbits.

Correction, within our solar system. We're not talking of a model anywhere close to our own.

Pet peeve: There is only one solar system, and that's the star system centered on Sol.

Serious comment: You haven't presented a model of a star system at all yet. You've been talking about broad generalizations and extrapolations made without real justification.

Once again, we're designing a new solar system not limiting us to our solar system.

Well the cosmic dust would have to be in orbit as well, but that can easily be modeled in.

You're missing the point, the cosmic dust would be an addition to the star system. To occlude undesired light and make the effects seemingly more unpredictable.

I'm not missing the point. I understand what you're saying. I'm just saying that I don't believe in its plausibility.

In space science, when we're considering a new planetary system, we look to what we already know exists and what we understand. When astrophysicists are looking at accretion discs, they look at mass loading and dust effects in the solar system (although I would say that they haven't been getting it quite right). This is how science works.

I'm just saying that, from my understanding of things, the star system would need to be in a nebula to get the kind of densities that you need; the star would need to to be moving quickly relative to the background dust to keep the star and planets from clearing the dust out; and the dust would have to be highly structured (going from zero density to really high density) on scale lengths of AU, compared to the light-year scale lengths of the nebula (ratio of 0.001%, extremely fine structure).

I seriously doubt the plausibility of that. And if it were possible, then I have serious questions about the impact on the planet. That would be dumping a lot of dust on the upper atmosphere.



In the end, I'm still with Benjamin on this one: I'd be interested in seeing a model of how any of these can work but, until then, I doubt that it's possible.

 

[Steerpike]

You could always make it artificial if that works for the story. Modified Dyson sphere built long ago by a mysterious race. Current inhabitants don't even have to know that is what they have. I don't know why it would be built for random cycles, but you don't necessarily need a natural explanation .

 

[Astner]

The last time I read up on it, it wasn't believed that there were orbits where a planet could do figure-eight orbits around binary stars.

I'd like to see the source for that, because I have a feeling that you're misinterpreting it.

The orbits that are stable are those where the planet is an elliptical orbit around one star and the other star is far out

Prove it.

You are technically correct, but the difference between considering the just the rotational period and the rotational and orbital periods together is pretty small until the (assuming prograde) rotational period approaches the orbital period.

First and foremost we work with two directions, the planetary rotation might be reverse to the orbital rotation. Secondly, the point was that we're dealing with the orbits as a variable.

And if you're doing this all through changing the orbit, what mass is going to be changing the orbit? The second star? Then you run into the issue of the figure-eight orbits.

What issue?

Pet peeve: There is only one solar system, and that's the star system centered on Sol.

Planetary system then, it's just semantics. In Sweden we use the same word for planetary system and solar system, my mistake.

Serious comment: You haven't presented a model of a star system at all yet. You've been talking about broad generalizations and extrapolations made without real justification.

The question we're discussing is: Could such a model exist?; Not: How would such a model look?

Just like you don't have to know detailed behavior of a certain function to prove certain attributes of it.

I'm not missing the point. I understand what you're saying. I'm just saying that I don't believe in its plausibility.

Well, your belief is not a factor in this debate.

In space science, when we're considering a new planetary system, we look to what we already know exists and what we understand. When astrophysicists are looking at accretion discs, they look at mass loading and dust effects in the solar system (although I would say that they haven't been getting it quite right). This is how science works.

No, observation is only part of science. We've never made any direct observations of a black hole for one, it's primarily a theoretical construction.

I'm just saying that, from my understanding of things, the star system would need to be in a nebula to get the kind of densities that you need;

Why?

the star would need to to be moving quickly relative to the background dust to keep the star and planets from clearing the dust out; and the dust would have to be highly structured (going from zero density to really high density) on scale lengths of AU, compared to the light-year scale lengths of the nebula (ratio of 0.001%, extremely fine structure).

Instead of picking numbers of off Wikipedia, get to the point. What's the problem?

I seriously doubt the plausibility of that. And if it were possible, then I have serious questions about the impact on the planet. That would be dumping a lot of dust on the upper atmosphere.

Once again, your belief has nothing to do with the debate. You either provide evidence, or you don't.

In the end, I'm still with Benjamin on this one: I'd be interested in seeing a model of how any of these can work but, until then, I doubt that it's possible.

I'm sorry, but that's not how debating works. One piece of evidence is worth more than a billion opposing opinions.

 

[Benjamin Clayborne]

The question we're discussing is: Could such a model exist?; Not: How would such a model look?

I'm going to say, once again, no. Such a model cannot exist.

Once again, your belief has nothing to do with the debate. You either provide evidence, or you don't.

I'm sorry, but that's not how debating works. One piece of evidence is worth more than a billion opposing opinions.

It's strange how you demand evidence for our position, when you in fact haven't provided a single shred of evidence that such a model could exist.

 

[ThinkerX]

Like I said earlier a 'world' that is actually a close orbiting, slowly rotating moon of a gas giant should produce most of the effects the OP is after and still be credible from a science POV.

(But after repeated migrane headaches trying to puzzle things through, I gave up on the concept.)

 

[Benjamin Clayborne]

Like I said earlier a 'world' that is actually a close orbiting, slowly rotating moon of a gas giant should produce most of the effects the OP is after and still be credible from a science POV.

(But after repeated migrane headaches trying to puzzle things through, I gave up on the concept.)

Close-orbiting a gas giant would be pretty obvious: most of the time there's a huge planet blocking half the sky... but it's also going to be a very regular, predictable process.

 

[ThinkerX]

Close-orbiting a gas giant would be pretty obvious: most of the time there's a huge planet blocking half the sky... but it's also going to be a very regular, predictable process.

If you also assume that the moon is rotating on its axis with a period equal to say...half or a third of its orbital period of the gas giant...you get a day/night cycle so complex it might give the (false) appearance of being random. The trick would be to have the moon orbiting just far enough out so its not tidally locked.

Depending on just what the rotational period of the moon is, and the duration of the orbit about the gas giant, you could end up with periods of protracted darkness...or daylight...or a series of fairly short day/night intervals.

But then again, I gave myself some serious headaches trying to puzzle this one out.

 

[Carl]

Thanks for the replies.

I wasn't thinking of a scientific reason. My first idea was of a realm, something that wasn't a typical planet and actually had a completely random rising of the sun and moon. The sun and moon would actually be two warring gods; whoever had the upper hand at the time would have their object (the sun or moon) dominate the sky.

This answers the original question you had. The two warring gods makes your idea completely feasable without having to go into complex scientific equations to model the planets path through a complex solar system. Keep it simple so that you don't lose your audience just describing the night sky.

I think your idea would make for an interesting world where anything would be possible.

 

[Jared]

Astner, I understand that on the internet, there are no faces or intonation. All you have is text. It is very easy to read tone into just words that are not meant.

But.

I find no way to read what you wrote to me in any light that does not go from abrasive to insulting to offensive.

Well, your belief is not a factor in this debate.

Instead of picking numbers of off Wikipedia, get to the point. What's the problem?

Once again, your belief has nothing to do with the debate. You either provide evidence, or you don't.

When I say things like "the way I understand it" or "I don't believe that that's true" or "I think that there might be another explanation for that," I am not hedging because I am uncertain. I phrase things like that because it's more polite than the blunt "this is wrong."

It is also the way that people in my field speak. I sometimes forget that not everyone speaks that way and it can cause confusion.


I picked up these speaking habits in the same place that I picked up the numbers I tossed out and the lingo that I used. It wasn't on Wikipedia, it was in graduate school when I was earning my doctorate in Space Physics.

Space Physics is the field that deals with things like dust in a planetary system. We strongly overlap with planetary scientists, who investigate topics like planetary formation, stable orbits, and orbital variations. (My Bachelor's in Geology makes this a bit easier since I already am familiar with Earth's formation and evolution.) This discussion thread lies fully within the realm of science that I've spent more than a decade studying.

I was trying to be polite and to not assert myself as a definitive authority because of my degrees (because I'm not, even though I know much more than the vast majority of people). But when you essentially call me disingenuous, ignorant, and a liar, I will set aside that inclination.


Astner, I strongly suggest that you walk away and calm yourself.

 

[Astner]

Astner, I understand that on the internet, there are no faces or intonation. All you have is text. It is very easy to read tone into just words that are not meant.

But.

I find no way to read what you wrote to me in any light that does not go from abrasive to insulting to offensive.

I'm not being offensive, I'm being direct. Belief is a non-factor in debate. You present- and explain your evidence and leave it at that.

Furthermore you're presenting numbers with five- or six significant figures which is of absolutely no relevance to the topic — numbers you more than likely attained from sites such as Wikipedia despite your educational background. Which further speaks of your unwillingness to concede on a topic you clearly did not initially grasp as you time after time again requested a specific model as verification for the existence of such a model.

When I say things like "the way I understand it" or "I don't believe that that's true" or "I think that there might be another explanation for that," I am not hedging because I am uncertain. I phrase things like that because it's more polite than the blunt "this is wrong."

It is also the way that people in my field speak. I sometimes forget that not everyone speaks that way and it can cause confusion.

Don't. If you find something wrong then you explain why you think it's wrong. You don't focus on the semantics worrying about offending me and then neglect to mention your reasoning for why it's wrong.

I picked up these speaking habits in the same place that I picked up the numbers I tossed out and the lingo that I used. It wasn't on Wikipedia, it was in graduate school when I was earning my doctorate in Space Physics.

That's funny because I recall when earning my Master's in Fundamental Physics people tended to be very direct. If you misused a Lie group while deducing symmetric relations in Yukawa couplings you'd have the error pointed out — and explained — the moment it was noted by a classmate or a professor, and no one would get offended by this.

I can't confirm or disconfirm your claims to an educational background and while I have my suspicions those are neither here or there.

Astner, I strongly suggest that you walk away and calm yourself.

And I'll suggest that you stay on topic, as for now you've only managed to derail the thread ignoring every argument of my reply. You'll either address the reply properly or I'll take it as a concession.

Besides, I'm not the one who just spent half a page complaining about how offended I got when someone constructively criticized me for using fallacious arguments and irrelevant numbers. You are.

 

[Benjamin Clayborne]

Besides, I'm not the one who just spent half a page complaining about how offended I got when someone constructively criticized me for using fallacious arguments and irrelevant numbers. You are.

*puts on moderator hat* This is getting personal and extremely off-topic. Any discussion about personal attitude is going to stop right now.

*takes off moderator hat* I'm still waiting for evidence supporting the assertion that a model can exist that allows for random day-night lengths.

 

[Steerpike]

*takes off moderator hat* I'm still waiting for evidence supporting the assertion that a model can exist that allows for random day-night lengths.

All you need in your model is a deity who actively intervenes in the universe and implements the random cycle. So take any model of a solar system you like, draw a box somewhere, write the word "deity" in it, and you're done

 

[Jared]

And I'll suggest that you stay on topic, as for now you've only managed to derail the thread ignoring every argument of my reply. You'll either address the reply properly or I'll take it as a concession.

All right. Let's start over.

You've stated that something is scientifically plausible. The burden of proof is thus on you. I then respond to your evidence.

To that end, I would greatly appreciate if you could collect and reiterate what arguments exactly I am supposed to respond to.

We are discussing a perfectly random day/night cycle where any day or night can last between (real world Earth) hours and days. You have suggested either complex orbits among multiple stars or cosmic dust. Here are my questions.


Dust
Are the grains orbiting the star? Why weren't they swept up in planetary accretion? Why haven't they collapsed in to the star from Poynting-Robertson drag or been pushed out from radiation pressure effects? Both of these effects work on short (compared to planetary lifetimes) time scales.

Any grains would be ionized, and thus vulnerable to pick-up by the stellar breeze/wind. In the solar system, ionization rates at Mars for molecules are something like 10^-6 /s. Given photoionization and stellar wind-driven ionization, ionization of the dust should be (much much) larger than 0.01% of that, but let's use that lower bound. In that case, the lifetime against ionization would be ~300 years. When a dust grain is ionized, it is removed by the stellar wind. So within ~3000 years, assuming a mature star and no other effects, all of the dust would be removed.

Are the grains restricted in star-centered distance? If not, why has keplerian shear not removed any coherent (integrated along the star-planet line) azimuthal structure? If so, how are they kept at one distance given that even small width lead to shearing on the scale of years (as seen by the dust)?

Is the dust coming off of objects orbiting inside of the planet? If so, how could they create a night over any appreciable region of the planet's surface?

How much dust would you need? I would start at a zeroth-order approximation where the minimum amount of dust is the number of micron-sized grains to fill a disk the size of the planet. If we take a planet with a radius of 6000 km (slightly smaller than Earth), then we'd require a little over 3x10^25 grains for any given occultation.

If we assume that the amounts of day and of night are equal and that the planet orbits at 1 AU, then we'd need [0.5 * 2 * pi * (1 Astronomical Unit) * (3x10^25 grains) * ((10^(-6) m)^3/grain) * (1000 kg/m^3)/ (12000 km) ~=] 10^15 kg of material at any given time (averaged over the lifetime of the random day/night). [The 1000 kg/m^3 is the density of water. A lowball for material and porosity.]

Remembering my estimation that all of the dust will be removed in 3000 years, if the star system is 3 billion years (for roundness) old, then ~10^21 kg of material must have been produced. That's over one percent the mass of Earth's Moon. This is an extremely rough estimate. It's assuming the dust is at the planet's orbit, it's lowballing the removal rate, it's estimating the density, it's a gross estimate of the size of the occulting particles. I would need to sit down and try this calculation for different configurations, but I think that the case only gets worse.

What is destroying any such massive objects near the sun and deploying the dust in such a broad pattern? If the random day/night started recently, what would have been it either occur smoothly over time or completely all at once (and spread out the dust in such a way that previously discussed issues are avoided)?



Notes.1: I have to head out, so I'll stop here for now. I have more questions about the effects of being within a super-star-system dust cloud. And about the planet flipping between stars.

You (Astner) asked before for me to prove that figure-eight orbits around binaries are unstable. Here's a quick link to NASA Goddard's website and a Bad Astronomy comment. If you have access to scientific journals, I can link doi's next time.

Useful things to consider for the two stars are Hill spheres, periodicities, slingshot effects, and linear combinations.



Notes.2: I did a quick check of my arithmetic, but I'm not infallible. If I made an error, please just point it out with what the correct value is.

 

[Carl]

Like I mentioned before and Steerpike mentioned in fantasy writing once the God or gods card is dropped your model is done. If this was a strictly Sci-fi book you would need some form of explanation for the randomness of it. As this original question stands I believe it has b
een answered.

 

[shangrila]

Yeah, honestly, I was never really looking for a scientific reason for it. I appreciate all the work the posters have put in to this thread and it's spawned more than a few ideas, but still, the original point was whether or not this idea was stupid. I'd seen random weather patterns and the like in conworlds before, but never something as radical as what I've suggested here and I was worried that it would come off as contrived, stupid or lame.

It's good to know it's not any of those, judging from the positive comments. So...thread objective achieved. Cheers

 

[Astner]

*takes off moderator hat* I'm still waiting for evidence supporting the assertion that a model can exist that allows for random day-night lengths.

I've addressed that earlier.

All right. Let's start over.

You've stated that something is scientifically plausible. The burden of proof is thus on you. I then respond to your evidence.

The evidence is that you're able to model the trajectory of the planet arbitrarily due to it being an overdetermined system. It's called the generalized- or weighted n-body problem.

We are discussing a perfectly random day/night cycle where any day or night can last between (real world Earth) hours and days.

Define random.

aDust
Are the grains orbiting the star?

Not necessarily, but your arguments are rather easy to address.

Why weren't they swept up in planetary accretion?

Because the dust doesn't get close enough to the planets.

Why haven't they collapsed in to the star from Poynting-Robertson drag or been pushed out from radiation pressure effects?

Free-body diagram balance between the two, assuming that the dust doesn't leave the planetary system.

Any grains would be ionized, and thus vulnerable to pick-up by the stellar breeze/wind. In the solar system, ionization rates at Mars for molecules are something like 10^-6 /s. Given photoionization and stellar wind-driven ionization, ionization of the dust should be (much much) larger than 0.01% of that

Why?

Are the grains restricted in star-centered distance?

Not necessarily, no.

If not, why has keplerian shear not removed any coherent (integrated along the star-planet line) azimuthal structure? If so, how are they kept at one distance given that even small width lead to shearing on the scale of years (as seen by the dust)?

Why would the dust have to be in a stable trajectory around one star? The sole purpose of the dust is to bloat out star-light, not to remain in orbit around a single star for years or decades. In fact the planet in question will leave the

Is the dust coming off of objects orbiting inside of the planet? If so, how could they create a night over any appreciable region of the planet's surface?

No.

How much dust would you need? I would start at a zeroth-order approximation where the minimum amount of dust is the number of micron-sized grains to fill a disk the size of the planet. If we take a planet with a radius of 6000 km (slightly smaller than Earth), then we'd require a little over 3x10^25 grains for any given occultation.

If we assume that the amounts of day and of night are equal and that the planet orbits at 1 AU, then we'd need [0.5 * 2 * pi * (1 Astronomical Unit) * (3x10^25 grains) * ((10^(-6) m)^3/grain) * (1000 kg/m^3)/ (12000 km) ~=] 10^15 kg of material at any given time (averaged over the lifetime of the random day/night). [The 1000 kg/m^3 is the density of water. A lowball for material and porosity.]

Remembering my estimation that all of the dust will be removed in 3000 years, if the star system is 3 billion years (for roundness) old, then ~10^21 kg of material must have been produced. That's over one percent the mass of Earth's Moon. This is an extremely rough estimate. It's assuming the dust is at the planet's orbit, it's lowballing the removal rate, it's estimating the density, it's a gross estimate of the size of the occulting particles. I would need to sit down and try this calculation for different configurations, but I think that the case only gets worse.

Three millennia is more longer than the earth would stay in orbit around one star. Furthermore the trajectory of the dust can be modeled too and may well have entered the solar system past with or after the planet in question did.

Notes.1: I have to head out, so I'll stop here for now. I have more questions about the effects of being within a super-star-system dust cloud. And about the planet flipping between stars.

I hope they are more relevant than your previous ones that build upon a specified

You (Astner) asked before for me to prove that figure-eight orbits around binaries are unstable. Here's a quick link to NASA Goddard's website and a Bad Astronomy comment. If you have access to scientific journals, I can link doi's next time.

Look up Kepler-16b.

Other than that, yes, I'd like to see these journals.

Though I wouldn't argue that stability is a necessity like you're implying though, in fact I'd argue against it since a stable orbit would have a periodic behavior thus not emulating the random element desired.