Random Day/Night Length

[shangrila]

This is an idea I had recently, so I thought I'd put it up here and see what people think and, ultimately, if it's worth pursuing.

Basically, it's as the title says; days and nights are random in length. They could last for a few earth days, a week, or only a few hours (that would be the minimum). A group of people do their best to predict it but it's more of an educated guess than an actual prediction, like weather forecasting in real life.

So my question would be; is this idea somewhat plausible to you? Or is it just too stupid to bother with?

 

[Astner]

The right answer is: If it fits the story.

From a scientific perspective it could work if you had a number of stars orbiting each other and planets, specifically the earth, leaving and entering new orbits -- orbits more attuned with the planets own rotation would make the nights and days longer -- around these stars.

In a thief-like setting it could be amazing.

 

[Benjamin Clayborne]

I wouldn't try to explain how it works if you do this, although keep in mind that if a daytime period lasts only a few minutes, the sun is literally racing across the sky. You could watch the shadows move.

Astrophysically, there's no plausible way to make this happen; changing the rotational speed of a planet requires colossal amounts of energy that would probably rip it apart. If you do do this, I would just make it an accepted fact of the world and not dwell on it.

 

[Astner]

The only thing that's of significance is the angular velocity relative to the orbit. So if the orbit change, as in you have a number of celestial bodies to occasionally tear the planet from one orbit to another then that would present a new day and night cycle.

 

[shangrila]

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.

 

[Penpilot]

It's a cool idea, and I agree, with Benjamin, just state it as fact and get on with the story.

 

[ShortHair]

It might work if you had several objects in the sky, some giving off light, the others occluding light. In other words, "night" would only be an eclipse involving two or more objects on (apparently) random paths. The star system might have several suns and the planet several moons. Another possibility is one sun and an asteroid belt very close to the planet (but outside its gravity well).

 

[Astner]

It might work if you had several objects in the sky, some giving off light, the others occluding light. In other words, "night" would only be an eclipse involving two or more objects on (apparently) random paths. The star system might have several suns and the planet several moons. Another possibility is one sun and an asteroid belt very close to the planet (but outside its gravity well).

Good idea, cosmic dust could work well. Assuming he's going for a scientific explanation.

The point is, it's not scientifically impossible so it won't ruin the suspension of disbelief even if he decides not to explain it.

 

[Jared]

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.

I agree with Benjamin Clayborne in that you can't explain it scientifically. So don't try.

About his in-sky and shadow motion comment...Is the planet round? Are day and night global? Where does the sun go during the night?

Scientifically, the moon is bright because it's reflecting sunlight. Will your moon be emitting its own light, or still reflecting sunlight from somewhere else?

Regardless of the mechanics of the sun and moon, you might think about the effect on temperature and weather.

 

[Astner]

I agree with Benjamin Clayborne in that you can't explain it scientifically. So don't try.

Exactly how is my model unscientific by any means?

 

[Benjamin Clayborne]

I agree with Benjamin Clayborne in that you can't explain it scientifically. So don't try.

About his in-sky and shadow motion comment...Is the planet round? Are day and night global? Where does the sun go during the night?

Scientifically, the moon is bright because it's reflecting sunlight. Will your moon be emitting its own light, or still reflecting sunlight from somewhere else?

Regardless of the mechanics of the sun and moon, you might think about the effect on temperature and weather.

Not to mention its effects on culture... and sleep cycles. People probably wouldn't put much stock in scheduling things in advance that required daylight, since you never knew how many "days" away something was. Timekeeping would probably be a huge deal, since you can't use a common natural phenomenon like the sun to tell time. Thick curtains would be a highly desired item, to block out sunlight when you needed to sleep and it happened to be daytime.

 

[Benjamin Clayborne]

Exactly how is my model unscientific by any means?

Shifting planets into different orbits like that would most likely result in tidal forces that would destroy them. Any such system would still need to be fairly regular; you might see changes in day duration over the course of several years. A system where one day is four hours long and the next day is twenty hours long would be so chaotic that any planet in it would be quickly torn apart, or end up so close to a star that the surface temperature would be in the thousands of degrees.

Also there's the fact that rapidly and drastically changing the rotational speed of a planet will also tear it apart. The amount of energy involved in a planet's rotation is huge. Earth's rotational energy is 2.138×10[sup]29[/sup] J. (By comparison, the energy of a 1000 kg car moving at 44 m/s (~100 MPH) is about 968,000 J. The planet has 220,867,768,595,000,000,000,000 times as much energy.) Any force that could change that substantially on anything less than a geologic timescale would rip the planet in half.

 

[Jared]

Exactly how is my model unscientific by any means?

The only thing that's of significance is the angular velocity relative to the orbit. So if the orbit change, as in you have a number of celestial bodies to occasionally tear the planet from one orbit to another then that would present a new day and night cycle.

Any such system would still need to be fairly regular; you might see changes in day duration over the course of several years. A system where one day is four hours long and the next day is twenty hours long would be so chaotic that any planet in it would be quickly torn apart, or end up so close to a star that the surface temperature would be in the thousands of degrees.

Also there's the fact that rapidly and drastically changing the rotational speed of a planet will also tear it apart. The amount of energy involved in a planet's rotation is huge. Earth's rotational energy is 2.138×10[sup]29[/sup] J. (By comparison, the energy of a 1000 kg car moving at 44 m/s (~100 MPH) is about 968,000 J. The planet has 220,867,768,595,000,000,000,000 times as much energy.) Any force that could change that substantially on anything less than a geologic timescale would rip the planet in half.

To support Benjamin, Wikipedia puts the Moon's day-lengthening effect at 31 milliseconds per century.

Additional issues are that tidal forces fall off strongly with distance. If something were capable of doing this, it would be close (see: satellites, co-satellites, co-orbiters, or planet the object is a satellite of). And it would be relatively massive.

It might work if you had several objects in the sky, some giving off light, the others occluding light. In other words, "night" would only be an eclipse involving two or more objects on (apparently) random paths. The star system might have several suns and the planet several moons. Another possibility is one sun and an asteroid belt very close to the planet (but outside its gravity well).

Any object in the sky bright enough to make it seem like day would have to be a star in the star system. If they operate under the laws of celestial mechanics, they would have periodic cycles. They would not be random, as the OP requested. The only stable orbits (that we have been able to find) are those where a planet orbits one star closely and the others are distant, or the planet orbits closely-packed stars at a distance. For the former, the length of day would be be a function of time of the year and of year. For the latter, the length of day would be a function of time of the year (like on Earth), but would not be a 50-50 split at equinox at the equator.

Asteroids are too small to occult the sun. Even if they could (like our Moon does), occultations are short and periodic. They are also not visible over more than small regions of the planet's surface.

Good idea, cosmic dust could work well.

Two issues with this one.

First, dust densities are extremely low: optical depths for large structures within the solar system are below ~10^(-5). If you include molecules, then Enceladus' plume could occult ~10-15% of the light in a small region. But 10-15% in a small area is not night (by any definition). [The images of dense nebula and such appear opaque because they are huge-huge-huge, not because they dense.]

Second, you would need a way to create a large-scale structure that is unstructured. In the solar system, Enceladus', Io's, and Pheobe's dust rings are structured. Dust columns created by Saturn's and Jupiter's magnetospheres are very narrow and structured (mostly, I think). Dust spikes in the solar wind are very narrow, are moving with the solar wind, and are relatively rare.


Basically, any variation would basically have to be periodic, and there's really no way to do it on short time scales.

 

[Ghost]

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.

Your concept sounds really cool! I think the society's adaptations have to make sense for this world. Other than that, I wouldn't worry too much about plausibility. Making your characters believable goes a long way in balancing out the fantastic elements.

 

[Steerpike]

Have a bunch of pulsars around and something in the atmosphere that causes illumination when the pulsar is directed at the planet. Make the cycles variable.

 

[Benjamin Clayborne]

Have a bunch of pulsars around and something in the atmosphere that causes illumination when the pulsar is directed at the planet. Make the cycles variable.

Stop trying to make this plausible! Besides, pulsars are periodic and have very short cycle times. The longest known pulsar cycle is less than 10 seconds.

 

[Steerpike]

Stop trying to make this plausible! Besides, pulsars are periodic and have very short cycle times. The longest known pulsar cycle is less than 10 seconds.

I thought there were some irregular ones for some reason.

Just have a bunch of them, going slower than real ones, and with some that are irregular. Maybe you could have interference between any given two is they are both pointed at the planet at the right time, so that sometimes waves from neither reach the planet.

Plausible? No

 

[ThinkerX]

I once did the groundwork for a world which would have differing day/night intervals.

In my case, said world was a not quite tidally locked moon of a gas giant - so you'd get a long day/night cycle (a few days each) just from the moons orbit, which would be about a week, plus eclipses of varying length whenever the gas giant or another large moon came between the moon and the sun. I went so far as to have a mythology of sorts worked out about this relationship. After multiple migrane headaches I finally decided against it - though originally 'Falling Towers' was set on that world.

 

[Astner]

Shifting planets into different orbits like that would most likely result in tidal forces that would destroy them.

Not necessarily, no. It depends on how you model it.

Any such system would still need to be fairly regular; you might see changes in day duration over the course of several years.

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.

A system where one day is four hours long and the next day is twenty hours long would be so chaotic that any planet in it would be quickly torn apart,

No it wouldn't, and if it would it would be scourged before it would.

or end up so close to a star that the surface temperature would be in the thousands of degrees.

Once again, not necessarily, it depends on how you model it.

Also there's the fact that rapidly and drastically changing the rotational speed of a planet will also tear it apart. The amount of energy involved in a planet's rotation is huge. Earth's rotational energy is 2.138×10[sup]29[/sup] J. (By comparison, the energy of a 1000 kg car moving at 44 m/s (~100 MPH) is about 968,000 J. The planet has 220,867,768,595,000,000,000,000 times as much energy.) Any force that could change that substantially on anything less than a geologic timescale would rip the planet in half.

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.

To support Benjamin, Wikipedia puts the Moon's day-lengthening effect at 31 milliseconds per century.

Additional issues are that tidal forces fall off strongly with distance. If something were capable of doing this, it would be close (see: satellites, co-satellites, co-orbiters, or planet the object is a satellite of). And it would be relatively massive.
Two issues with this one.

Do you know why that is? Because the moon has an inertia on earth's rotation. Which is irrelevant to the current system.

First, dust densities are extremely low: optical depths for large structures within the solar system are below ~10^(-5).

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

If you include molecules, then Enceladus' plume could occult ~10-15% of the light in a small region. But 10-15% in a small area is not night (by any definition). [The images of dense nebula and such appear opaque because they are huge-huge-huge, not because they dense.]

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

Second, you would need a way to create a large-scale structure that is unstructured. In the solar system, Enceladus', Io's, and Pheobe's dust rings are structured. Dust columns created by Saturn's and Jupiter's magnetospheres are very narrow and structured (mostly, I think). Dust spikes in the solar wind are very narrow, are moving with the solar wind, and are relatively rare.

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

Basically, any variation would basically have to be periodic, and there's really no way to do it on short time scales.

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.

 

[Benjamin Clayborne]

Not necessarily, no. It depends on how you model it.

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