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Author Topic: Planet of Convicts - Subculture (Was: Short-Seasoned Planet)  (Read 4385 times)

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Offline TheGlyphstoneTopic starter

After a bit of poking around, question-asking, and general uncertainty, this seemed like the best place for this topic, it being of a strictly academic nature.

In a nutshell, I'm trying to create a planet for an RP (technically, an adventure arc for a sci-fi RPG) with some rather odd environmental conditions...specifically, I'm trying to have a world where seasons are shorter than 'normal' - one quarter of the year in spring, one quarter summer, one fall, and one winter, for however long one quarter of a year might be; what I want is shorter seasons, so that one solar year would, say, include two or more summer 'seasons'. I could always just say "aliens did it", but I want to base it at least partially in real astrophysics, hence my pleas to the learned minds of E. Axial wobbling? Elliptical orbit? Binary star system? I dunno.

TLDR: If I had unlimited power and wanted to modify Earth so that Spring/Summer/Fall/Winter only lasted for a month each, repeating three times before the planet finished a lap around the Sun, would it be possible?

« Last Edit: June 12, 2011, 02:21:50 PM by TheGlyphstone »

Offline Caeli

Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #1 on: June 11, 2011, 02:44:49 PM »
I'm no expert, but couldn't that be accomplished by having the earth move faster along its orbit? I'm assuming that the lengths of your days (determined by how fast the earth rotates) will not change, only your seasons; since seasons are determined by the tilt of the earth (on its axis) and its position along its orbit around the sun, shorter seasons of roughly equal length could be accomplished by making the earth move faster along its orbit.

Now, what I'm not sure about is whether being a certain distance away from the sun predetermines how fast you travel around it. But to my mind, shorter seasons would be accomplished by speeding up the earth, assuming that everything else (axial tilt, distance of orbit, etc.) remains the same.

Not sure about your TLDR, but if I try to think about it logically, I don't think it's possible. Might be different if it was a binary star system?

Offline Oniya

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Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #2 on: June 11, 2011, 02:56:00 PM »
With a standard planetary orbit (relatively low eccentricity), the seasons are due to axial tilt 'spreading out' the area that a given group of sunbeams lands on (insert traditional 'flashlight' demo here).  We're actually closer to the sun during the winter months than in summer.  Severe axial wobbling could give you the same effect, but I'm not sure how stable that would be in the long term.

A highly eccentric orbit would give you a greater variance in base temperatures (the overall average of both north and south hemispheres), but the times when the distance to the sun is closest would be shorter than the times when the distance to the sun is farthest, so the colder base temperature would last longer.

Binary stars would eclipse each other periodically, which would make the amount of solar radiation reaching the planet fluctuate - maybe if that was fast enough, then you'd have a faster set of 'seasons' (summer being when both suns were non-occluded, and winter being when one was eclipsed), but you'd have to set the planet far enough away that the dual sun didn't give you something like Tatooine.  I'm also not sure how stable the three-body orbit would be in that configuration.

Sorry, no real answers, but maybe a bit of data to chew on?

Offline gaggedLouise

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Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #3 on: June 11, 2011, 03:07:28 PM »
The seasons on earth do not depend on the actual stretch of the orbit, that is, they have nothing to do with the distance to the sun at given points in the orbit. The center of the earth is actually closest to the sun around New Year, and that means some parts of the surface are closest at that point too, even in the northern hemisphere, but of course that doesn't translate into warmer weather or more influx of heat. It's the tilt of the earth's axis that does it. Not easyu for me to explain either but it can be found in a decent book about geophysics. When the axis is titled away from the sun on the northen meuispehere, the sun is lower in the sky at noon and light comes in at a less sharp angle, so the rays will lose more heat. - I see Oniya nailed some of this too.

What you would need might be a planet whose axis tilt is changing over the course of a year. I'm not sure that would be stable in solar system terms. The direction of the axis of the earth is moving very slowly in a cruised circle around the polar regions of the sky. For the last thousand years or so it's been pointing very close to the Northern Star; in a couple thousand years time from now it will point at Vega. A full circle takes 26.000 years.

If the earth had no tilt at all but pointed at a straight angle to the plane of motion of the ecliptic (the "plane" where the planets are moving) we would basically have no seasons at all. But the shift in how many degrees it's tilted is very small during a turn of the 26.000 year cycle, the movement is around the sky, like a spinning top in a near circle, not up and down. I reckon a major variation in the size of the tilt (the declination of the axis) would have made the planet unstable a long time ago. It's hard to come up with anything that produces a double round of seasons but at the same time won't make the planet run out of orbit over time. Binary or triple star systems could work, but if the stars are both of them close enough to function as primary sources of warmth and light in a way that would sustain advanced life, then they would likely make the orbit of the planet unstable long before there were any intelligent beings or even large creatures on it.
« Last Edit: June 11, 2011, 03:13:57 PM by gaggedLouise »

Offline TheGlyphstoneTopic starter

Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #4 on: June 11, 2011, 03:09:59 PM »
The simplest solution is to just have a very short 'year', yeah. If all else fails, I can go with that.

If a heavy axial wobble would theoretically work, I might go with that - I don't need to be too concerned with things like long-term stability, because the concept only needs to make sense on the surface, or enough where it works when you squint and tilt your head sideways - it's not going to be published or anything. :)

Offline Oniya

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Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #5 on: June 11, 2011, 03:25:10 PM »
The seasons on earth do not depend on the actual stretch of the orbit, that is, they have nothing to do with the distance to the sun at given points in the orbit. The center of the earth is actually closest to the sun around New Year, and that means some parts of the surface are closest at that point too, even in the northern hemisphere, but of course that doesn't translate into warmer weather or more influx of heat. It's the tilt of the earth's axis that does it. Not easyu for me to explain either but it can be found in a decent book about geophysics. When the axis is titled away from the sun on the northen meuispehere, the sun is lower in the sky at noon and light comes in at a less sharp angle, so the rays will lose more heat. - I see Oniya nailed some of this too.

Yes, that's the 'classic flashlight' demo I was talking about. :-)  When I brought up the distance to the sun, I was thinking of an orbit that is much longer and flatter than our solar system has - closer to a comet-style orbit.  The planetary orbits (with the exception of Pluto) are actually quite close to being circular, which is why our seasons have no real dependence on distance from the sun.  The problem with that is that the further you get from the sun, the slower you go, so the 'summer' caused by being exceptionally close to the sun would be relatively fast compared to the 'winter' caused by being at the farther end.

Offline gaggedLouise

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Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #6 on: June 11, 2011, 03:31:21 PM »
Venus has a 225-day year but its own rotation - its "day/night" time - is heavily locked to the sun, so a diurnal period lasts for many months on end - it's even slightly longer than a Venus year! I'm not sure but I 'd reckon that must be more likely to happen the closer a planet is to its mother star, and so, the shorter its year.

Venus' axial tilt is just 3 degrees, as against 23 degrees for Earth, so it's never had that factor driving any seasons either.

It might work to presuppose a "wandering star" has come near the solar system you're constructing at this (late) phase in its history, and is slowly spinning through it. Not strong enough, or close enough, to pull the inner planets out of their orbits, but still important enough to alter the seasons on some of them because there is now a secondary source of light. Well, that could mean some parts of the planet almost never experience full night anymore...  :D


« Last Edit: June 11, 2011, 04:59:29 PM by gaggedLouise »

Offline TheGlyphstoneTopic starter

Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #7 on: June 11, 2011, 03:32:50 PM »
Hm....are trinary star systems possible? I'm picturing a reversal of the above situation that might result from two normal stars in a rotating orbit around a third star - a brown dwarf with almost no heat output, but enough gravity to keep a planet orbiting it in an elliptical path. If it works like I picture, that'd then give you two long summers and two short winters

Offline gaggedLouise

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Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #8 on: June 11, 2011, 03:45:33 PM »
Yes, triple star systems exist. Not that uncommon I think. I reckon the model you suggested now with a dark dwarf (a "dead star") at the centre would require it to be the heaviest star in the system, or it wouldn't be able to keep the two other stars in circular or near-circular  orbit around it. Not sure if you could have that unless there's some very special circumstances, normally a "sun-type" star would outweigh a tiny, dead black dwarf because the latter one has long since burnt all its gas fuel and/or suffered a severe explosion (a nova or supernova, which would kill any planet in the neighbourhood). So it couldn't really be the dynamic or gravitational center of the system. Unless it's something very special, a neutron star for example, but those are mostly formed after nova or supernova events.

Offline TheGlyphstoneTopic starter

Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #9 on: June 11, 2011, 03:51:02 PM »
Would a neutron star be able to hold a planet in orbit without sucking it in and obliterating it in the process, since by design it'd need the planet between it and the outer orbiting star pair for these effects to happen? It'd have to be a wandering planet that got scooped up by the star after said supernova, but I imagine it'd be a fine line between capturing into a stable orbit and gobbling it up entirely.


On a momentary tangent, since Venus was brought up - if Venus had a more palatable atmosphere, would it produce a planet of perpetual spring/summer?

Offline Oniya

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Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #10 on: June 11, 2011, 04:00:45 PM »
Would a neutron star be able to hold a planet in orbit without sucking it in and obliterating it in the process, since by design it'd need the planet between it and the outer orbiting star pair for these effects to happen? It'd have to be a wandering planet that got scooped up by the star after said supernova, but I imagine it'd be a fine line between capturing into a stable orbit and gobbling it up entirely.

You'd have to have the right orbital distance.  Basically, the planet's speed around the star or star grouping would need to be equal to the escape velocity at that distance.

On a momentary tangent, since Venus was brought up - if Venus had a more palatable atmosphere, would it produce a planet of perpetual spring/summer?

The tricky bit would be the back-side.  Venus's temperature is fairly constant because of the heavy atmosphere keeping all of the sun's energy in.  A less 'greenhouse' like atmosphere might not allow for the part of the planet that faces away from the sun to warm up enough (in the manner of Mercury.)  The most habitable area would be the 'twilight' area.

Offline TheGlyphstoneTopic starter

Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #11 on: June 11, 2011, 04:06:28 PM »
Maybe I should have been more clear - for 'palatable atmosphere', I meant something with more oxygen, and clouds of something other than sulfuric acid. The same sort of dense cloud cover, but with an atmospheric mix that could support human life.

Offline gaggedLouise

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Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #12 on: June 11, 2011, 04:46:02 PM »
Maybe I should have been more clear - for 'palatable atmosphere', I meant something with more oxygen, and clouds of something other than sulfuric acid. The same sort of dense cloud cover, but with an atmospheric mix that could support human life.

It's too dense to allow a planet of that kind (and that close to the sun) to support any advanced biology, at least the kind of evolution of life we know, anything in the way of the chain: marine life -> photosynthesis -> advanced green plants -> increased oxygen  -> larger animals -> intelligent life, etc. In the early times, the atmosphere of the Earth had next to no free oxygen and on the other hand, it's never been near as dense as the atmosphere of Venus is now. If Earth had had that kind of thickness to its cover it would have blocked the path to advanced life.Before the space age some astronomers thought Venus housed dinosaurs (or, um, similar creatures) but that's long since a gone idea.

But as a thought experiment: yes, if Venus had had a more earth-like atmosphere and kept the same low tilt of its axis, but also had a much shorter day/night period, it could, in theory, have had conditions of constant spring or summer.
« Last Edit: June 11, 2011, 04:49:21 PM by gaggedLouise »

Offline TheGlyphstoneTopic starter

Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #13 on: June 11, 2011, 05:22:01 PM »
If it helps any, the final concept is for this planet to be a dedicated farmworld (or agri-world, in setting parlance), so I'm trying to figure out ways to either maximize the growing season, or give the planet as many growing seasons as possible in a single 'year'.

Offline gaggedLouise

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Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #14 on: June 11, 2011, 05:33:46 PM »
If it helps any, the final concept is for this planet to be a dedicated farmworld (or agri-world, in setting parlance), so I'm trying to figure out ways to either maximize the growing season, or give the planet as many growing seasons as possible in a single 'year'.

It could be better to locate it on a moon orbiting a large planet. The planet might be maybe half, or one-third, of the diameter of Jupiter, but it would be much closer to its mother star than Jupiter is. the moon would have a much more eccentric orbit than most of the big moons in the solar system, maybe tilted vs the planet's equator too; that would give it some obvious variations both in its distance to their mother star and in its angle to her, but still keep it close enough all the time to sustain a rich biological life.

Offline Oniya

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Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #15 on: June 11, 2011, 05:50:01 PM »
Perhaps a semi-nomadic culture with established farms that they move between as the optimal growing season permits?  To put it in Earth terms, a farmer with a place in Kansas packs up after fall harvest and flies to Australia for spring planting.

Offline TheGlyphstoneTopic starter

Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #16 on: June 11, 2011, 05:54:51 PM »
It could be better to locate it on a moon orbiting a large planet. The planet might be maybe half, or one-third, of the diameter of Jupiter, but it would be much closer to its mother star than Jupiter is. the moon would have a much more eccentric orbit than most of the big moons in the solar system, maybe tilted vs the planet's equator too; that would give it some obvious variations both in its distance to their mother star and in its angle to her, but still keep it close enough all the time to sustain a rich biological life.

That could work.

As for the culture, the planet in question is also part of a galactic-scale empire, so I can put whatever sort of culture I want on it (at the moment, it's a combination farmworld/prison planet, staffed by death row convicts on commuted sentences)...but I like the concept of the rotating farms regardless.

Offline Shjade

Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #17 on: June 11, 2011, 05:55:36 PM »
I'm curious as to the importance of having these seasons counted as a single year. What's the difference to farmers if they have 4 seasons in 4 months out of a 4 month year or 4 seasons in 4 months three times in a 12-month year? The farming's the same either way.

Offline TheGlyphstoneTopic starter

Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #18 on: June 11, 2011, 05:59:58 PM »
I'm curious as to the importance of having these seasons counted as a single year. What's the difference to farmers if they have 4 seasons in 4 months out of a 4 month year or 4 seasons in 4 months three times in a 12-month year? The farming's the same either way.

Only because a 4-month year would mean the planet was whipping around its parent star at an absurdly fast speed. Mercury's year-length is roughly 3 months, and no habitable world could exist that close to a star. A cooler, non-yellow star (letting the planet orbit closer) wouldn't help, because then the orbital distance would be larger. The dictionary definiton of a year is "one trip around the sun/star", not "a cycle of seasons".
« Last Edit: June 11, 2011, 06:01:39 PM by TheGlyphstone »

Offline Oniya

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Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #19 on: June 11, 2011, 06:01:56 PM »
Either that, or the planet's moon goes around the planet slower.  The length of an earth-month was originally derived from the moon's cycle.

(Random, useless trivia)

Offline TheGlyphstoneTopic starter

Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #20 on: June 11, 2011, 06:08:36 PM »
Still, I can't get around this by playing semantics with the definition of 'year' - a year may be 12 lunar months, but it also happens to be 365.25 solar days - the planet would have to rotate incredibly slow.

Offline gaggedLouise

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Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #21 on: June 11, 2011, 06:14:49 PM »
Either that, or the planet's moon goes around the planet slower.  The length of an earth-month was originally derived from the moon's cycle.

(Random, useless trivia)

The months have become longer over time: the moon is increasing its distance In the age if the dinos, or still earlier, the months were shorter, just 25 or 23 days. You can see this in fossilized corals from those distant ages. I remember how thrilled I felt when I first read of this.

Actually I think trhe rotation of the earth is slowing too, so in let's say 200 million years the number of days would be lower than 365 - and we'd have only, like eleven new moons a year?

Offline gaggedLouise

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Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #22 on: June 11, 2011, 06:18:57 PM »
Still, I can't get around this by playing semantics with the definition of 'year' - a year may be 12 lunar months, but it also happens to be 365.25 solar days - the planet would have to rotate incredibly slow.

yes, but Oniya and me are using "year" of course in a sense that relates to the length of an orbiting of the sun on whatever planet it is. So one Jupiter year is twelve Earth years, and so on. If the world we're talking of is a moon, then its year is roughly equal to the time its planet will take to orbit its (main) sun; after all that star is the ultimate source of its warmth and its seasons.

Offline TheGlyphstoneTopic starter

Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #23 on: June 11, 2011, 06:21:30 PM »
True dat. So how would being a large moon around a planet - say, a gas giant - in the star's habitable zone affect its seasonal cycle?

Offline Oniya

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Re: Short Season Length (Astrophysics and Worldbuilding questions)
« Reply #24 on: June 11, 2011, 06:27:11 PM »
Now I think you're on to something.  Lunar periods are bit more variable (compare Deimos and Phobos to Earth's moon), and you could possibly arrange it so that the moon crosses between the planet and the star as many times as you want.  Behind the planet would be - if nothing else - a low light situation, not so good for growing - unless you have mushroom farms.  In front of the planet, you'd have more solar radiation -> better growing conditions.