Saturday, September 18, 2010
Tuesday, February 06, 2007
What Time Is It?
Time is a vexing problem for the fantasy-sci/fi writer whose world is not populated by humans familiar with our standard time measurement system. A writer is stuck with creating a time standard that makes sense for their world.
We modern humans are time-obsessed creatures. We constantly want to know what time it is, and what time it will be. We are surrounded by clocks, watches, and calendars. It is the one measurement that is nearly earth-universal. Almost all societies on Earth use the familiar seconds-minutes-hours time slices of the day. This began from the earliest days of civilization, way back in Mesopotamia, somewhere between 5,000 and 8,000 years ago.
The Mesopotamians sliced the day into four sections of six hours each, giving us a 24 hour day. Each hour was divided into quarters, until much later, when it was segmented into 60 slices called minutes. Then, around the 1670s AD, seconds were added as another refinement. This gives us what is now the familiar 86,400 second day.
Earliest society cared mostly about the seasons. Winter, Spring, Summer, Fall, these were important time periods that one needed to be able to plan for. So a calendar was helpful in keeping track of the days. It wasn’t long before they realized that the seasons repeated themselves about every 365 days.
Separating the day into various segments became important mostly through religious practice. Monks and nuns, and often the general populace as well, were expected to do certain things at particular times of the day. Bells or gongs would be rung, or priests would sing out. Government duties became regimental, with meetings only occurring at certain times.
All of these bells and gongs and singing relied primarily on the sun’s position, read via a sun dial. But the visibility of the sun was not always reliable (and, of course, useless at night), so burning candles, dripping water, and falling sand (i.e.- the hourglass) were put into use.
In England's medieval period, before pendulum clocks, monks would ring the bells of the church on an hourly basis using hourglasses and candles to mark the time, and they divided the day into twelve segments. This created a relativistic hour throughout the year. Since England is so far north, the winter day is about eight hours long, and a summer day is eighteen. So dividing a winter day into twelve parts created hours only 40 minutes long, while in the summer they were an hour and a half! Springtime was hard on the monks, because the midday meal progressively started later. So the hunger-panged priests would speed up the ringing of the bells in the morning and slow it down in the afternoon, all so they could have their meal when their stomach expected it.
What does all of this mean for the fantasy-sci/fi writer? It means that if the writer’s world has no connection to Earth and humans, then an entirely new system must be created for these creatures to use.
If it is a primitive society, then there won’t be much separation in time. Days and seasons, maybe lunar months (if your world has a moon), but that’s about it. As a civilization becomes more complex, however, so does the time system, out of necessity. Days become segmented, and further refined, calendars get important future dates, and special days, and so forth.
The problem is, even once you’ve created this new time system, you have to name all the units, and then convey to the reader all of this knowledge, all without boring them to tears, or confusing them to the point of exhaustion.
Step one is to note that your work is a ‘translation’ of this society. We humans are reading this text about some world that has no connection to Earthy humans. So this English text is a telling of the events, and therefore there is translation taking place. When one writes that, “Marec walked over to the rock,” one doesn’t put in the alien’s word for ‘walked’ or ‘rock’. One assumes, however, that ‘Marec’ is at least a rough approximation of Marec’s true alien name.
However, if Marec is quoted as saying, “I will meet you in one hour’s time,” there is a disconnect. How would Marec know how long an hour is? Why would his society use hours, when that is a human invention? Is it a translation for whatever an hour is in his world? Perhaps… but the more a writer interjects words that are human inventions the more the aliens sound like poor knockoffs of humans. It’s like a primitive alien telling someone that, “we need to retrofit this altar so that it can hold more people.” The world ‘retrofit’ is just too modern. An author must translate the aliens’ words in such a way that the flavor is retained. A primitive society needs to sound like a primitive society. A magical society needs to sound magical.
So generally, an author will create names for time slices that are similar to the ones we are familiar with. And a calendar will be created, with various segments, counting up to that world’s year. Often, calendars will be patterned off of natural events, like seasons, moon orbits, or even perhaps mating periods.
As an aside, this naming convention needs to be used for the fauna and flora of the world as well. One doesn’t want to read that, “Marec held his cat, slowing petting her long shiny coat as he watched the procession.” The reader’s suspension of disbelief jumps at the word ‘cat’. What’s a cat doing on this alien world? An easy way around that many authors use is to just have a creature that is similar to a cat, and give it a different name. “Marec held his folum, slowly petting her long shiny coat as he watched the procession.” This means you need to keep good notes on all of these creatures’ names and vital information.
As an example of a time system, in a world I created way back in my youth I had six seasons: Torc (Winter), Suu (Spring), Ramal (Wet), Ar (Wind), Su (Hot), and Miluc (Fall), with a 216 day year, giving 36 day seasons. I then divided each season into three 12 day ‘weeks’, using the words ‘Rising’ and ‘Falling’ for the first and third week of that season. So Rising Torc was the first twelve days of winter, just Torc for the second week, and Falling Torc for the last week. This all meshed together nicely, probably a little too nicely, for the chances that a planet has exactly 216 rotations for every revolution is rather unlikely, but what the hey, it fit with what I needed. Each season was also associated with a color and an element in the society.
I divided the day into ten daylight hours (called tir), and ten night hours (sut). So 3 tir was three ‘hours’ after sun rise. Of course, we don’t know how this correlates with human time, because we don’t know the orbital period of this fantasy planet in Earth units. Just because it has 216 days in one of its years, doesn’t equate to anything on Earth. But it doesn’t really matter, other than I let one fantasy tir equal to about an hour. Which means it has twenty-hour days, about, and 216 days to a year, meaning that its years are shorter than Earth’s. Which would put its orbit closer to the sun. But that’s okay, because I had this world’s sun be a small orange-yellow, about half the mass of ours.
I divided each ‘hour’ into ten units as well, using the prefix ‘uli-‘. So ulitir was a tenth of a tir. Ulisut was a tenth of a sut, but equal to the same amount of time, its just one was used during the day, the other at night. Since this was a magical-medieval fantasy world, I didn’t bother to slice time any further.
I also named the twelve days of each week, and created holidays, and various important dates and times for the society.
An author who decides to write a fantasy-sci/fi world that has no connection to Earthly humans has quite a job ahead of them. Time and space measurement, animals, plants, people and proper names all have to be created, named, and cataloged so the world makes sense.
We modern humans are time-obsessed creatures. We constantly want to know what time it is, and what time it will be. We are surrounded by clocks, watches, and calendars. It is the one measurement that is nearly earth-universal. Almost all societies on Earth use the familiar seconds-minutes-hours time slices of the day. This began from the earliest days of civilization, way back in Mesopotamia, somewhere between 5,000 and 8,000 years ago.
The Mesopotamians sliced the day into four sections of six hours each, giving us a 24 hour day. Each hour was divided into quarters, until much later, when it was segmented into 60 slices called minutes. Then, around the 1670s AD, seconds were added as another refinement. This gives us what is now the familiar 86,400 second day.
Earliest society cared mostly about the seasons. Winter, Spring, Summer, Fall, these were important time periods that one needed to be able to plan for. So a calendar was helpful in keeping track of the days. It wasn’t long before they realized that the seasons repeated themselves about every 365 days.
Separating the day into various segments became important mostly through religious practice. Monks and nuns, and often the general populace as well, were expected to do certain things at particular times of the day. Bells or gongs would be rung, or priests would sing out. Government duties became regimental, with meetings only occurring at certain times.
All of these bells and gongs and singing relied primarily on the sun’s position, read via a sun dial. But the visibility of the sun was not always reliable (and, of course, useless at night), so burning candles, dripping water, and falling sand (i.e.- the hourglass) were put into use.
In England's medieval period, before pendulum clocks, monks would ring the bells of the church on an hourly basis using hourglasses and candles to mark the time, and they divided the day into twelve segments. This created a relativistic hour throughout the year. Since England is so far north, the winter day is about eight hours long, and a summer day is eighteen. So dividing a winter day into twelve parts created hours only 40 minutes long, while in the summer they were an hour and a half! Springtime was hard on the monks, because the midday meal progressively started later. So the hunger-panged priests would speed up the ringing of the bells in the morning and slow it down in the afternoon, all so they could have their meal when their stomach expected it.
What does all of this mean for the fantasy-sci/fi writer? It means that if the writer’s world has no connection to Earth and humans, then an entirely new system must be created for these creatures to use.
If it is a primitive society, then there won’t be much separation in time. Days and seasons, maybe lunar months (if your world has a moon), but that’s about it. As a civilization becomes more complex, however, so does the time system, out of necessity. Days become segmented, and further refined, calendars get important future dates, and special days, and so forth.
The problem is, even once you’ve created this new time system, you have to name all the units, and then convey to the reader all of this knowledge, all without boring them to tears, or confusing them to the point of exhaustion.
Step one is to note that your work is a ‘translation’ of this society. We humans are reading this text about some world that has no connection to Earthy humans. So this English text is a telling of the events, and therefore there is translation taking place. When one writes that, “Marec walked over to the rock,” one doesn’t put in the alien’s word for ‘walked’ or ‘rock’. One assumes, however, that ‘Marec’ is at least a rough approximation of Marec’s true alien name.
However, if Marec is quoted as saying, “I will meet you in one hour’s time,” there is a disconnect. How would Marec know how long an hour is? Why would his society use hours, when that is a human invention? Is it a translation for whatever an hour is in his world? Perhaps… but the more a writer interjects words that are human inventions the more the aliens sound like poor knockoffs of humans. It’s like a primitive alien telling someone that, “we need to retrofit this altar so that it can hold more people.” The world ‘retrofit’ is just too modern. An author must translate the aliens’ words in such a way that the flavor is retained. A primitive society needs to sound like a primitive society. A magical society needs to sound magical.
So generally, an author will create names for time slices that are similar to the ones we are familiar with. And a calendar will be created, with various segments, counting up to that world’s year. Often, calendars will be patterned off of natural events, like seasons, moon orbits, or even perhaps mating periods.
As an aside, this naming convention needs to be used for the fauna and flora of the world as well. One doesn’t want to read that, “Marec held his cat, slowing petting her long shiny coat as he watched the procession.” The reader’s suspension of disbelief jumps at the word ‘cat’. What’s a cat doing on this alien world? An easy way around that many authors use is to just have a creature that is similar to a cat, and give it a different name. “Marec held his folum, slowly petting her long shiny coat as he watched the procession.” This means you need to keep good notes on all of these creatures’ names and vital information.
As an example of a time system, in a world I created way back in my youth I had six seasons: Torc (Winter), Suu (Spring), Ramal (Wet), Ar (Wind), Su (Hot), and Miluc (Fall), with a 216 day year, giving 36 day seasons. I then divided each season into three 12 day ‘weeks’, using the words ‘Rising’ and ‘Falling’ for the first and third week of that season. So Rising Torc was the first twelve days of winter, just Torc for the second week, and Falling Torc for the last week. This all meshed together nicely, probably a little too nicely, for the chances that a planet has exactly 216 rotations for every revolution is rather unlikely, but what the hey, it fit with what I needed. Each season was also associated with a color and an element in the society.
I divided the day into ten daylight hours (called tir), and ten night hours (sut). So 3 tir was three ‘hours’ after sun rise. Of course, we don’t know how this correlates with human time, because we don’t know the orbital period of this fantasy planet in Earth units. Just because it has 216 days in one of its years, doesn’t equate to anything on Earth. But it doesn’t really matter, other than I let one fantasy tir equal to about an hour. Which means it has twenty-hour days, about, and 216 days to a year, meaning that its years are shorter than Earth’s. Which would put its orbit closer to the sun. But that’s okay, because I had this world’s sun be a small orange-yellow, about half the mass of ours.
I divided each ‘hour’ into ten units as well, using the prefix ‘uli-‘. So ulitir was a tenth of a tir. Ulisut was a tenth of a sut, but equal to the same amount of time, its just one was used during the day, the other at night. Since this was a magical-medieval fantasy world, I didn’t bother to slice time any further.
I also named the twelve days of each week, and created holidays, and various important dates and times for the society.
An author who decides to write a fantasy-sci/fi world that has no connection to Earthly humans has quite a job ahead of them. Time and space measurement, animals, plants, people and proper names all have to be created, named, and cataloged so the world makes sense.
Tuesday, October 25, 2005
World Building 101: Today's Topic: That's Heavy, Man!
Gravity is what holds the universe together on the grand scale of things. All mass has gravity, which means, everything has gravity, because nothing, so far, has been found to be without mass. What is mass? Mass is energy, in one form or another. So all the universe is but an ephemeral net of energy, bent and twisted by the four basic forces: Gravity, Electromagnetism, Weak and Strong. I'm going to concentrate on the heavy subject of Gravity in today's lecture.
Gravity holds the Earth together. It keeps the atmosphere on the surface of the planet, and the oceans, and all the stuff living on it. The steady pull of gravity is what makes us weighable. If you step on a scale, you are measuring the pull of the Earth. If you were on Mars, the pull would be less, since Mars is less massive than the Earth.
What is the gravity on your fantasy world? Can it be less? Can it be more? Yes, and yes, within a certain range.
If your world is as massive as Mars, which is 38% the size of the Earth, then the pull would be 0.38 that of Earth's. Meaning a 100 pound rock would weigh only 38 pounds on your planet. It would still have the same mass, it would just be more buoyant... as if you had help hefting it.
This is where things can get confusing. Mass and weight are two different things. Only on Earth does a 100 lbs rock have 100 lbs of mass. Out in space it may be weightless, but it's not massless. It is always a 100 lbs mass.
Life on a world with less gravity would provide for larger growth. Large creatures are curtailed in their growth by the square-cube law. Larger objects get bigger by volume, as in cubic feet, while they must support themselves as a cross-section of their skeletons. Cross-sections are measure in square inches. If an animal doubles its size, then it has become eight times more massive (2x2x2), while its bone support has only increased by a factor of four (2x2). So the bones have to become even more massive to support the extra mass. This becomes progressively more difficult as the animal gets bigger and bigger.
(Learn more about The Square-cube law)
The whole subject of large creatures is still debated, with gravity providing but one of many limitations on being big, including landmass and biodiversity.
On a planet more massive than Earth, the animals would have a lesser upper limit, since the square-cube law applies stronger. On a planet twice as massive as Earth, you probably wouldn't have elephants, or if you did, they would have much thicker legs.
Gravity also greatly determines the atmospheric pressure of the planet. The lighter the planet, the lighter the atmosphere; the heavier the planet, the thicker the air. (Smaller planets can have thick atmospheres, from volcanic eruptions and other chemical events, but it will be short-lived, geologically speaking). I'll get into atmospheric composition in another lecture.
So what is a fantasy author to do? Make your planet smaller, larger, or about the same as Earth? Make it too small and there's not enough gravity to hold an atmosphere. Make it too large and the surface becomes slushy from the strong internal convections.
A small world makes feats of strength more believable -- but remember that mass stays the same. Lifting a car would be easier, but stopping a speeding train would be just as hard. And a less massive planet would make it easier to fly, except that smaller planets usually have less air (If you want to have large flying creatures, you'd have to have a world that is still producing its atmosphere, making it thick enough for flying, and coupled with the lesser gravity).
A large world would likely have a thicker atmosphere, smaller animal and plant life, and more chaotic plate tectonics. Cloud formation is easier under more pressure, and wind dynamics are more persistent. A storm may persist for several years on a heavy atmospheric world, circling the globe many times as it rages.
Gravity holds the Earth together. It keeps the atmosphere on the surface of the planet, and the oceans, and all the stuff living on it. The steady pull of gravity is what makes us weighable. If you step on a scale, you are measuring the pull of the Earth. If you were on Mars, the pull would be less, since Mars is less massive than the Earth.
What is the gravity on your fantasy world? Can it be less? Can it be more? Yes, and yes, within a certain range.
If your world is as massive as Mars, which is 38% the size of the Earth, then the pull would be 0.38 that of Earth's. Meaning a 100 pound rock would weigh only 38 pounds on your planet. It would still have the same mass, it would just be more buoyant... as if you had help hefting it.
This is where things can get confusing. Mass and weight are two different things. Only on Earth does a 100 lbs rock have 100 lbs of mass. Out in space it may be weightless, but it's not massless. It is always a 100 lbs mass.
Life on a world with less gravity would provide for larger growth. Large creatures are curtailed in their growth by the square-cube law. Larger objects get bigger by volume, as in cubic feet, while they must support themselves as a cross-section of their skeletons. Cross-sections are measure in square inches. If an animal doubles its size, then it has become eight times more massive (2x2x2), while its bone support has only increased by a factor of four (2x2). So the bones have to become even more massive to support the extra mass. This becomes progressively more difficult as the animal gets bigger and bigger.
(Learn more about The Square-cube law)
The whole subject of large creatures is still debated, with gravity providing but one of many limitations on being big, including landmass and biodiversity.
On a planet more massive than Earth, the animals would have a lesser upper limit, since the square-cube law applies stronger. On a planet twice as massive as Earth, you probably wouldn't have elephants, or if you did, they would have much thicker legs.
Gravity also greatly determines the atmospheric pressure of the planet. The lighter the planet, the lighter the atmosphere; the heavier the planet, the thicker the air. (Smaller planets can have thick atmospheres, from volcanic eruptions and other chemical events, but it will be short-lived, geologically speaking). I'll get into atmospheric composition in another lecture.
So what is a fantasy author to do? Make your planet smaller, larger, or about the same as Earth? Make it too small and there's not enough gravity to hold an atmosphere. Make it too large and the surface becomes slushy from the strong internal convections.
A small world makes feats of strength more believable -- but remember that mass stays the same. Lifting a car would be easier, but stopping a speeding train would be just as hard. And a less massive planet would make it easier to fly, except that smaller planets usually have less air (If you want to have large flying creatures, you'd have to have a world that is still producing its atmosphere, making it thick enough for flying, and coupled with the lesser gravity).
A large world would likely have a thicker atmosphere, smaller animal and plant life, and more chaotic plate tectonics. Cloud formation is easier under more pressure, and wind dynamics are more persistent. A storm may persist for several years on a heavy atmospheric world, circling the globe many times as it rages.
Tuesday, September 27, 2005
World Building 101: Today's Topic: Holy Magnitude!
Space is huge. Really huge. Mind-bogglingly, oh-my-gawd huge. Trying to wrap your brain around just how huge space is is a daunting task. But we'll give it a try.
Why does one need to know just how huge space is? Well, it allows you to do something amazing. Winning the lottery sort of amazing. You can imagine your world just about anyway you want, and if it can theoretically exist, then chances are it does, or did, or will. The numbers are on your side.
Our solar system is comprised of our lonely sun, a single star, and eight decently large planets, four rocky and four slushies, and a multitude of smaller icy planetoids. (Nine? You say? Well, not really, since Pluto hardly qualifies... but I digress).
How many more stars are out there in our galaxy? About 200,000,000,000. That's two hundred billion suns in our local Milky Way galaxy alone. And how many galaxies are there? Well, current estimates put the value around 100 to 300 billion galaxies. Our Milky Way is considered pretty large on the ol' galaxy scale, so we can't use it as an average, but assuming an average of only 1 billion stars per galaxy we end up with 100,000,000,000,000,000,000 stars in the known universe! That is a lot of stars! That is ten raised to the twentieth power, also called a hundred quintillion.
So, assuming for the moment that only one percent of those stars have planets in stable orbits, and assuming only one percent of those have been around long enough for life to form on the planets, and further assume that only one percent of those actually have planets in the right orbital temperate zone, and assume that one percent of those have the right collection of elements to start life, and in the right proportions. How many planets does that give us? That reduces our huge number solar systems by eight powers of ten, leaving 1,000,000,000,000 planets that have all the right stuff for life. One trillion planets. Odds are, one of them fits your profile.
Now, my 'one percent' assumption could be off, it could be off a lot, but even if it's off several magnitudes, we still have plenty of life producing planets to choose from. (This thought experiment is brought to you by something called the Drake Equation.)
What I'm getting at is that a fantasy writer doesn't have to worry about the odds of a habitable planet existing. Chances are, it does. Somewhere out in the vastness that is space, a planet probably exists with that blue sun, three distinct rings, and two moons that you want.
The real problem is distance. Space is huge, as I've said. And most of it is filled with nothing (or dark matter, which is still mostly nothing). Traveling from one solar system to another is a monumental undertaking.
Most stars are light years apart. A light year is about six trillion miles.
How long would it take to travel a light year? Well, Voyager 1, our own unmanned space probe sent out 28 years ago (in the summer of '77 - and still running, I might add!), is now 8,700,000,000 miles away. That's about 0.15% of a light year. At that speed (about 38,000 mph), it will be another 18 thousand years before Voyager 1 is one light year away.
Even assuming you made a craft that travels a thousand times faster than Voyager 1, it would still take you a good 18 years to get one light year. And our nearest neighbor, Alpha Centauri, is four light years away! That's 72 years at 38 million mph. And, of course, once you got there and tried to phone home, you'd have to wait four years for the signal to reach Earth, and another four years for the answer to come back. It's hard to carry on a conversation with an eight-year lag time! Can you hear me now?
And, traveling very fast creates new problems, problems that are weird and spooky, which I'll save for a some future lecture.
All this humongous distance of space is the reason why sci-fi writers invented warp drive. Flying from star system to star system via faster-than-light space travel is de rigueur. It is so much nicer to be sitting around playing holographic chess for a few hours while hurtling through space at super-light speed rather than waiting a whole lifetime just to reach your stellar neighbor.
In summary, space is huge and empty, yet contains billions and billions of stars, some of which probably have a habitable planet orbiting it that can be your fantasy world. But good luck getting there.
Why does one need to know just how huge space is? Well, it allows you to do something amazing. Winning the lottery sort of amazing. You can imagine your world just about anyway you want, and if it can theoretically exist, then chances are it does, or did, or will. The numbers are on your side.
Our solar system is comprised of our lonely sun, a single star, and eight decently large planets, four rocky and four slushies, and a multitude of smaller icy planetoids. (Nine? You say? Well, not really, since Pluto hardly qualifies... but I digress).
How many more stars are out there in our galaxy? About 200,000,000,000. That's two hundred billion suns in our local Milky Way galaxy alone. And how many galaxies are there? Well, current estimates put the value around 100 to 300 billion galaxies. Our Milky Way is considered pretty large on the ol' galaxy scale, so we can't use it as an average, but assuming an average of only 1 billion stars per galaxy we end up with 100,000,000,000,000,000,000 stars in the known universe! That is a lot of stars! That is ten raised to the twentieth power, also called a hundred quintillion.
So, assuming for the moment that only one percent of those stars have planets in stable orbits, and assuming only one percent of those have been around long enough for life to form on the planets, and further assume that only one percent of those actually have planets in the right orbital temperate zone, and assume that one percent of those have the right collection of elements to start life, and in the right proportions. How many planets does that give us? That reduces our huge number solar systems by eight powers of ten, leaving 1,000,000,000,000 planets that have all the right stuff for life. One trillion planets. Odds are, one of them fits your profile.
Now, my 'one percent' assumption could be off, it could be off a lot, but even if it's off several magnitudes, we still have plenty of life producing planets to choose from. (This thought experiment is brought to you by something called the Drake Equation.)
What I'm getting at is that a fantasy writer doesn't have to worry about the odds of a habitable planet existing. Chances are, it does. Somewhere out in the vastness that is space, a planet probably exists with that blue sun, three distinct rings, and two moons that you want.
The real problem is distance. Space is huge, as I've said. And most of it is filled with nothing (or dark matter, which is still mostly nothing). Traveling from one solar system to another is a monumental undertaking.
Most stars are light years apart. A light year is about six trillion miles.
How long would it take to travel a light year? Well, Voyager 1, our own unmanned space probe sent out 28 years ago (in the summer of '77 - and still running, I might add!), is now 8,700,000,000 miles away. That's about 0.15% of a light year. At that speed (about 38,000 mph), it will be another 18 thousand years before Voyager 1 is one light year away.
Even assuming you made a craft that travels a thousand times faster than Voyager 1, it would still take you a good 18 years to get one light year. And our nearest neighbor, Alpha Centauri, is four light years away! That's 72 years at 38 million mph. And, of course, once you got there and tried to phone home, you'd have to wait four years for the signal to reach Earth, and another four years for the answer to come back. It's hard to carry on a conversation with an eight-year lag time! Can you hear me now?
And, traveling very fast creates new problems, problems that are weird and spooky, which I'll save for a some future lecture.
All this humongous distance of space is the reason why sci-fi writers invented warp drive. Flying from star system to star system via faster-than-light space travel is de rigueur. It is so much nicer to be sitting around playing holographic chess for a few hours while hurtling through space at super-light speed rather than waiting a whole lifetime just to reach your stellar neighbor.
In summary, space is huge and empty, yet contains billions and billions of stars, some of which probably have a habitable planet orbiting it that can be your fantasy world. But good luck getting there.
Friday, September 16, 2005
World Building 101: Today's Topic: Color Me Blue!
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Stars come in various colors, depending upon how hot they are burning. Blue is the hottest, followed by white, then yellow and red.
Can your fantasy world have a blue, white, or red sun, rather than a 'normal' yellow sun? Possibly. I'll talk about each one.
A blue star is burning hydrogen just like our yellow sun, but at a much faster rate. It must be many times larger than our sun in order to have enough gravitational pressure to up the temperature to the blue range. This means it won't last as long (the whole a candle that burns twice as bright lasts half as long thing).
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What would a blue sun look like? Well, it would be a smaller disc, since the temperature is so much higher the planet needs to be father away to have a similar climate. But it would very bright, like the difference between a yellow incandescent and a blue-beam headlight.
White stars come in two flavors: main and dwarf. A white main sequence star is just a star like our own, but a few times larger. It won't live as long as our sun, but should still be good for a few of billion years worth of stable solar energy. So no problem having a world orbiting a main sequence white star.
White dwarves, on the other hand, are old stars that have already gone through the red giant phase. This means that any planet orbiting the star has been engulfed when the star expanded to a super-size red sun. So, there wouldn't be any stable planet orbiting a white dwarf star close enough for the solar energy of the dwarf to keep the world temperate.
Red stars also come in two flavors: Giant and main. A red giant is a blue, white, or yellow star that has used up all of its hydrogen and is now burning helium. Red giants are huge, puffed up versions of the original star. Our own sun will become a moderately large red giant in about 5 billion years. It will expand and engulf the four inner planets (Mercury, Venus, Earth, and Mars). At that point, moons orbiting Jupiter might become life-supporting. But that phase will only last for a few million years at most. So, one could have such a world, but the life would probably need to come from somewhere else.
Main sequence red stars are stars with a mass slightly less than our sun, 80% to 30% of our sun's mass. It burns cooler, and therefore has a red hue. These types of stars are quite common, probably the most common, and are very stable. So a fantasy world orbiting a main sequence red is no problem at all.What would a red sun look like in the sky? It would be a larger disc than our own sun, and have an amber or orange hue. The infrared spectrum would be stronger than our own yellow sun, and therefore the sunlight would 'feel' hot.
What about smaller than a small red main sequence? Suns that small don't have enough gravitational pressure to cause nuclear fusion, and therefore don't give off light. So-called 'brown' and 'black' stars (not to be confused with a black hole), these stars give off infrared light only. A planet could orbit around such a star, and life could possibly exist, for the infrared heat could keep a planet from being a frozen hunk of rock.
More info on stellar classification can be found here.
Friday, September 02, 2005
World Building 101: Today's Topic: You've Got Twins!
Having a twin solar sunset has to be one of the cooler images in the science fiction/fantasy genre. That and dragons...
A solar binary, a system where two stars orbit each other, is actually quite common in our universe. Our closest neighbor, Alpha Centauri, is a binary (actually, it's a triple, with a third red dwarf star out far from the main pair). Star pairs, and double pairs, occur throughout the galaxy in high numbers.
The question becomes, can a planetary system exist in a binary (or higher) system? Or can only the lone stars, like our sun, manage to keep planets in a stable orbit?
The answer is, sometimes. The trouble is that many of the binary systems have stars that are very close to each other, so close that the two gravity wells are overlapping to a huge degree. This makes it highly unlikely that a planet could develop any sort of stable orbit about either sun. If a planet was circling one star, then each time it came near the other star the tidal effects would be large enough to shear the planet apart, or at least pull it out of orbit.
So, to have a planet orbiting a sun that's part of a binary system necessitates that the two suns are a good distance apart. How far apart? Well, there's a lot of math involved, but once it is all said and done it works out that the second sun must be at least five times the distance from the planet to the primary sun.
For example, Alpha Centauri's two main suns are 11 AU (Astronomical Unit: The distance from the Earth to the Sun, about 93 million miles) apart from each other on their closest approach. Meaning that a planet could be orbiting one of the suns as long as it was less than 2 AU from it. So, the Earth could exist in an orbit about Alpha Centauri A or B.
But, as viewed from the surface, the second sun would look a hundred times smaller and fainter than the primary. This is because that while the Earth is one AU from the primary sun, it would be ten AU from the secondary, and light drops off in brightness at the square of the distance (10 x 10 = 100). This is still much brighter than our moon, even during a full moon, and would lend an eerie orange glow to the landscape. The third sun, Proxima Centauri, would just be a little red dot, as its distance is 13,000 AU from the two pairs, and its less bright to begin with.
So, as a fiction writer, binaries, trinaries, and more are certainly possible, but one needs to take into account that the planet will be circling a primary sun, and all the other suns will be progressively further out, by a factor of at least five.
But, Professor Thule, what if the second sun is a giant star, you ask? That's certainly another possibility. Suns come in many sizes, from the little red dwarf to the mighty blue super-giant. This implies a chance where a planet circles a medium-yellow star like our sun, but then have a second sun that is a giant, and while farther away, is many times bigger, thereby making it appear as if the two suns are equal in the sky. Now, giant stars have giant gravity wells, and our ballpark factor of five becomes a factor of ten or even twenty.
We can try this using Betelgeuse, a red giant some 400 light years from our solar system. It's a huge sun, 270 million miles across, big enough that if was dropped down in our system the Earth would be inside of it!
Assuming, for the moment, that one put our sun in orbit about Betelgeuse, could you get a double sunset? Yes. Betelgeuse is about 13,000 times brighter than our sun. So, if it was a bit more than a hundred AU from Earth, it would look as bright as our sun. So we have a factor of 100, more than enough to insure that the planet doesn't get pulled apart from the tidal effects of the second sun. Note that the Earth would now be receiving twice as much solar energy, and would therefore get much hotter. So, as a fantasy writer, you'd have to back off both suns a bit so that the total energy is about the same as one sun.
The problem, however, is that giants and super-giants have a tendency to be unstable. Meaning they often change in brightness, or go supernova into oblivion. This would be devastating for a planet's inhabitants.
In summary, a world can be part of a double sun system. In most cases, the second sun would be a dimmer, smaller sun to the primary. But, in a special case, both suns could appear to be the same size.
A solar binary, a system where two stars orbit each other, is actually quite common in our universe. Our closest neighbor, Alpha Centauri, is a binary (actually, it's a triple, with a third red dwarf star out far from the main pair). Star pairs, and double pairs, occur throughout the galaxy in high numbers.
The question becomes, can a planetary system exist in a binary (or higher) system? Or can only the lone stars, like our sun, manage to keep planets in a stable orbit?
The answer is, sometimes. The trouble is that many of the binary systems have stars that are very close to each other, so close that the two gravity wells are overlapping to a huge degree. This makes it highly unlikely that a planet could develop any sort of stable orbit about either sun. If a planet was circling one star, then each time it came near the other star the tidal effects would be large enough to shear the planet apart, or at least pull it out of orbit.
So, to have a planet orbiting a sun that's part of a binary system necessitates that the two suns are a good distance apart. How far apart? Well, there's a lot of math involved, but once it is all said and done it works out that the second sun must be at least five times the distance from the planet to the primary sun.
For example, Alpha Centauri's two main suns are 11 AU (Astronomical Unit: The distance from the Earth to the Sun, about 93 million miles) apart from each other on their closest approach. Meaning that a planet could be orbiting one of the suns as long as it was less than 2 AU from it. So, the Earth could exist in an orbit about Alpha Centauri A or B.
But, as viewed from the surface, the second sun would look a hundred times smaller and fainter than the primary. This is because that while the Earth is one AU from the primary sun, it would be ten AU from the secondary, and light drops off in brightness at the square of the distance (10 x 10 = 100). This is still much brighter than our moon, even during a full moon, and would lend an eerie orange glow to the landscape. The third sun, Proxima Centauri, would just be a little red dot, as its distance is 13,000 AU from the two pairs, and its less bright to begin with.So, as a fiction writer, binaries, trinaries, and more are certainly possible, but one needs to take into account that the planet will be circling a primary sun, and all the other suns will be progressively further out, by a factor of at least five.
But, Professor Thule, what if the second sun is a giant star, you ask? That's certainly another possibility. Suns come in many sizes, from the little red dwarf to the mighty blue super-giant. This implies a chance where a planet circles a medium-yellow star like our sun, but then have a second sun that is a giant, and while farther away, is many times bigger, thereby making it appear as if the two suns are equal in the sky. Now, giant stars have giant gravity wells, and our ballpark factor of five becomes a factor of ten or even twenty.
We can try this using Betelgeuse, a red giant some 400 light years from our solar system. It's a huge sun, 270 million miles across, big enough that if was dropped down in our system the Earth would be inside of it!
Assuming, for the moment, that one put our sun in orbit about Betelgeuse, could you get a double sunset? Yes. Betelgeuse is about 13,000 times brighter than our sun. So, if it was a bit more than a hundred AU from Earth, it would look as bright as our sun. So we have a factor of 100, more than enough to insure that the planet doesn't get pulled apart from the tidal effects of the second sun. Note that the Earth would now be receiving twice as much solar energy, and would therefore get much hotter. So, as a fantasy writer, you'd have to back off both suns a bit so that the total energy is about the same as one sun.
The problem, however, is that giants and super-giants have a tendency to be unstable. Meaning they often change in brightness, or go supernova into oblivion. This would be devastating for a planet's inhabitants.
In summary, a world can be part of a double sun system. In most cases, the second sun would be a dimmer, smaller sun to the primary. But, in a special case, both suns could appear to be the same size.
Thursday, August 25, 2005
World Building 101: Today's Topic: Tilt a World!
Our Earth is tilted at a 23.5-degree angle in its orbit about the sun. We spin like a tilted top and this accounts for our seasons. When the northern hemisphere is tilted away from the sun it’s winter up there. Six months later it’s summer because the tilt is now towards the sun. In the southern hemisphere, it’s exactly six months different: When it’s summer in the United States, it’s winter in Australia.
Some assume that during the winter the sun is farther away, and in the summer it’s closer. But that has very little impact on the seasons. The Earth’s orbit is only slightly elliptical. It varies from about 92 to 94 million miles away from the sun.
This tilt of ours creates a wide temperate zone where we get four distinct seasons: Winter, Spring, Summer, and Fall. A larger tilt would create a harsher difference between a cold winter and a hot summer. A smaller tilt, or no tilt, would pretty well eliminate the seasons. If, however, the planet had a large elliptical orbit, then that would create seasons that would affect the whole planet at the same time in the planet’s year.
The planets in the solar system vary considerably in tilted-ness. Mercury isn’t tilted at all, while Uranus is at 82 degrees (almost lying on its side), and Mars is very similar to Earth at 25 degrees.
So a fantasy world could really have any tilt you’d like, and an eccentricity (a measure of elliptical-ness) greater than Earth’s. The more tilt you give it, the more extreme the temperatures are going to be. If you had a planetary tilt like Uranus’s, then for half the year you wouldn’t see the sun at all. It would be a very cold, very long, night. Then the sun would start to peek on the horizon, making little circles in the sky. As the year wore on, the sun’s little circle would get higher and higher in the sky, and then finally set on the opposite horizon. The summer would be one long, very hot, day. Such extremes would beg the question of how plants and animals would survive. Presumably, life would find a way.
The tilt of a planet slowly rotates about itself like a tilted top… very slowly. It is called the Precession of the Equinoxes, and for Earth, the loop takes 26 thousand years. This moves the seasons slowly backward in the calendar year.
All of this can play heavily in your fantasy world building. From the tilt of the planet and the eccentricity of its orbit you can have massive winters and unrelenting summers, or mild, practically non-exist seasons.
And as for the philosophical and religious implications of a tilted planet, just look at how the Mayan’s viewed it all.
Related to tilt, we have spin. A planet spins (rotates) on its axis as it orbits the sun. The rotation, over time, will slow down. The Earth’s spin is currently at about 365 spins per orbit, giving us our 365-day year. A planet could spin faster, or slower. If it slows down completely then it will rotate exactly once per year, meaning one side (the heavier, or denser side) will face the sun, while the opposite side is forever in the dark.
This allows your fantasy world to have very short days, or very long ones. A planet can even spin in the opposite direction to Earth’s, meaning the sun would rise in the West and set in the East. (Of course, if the denizens of your fantasy world know nothing of Earth, then ‘opposite’ of it means nothing. The sun merely rises and sets.)
Some assume that during the winter the sun is farther away, and in the summer it’s closer. But that has very little impact on the seasons. The Earth’s orbit is only slightly elliptical. It varies from about 92 to 94 million miles away from the sun.This tilt of ours creates a wide temperate zone where we get four distinct seasons: Winter, Spring, Summer, and Fall. A larger tilt would create a harsher difference between a cold winter and a hot summer. A smaller tilt, or no tilt, would pretty well eliminate the seasons. If, however, the planet had a large elliptical orbit, then that would create seasons that would affect the whole planet at the same time in the planet’s year.
The planets in the solar system vary considerably in tilted-ness. Mercury isn’t tilted at all, while Uranus is at 82 degrees (almost lying on its side), and Mars is very similar to Earth at 25 degrees.
So a fantasy world could really have any tilt you’d like, and an eccentricity (a measure of elliptical-ness) greater than Earth’s. The more tilt you give it, the more extreme the temperatures are going to be. If you had a planetary tilt like Uranus’s, then for half the year you wouldn’t see the sun at all. It would be a very cold, very long, night. Then the sun would start to peek on the horizon, making little circles in the sky. As the year wore on, the sun’s little circle would get higher and higher in the sky, and then finally set on the opposite horizon. The summer would be one long, very hot, day. Such extremes would beg the question of how plants and animals would survive. Presumably, life would find a way.
The tilt of a planet slowly rotates about itself like a tilted top… very slowly. It is called the Precession of the Equinoxes, and for Earth, the loop takes 26 thousand years. This moves the seasons slowly backward in the calendar year.
All of this can play heavily in your fantasy world building. From the tilt of the planet and the eccentricity of its orbit you can have massive winters and unrelenting summers, or mild, practically non-exist seasons.
And as for the philosophical and religious implications of a tilted planet, just look at how the Mayan’s viewed it all.
Related to tilt, we have spin. A planet spins (rotates) on its axis as it orbits the sun. The rotation, over time, will slow down. The Earth’s spin is currently at about 365 spins per orbit, giving us our 365-day year. A planet could spin faster, or slower. If it slows down completely then it will rotate exactly once per year, meaning one side (the heavier, or denser side) will face the sun, while the opposite side is forever in the dark.
This allows your fantasy world to have very short days, or very long ones. A planet can even spin in the opposite direction to Earth’s, meaning the sun would rise in the West and set in the East. (Of course, if the denizens of your fantasy world know nothing of Earth, then ‘opposite’ of it means nothing. The sun merely rises and sets.)
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