Axial Tilt

The line between writing fantasy and writing science fiction gets even blurrier when you spend an hour trying to figure out what orbital mechanics are necessary to create a daily solar eclipse in a certain region of a planet without having to change its axial tilt and thus eliminate seasons as a whole just so the medieval-era people who live in said region can use the eclipse as a basic time measurement.

All because someone giving directions and saying “you’ll be there by firstmoon” sounded kinda nifty.


7 Ways Earth Would Change If Our Moon Were Destroyed

6.) Our axial tilt would be unstable. This is an unfortunate one. Earth spins on its axis, tilted at 23.4° with respect to our orbital plane around the Sun. (This is known as our obliquity.) You might not think the Moon has much to do with that, but over tens of thousands of years, that tilt changes: from as little as 22.1° to as much as 24.5°. The Moon is a stabilizing force, as worlds without big moons – like Mars – see their axial tilt change by ten times as much over time. On Earth, without a Moon, its estimated that our tilt would possibly even exceed 45° at times, making us a world that spun on our sides. Poles wouldn’t always be cold; the equator might not always be warm. Without our Moon to stabilize us, ice ages would preferentially hit different parts of our world every few thousand years.”

Our Moon is pretty unusual as far as the Solar System goes: of all the planets, our Moon has the largest mass and radius ratios when compared to its parent planet. It’s enough to not only illuminate our night sky quite fiercely – the full Moon is 14,000 times brighter than the next brightest object in the night sky – but it has some significant gravitational effects on our world. You might think this is restricted to the tides, but that’s not the full story. The day lengthens, our axial tilt is stabilized, and even without a Moon, we’d still have tides after all! Yet destroying the Moon, even in our imaginations, gives us a way to help envision all the things it actually brings to Earth, for better and for worse.

Come learn all seven ways our Earth would change if our Moon were destroyed. Did you know all seven?

(A table of contents will be available at the end of the series. In the meantime, you can find previous installments in the space building tag and other original posts in the posts by pear tag.)

Part Nine: Moons, Moons, and More Moons

Just like how planets orbit a star and the stars orbit the center of a galaxy, and two stars might orbit each other, and two pairs of stars might orbit each other, and asteroids sometimes orbit each other, so too do planets get their own tag-alongs orbiting them. These celestial bodies–natural ones, mind, not constructed ones–are called moons or satellites.

Moons are defined by both size and composition. Major moons have enough mass that they retain a mostly spherical shape while minor moons are smaller, with less mass, and therefore are frequently oddly shaped. The key to size and shape is 200-300km in size, with minor moons being less than that size and major moons being larger. Moons tend to be comprised of either rock or ice, depending on where in the system it’s located. Obviously, like the formation of icy planets, icy moons must form outside the frost line.

Gas Giants:

Moons collect around gas giants in kind of three groups:

  • Small, irregular rocky minor moons gathered in an orbit on the outer edge of where the planet could potentially have rings. They are generally only 10-100km in size and make sure to leave 0.25-1.5 Earth-radii of space between each other.
  • A handful of large major moons gathered in orbit outside where the planet’s rings are. They leave more than half the planet’s size between each other. They may even have minor moons of their own.
  • Tiny, irregular minor moons–often captured asteroids–orbiting distantly, at the very edge of where they’re able to orbit. Generally in the 10s of kilometers in size, these minor moons orbit on very eccentric and inclined paths, and sometimes even backwards (retrograde).

Don’t forget! Moons clear out the debris from their orbits paths! So if you position a moon in the midst of a gas giant’s rings, they’ll create a gap in the rings where they orbit. Some major moons of gas giants cause major gaps in the rings, even though they’re not actively orbiting in the rings to clear it out. The reasons for this are a bit complex, but if you wanted to build a ringed gas giant with a major moon close-ish to the planet and a major gap in its rings, you totally could!

Terrestrial Planets:

Terrestrial planets don’t tend to accumulate many moons. They may have enough gravity to pull in some asteroids to become moons, like Mars’ two moons. (Remember that asteroids are mostly chunks of rock that are small enough that they would be considered minor moons.) To go along with this, distant planets are likely to have more moons, and close-in planets will have less.

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Today, Wednesday the 21st of December, is the winter solstice in the northern hemisphere. When viewed from northern latitudes, the Sun will make its lowest arc through the sky along the southern horizon. The day of the winter Solstice has the shortest length of time between sunrise and sunset and hence the fewest hours of daylight.

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The earth’s movement creates a few cycles. First of all, it rotates on its axis about once every 24 hours, producing sunrises and sunsets.  At the same time, it’s making a much slower cycle, orbiting around the sun approximately every 365 days. But there’s a twist. Relative to the plane of its orbit, the Earth doesn’t spin with the North pole pointing straight up. Instead, its axis has a constant tilt of 23.4º. This is known as the Earth’s axial tilt, or obliquity. This seemingly minuscule tilt is the reason…for the seasons.

Another feature of the Earth’s revolution is its orbital eccentricity. The earth’s orbit around the sun is an ellipse, with its distance to the Sun changing at various points. The corresponding change in gravitational force causes the Earth to move fastest in January when it reaches its closest point to the sun – the perihelion – and slowest in July when it reaches its farthest point – the aphelion. The Earth’s eccentricity means that solar noon – the time when the sun is highest in the sky – doesn’t always occur at the same point in the day. 

Learn about the Sun’s analemma by watching the TED-Ed Lesson The Sun’s surprising movement across the sky - Gordon Williamson

Animation by TED-Ed

anonymous asked:

Hi Blue!! I saw in the other ask you said something about a planet's orbit affacting the seasons? Could u explain?

Yes! What an excellent question. To have a little explanation of gravity and how you can use it in your stories, go here.

Planetary Seasons

A planet’s year is the time it takes for the planet to complete one orbit around the sun. Scientifically speaking, we call this a planet’s revolution period. The most obvious effect this has on a planet is it’s seasons. Seasons occur because a planet’s axis is generally tilted in respect to the plane of it’s orbit. For Earth, this tilt (or obliquity, scientifically speaking) is about 23.5°. Over the course of a year, each hemisphere is tilted alternately toward and away from the sun. During winter, when that hemisphere is tipped away from the sun, solar heating is less effective for two reasons: sunlight is hitting the earth at a shallower angle, and the days are shorter so the sun doesn’t shine as long. The opposite happens in the summer.

On a planet, the intensity of the seasons depends on the latitude, or the angular distance of a position on the planet north or south of the equator. On Earth, the conditions at the equator hardly change over the year, whereas the poles go from uninterrupted daylight to uninterrupted night. But even in temperate latitudes, the effects are not unnoticeable. At 40°N, for example, which is the latitude of Lisbon, San Francisco, Istanbul, and Beijing, the total heating on the summer solstice (the longest day of the year, somewhere between June 20-22) is three to four times as much as on the winter solstice. 

We use the obliquity and latitude to determine climatic zones. The Arctic and Antarctic circles, which define Earth’s polar regions, are 23.5° from the poles, a distance set by the 23.5° tilt of the axis. These circles are simply the outermost limit at which the sun does not rise or set on at least one day of the year. Similarly, the tropics of Cancer and Capricorn, which are 23.5° from the equator, mark the latitudes farthest from the equator where the sun will be directly overhead on at least one day out of the year. This region is defined as the tropics, or “torrid zone” where the seasons are barely noticeable. Anywhere between these two extremes, we call the temperate zones.

Applying This To Science Fiction

The intensity of the seasons is set by the amount of axial tilt. From this we can deduce that seasons themselves are not inevitable. If a planet’s axis were upright, seasons wouldn’t even occur, and differences in the year and placement of the planet in it’s orbit would only be noticeable by the changing patterns of the constellations in the night sky. A small tilt (or no tilt) like in this example would have some subtle implications. For example, much of the water supply in Earthen temperate climates comes from snowmelt. If there’s no winter, there will be no snow, and this means deserts are likely to be more widespread. Because the poles would always receive minuscule amounts of heating, the climate zones would be much more extreme. Some tilt, like Earth’s moderate 23.5°, helps even out the heating over the whole planet. For a planet to receive a completely even heating for both the poles and the equator over the course of a year the value of the tilt would have to be ~54°.

But having a greater value obliquity would cause extreme seasons, and this would lead to extreme climate. For a planet with a tilt of 90°–which would mean lying on it’s side, much like Uranus–the Arctic and Antarctic circles  would coincide with the equator, meaning there would be neither tropical or temperate zones. Seasons would be extreme indeed: for over nearly half the planet, the sun would never set during the summer, and never rise during the winter. Only during spring and fall, when the sun would shine on the planet’s side, would the sun rise and set like we’re used to on Earth. 

What would this mean for my characters?

Well, such an extreme tilt could cause any intelligent species to migrate, in order to stay in more habitable regions. Such consistent mass migration would be a significant part of culture: everything would need to be mobile. This could also cause tensions between groups of people as they try to find space to settle or run into each other while migrating. A culture that depends solely on this nomadic lifestyle could be interesting to explore, and for a real-world comparison I would study the culture of the Mongols.

Otherwise, if migration wasn’t a culture norm for the citizens of your planet, then they would have to be prepared to survive in extreme heat and desert-like conditions, followed by a moderate time, followed by intense and everlasting winter and night. Challenges would include shelter and survival (a species that could survive both desert and arctic climates would be incredibly interesting to develop) and a food source. For humans to live on such a planet would require an abundance of technological advances that you would be free to create for yourself in the realms of your story!

Other Ways to Have Seasons

Believe it or not, axial tilt is not the only way to have seasons! According to Kepler’s Laws, planets travel in an elliptical orbit, which means it does not have to be perfectly circular. If a planet had an elliptical orbit, it would mean that the seasons were caused by differences in distances to the sun! What makes this interesting, is that a planet would experience the whole season at a same time. Which would make it more similar to ice ages and then moderate summers (think Game of Thrones, here). So the planet would have similar day/night cycles like Earth but much more extreme, and maybe even longer seasons depending on the severity of the ellipse. 


Thanks for asking this question! I had such a fun time answering this. I love answering space questions. Also, tag me or send me links to your stories and fics so I can check out your science fiction in progress. 

love Blue

saut--dans--le--vide  asked:

Hello! I love your blog! 😁 I was just wondering if you had any posts about creating a world? From scratch/your imagination/etc. Something that resembles the Character Sheet you created? Thank you! 💝

//Sure thing! It got long- Feel free to pick and choose. Please note some of this was inspired from this generator.

Planet Creation

Planet Name: [And how to pronounce it]
Diameter: [Of the planet]
Core Type: [Molten?]
Density: [ _ times that of the Earth- unless of course it is the Earth]
Mass: [Same as above^]
Gravity: [Same as the above]
Atmosphere Type: [I can’t really list them all, so best to research]
Atmospheric Pressure: [ _ times that of the Earth, unless it is the Earth]
Surface Water: [How much water covers the planet? How many oceans? Lakes?]
Surface Divisions: [How many continents? Is it all one large mass connected together?]
Axial Tilt: [Earth is 23.44°]
Number of Moons: [Are they all visible?]
Moon Name(s): [And how to pronounce them]
Star System Type: [Binary (two stars)? Other?]
Star Details: [Type]
Star Name: [And how to pronounce the name]
Solar System Name: [And how to pronounce it]
Number of Gas Giants in System: [Self explanitory]
Number of Asteroid Belts in System: [Self explanitory]
Other Planets: [Include the number and the names]
Hours in a day: [Earth has 24]
Number of days in a year: [Earth has 365]
Number of months: [Earth has 12]
Common Climate: [What kind of rain does this planet have? Does it get any rain? Snow? Sun?]
Common Dominating Species: [Or rather, the focus of said world; aka in a story about Earth, it would be humans]

Species Creation


Home Environment: [Grassland, sea shore, open country?]
Basic Diet: [Omnivore? Carnivore?]
Feeding Method: [Hunter? Browser? Farmer?]
Metabolism: [Are they warm blooded?]
Type of Society: [Pack? Herd? Hive? Solitary?]
Creature Size: [Compared to human]
Creature build: [Light, medium, heavy, etc?]
Average weight: [On a range, aka ‘120 lbs - 200 lbs’]
Position in Food Chain: [Middle, bottom, top?]
Galactic Social Standing: [Trades? Militants? Hostile/friendly?]
Racial Wealth: [Poor, average, wealthy?]

Reproductive Strategy and Life Cycle

Number of Offspring: [On average, and maximum amount]
Commitment to Young: [Average, low, high?]
Lifespan Average: [Earth years]
Number of Sexes: [Don’t have to answer if you’re working with humans- chances are you already know]
Method of Birth: [Again, don’t have to answer if you’re working with humans]
Misc. Reproductive Info: [Keep in mind aliens that have ovoviviparity as a mode of reproduction in their society aren’t likely to have breasts]

Body Plan and Biology

Movement Method: [Do they walk? Fly? Teleport?]
Symmetry: [Are they bilateral, like vertebrates?]
Posture: [Upright? Semi-upright? Horizontal?]
Number of Limbs: [In total]
Number of Walking Limbs:  [How many limbs are used for walking?]
Number of Handing Limbs: [Of the total limbs, how many are used for grasping objects?]
Number of Extra Limbs: [Do they have the same strength, dexterity, and sensitivity of the other limbs? Tails? Extra appendages?]
Natural Weapons: [Venom? Claws? Fangs? Tails?]
Integument Type: [Armour Plates? Skin- like humans? Heavy chitin?]
Voice Box: [Normal frequency range? Do they speak out their mouths?]
Average Appearance: [Skin colors, limbs, extra limbs, eyes, ear shape, facial shape, body shape, height, weight, skin patterns, hair colors, etc]


How many senses: [Total]
Number of Eyes: [Total]
Eye Placement: [Wide? Close together? On the face?]
Vision: [Poor? Excellent?]
Hearing: [Poor? Excellent?]
Kinesthetic: [Poor? Excellent?]
Taste: [Poor? Excellent?]
Smell: [Poor? Excellent?]
Other: [Anything else?]

Personality Traits

[List of common traits your species are known for]
[Include if they’re more curious than humans, etc]


Strength: 0/10
Dexterity: 0/10
Intelligence: 0/10
Health: 0/10
Magic: [if applicable] 0/10
Balance: 0/10
Charisma: 0/10
Suspicion: 0/10
Empathy: 0/10
Curiosity: 0/10
Concentration: 0/10
Open Minded: [How do they feel about other species?] 0/10
Social Need: 0/10

Other Important Information

Religion: [Include deities]
Language: [Is it spoken? Signed?]
Names: [Are there common names? Any forbidden names?]
Population: [On average, how many are on the planet, how many are there in total, and how many per settlement/herd/hive/pack/etc.?]
Life Cycle: [How quickly do they age, and how fast do they mature?]
Technology: [How advanced are these species?]
Intelligence: [How smart are these species?]
Culture: [Fashion, the arts, entertainment, holidays, customs, traditions, languages, etc.]
Dating/Courting: [What starts the process? What are relationships like? Is there even any dating? What about marriage?]
Society: [Social structure, family life, roles/divisions, gender roles, gender identity, sexuality/love, common gestures, race, ethnicity, politics, etc.]
Government: [Government type, laws, punishment, finances, history, defense, education, medicine, transportation, economy, etc.]
Housing Structures: [How close do they live to each other? How secure are these buildings? Common materials? Practicality?]
Magic: [Is there any magic? Common terminology? Characteristics? Elements or types? Banned/forbidden abilities?]

Isharay - Chapter Seven

(Can’t link to AO3 because of stupid tumblr tags. Please find me anyway?)

Chapter Seven - Redacted

When it was over, it was almost like nothing had changed. Sara’s heart was still beating - sluggishly, maybe, but quickly enough to confirm she was still alive. Her lungs were still working. There was no shifting of the universe’s pillars; no sudden implosion to reinvent her from the inside out.

But her head felt strangely quiet. The world around her felt suddenly dull.

They hurried Cora back to the Tempest. She didn’t say anything as she left, and Sara didn’t want her to. Lexi laid a hand on Sara’s shoulder on her way out the door - we’ll see you soon, I’m sure - but Sara didn’t bother to respond.

She managed to lay there for ten quiet, lonely minutes. Kandros had left one of his security staff behind, but Sara barely noticed he was there. Reaching for coherent thoughts felt like reaching out over a precipice. She dangled there on the edge for a time, scrambling to find herself an anchor - but there was nothing.

Just silence.

When she climbed off the bed, she expected to stumble. When she crossed to the door, she was waiting for a fall. She stayed steady, though, even as she moved along the sterile white-chrome corridor beyond; even as one shapeless hallway blurred into the next. She wasn’t sure where she was going. She wasn’t sure how to get out.

She only knew that she needed to.

She wasn’t sure how Reyes found her, either. One moment, she was alone; still waiting for that fall. The next, he was there - and he already knew. His face was stripped of all expression, but Sara could see it in his eyes.

And then the fall finally came.

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cosmic witchcraft 101: uranian magick ♅

Uranus is the seventh planet from the Sun and the solar system’s first ice giant. The planet is most known for its extreme axial tilt, approximately 98 degrees. Scientists are uncertain as to how Uranus was forced on its side like this but believe a major impact is likely. An Earth-sized protoplanet is theorized to have collided with Uranus during the early formation of the solar system.


  • Uranus is visible to the naked eye in dark areas, but ancient astronomers never recognized it as a planet due to its dim light and slow orbit. It was officially discovered by William Herschel in 1781.
  • Uranus takes 17 hours to complete a day and 84 years to revolve around the Sun.
  • Methane makes up a large portion of Uranus’s atmosphere, and its ability to absorb red light gives the planet its cyan color.
  • Uranus’s moons are named after characters in Shakespeare plays.
  • Some scientists believe beneath its atmosphere, Uranus could hold an ocean of liquid diamonds.

Magickal Correspondences*

Colors: blue, cyan, white, purple

Intents: change, innovation, technology, subverting authority, challenging tradition, independence, inspiration, energy, freedom, equality, revolution

Herbs: fennel, cloves, nutmeg, chamomile, coffee, ginger, eucalyptus, garlic, cinnamon, lime

Crystals: aventurine, quartz, diamond, labradorite, blue topaz, aquamarine, amethyst, amazonite, fluorite, snowflake obsidian, moldavite, tourmaline

*some of these correspondences are based on traditional associations and some are based on my personal associations

Day and Night on Alternia!

So quite a while back I was drawing a picture from a rp about one of my trolls going out “at night” to catch fireflies in the dark before realizing Alternia is backwards, so there was nothing special about going out “at night”, all trolls go out “at night” and there was nothing analogous to our nightime when a troll could go out to catch fireflies in the dark. It’d be dumb to go catch fireflies when the sun is up! Which got me thinking about the cycles of day and night, and since anontrolls just made a post about the same thing, I got inspired to actually write this up!

As a note: this is highly highly non-compliant with canon facts regarding the number of perigees, equinoxes, and bilunar perigees Alternia seems to have because canon is CONFUSING.

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writing prompts

I thought I’d put all the prompts I’ve given people in the last few days in one post and send them out.  If you decide to write a prompt, please tag me, I’d love to read what you write!  Please also feel free to take whatever idea you wish from the prompt itself.  Change what you want.  Write what strikes you.

  1. There is music in the lines of his body, a singing in his eyes.
  2. She’s never been kissed like this, no - oh, there’s the ground spinning away in the circle of his arms.  There’s her heart tilting, an axial shift.
  3. She is like a hummingbird, bright and flashing, sunlight chased across the sky, mind working at a hundred beats per second.
  4. Death, death, death, and the battlefield his skin, cut and abraded, bruised and punctured.
  5. She wants such a simple thing, she knows.  Of all the things in the world to long for, the injustices she could bring to light, the wrongs she could undo - oh, she just wants to wake up with his scent suffusing her skin.
  6. It’s funny how she’s never noticed these things about him.  Truth is, expertise only lends itself to a deeper lust for knowledge.
  7. A mirror, she thinks, she is a mirror.  Lips touch lips, fire calls to fire.
  8. The realization strikes him like a hammer on a dulcimer string.  It hits him so hard he oscillates with it, and is surprised that the ground does not yawn from his feet in cracks, that the people standing by are not sympathetically moved.
  9. She lies with the speed of a falling star, elegant and beautiful and cutting.
  10. The aftermath is a stillness which roars.  Where are her mundanities now? she wonders.
  11. He looks at her as if she is new, touches her like he is afraid to spoil her.
  12. It is impossible to tell how long they have burned in the blue heat of her ardor.  Like wildfire or summer lightning it is over fast, not meant to endure.
  13. He’s good at so many things, better than good, an expert, really - except for this.  Romance.  Shows of affection.  Consideration.  That utterly infuriating lunkhead.
  14. When he smiled, all she could think of was #FFFFFF.
  15. A sigh.  His intent is manifest on his tongue, the touch of his desire clear in the sweep of his eyes.
  16. What is routine but a slow, even spiral towards death?

How Science Can Learn More About ‘Proxima b’ And All Earth-Like Worlds

“This planet is almost definitely tidally locked to its star, meaning that the same hemisphere always faces the star and the opposite hemisphere always faces away, just like the Moon does to Earth. The star itself is active and flares frequently, meaning that catastrophic radiation impacts the Sun-facing side quite regularly, but never touches the dark side. And the “seasons” are determined by the ellipticity of its orbit, rather than its axial tilt. But there’s still so much left to learn, and we have a number of different technological avenues to explore – including potentially all of them – if we want to learn more about it.”

Now that we’ve learned the nearest star to our Sun, Proxima Centauri, has a rocky planet at the right distance for liquid water, it’s time to consider how we might learn the answers to our burning questions about it and all nearby Earth-like exoplanets. What’s the atmosphere like, and what does it consist of? What does the surface of the world look like, and what’s on it? And is there life, or intelligent life, present at all? There are three ways to conduct these searches, and they’re all complementary. We can use giant ground-based telescopes, including arrays of telescopes, for high-resolution spectroscopic images of these worlds. We can use space-based telescopes with coronagraphs or starshades to image these worlds directly over time. Or we could undertake a journey across space, and visit the system directly to obtain in situ measurements we could never get from afar.

If this doesn’t inspire you to invest in astronomy and learning more about the Universe, perhaps nothing will!

Spectacular Settings

When I’m looking at a story, one of the simple things I look at is setting. There are so many aspects to setting, so let’s just look at a few:

1) Is your milieu intriguing? Many authors will set a story in the most blasé of places. Often, the story is set “somewhere in the USA”. While for certain types of stories this may be completely appropriate, in most cases it’s not. It’s as if the writer has suffered brain death and couldn’t bother to come up with a real milieu. In most cases, it helps if you choose a particular place to set your story, and a particular date.

2) Is the world fully created? If you’re using a real-world setting, then “creating” that world is a matter of capturing it—learning its history, culture, and future. It’s not enough just to research a setting, you have to know it, get it into your bones. This usually means that you must travel to that setting and spend some time there. You can’t just blow through Amarillo, Texas and expect to really know the place.

In a science fiction tale, if you want to set your story on a planet, then creating a setting might require you to decide what kind of star system your planet is set in, along with the planet’s composition, rotation, axial tilt, number of moons, type of atmosphere, and so on. You may have to think about how to create alien life-forms, and develop their life-cycles, and perhaps create their histories, languages, and societies. Just getting those kinds of details takes some concentration.

If you’re creating a fantasy world, then you may have to look even further—into creating the flora and fauna of your world, along with cultures and subculture, the magic systems and economic systems, societies, languages, histories, religions, and so on.

So I look at how robust your setting is. I consider how fully developed it is. I ask myself, “Has this author put enough thought into the setting to create the illusion that this is a real place?”

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This is as far from beautiful as possibly possible, buuut it’s science-y fun. I spent two evenings on Thalissic atmospheric circulations, based on my earlier musings about axial tilt, sun zenith and tectonic activity. These results are, in turn, the base for Thalissic climate daydreaming.

I used German terms, so maybe it’s a bit hard to read - the “ITC” is the innertropical convergence zone (ITCZ), the “subtropischer Hochdruckgürtel” is the subtropical high-pressure belt, the “Polarfront” is the polar front, “H” is for “high” and “T” is for “low”. Look how far north and south the ITCZ wanders on this planet! I’m really excited to carve out the climate. :3

The basic milestones of the Cybertronian vorn; events which the great majority of the population would recognise. Also includes the basic regular Rites and a few notes on the Cybertronian week.

+ DISCLAIMER: This is a headcanon for my TF:P-based AU project Book of Hours. Due to lack of canon elaboration on the topic at hand, I’ve had to make shit up. I had a great deal of fun doing so. Don’t take it too seriously.

>> See also: 

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