Terrestrial Moons

That's no moon...actually it is. All the facts and knowledge on terrestrial planet moonbuilding.
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► DISCUSS THIS EPISODE ON REDDIT: goo.gl/2RvTLr
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WATCH MORE:
► Stars : goo.gl/DTefZk
► Galaxies : goo.gl/y1d4zn
► Planetary Systems : goo.gl/jQy3o2
► Planets : goo.gl/KWhpYd
► Orbits : goo.gl/hhqZ7z
► Languages : goo.gl/KUng4y
► Seasons: goo.gl/ekyzh5
► Moons: goo.gl/swLfbo
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ARTIFEXIAN ON THE INTERWEB:
► KZbin: / artifexian
► Facebook: / artifexian
► Twitter: / artifexian
► Podcast: www.artifexian.com/
► Reddit: / artifexian
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EQUATIONS:
► Density: (% x p) + (% x p) ... etc
► Mass: R^3 * p
► Surface Gravity: M / R^2
► Hill Sphere: a * (m / M)^(1/3) x 235
► Roche Limit: 2.44 * R * (pp / ps)^(1/3)
► Orbital Period: 0.0588 * (R^3 / (M+m))^(1/3)
► Ellipsoid Mass: p(4/3)πabc
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CORRECTIONS:
2:17 - I say "10% iron", it should be 9%. My voiceover is incorrect but all the figures on screen are correct.
5:52 - I say "0.0558" but it should be 0.0588. Again the visuals are correct but the voiceover is off. Apologies.
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CREDITS:
Music:
"Unwritten Return" Kevin MacLeod (incompetech.com)
Licensed under Creative Commons: By Attribution 3.0
creativecommons.org/licenses/b...
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Thank you all so much for watching…Edgar out!

[@DaniTheDeer]

One day my D&D world will get to space age and all these calculations will come in handy

[@Artifexian]

+Joseph Stalin #futureproofing

[@thomasmueller618]

me too. well, the tabaxis are kinda close to space age, but thats just because they spam divination and used magic to make a tower that roughly goes up to a geostationary orbit

[@thomasfrancovitch123]

@@thomasmueller618 If you need more time to figure it out, you could always have a tower of Babel situation...

[@thomasmueller618]

except for no god lives in space so theres no point in that also the tabaxis know comprehend languages

[@therandomhat_]

@@thomasmueller618 It's a bit late, but perhaps unlucky asteroid hit? Or a depression in magic level making the tower unstable? Politically instability and some anarchist blows up the base? Just some ideas.

[@Meinvo]

Me: "I'm so happy that I can get away from physics after I graduate HS" Me watching your video to make my own moon for my world: ">:("

[@overloader7900]

Worldbuilders, more like scientists

[@snoodge-cv7fj]

I love the fact that the >:( is in quotation marks

[@ryansreborns]

LEGIT I JUST GOT INTO WORLDBUILDING AND AFTER A YEAR OF NOT DOING PHYSICS, AND TWO YEARS OF NO GEOGRAPHY, IVE HYPERFIXATED ON WORLDBUILDING AND NOW IM DOING ASTROPHYSICS AND GEOGRAPHY 😭😭

[@smartart6841]

@@snoodge-cv7fj yea, they said "greater than colon opening bracket"

[@kaw57_]

@@Ligerbee yes

[@RoflZack]

"veritable orgy" I subscribed.

[@yerdasellsavon9232]

So did I

[@suthinscientist9801]

Just imagine an Earthlike planet with two or three moons. That would be a gorgeous sight to see 2 or 3 moons in the sky. Not to mention the colonization potential for any civilization arising on the planet when they get space travel.

[@extratropicalcyclone8567]

Those 3 moons u mentioned would have to be between 700 km to 1500 km to diameter as not to make the habitable planet it orbits tidally lock and those low diameter moons would have low mass and low gravity which would render them without any atmosphere and life

[@tanoshiofm3852]

@@extratropicalcyclone8567 As someone who was planning a planet of three moons. This comes useful. Thank you.

[@tanoshiofm3852]

@@extratropicalcyclone8567 One question, what would three moons do to a planet? My planet has 2.05 Earth masses and 1.21 Earth radii. My moons diameters are 722 Km, 739 Km and 1157 Km.

[@aquarius5719]

Try watching Jupiter with a telescope. You will see a small solar system. If you search "retrovision orbiter tutorial" you will find a video that has description containing a link to download a space sim made by a professor from London. And you will see also links to HTML tutorials on how to do maneuvers like meeting a space station or going to other planets. It uses realisric physics so everything you do would be done by a real astronaut. You may travel solar system with this sim. You will love the sight.

[@iamasalad9080]

5

[@dionemoolman]

Another reason why gravity shouldn’t be calculated on minor moons is due to how little gravity there is. Phobos has a surface gravity of a few millimetres per second squared, and has an escape velocity small enough to achieve using muscle power.

[@procrastinator99]

I love your derpy Sun.

[@Artifexian]

+procrastinator99 He loves you right back :)

[@procrastinator99]

D'aaaawwww.....

[@justinlawrence8244]

+Artifexian will you ever cover exotic objects such as gas dwarves or maybe even a toroidal planet? Also how massive would you say a moon has to before it becomes a double planet? for example say the moon was about the mass of Mars assuming it keeps a stable orbit (of course it be farther out) but would the moon still be the moon or would it be a double planet?

[@AYYKAYY8008]

+procrastinator99 yeh

[@fromlaoswithoutlove]

It's not derpy.

[@stsaby]

For those using the equations pasted in the doobly-doo, the Orbital Period should be a square root (R^3 / (M + m))^(1/2) rather than the cube root written out. It's correct in the video, just a slight discrepancy. Thank you for all the work you've put into these incredible videos Edgar! They're super informative and engaging. I've been going through them recently myself to build my world and it's helped immensely!

[@Niker107]

I'm so glad I found this channel. This content is both extremely educational and super fun to watch. And useful, of course, in-case anybody loves writing lots of super detailed lore. Keep up the amazing work!

[@MellonVegan]

"Who doesn't like Fibonacci inspired..." cue Lateralus

[@Artifexian]

+Tobias Ommer Yes! Tool for the win!!!

[@asloii_1749]

@@Artifexian Holy shit. Artifexian likes Tool. This is amazing

[@tamerlane9889]

Just imagine if the earth had like 1000 minor moons or a habitale moon . Looking up and see a whole world!

[@Crimson67able]

+MaarMassinGaming *A whole new world

[@tamerlane9889]

+心情 indeed

[@Crimson67able]

+MaarMassinGaming Please tell me you got the Disney reference.

[@shealupkes]

+心情 shining, shimmering, splendid.

[@kXa_R]

imagine if earth was a gas giant! it would have these moons: moon, io, europa, ganymede, enceludus, titan, triton, miranda, phobos, deimos, pandora, and daphnis there are planets as moons: pluto, mercury, haumea, sedna, venus, mars, and earth (rocky planet OoO) rings: size: 30,000 km, material: iron, ice, granite, silicate, graphite, led, and dust, layers: 10, inclination: 23.4 degrees (earths axial tilt xD)

[@otakuribo]

I can't wait for the calendar-building episode. :D Will you be discussing horology as well? Because I imagine worlds with exotic sun situations (like binary systems) would have very unique sundials.

[@Artifexian]

+Elliot Grey Probably, but I haven't been giving much thought to calendar building yet.

[@otakuribo]

+Artifexian Oh, well; don't rush it. I'll still be looking forward to it. :)

[@sparkys7231]

Also will there be there be a video about binary planet systems?

[@tuxcup]

*hears all these terms* *Realises I have already forgotten about the KSP tutorial*

[@billybassoon10]

my life in a nutshell

[@jonathanho1451]

How is 2.44x1.2x(0.87/0.68)^1/3=2.65? Shouldn't it equal 3.1786? SOMEBODY PLEASE HELP

[@eduardovieira303]

Same result here. In both Excel and the Calculator.

[@eduardovieira303]

I mean, same result as you, 3.17.

[@parthiancapitalist2733]

Jonathan Ho lol did he mess up when typing it on the calculator?

[@thecapacitor1395]

Can't wait for habitable moons! :D

[@Artifexian]

+The Capacitor Hopefully, it'll be coming up soon.

[@Redpilled_Retribution]

@@Artifexian please make that video

[@lotusnaturals1897]

@@Redpilled_Retribution he did, same vid as gas giant moons

[@zeddash]

I am loving the amount of detail you are going into and fitting it into a video less than 11 minutes long

[@JAM-rp6fi]

Dude, this series is SO helpful for game development! I'm subscribing!

[@BloodSprite-tan]

great video i like the bit about two orbiting habitiable planets.

[@Artifexian]

+Moth Great! Glad you enjoyed.

[@shanemcgrath5089]

How about four habitable planets.

[@BloodSprite-tan]

Shane Mcgrath that would be fun.

[@NikodAnimations]

How about 1 major moon and 1 captured asteroid moon

[@pieguy6992]

You should make a video on the complications of multiple-body planetary/stellar systems (such as trinary star systems or double-planet planetary systems with moons)

[@SkwithOv]

You make everything seem so easy, I appreciate it so much! Currently watching all your videos and marking the ones I need to repeat when seriously worldbuilding later

[@popslyme4280]

I've been bored watching the same videos over and over during lock down, so I thought I would come here to watch some of your videos. I haven't been here in 3 years. It's great to see this again.

[@trajectoryunown]

"Orgy of Moons" would make for an amazing band name

[@jonasbindslev9894]

The more I watch your videos, the more it occurs to me how fucking insane it is that we've had people on the moon.

[@qaiser648]

Battle typhoon How can you put people on the moon if the moon is a hoax?

[@jonasbindslev9894]

NaziDoge How can you send a rocket from Earth if the Earth is a disc?

[@thefishingboy2065]

EARTH IS A SPHERE U FLAT EARTHER! Wait, lemme calm down. I'll explain how it is spherical. 1. Gravity finds a shape that takes up as less space as possible, like a sphere. 2. Gravity condenses planets into spheres due to my first reason. 3. If Earth was a disc, ships,boats, etc. would fall off the edge. And there you go.

[@Chrischi3TutorialLPs]

your channel really makes me wanna create a star system where i go through the life of an entire species from their sentience developing to the times they start exploring their system on their own and create the languages to go along with it.

[@Dog-eg8lc]

Great video, Edgar! I already started creating some moons for my system, but at least i can add a few more details now, and refine some previous ones. Thanks again!

[@Artifexian]

+Dog Dog No probs, buddy. Glad you got something outta this.

[@Graeko]

Artifexian out of context: “veritable orgy of moons”

[@vapenation7061]

Why doesn't your channel have much more views/subs? It totally deserves it

[@pennergmeindl6229]

+toyota prius memes Because you need to use your brain way too much for most people to enjoy his videos.

[@parthiancapitalist2733]

Penner Gmeindl well I mean you do have a calculator, and he literally tells you what to do, you just need to put your own values. So easy, but when people hear "divided by" they have a heart attack

[@wrath642]

Edge

[@TRAVELLEROFWORLDS]

Enthralled with this channel. Love it.

[@NikolajLepka]

Your videos are startring to feel more and more professional and well-spoken really nice to see some improvement! keep it up, Edgar!!

[@Artifexian]

+Nikolaj Lepka Super! Glad that your enjoying the new style. :)

[@Artifexian]

+Nikolaj Lepka Super! Glad that your enjoying the new style. :)

[@SamuraiBonesie]

I'm thinking about drawing/mapping out my own celestial body. Thanks for this

[@oliverchandler8050]

ive just got to say, im loving the new art style.

[@bulgeo09]

I just found your Chanel through xidnaf and love it keep up the good work

[@jamesc.2054]

Best channel ever. I would love to see a vid regarding calendars.

[@matthewbartlett9222]

+Artifexian Could you do a video on the habitability of tidally locked planets around red-dwarf stars- especially the Gliese 667C system that may have three or four potentially habitable worlds. I'm picturing a specific type of planet that has certain characteristics to make it more habitable and produce a wider variety of niches for life. Let me explain... Let's assume the planet is massive enough to have an atmosphere that effectively distributes heat away from the day side and towards the night side (i.e. no temperature extremes drastic enough to boil oceans away or freeze them completely solid). Doesn't the process of rising hot air and sinking cold air mean that there could be nearly perpetual storms along the "polar equator" as I'm calling it? Imagine the planet has plate tectonics, so mountains could form and produce permanent shadows on the day side, with the shadows getting longer the closer the mountains are to the the night side. These shadows (which would exist over geological time scales) could host endemic ecosystems completely different from the night side, possibly including bioluminescence. Towards the night side, there would be increasingly more aerosynthetic plants and increasingly less photosynthetic plants. Aerosynthesis is my idea of plants evolving to harness the kinetic energy from the very reliable and constant winds always blowing from the same direction, but it would be exclusive to areas with no or very little sunlight, since they would easily be outcompeted by photosynthetic plants elsewhere. There could even be black forests on the day side taking advantage of the dim starlight with dark pigments. I'm also considering a mildly elliptical orbit that causes some libration so that the sun bobs up and down along the polar equator. This could produce a similar day-night cycle to Earth, albeit slightly longer- between 3 and 60 days depending on the orbit and mass of the red dwarf star. It would also have to be spinning fast enough to produce a dynamo effect for a magnetic field, so somewhere along the lower limit would be better. I'd imagine any intelligent species arising there would evolve on the landmasses along the polar equator. It would at least be the most friendly to complex life. Imagine a ring of city lights along the polar equator. I've made some amateur maps, but I'd like to see what you do with it. What do you think?

[@markenangel1813]

i didn't expect 6 paragraphs...

[@NikodAnimations]

For life to survive well, you need the star to be somewhat calm, like Ross 128.

[@blakechalmers4828]

2:30 How did he get 0.66 from 3.62? What equation did he use?

[@dionemoolman]

He’s comparing the density to Earth, which is 5.51 g/cm^3. 3.62/5.51 = 0.66.

[@llamazilla8712]

Thank you SO much

[@smartart6841]

I assume he does 3.62÷earth's density,to get its density in earth densitiess

[@dunkin15151]

I don't know how it is that I've only just found your channel, awesome stuff! Real emergency 4th year exoplanets revision....

[@vicviper319]

The quality of your vids continue to increase! Build on Artifexian

[@Artifexian]

+Bryant Adorno Cheers, buddy. Glad you enjoyed.

[@CZPC]

I love your videos very informative. I think I may make a solar system one day...*looks up at sky*

[@haiperbus]

One day could you make a video going into more detail about binary planets and the criteria for habitable ones?

[@Lucas72928]

Awesome video, I've been waiting for this one for a while...

[@Artifexian]

+LucasFlecoRepe Super! But sorry about the wait.

[@Lucas72928]

Artifexian Shouldn't be sorry, there was lots of cool stuff in the middle!

[@sparkys7231]

How long until the habitable moons video? Cheers your videos are brilliant!!!!

[@HankScorpio]

@ 6:01 "After another bout of intense number vomit" Ha ha ha had me crying in laughter ж-D

[@wcwyes]

think you'll ever do a video on the extended ipa?

[@reececrump8483]

dude...this is amazing. when I make up a fantasy world I either a: don't even consider physics and disregard the improbable for the sake of making a cool setting. _or_ b: use an existing exoplanet's characteristics when I want to have a feasible world as apposed to an imaginative one. But to bust out the text book and abacus to consider what style of solar system is physically possible? that takes dedication. well done.

[@angus4459]

Thank you som much for this Artifexian+ In your next video could you add something about moons with moons (satellites)? Thank you

[@Raptorclaw62]

Hi Artifexian! I was wondering, is there a calculation for these three things: 1) how easily spottable planets in the system are from the main inhabited planet 2) same for moon(s) around that planet 3) making the moon the right size and distance away to still get solar eclipses (same apparent magnitude) I think all of these would really help with worldbuilding! If my people can clearly see two moons, they might be the main deities, and if 7 planets are easily visible and known, perhaps a pantheon of gods may be intertwined to them, much like the Roman gods and our planets! Thanks for helping :)

[@brainzpvz2592]

Yes, indeed there are. The measurement for apparent size of an object is angular diameter. To work out the angular diameter of a planet/moon/sun in the sky of your planet, use the equation: 2tan^-1 * (D/2r) Where D is the diameter of your planet/moon/ect. in km, and r is the distance to it in km. You will get your answer in degrees. For example, if you do this for the moon, it will look like this: 2tan^-1 * (3,474 / 2 * 380,000) and we get ~0.53° degrees in the sky. Do it for the sun: 2tan^-1 * (1,392,700 / 2 * 150,000,000) = ~0.53°. Do it for earth from the moon, 2tan^-1 * (12,742 / 2 * 380,000) = ~1.92°. ect, ect. The absolute limit of human perception is about 1 arcminute. below that planets/moons will just appear like stars to the naked eye, like all the planets in our solar system do. Above that you will be able to discern phases and shapes of planets/moons to the naked eye. To convert degrees to arcminutes, simply multiply by 60. The moon and sun are roughly ~30 arcminutes. To convert to arcseconds, which is the next step down from arcminutes and is generally used when describing planets, simply multiply your number in arcminutes by 60 again. As for working out brightness of planets/moons, well Artifexian has a video on that kzbin.info/www/bejne/Z6SwZ4x4obCanZY but I will paraphrase the equation for brightness here: I * A * B * r^2 / D^2 * d^2 Note: I have added in the I value to account for the amount of the planet/moon illuminated. where I is the amount of the observed planet/moon illuminated, (measured from 0 to 1, where 0 is nothing illuminated, eg. new moon, and 1 is fully illuminated, eg. full moon), A is the albedo the planet/moon (measured from 0 to 1, albedo is the reflectivity of an object. 0 is a perfect absorber of light, 1 is a perfect mirror. For reference earth's is 0.3. The albedo values for all the other planets can be seen here astronomy.swin.edu.au/cosmos/a/Albedo if you don't know your planet/moon's albedo, just pick something similar to the planet it is most similar to) B is the brightness of your star in watts (The sun = 3.846 * 10^26 watts. To get your star's value multiply this number by your star's luminosity relative to the sun) r is the radius of the planet/moon you are observing in metres, D is the planet/moon's distance from the star, also in metres, and d is the distance to the body you are observing, again in metres. You will get an answer in w/m^2. For reference the sun is roughly ~1,368 w/m^2 For example Do this for the full moon: 1 * 0.12 * (3.846 * 10^26) * 1,737,000^2 / 150,000,000,000^2 * 380,000,000^2 = ~0.0429 w/m^2 Venus greatest elongation: 0.5 * 0.75 * (3.846 * 10^26) * 6,052,000^2 / 108,000,000,000^2 * 104,096,109,000^2 = ~4.18 * 10^-5 w/m^2 Jupiter at opposition: 1 * 0.34 * (3.846 * 10^26) * 69,911,000^2 / 760,000,000,000^2 * 610,000,000,000^2 = ~2.974 * 10^-6 w/m^2 Uranus at opposition: 1* 0.3 * (3.846 * 10^26) * 25,362,000^2 / 2,960,000,000,000^2 * 2,960,000,000,000^2 = ~1.0728 * 10^-9 w/m2 Simply run this equation for your own planets/moons. A few notes: Any number above Venus' value, as listed above, will be visible during the daytime and cast shadows during the night if there are no other lights nearby or other brighter celestial objects. Uranus lies near the naked eye brightness limit in light pollution free zones, so anything above Uranus' value would be visible to the naked eye. Keep in mind however, that even though planets brighter then Uranus would be visible to the naked eye, if they are much dimmer than Saturn they may not be identified as planets as they would blend in heavily with the stars. As such, Even though Uranus is visible to the naked eye (albeit only barely) it wasn't recognised as a planet till only a couple of centuries ago. So maybe a loose rule of thumb might be that planets would only be recognised as planets if they are halfway between Uranus and Saturn in brightness. So for your pantheon of planets idea you might want all of your planets to at least meet this criteria, but preferably at least as bright as Saturn to be considered gods or deities. Now, eclipses; To get a total solar eclipse you just need to make sure you moon doing the eclipsing just has to have a similar/larger angular diameter than your sun (which we went over how to calculate earlier). (It actually has nothing to do with the apparent magnitude, as that is a measure of brightness and not angular size, I do not know how to calculate it but I will leave you with the wikipedia article if you are interested en.wikipedia.org/wiki/Magnitude_(astronomy) ). If you want your sun's corona to be visible, like it is to use during total eclipses to us, then you need to make sure your moon has to have a very similar angular diameter to your sun, like our moon is. If you want an annular eclipse, also known as a ring of fire eclipse, then your moon has to have a smaller angular diameter than your sun. You don't need your moon to be permanently further, however, just have a somewhat elliptical orbit like our moon so it changes it's angular diameter over the course of it's orbit, so we have annular eclipses and normal eclipses. An interesting thing to think about may be moons with atmospheres or a habitable moon orbiting a planet with an atmosphere. During a lunar eclipse, it doesn't just go dark like earth, the moon is bathed in sunlight scattered by earth's atmosphere, giving it a blood red colour; a blood moon. If the moon eclipsing the sun had an atmosphere, a similar thing may happen to the planet, and it may be bathed in blood red light, which could have massive cultural implications. However cool this may sound, it is very unlikely a lunar-size moon orbiting a terrestrial earth-like planet could have an atmosphere; because of it's size it's iron core will cool quickly and it will lose it's magnetosphere, allowing the solar winds to strip it's atmosphere, like what happened to Mars (although mars still managed to retain some of it's atmosphere because it is a full size planet and has a higher gravity than any moon. It also does still have a magnetosphere (although it is not global and very weak). A moon wouldn't because they are obligatorily tidally locked so they rotate very slowly. Also, although being a moon, Titan avoids this issue because it is in Saturn's magnetosphere and is thus protected from solar winds, and the sun is also far weaker at Saturn's distance.) This issue could be fixed if your planet was in a binary planet system, with two planets orbiting each other both not tidally locked and both massive enough to be capable of sustaining magnetospheres and holding onto atmospheres. Alternatively your planet could be a habitable, earth-like moon orbiting a giant planet such as a gas/ice giant. That way when the sun fell behind the planet, which it often would on a habitable moon system, the light would be scattered by its huge thick atmosphere and would likely result in a deep red colour across the moon. Although in this setup, as the eclipses would be a common occurrence (it would vary depending on the moon's inclination, either being a daily thing for a moon with low inclination or a seasonal thing, happening during the equinoxes on higher inclination orbits) you would loose the spontaneity of the eclipses and thus loose the scare factor involved with your world being bathed in blood red light. Either way both scenarios would provide a very unique and terrifying eclipse. Oh, my, sorry for making this comment an absolute essay, lol, but I hope it helps answer some of your questions!

[@Raptorclaw62]

@@brainzpvz2592 thank you so much for the response, I love the essay. It truly is super helpful :)

[@spikethelizard2770]

4:55 might be and issue with the equation. I got 3.18 instead of 2.65. For reference, I did 2.44x1.2x(0.87÷0.68)^(1÷3)

[@Harbinjero]

So glad to hear I wasn't the only one.

[@inditsnotdenon922]

You know what's funny? I generally am not able to keep up with the video but I still listen because I really like your voice. Top notch genes there

[@pigging3048]

Finally! yes thank you! Ive been waiting for this video! yes!!! Good job!

[@Artifexian]

+Pigging Super glad to be of service. I will be doing moon videos so stay tuned.

[@RobinHilton22367]

Error in your video at 4:57 -> You rounded density of your moon earlier to 0.66 earth densities yet in this you have somehow changed it to 0.68 earth densities. Using earlier rounded number you'd get 3.2 times the Radius of the earth. Even using 0.68 I still get 3.178 times the Radius of the earth and not the 2.65 you got. Any help/clarification here would be much appreciated?

[@Artifexian]

+Robin Hilton Whoops! That figure should be 0.66 and the answer should be 3.2. My bad...don't know what happened there. You are totally correct.

[@RobinHilton22367]

+Artifexian Cheers. I run everything from your videos through a growing excel spreadsheet to speed up creation and then moving it from Excel to C#. Eventually will be able to generate entire galaxies in a single fell swoop and then be able to explore them :)

[@Artifexian]

+Robin Hilton Awesome!

[@ozeum20]

@@RobinHilton22367 Ohhhh, brother... 3 years and now I am moving this mechanics to C#

[@draighaeromos6997]

How do you get to the 0.66 from the 3.25(something)?

[@augustovasconcellos7173]

Could an earthlike moon ( orbiting an earthlike planet, of course) have a ring, or would the planet's gravity just rip it apart?

[@augustovasconcellos7173]

Also, can a habitable planet have two moons that orbit their combined center of mass? Kind of like a double star or a double planet system.

[@augustovasconcellos7173]

And does what does a moon need in order to stabilize the tilt of a habitable planet? Is there a way I can calculate them based on the size and density of the planet and the moom? And is it obligatory that the moon is tidally locked?

[@jordibear]

Moons can have rings. Our moon could even have rings, albeit small ones. This is allowed by the Hill Sphere of the moon, which is a region where the moon's gravity dominates over Earth's gravity. Binary moons, now this is getting a little trickier. It's possible, but not likely. The planet would have to be very massive, like a gas giant, and the moons' orbits would have to be large enough. Otherwise it would be highly unstable. But that's only a maybe. It could be that any configuration of binary moons is unstable. But it's never been modelled or observed, so we have no idea.

[@parthiancapitalist2733]

Augusto Vasconcellos dude, you can put rings on a moon orbiting a moon orbiting a moon, but you need to make sure that the others moons don't have very much influence on it, so they should all be close to the object they orbit. My planetary system actually features a moon of a moon of a moon (it's like a 35x40x80km wide moon)

[@iapetus6110]

@@jordibear yes ,one of saturns moons Rhea has rings and is the only moon with rings unfortunately

[@fortissimomezzo7527]

Your drawings and are amazing, and your explanations are easy to understand.

[@iteragami5078]

Artifexian, I think it would be great if you collaborated with mintephysics since you both share similar drawing styles and scientifical topics.

[@DarthBiomech]

Wait, but is it proven that Earth would be uninhabitable if it had no moon, or this is just a hypothesis? I feel that this is highly unlikely that planet must be virtually identical to Earth to have biosphere.

[@Artifexian]

+Darth Biomech No it hasn't but a large moon helps...a lot. I've learned today, from commenters, that there are hypothesis floating around that don't require a large moon for habitability. This is worth checking out. www.astrobio.net/news-exclusive/the-odds-for-life-on-a-moonless-earth/

[@DarthBiomech]

+Artifexian Oh, thanks)

[@seraphina985]

+Artifexian It's plausible that some degree of axial instability might be tolerable also though then you would need to think about that when building your biosphere. Large land animals should probably be built to be able to sustain travel like 50-80 km/day or so for up to several weeks at a time, flight would likely be a more popular adaptation too. Plants would need to evolve to make heavy use of species that liked the same climate as them to ensure their seeds get relocated and such too. In theory it works provided you don't make things too extreme I would imagine that if the axis shift was never higher than say 45 degrees over the course of the planets orbit, at least then the climate shifts would be happening at rates similar to seasonal variation which is slow enough that life could probably evolve adaptations for it.

[@amayasasaki2848]

What about that there would be no tides without the moon?

[@seraphina985]

+Amaya Sasaki While there are some theories that potentially cyclical daily wet and dry cycles might have helped concentrate the required molecules that doesn't necessarily only happen with tides. Highly humid regions can get a predictable downpour that occurs like clockwork after the sun passes the zenith too, the positive feedback cascade when air at 100% rel starts to cool is very effective in that regard. Granted lack of one of the main drivers which create the littoral ecological niche would probably reduce the prevalence of some kinds of species and it might make a land-marine or marine-land evolutionary transition take longer due to less of a borderline environment existing but it probably would still happen eventually. Fact is that suddenly being able to access new resources few other species are already competing for is a massive advantage.

[@geoffreybrunell5592]

I get that it's unlikely for uninhabited terrestrial planets to have any major moons. However, I think it's pretty unreasonable to say that uninhabited terrestrial planets should not have any major moons at all considering that Pluto has a major moon (yes I know that Pluto is a dwarf planet, but it still has the properties of a terrestrial planet).

[@geoffreybrunell5592]

+Katie Katie Since when did I say that all uninhabited terrestrial planets should have a major moon?

[@bluewisdomtriforce]

I was waiting for one about moons, thank you

[@Artifexian]

+bluewisdomtriforce You're welcome. I'll prob make a couple more moon videos so stay tuned.

[@bluewisdomtriforce]

+Artifexian yay! :-)

[@sparrowruth]

awesome video!! I used it to retcon a non-earth-identical moon into my Earth-identical and Sun-identical system, and was able to fiddle the numbers around to a point where the lunar cycle fit with my pre-established calendar Thanks!!!!

[@Nicetrybro563]

I'm having issues recreating the same result as of 2:31. I tried to divide 3.62^3 by the density of Earth to get 0.66, alongside anything I could think of and nothing worked, please help.

[@bluestar4408]

Same

[@sledzsledzowski7146]

orbital period equation is different in the video and in the description.

[@WeatherWonders]

The one in the description is definitely incorrect. I believe an accurate expression is 0.05865 * sqrt(R^3 / (M + m)) with R being the semi-major axis. I got this expression based on this source: www.bths.edu/ourpages/auto/2008/12/18/41272821/Calculating%20the%20Period%20_T_%20of%20the%20Moon.pdf Not sure what the best coefficient is, but the one I used gives a reasonably accurate result when you calculate for Earth's moon.

[@edibleapeman2]

I haven't been subbed for very long, but goddamn is it nice knowing I'm not the only one thinking about this shit. NEVER STOP.

[@Artifexian]

+edibleapeman Oh, I'm gonna keep going...don't worry about that.

[@dutchdrawer2798]

Nice one again, I did my own moon directly after watching ^-^

[@francisfernando8341]

Moon in mars: Deimos and Phohos Moon in Earth: Moon Most Biggset Moon: Jupiters Biggest Moon

[@user-qh5jk1mn5i]

?

[@vukman2665]

Francis Fernando Earth's moon is named Luna and that means moon

[@cheekybum1513]

Vuk Man its luna in some romance languages but it just means moon.

[@sulphuric_glue4468]

I prefer the videos where you draw stuff

[@WhisperingShade]

Thanks for a good vid. Maybe you could explain the moons having moons bit sometime and just how many moons a major moon could have.

[@IvanSN]

Oh oh! Would it be possible for a major moon to have its own major moon, or would it have to be a minor moon?

[@IvanSN]

(I'm going to be doing my own world building soon and I'm very very much interested.) ^^

[@emperorpalpatine2957]

+Ivan Solomon Nathan well the moon that is orbiting the main moon needs to be small, smaller than the object that its orbiting or else the moon will get launched out of orbit and possibly crash into the planet or out of the system in general and it depends on the size of your main major moon and the size of your planet so yeah it would most likely have to be a minor moon.

[@IvanSN]

Ebony Well, I knew it would have to be smaller, but what if the planet and moon are big enough for the smaller moon to still be greater than 300 km? Surely that could work?

[@Artifexian]

+Ivan Solomon Nathan In terms of worldbuilding, sure why not! There's nothing in the math that forbids it (at least nothing I can see). IRL might be a different story. Maybe try and keep the second moon very very small (radius, mass etc). The larger you make the bodies the more I'm inclined to not believe the system...if you get me.

[@IvanSN]

Artifexian I understand that completely. Thanks Artifex! ^-^

[@lulujuice1]

The roche limit is wrong? I keep trying it on any calculator I can find, I can not get 2.65, and that is *your* example planet.

[@lotusnaturals1897]

i tried for HOURS and never got what he did

[@lulujuice1]

@@lotusnaturals1897 i know, it's so frustrating ;-;

[@Rossomak94]

Could you please do an episode on tides caused by moons (both in the sense of elliptical tides and ocean tides) and what happens when you have multiple moons, or if your moon has a moon?

[@kbomb1235]

One of the things I'm having an issue with in US2 is placing my planets at a specific distance from a star or other planets. I love using your calculations to figure it out but I think another series for you to do would be to show how to build planetary systems in US2.

[@fluffyllama1505]

Will this series ever come to creating species, including human-like species and also reptiles, birds, insects, etc?

[@Artifexian]

+Fluffy Llama Eventually, yes. But it'll be a long long time before I'm ready to tackle these topics.

[@fluffyllama1505]

That's okay, these videos are just as great ^_^

[@prevalent1172]

+Artifexian i can't wait to see this. squeals in joy

[@thejurassicwarewolf3300]

i have incredibly high doubts that aliens would look like anything but earth animals

[@GameMaster10K]

how did i get here, i want to get to these kinds of things more often.

[@jasonlewis4438]

Note: Mainly icy bodies can have smaller radius, yet still be gravitationally rounded. Ex: Mimas is smaller than Pallas, and yet Mimas is round while Pallas isn't. The Gravitational Rounding Radius for mainly rocky bodies are at 800 km at least. So you can't have an Inner Terrestrial Major moon smaller than 800 km...

[@adeon5544]

Thank's so much for this new video ! Very interesting one more time !

[@Artifexian]

+Adeon Super! Glad you enjoyed, buddy. :)

[@Nosirrbro]

Just a note, life can absolutely form without a moon, and there is no reason having or not having a moon would make earth hot enough to boil away the oceans. Why did you include that photo? Anyways, ever heard of migration? Yeah, that's a solution to destabalized tilts, along with evolution. Also, Earth's tilt does move as well. Moons help life a reasonable amount but not having one does not provide any detriment whatsoever, especially givn that the main difficult part for life is it's initial random formation.

[@Ezullof]

+Nosirrbro To be fair, we don't know how random if life formation. Maybe it's a pretty common things for earth-like planets at birth - but then it disappears quickly, or it "fails" to become complex. The difficult part could be one of the three : either the initial borth, the survival, or the complixification.

[@Nosirrbro]

Napishtim Yeah, but really once you get to the point of complex sea life there really isnt much stopping the life at that point, and undersea life doesn't really care about any of the things that a moon provides. A way of thinking about it is a quality of life for land life, but in no wasy a prerequisite

[@MrMichkov]

+Nosirrbro But they make it much more likely for complex life to evolve and survive. Even life under the sea would have a hard time with massive axial shifts changing the climate all the time. Also there is the issue of asteroids which a moon might help with a bit, though the jury is still out on that case.

[@Nosirrbro]

Michkov Well for one Earth has still had it's fair share of asteroid impacts, and while a moon will absorb or deflect some the vast majority that would hit a moonless planet would hit a planet with a moon as well, just possibly in a slightly different location. And 'massive axial shifts changing the climate all the time' is a bit of an overstatement. Axial instabilities happen over hundreds of thousands to millions of years, plenty of time for migration, adaptation and evolution. Once unicelular life becomes at least slightly common on one part of any planet it is pretty much a guarentee that eventually complex land and sea lifeforms (Assuming the planet actually has land) are going to happen one way or another assuming the planet doesnt get annihilated or hit with an unreasonable sized asteroid that should only exist around that planet during the formation of it's star system. Don't need a moon.

[@parthiancapitalist2733]

nosirrbro well I already constructed my lunar calendar, so lol

[@EriqireM]

Hey Artifexian, are binary moon systems a thing? aka, can moons orbit eachother?

[@KlaxontheImpailr]

Check 5:05

[@EriqireM]

+Eric Southard not moons of moons but two moins which each orbit a point outside their volume.

[@KlaxontheImpailr]

+Edward McCarthy if there can be moons of moons then a "double moon" system would be a logical extension.

[@taimao2]

he goes over that when he talks about habitable worlds as an aside.

[@eitve]

When i saw your video on the first page i thought worldbuilding is some sort of a game, but when i just played scientific videos and it came to your video. Noice Sciejans stuf m8.

[@connielewis6290]

Are you planning to do a video on what effects having multiple moons orbiting a terrestrial planet would be? Such as tidal lvl/frequency, climate, different types of eclipses etc?

[@orsonzedd]

I disagree that moons are needed for habitability. It's really just that we evolved with one.

[@owlet6392]

Our moon both caused and stabilized our tilt. Without that tilt, we got nada.

[@orsonzedd]

I don't think that necessarily follows

[@owlet6392]

Which part? Can you explain?

[@orsonzedd]

I don't think it's necessary to have tilt for a planet to have life. really, we're just used to being super cosy comfortable, but not all life is like that, and some, I'm thinking of Tardigrades right now, are very adaptable to a wide range of environments. I mean maybe humans couldn't have evolved without a moon, but that's really not the point because we've already evolved.

[@therandomhat_]

Life COULD exist without a moon, but we would be like Mars (Which has constantly changing axil tilt) and would struggle to survive.

[@theskv21]

But why shouldn't uninhabited planets have major moons? Makes no sense.

[@33ev502]

+Eamon Bohan because the chance of multiple moon making collisions is very slim.

[@MechanizedArtist]

+РоБокинГ Jupiter and Saturn both have "major moons" as defined by Artiflexian: moons which have enough gravity to be roughly spherical. Io, Europa, Ganymede, Callisto, just to name a few of Jupiter's natural satellites

[@33ev502]

MechanizedArtist Well yes, but in this case were talking about terrestrial planets, that aren't past the frost line

[@ferguson704able]

Who says they can't?

[@parthiancapitalist2733]

Eamon Bohan well they _can_ but it is irrelevant. But whatever you want! Don't go too far though, terrestrial planets probably won't have 3 major moons

[@cursedalien]

Hey, I would really like a walkthrough on how the Hill Sphere Calculation is done, because there are multiple units of mass, so I'm hesitant to simplify the equation.

[@guaymaster]

Great video! Are you going to keep doing the conlang videos with Xidnaf? Or was it a one timer?

[@Artifexian]

+guaymaster So, far it's a one timer. We made no plans to collab again but never say never.

[@wires-sl7gs]

The Earth doesn't need to have a moon for organic life. there is edivence that earth may of had life before the moon was made.

[@matthewbartlett9222]

+2000wires gamming (wires) Even if there was life during the Late Heavy Bombardment period, it would have all died out when the moon formed. How would any of that evidence have survived the collision of Theia with the proto-Earth? It had enough kinetic energy to liquify the entire planet.

[@wires-sl7gs]

Matthew Bartlett Am only saying what I remember hearing, all I remember is that I heard there was Edivence for it. I also watch a doctumenty about what if we didn't have a moon and it said we would still have life but nothing as smart as us, also it said we wouldn't have jungles without the moon.

[@Ezullof]

+2000wires gamming (wires) I think it's rather that there is no evidence that life cannot be supported on planets with no moon. So far we only discovered life on Earth, so there is no evidence for life in other conditions than earth, only theories.

[@Titanic-wo6bq]

"90% Silicate, 10% Iron, and 1% water ice" but... that's 101%

[@phonerepair4436]

He said 9% Iron.

[@vitano5681]

hey soon could you do a video on how to actually map the world both by regions and world map, thanks love ur content

[@1998tkhri]

Great video! I came here from your collab with Xidnaf, and did think you deserved it, so I subscribed. With this video, I never realized how much math went into making satellites! That's incredible. However, I should point out- Other Mistakes I noticed: 1) 2:26 - 2:30 - you say 3.72, but the screen says 3.62 2) 2:30 - 2:33 - you say 0.68, but the screen says 0.66 3) 4:47 - 4:55 - you say "to the third power," the screen says what my dialect of English would pronounce "to the power of a third." This could just be a dialect thing. Also, if the screen is correct, you could use cube roots. 4) 5:38 - you say "2 degrees," but the screen says "i = 2^0." I get that 0 could be a placeholder for the degrees symbol, but want to make sure you're aware. These are all minor, and but should be pointed out. Keep up the good work! If I may, I wish you would do more conlang videos. I'm making a conlang for a fictional human civilization in the game NationStates (if you're on it, do check out the region I'm in- Esamir), and a whole worldbuild is a little overkill (besides, I'm not a moderator, and don't have power to do so anyway), but nationbuilding and languagebuilding is not!

[@Artifexian]

+Eliran Sobel I refer to point 1 and 2 at the end of the video. Point 3 I think is a dialect thing and point 4 is correct. By rights I should have used a proper degree symbol. Apologies for that. Tell me more about NationStates....I do not know what this is.

[@secretchannel1764]

Wow this is best likes to dislike ratio ive seen

[@InternetLaser]

What about Gas moons? Our sun has four Gas satellites.

[@InternetLaser]

***** Yeah really. Sure, a gas moon could only ever really orbit a gas planet, but it's still possible.

[@InternetLaser]

***** a gravitationally bound body comprised primarily of materials in their gaseous state that has reached hydrostatic equilibrium. IE: an object not unlike one of the gas planets we have in our solar system that is orbiting a much larger gas planet (10 Jupiter masses)

[@jordibear]

Okay so, it's difficult to say for sure (because no such system has ever been observed), but we can make some pretty well educated guesses and estimations. Gases are highly volatile, and have a lot of freedom of movement. This means they have a higher tendency to escape. So, a planet must be massive enough that it can hold on to all this gas. And it's just highly unlikely that such a moon could form while in the vicinity of a much more massive parent planet, which would strip away any of the gas from such a moon. Not impossible, just incredibly unlikely. However, if you consider a gaseous planetary binary (Two gas giants of roughly equal mass orbiting each other) this is more likely, yet still unobserved. But, if we consider the definition of a planet as a body having cleared it's orbit of all objects of a similar mass, such a system can't exist by definition. It would be something else entirely, but not planets.

[@franklinkz2451]

Your foul ass mouth is a Gas Moon... lol oh shit sorry! I really didnt look close enough at the orher guys name lol it looked like you were just saying Fuck everyone and then respond to them😂 I really do suck! But in a more serious note, a gas moon would be physically impossible, the gravity of the planetary body it would be in orbit of would strip away its gasses or the star they both orbit’s solar winds would strip it clean due to a moons very low gravity to hold its gas to it

[@franklinkz2451]

Ja-Shwa Cardell but that was and is a very cool idea, we have found stars, planets and everything else we thought could not exist, Exist! but yet there it is so i could never say with 100% confidence that a gas moon could never exist somewhere out there! And kudos for about the most unique question about cosmology I have ever heard; Ever!👍

[@zjonathan09]

Nice video. I hope that in the next video about habitible moons you can mention pandora from Avatar.

[@evin290]

Please make a video about a habital double planet system. That sounds extremely exciting!!

[@Artifexian]

+evin290 Perhaps...but it's actually not the most exciting thing that can be sone with habitable moons. Stay tuned! ;)

[@kieubasiarz]

Waiting for a video dislike... they're very rare.

[@DasEtwas]

2 :o

[@HankScorpio]

+DasEtwas Those two people should be identified and shamed for misuse of dislikes.

[@DasEtwas]

Johnny Wings aye

[@kieubasiarz]

Johnny Wings I didn't dislike, just waiting for more haters.

[@DasEtwas]

Yeah we got that :)

[@ivarkristinsson5510]

These videos are one of my favorite to watch and I really want to make a world but I have no idea were to start.

[@claytonkrumm143]

+Ívar Kristinsson start with his first episode, then marathon away following his steps

[@Artifexian]

+Ívar Kristinsson Start with the first video I ever made and wrong through them in order building as you go. By the time you get to this video you'll have made a stars, galaxies, planets, moons, seasons (sorta) and will have a start on a language.

[@claytonkrumm143]

Artifexian Hi

[@ReyGarza]

Thanks for this video. I think I want to try out a double planet system.

[@Jsome13]

I do believe that instead of the hill sphere formula you should use the sphere of influence formula for determining the outermost distance your moon can be from your planet, Edgar.

[@talitajames7652]

cant wait for the calendar building!

[@Dominikbeck12]

Correction : Actual density of the composite moon of earthlike world would be slightly lower, since V1 + V2 + V3 = V conservation of volume, hence m1/ρ1+m2/ρ2+m3/ρ3 = m/ρ Dividing by m : w1/ρ1+w2/ρ2+w3/ρ3 = 1/ρ where "wk" are percentages given. So numerically ρ = 3.34 gcm-3 On the other hand, this kind of videos are rare on KZbin, and sofore but not only they are spectacular, you make me a happy subscriber :)

[@FellowRabbit]

Do you have plans to go more in depth on habitable planets with more than one major moon? It would be interesting to know how they would both affect the tides and how they would otherwise interact with the planet.

[@IAMCUBEMAN]

I'm really liking this new animated style, BTW.

[@Artifexian]

+Bradley Neon Cheers, I really wanted to learn how to do digital animation so I'm glad you like it. Need to get faster at it though. At the moment it's taking forever to produce a video.

[@IAMCUBEMAN]

+Artifexian I wish you luck!

[@maxwchase]

So far as stabilizing axial tilt, the paper you sourced some of the season-building video from (stuff like the heat dynamics reversing at 54 degrees tilt) mentioned that they simulated having Jupiter closer to Earth, and that ended up more stable without the moon than with, and I think closer Jupiter+no moon was comparably stable to the actual arrangement. So, it might not be strictly necessary to give a habitable world a major moon.

[@lightspeedlife8299]

+Artifexian I found another small speaking mistake. At 4:35, you say "...to the third power" but you mean to the *one-third* power. Your videos are fantastic, by the way! Thank you for doing this! Going to check out your habitable moons video now :3

[@asailijhijr]

Yaaay! Another one!

[@Triumphantable]

i thought you were one of those science youtubers with like, 500k subscribers or something, but then found 30k subs! wow, but keep up the good work

[@bellpara5725]

I'm doing a project like 6 years later and this is still so useful!!! Also, I dont know how but my moons orbital period is longer than my planets orbit around its star