All Questions
58 questions
3
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2
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How to calculate the Draconic month on a fictional world
I am working on a world and want to be able to find out when Eclipses occur, and I found you need to know the Draconic Month, I think I have everything I need to find it, I have the inclination to the ...
- 589
2
votes
1
answer
158
views
Could one moon appear to always follow/lead another in the sky?
Is there any way a second moon would appear to hang out near the closer one in the sky? For example always appearing either ahead of or behind throughout the year, or even alternating between those ...
- 53
2
votes
3
answers
403
views
How would a planet's surface be younger than the planet itself? [closed]
Europa, one of Jupiter's moons, is 4.5 billion years old (like Earth.) However, its surface is only 20-180 million years old. What could lead to a planet/moon's surface being younger than the planet/...
2
votes
2
answers
247
views
What astronomical situation could account for the PERCEPTION of a very erratic day / night cycle for a planetbound population with limited science?
I would like to create a world that is at a roughly medieval level of scientific understanding and which - as far as it appears to the inhabitants of that world - has a highly erratic day and night ...
- 21
0
votes
0
answers
147
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Can there be habitable moons despite heavy changes in axial tilt of their mother body?
Ok so i created a gas giant with 10 Jupiter masses and like 9 moons between 0.8 and 1.5 earth masses. All exept the most distanced of those moons are tidally locked to the gas giant and their axial ...
- 173
3
votes
1
answer
177
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Can a tidally locked planet with two counter-orbit moons exist for at least 100,000 years?
I believe it is true (correct me if I'm wrong) that a planet with a significant moon such as ours cannot be tidally locked. The orbit of the moon would continue the rotation of the planet and must, ...
- 132k
0
votes
2
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649
views
Space Elevator for Ganymede
My settlement on Jupiter's moon Ganymede is to get a space elevator. Unfortunately, I am completely overwhelmed with the math: How long would the cable have to be to the stationary anchor point in ...
- 265
3
votes
1
answer
122
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Geological activity and of superearth - cannonball moon system
I understand that this situation is hypothetical -- I just need a piece of advice to make it more realistic.
In my story, there is a superearth of 4,5 Earth masses and 1,35 Earth's radius, rotating ...
- 31
1
vote
1
answer
66
views
Could a substantial atmosphere protect a large moon from radiation belts like those seen in Jupiter's magnetosphere?
I'm imagining a moon with a mass of 0.25M (so 10 times larger than Ganymede), in Ganymede's position orbiting a gas giant like Jupiter. Maybe the atmosphere is anywhere from 0.1 - 1 bar. Would the ...
- 985
4
votes
2
answers
114
views
What would happen on a binary planet if they captured a new moon into orbit?
I've been working on a world where the origin of the magic system is a catastrophic event that ripped the surface of the planet apart allowing magical energy from beneath the crust to escape to the ...
- 41
3
votes
3
answers
1k
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Could a planet without an orbiting moon still be habitable to human life in at least one small pocket? [closed]
No moon likely means no tides. Does this make a planet half water, half land, or similar divisions? Do freshwater and saltwater have separation? Or would it just be a planet like ours, with delineated ...
- 47
16
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17
answers
5k
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What would cause a moon to become much brighter only a few times a year?
I initially wanted to create a culture that used tides to tell the seasons, I'm sure I still can, but a question on here (I can no longer find it) made me wonder if I could set up a world where one of ...
- 2,462
7
votes
4
answers
541
views
Would it be possible to have an earth-sized planet have much larger tides while remaining habitable?
I want a planet with roughly the same mass and volume of earth to have tides on a much larger scale than earth, enough that the coast would be extended for at least several hundred feet at low tide in ...
- 507
6
votes
2
answers
601
views
What would happen on the surface of a terrestrial planet captured by a gas giant?
So, from what I've read of Porter & Grundy (2011), most gas giant planets orbiting within their star's habitable zones are thought to have migrated there from further out in the solar system, with ...
- 131
-1
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1
answer
90
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How great could tides be on Earth (or an Earth-like planet) if you swapped the Moon? [closed]
Assuming a planet would have Earth's surface gravity and about the same share of it's surface covered by water, how great could you make tides if you could make the moon bigger, smaller, denser, less ...
- 765
8
votes
4
answers
2k
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Is there a plausible way to have a Gas Giant with two or more earth to mars sized moons orbiting it in the Habitable zone?
A hypothetical scenario I'm batting around in my head is a Habitable Gas Giant system consisting of a roughly Saturn sized body orbiting a sun like star at a comfy goldilocks zone distance. Orbiting ...
- 766
6
votes
1
answer
400
views
The Earth and Moon resolidify under a bluer star, their outer layers evaporated and burned away. What do they look like now?
(This is the third in a series of questions, starting with Moved into further orbits to protect them, how much damage do Earth and Moon take when the Sun expands? and How soon does the Earth's ...
- 460
4
votes
2
answers
379
views
How can I have an Earth-like moon?
My story takes place on the moon of a large gas giant planet. I have been trying to decide on a way for the moon to be as Earth-like as possible, but I have now decided to ask the community for help, ...
- 6,322
7
votes
9
answers
2k
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Realistic ways a Planet or Large Moon could have Variable Day/Night periods
Hello I imagine this is a pretty straightforward question, perhaps already covered in another post, but I wanted to get extra perspectives and options for achieving this type of planet or moon. So ...
- 159
5
votes
3
answers
409
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How to get rid of the rainforest for a desert moon with only habitable poles?
I wanna build a habitable desertworld which is a gas giant moon. The desired and already semi-fixed parameters are:
mass between 0.4 and 0.25 Earth-masses
only 10 to 30 percent global ocean cover, ...
- 17.2k
4
votes
2
answers
420
views
What would be the effects of replacing the Moon with an Earth-like planet?
Let's assume that for whatever strange -- probably magical -- reason, the Moon was suddenly and instantaneously replaced by a planet identical to Earth in terms of mass and size. Its orbital path is ...
- 1,067
11
votes
2
answers
570
views
How long would this eclipse last?
For a moon orbiting a gas giant which is in turn orbiting a star, I want to know how long the eclipse would last for an observer standing on the moon when the planet passes between the moon and the ...
- 4,153
7
votes
5
answers
457
views
160 Year Solar Orbital Period & 1.9 Year Moon Orbital Period - Is it possible?
A defining factor of my world is the hardships inhabitants have to face when surviving long seasons. Due to the extreme length of a year, time is largely measured by moon cycles. I need to make sure ...
- 173
11
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3
answers
1k
views
What is the maximum orbital time for my moon around my planet?
I fear the math involved is beyond my capabilities on this one. I have what I consider to be more than a Layman's understanding of the physics involved, and I believe I can follow the math well ...
- 4,153
8
votes
3
answers
369
views
Is this planetary moon's calendar possible?
I'm attempting to create a world that has very brutal, hard swinging weather and environments, leaving much of the planet desert-like. The world I've designed is a moon of a gas giant.
The Parent ...
- 2,027
10
votes
4
answers
542
views
A brighter moon that's harder to see
In honour of the full moon an odd moon question for you all.
The idea is to create a situation in which the inhabitants of a world believe utterly that the moon only exists at night. I'd also like to ...
- 51k
21
votes
5
answers
4k
views
Would a planet appear to wax and wane as observed from its moon?
Assuming that the observer is on the moon for a full lunar cycle, would the appearance of the planet wax and wane, would the moon's shadow occlude the planet during an eclipse while on the moon?
- 211
4
votes
3
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439
views
Can moons counteract each other?
Would two moons of equal size and distance on opposite sides of a planet counteract each other's tidal pull?
- 1,122
3
votes
3
answers
3k
views
Is it possible for a planet to have three moons?
If you have ever played an Elder Scrolls game and observed the night sky, you'd notice that there are two moons (most notable in Oblivion and Skyrim). They both orbit Nirn, the planet the game is ...
- 119
11
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4
answers
417
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Could a gas giant's moon have stable rings?
The planet orbits a supermassive gas giant, almost double the size of Jupiter. But the planet orbiting it is also supposed to have rather large rings in my story.
Question: Is it possible for a moon ...
- 1,032
1
vote
3
answers
615
views
Planet half the size of earth with two moons. Livable? Climate Range?
This planet I am proposing is approximately half the size and mass of earth and has two moons. The moons are respectively 1/8th and 1/10th of the size of the planet.The moons orbit the planet at ...
- 23
4
votes
1
answer
326
views
That's a big planet, but how big is it?
If a tidal locked terrestrial sized moon with 0 eccentricity, 0 incline, and was orbiting .01 AU away from a gas giant with 12 Jupiter masses (which would have approximately the same radius as Jupiter)...
- 159
3
votes
0
answers
117
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Can you have an eccentric horseshoe orbit for long? [duplicate]
I'm going to keep it simple, so I can maybe get an answer. Can you have two habitable terrestrial sized moons of a gas giant or brown dwarf in a stable horseshoe orbit (50+ million years) that is also ...
- 159
9
votes
3
answers
347
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Is it possible for a planetary ring to exist beyond a planet's Roche limit?
So my story takes place on a moon orbiting a gas giant about the size of Jupiter and I was wondering if it was at all possible for a planetary ring to exist beyond the planet's Roche limit. I ...
- 121
2
votes
2
answers
434
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Binary Stars with planets in P-Type orbits
For a gas giant to have a habitable Earth-like moon, in a P-type circumbinary orbit with the stellar classes of the 2 stars being A7 type III and F2 type IV separated by a distance of 2AU to 3AU, what ...
- 21
2
votes
1
answer
610
views
How could a TINY Second Moon minimally affect Earth? [duplicate]
So I found this site through this other question asking generally about what Earth would be like with two moons. However, these responses, like pretty much everything else I've been able to find ...
- 29
2
votes
0
answers
103
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What effect would 2 Luna-like moons have on an Earth sized (and ecologically Earth-like) planet? [duplicate]
Assume for the sake of argument that both moons are very similar to ours, in size and composition. Perhaps one is slightly smaller than our moon, while the other is slightly larger.
Furthermore, in ...
- 21
35
votes
6
answers
6k
views
What's the smallest reasonable natural planet or moon with Earth-like surface gravity?
We all know that equation for surface gravity is
$$ g = \frac{4\pi}{3} G \rho r $$
So if we want Earth-like surface gravity of $ g = 9.81 $, then the equation for radius is
$$ r = \frac{3 g}{4\pi G ...
- 33.4k
3
votes
1
answer
104
views
Can an ocean moon with a mass of 0.5 earth masses stabilize the axial tilt of a planet two times bigger than earth?
The world will going to be the homeworld of an hairless feline humanoid race, but I want to see the plausibility of this scenario?
- 231
24
votes
3
answers
4k
views
Realistic sky of an Earth-like moon orbiting a gas giant (length of day and size of celestial bodies)
I'm trying to work out what the sky looks like on an Earth-like moon, in particular the length of day and apparent size of the other celestial bodies: the gas giant's size, the gas giant's other moon'...
- 487
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6
answers
1k
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Giving a Planet Sunburn
How can I make a colonizable planet/moon that receives intense UV/x-ray radiation on parts of its surface while receiving much less on the rest of it?
The most obvious way of doing this is to have the ...
- 1,768
21
votes
3
answers
4k
views
Reality Check: Habitable moon around earth-like planet
For a complex world-building scenario I want a habitable moon orbiting a habitable earth-like planet. The habitable moon should allow for flora, fauna and landscape as similar to earth as possible. ...
- 591
12
votes
8
answers
6k
views
What would a planet with no moon look like?
Consider a planet identical to Earth except that it has no moon.
How long is the complete day-night cycle on this planet? I've heard that having no moon would speed up the planet's rotation, ...
- 239
5
votes
1
answer
323
views
Could my moons-planet system be stable?
In my fictional world I have selected all parameters to maximize the Hills Sphere of my planet. The planet has three times Earth's mass and it is located in 2 AU from its star that's 1.4 times more ...
- 53
12
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6
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3k
views
Can a planet without one or more moons be habitable?
My titled question was, can a planet without one or more moons be habitable?
In more depth, how would that planet be affected overall, without the moon to affect the tides and without providing light ...
- 185
0
votes
1
answer
380
views
How close can two Earths be without becoming tidal locked?
I have decided to change the numbers to make it easy on Hohmannfan. These two planets, for all intents and purposes, are identical to Earth, with he moon replaced by another Earth. So now the question ...
- 7,026
4
votes
2
answers
324
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If Earth had an ellipsoidal moon, would that change tides and such?
I'll be honest here; I don't know much about the physics of planets and planetary systems, etc. However, I've been looking into ellipsoidal moons, and most of what I've found is about Nix, one of ...
- 73
13
votes
2
answers
2k
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What are the parameters of a planet having multiple moons?
I'm not sure if this question belongs here or over on Physics Stack Exchange.
The Earth and Moon are unique in the Solar System in that the Moon is a significant size compared to the Earth, at 1/4 ...
- 10.5k
15
votes
2
answers
6k
views
What would happen to Earth if the Moon was destroyed?
In the movie Oblivion, the Moon has been destroyed by invading aliens. Several shots of the moon show what is left:
If the moon was somehow shattered like this, what would the effect be on Earth?
8
votes
2
answers
2k
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Seasons/Months on a Habitable Gas Giant Moon
My moon is the basis for a fantasy setting, but I just can't bring myself to abandon science and say "a wizard did it." I want to make the months and seasons realistic, and I want to find a way to ...
- 2,568