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Questions tagged [gravity]

For questions about the universal accelerative force between all objects.

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I need flying cities!

Writing about suspended cities within a planet's atmosphere! The story itself focuses on the air forces that fight for each of the hundreds of floating city states living in the sky, but that's here ...
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1answer
73 views

what exactly i̇s the gravi̇tati̇onal force? [on hold]

As I read in other web pages, gravitational force is the attraction force of 2 objects. But when I think about it, it seems like it is the force actiong upon us, like pushing us. On the other hand we ...
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2answers
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Could the TRAPPIST-1 planets have moons?

The TRAPPIST-1 planets are all very close to each other and thus are subjected to strong gravitational forces amongst each other and to the red dwarf they're orbiting. Would it be possible for them to ...
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1answer
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How does the n-body-problem affect a star system around a red dwarf?

So my story is set in the TRAPPIST-1-system and a rogue planet enters the system. When it's still far off, a scientist discovers that one of the numbers is slightly off. (She has some tables that ...
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417 views

Lifting Gas in a world with 1/3 of earth's gravity

As many of us probably know airships were one of the great forms of transportation in the 20th century but a great hindrance to their development was weight. In a world I am currently constructing the ...
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5answers
179 views

Big and fast rogue planet

There is a big, very big planet that is travelling fast, very fast. It’s a rogue planet (not attached to a star system). It’s going to pass close, very close to the earth. The earth is probably going ...
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5answers
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Building muscle in high G to be stronger in normal gravity levels?

In micro-gravity and zero G, people's muscles deteriorate. If you sent a set of already very physically fit soldiers to train/live on a high gravity planet, would they perform better than other ...
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6answers
644 views

Can a collision with a neutron star make a planet via the can-o-snakes method?

Simplistically, a neutron star is a celestial body with enormous mass crushed into a small volume. That crushing force is gravity and the result, one might think, is atoms packed much more closely ...
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Are there any plausible 'alternative' methods of planetary formation?

The selected answer on this question provides an extremely good, and detailed, description of what is generally accepted to be the main (only?) way a terrestrial planet can form, i.e. through ...
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5answers
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Can the Sun lose enough mass that Saturn's current velocity becomes escape velocity?

Imagine that, through some cosmic phenomena not yet understood, the Sun 'burps' and ejects a vast amount of its mass into the cosmic void. A huge coronal discharge, perhaps. A pressure bubble inside ...
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3answers
379 views

Is there software to help me model tides?

I have a planet orbiting a roughly Sun-like star, accompanied by a moon that's a bit more massive than our own Moon. The surface is about two-thirds water and one-third land, with most of the land in ...
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2answers
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A balloon that can float to space [closed]

I’ve heard there are materials that can withstand the image sort of the earth’s atmosphere, such as carbon nanotubes and Kevlar. Supposedly, a perfectly constructed bridge of such material could be ...
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1answer
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Given the mass and composition of a planet, can one determine what the radius should be?

I'm trying to auto-generate random solar systems, and I'm basically just allocating 2% of the total system mass to planets (and moons). It provides interesting results, I always have a few gas giants, ...
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4answers
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Would weights in clothing be an adequate way to compensate for low gravity?

Would heavier clothing solve the problem of bone and muscle loss in Martian gravity? It doesn't have to be a perfect solution, I just don't want my Martian colonists to be total wimps compared to ...
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2answers
245 views

Are there currents in space? Space flotsam?

You know how there are some beaches in the world where tons of sea glass or other random sea trash washes up, just because the currents and the shape of the land naturally collects it all there? I was ...
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1answer
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Aritifical Gravity through Rotating wheel generalisation in a spatial 4th dimension

I'm taking the example of a rotating wheel space station, in which artificial gravity is created through rotation due to the inertia inside. The idea in the 3D environment is that the wheel (2D) is ...
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2answers
94 views

Earth-like planet which is smaller but has the same gravity

If there were a planet similar to earth where the lines of latitude and longitude were half as far apart (about 35 miles instead of about 70), but the planet's density were increased to compensate for ...
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2answers
140 views

A sudden decrease of gravity on Earth [closed]

I have an idea about a story where gravity suddenly changed and became about 10-20% weaker (lower). Humanity now needs to adapt to the new situation. What disasters and catastrophes would this sudden ...
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6answers
399 views

How could you tell if someone was messing around with your gravity?

I'm working on a story involving first contact with an alien species that bases their space travel on directly manipulating gravity fields. My question is not about how that would work, but rather how ...
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3answers
176 views

Largest artificial planet

How large could a solid planet be (in theory) without becoming a star or black hole? Too much in the way of light elements would lead to thermonuclear ignition, but too many heavy elements would ...
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3answers
144 views

Making a 180 degree turn around a star

For a book under construction, I need a starship to make a 180 degree turn rather quickly. Give him sub-light speed in a star system (no relativistic effects) and on a path to the system primary. I ...
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2answers
94 views

Gravity being weaponized for its time altering properties

Physics isn't my strong suite, but I'm trying to understand if something could be theoretically possible in some highly advanced future: Would it be possible for an advanced civilization to invent a ...
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22answers
5k views

Plausible hypothesis on why gravity might fail on earth

I've been grappling with a story for a while, involving a scenario where gravity starts to fail. The goal of the story is mostly how people react to the knowledge that the world will end. But, I also ...
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4answers
292 views

Alternative to gravity inside a Dyson Sphere?

On the inside of a Dyson sphere there is effectively no gravity. Is there an alternative method to keep people on the inside surface from floating around? I know it could spin and that would keep ...
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4answers
2k views

Simulating gravity in a gravity-less universe

In my fantasy universe, there is a disc-shaped world that has a flat surface that has roughly the same atmosphere as Earth (see this); the atmosphere moves along with the world. There is no gravity in ...
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3answers
87 views

Conditional deniability of a natural asteroid belt with an atmosphere?

Is it unreasonable to suspend one's disbelief that an asteroid belt naturally formed with enough mass distributed through the belt to justify the formation of a belt-wide atmosphere given the ...
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3answers
237 views

Is it possible for humanoid life to develop on a 1.4 G planet?

I'm writing a JRPG-inspired novel set on a planet with 1.7 Earth masses and 1.4 Gs, but is it possible for life to even develop on such a high-gravity planet in the first place? I tried scouring the ...
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3answers
166 views

What should the size of my moons be?

(Not entirely sure if this is the right place to ask this but hopefully I'm right!) I'm writing a novel and the planet this novel takes place on has two, twin moons of approximately the same size. ...
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2answers
145 views

Effect of 1.5g (Induced hypertension health effects?)

On this planet, gravity faces many fluctuations, but humans spend most of the time in 1.4-1.5 gravity. During these periods (usually lasting about 5-7 days) I was thinking I'd have them increase salt ...
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6answers
325 views

Would lower gravity lead to earlier spaceflight?

This is in regards to the Tyranny of Rocket Fuel. Summed up: Heavier ships need more fuel which makes them heavier, etc. You end up with diminishing returns. This is compounded by higher gravity - ...
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6answers
448 views

What would happen to the Moon if it was lowered onto the Earth?

An absolute madman of a scientist tractors the Moon from it's orbit, and carefully lowers it through the Earth's atmosphere and gently brings it to rest upon the Earth's surface. There is no reentry, ...
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9answers
11k views

What are the effects of slicing the Earth in half with a particle beam?

Scenario: An exact copy of our world is sliced in half by a particle beam. The beam has a diameter of 40 meters and moves at a speed of 0.999c. The beam slices the earth from top to bottom in 600 ...
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3answers
242 views

Magic: Reality check of effects of mass-altering magic

I'm looking into magic systems for my fantasy world, and among other things, I want to make sure that I have the effects right. One such magic system allows the user to create a small 'bubble' of ...
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2answers
132 views

Reality Check: Planet with low gravity and water vapour

Using Artefaxian's excellent spreadsheet I have created a basic idea for my planet, but in the 'Stability Checker' part my low gravity planet is unable to hold H2O. I am wondering if it is possible ...
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7answers
7k views

5km artificial planet, with same gravity as on Earth

So, the idea in a story is that in far far future there’s a trend that rich people, they are able to buy themselves planets. Tiny little planets with sizes 4-6 km (3-4 miles) in diameter. The company ...
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2answers
148 views

Multiple moons but only one of them is tidally locked to its planet?

A habitable planet with multiple moons, only one of which is tidally locked to the planet: is this general scenario possible? I understand that tidal locking takes a very long time to happen. So ...
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5answers
388 views

How would gravity affect a structure that completely encircled the earth

If a circular structure could be built that would wrap around the entire earth, but was of a larger radius, would it 'float' above the earths surface or would it somehow fall onto the surface at some ...
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4answers
232 views

Hyperdense Object

If a planet has a core of super-dense material, how might that effect the geological composition of that planet? Specifically: imagine a lunar-sized planet, with earth-like geology and density. If ...
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6answers
169 views

Reasons People Wouldn't Weaponize These Gravity Machines

So when making my space stories I have put them in a technological time in history where gravity manipulators are available to the common creature and you can use it to go to other planets and live in ...
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3answers
632 views

How much artificial gravity could create a black hole?

In my world, people have powers based on the four fundamental forces. One of my characters can generate spontaneous gravity to crush his opponents. He's also resistant to his own power (so I ignore ...
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5answers
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What are the safety margins for destroying a planet from space?

My empire's flagship, the Persecutor class UJBHE1 Abhorrent, rides into the home system of my greatest enemy, Baron Obsequious, levels its Death Ray2 at his beloved home, and pulls the trigger.3 ...
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3answers
278 views

Humanoids in Super Earth

So, I was reading this article about how difficult it would be for any alien race to escape an exoplanet with about 10 times the mass of Earth. It states they probably would even lack satellites. ...
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3answers
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How large can surface gravity anomalies grow before the planet becomes uninhabitable?

Is a planet with varying fields of gravity possible? Yes. Earth has varying gravitational fields at various different times due to various factors, mainly location based. How extreme can I make these ...
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3answers
94 views

Solutions for sustainable living in reduced gravity environment

I am building an idea for a terraformed environment with 1/6 the gravity of Earth, with a permanent human colony that has been established and sustained for 40+ years. I have thrown around a few ideas ...
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2answers
195 views

Effects of gravity upon weather?

So there are loads of things that are taken into account with weather from geology to water currents to axial tilt etc. But i am wondering what the effects would be on weather on planets with varying ...
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7answers
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Could a cave-in or avalanche in low gravity be dangerous?

I have a character on the surface of Enceladus, one of the moons of Saturn. It has an icy surface on top of what is believed to be a liquid ocean. There is no atmosphere, though near its south polar ...
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1answer
127 views

What happen to gravity if time is suddenly running backward? [closed]

From my naive understanding of Einstein theory of relativity: gravity is not a force but only a consequence of inertia in a world where mass deforms the space-time. Without time, no gravity is ...
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2answers
206 views

I want a layer out of frozen clouds floating around my planet. How could that work?

Beforehand: I must excuse my english. It's not my native language. Neither take this question too seriously. It's a stupid concept and I don't think that I will keep it by. It's just very "cool" to ...
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4answers
249 views

Valid justification for “GMO mech suit”

I'm writing a story about a group of humans (or humanoid people) that are living on a spaceship that's orbiting a planet with high gravity; the force is too much for direct human involvement. There ...
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2answers
72 views

How big would be a planet with a fifth of Earth's gravity? [closed]

First of all, I want to make clear that I don´t know how to calculate the gravity of a planet in m / s². Starting from there, I don´t know any formula referring to this knowledge and that is why I am ...