Questions tagged [gravity]

Questions regarding the attractive force present between two masses. If about research in artificial gravity (i.e. manmade substitutes for gravity), please use the artificial-gravity tag.

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Science Contest Topic (space exploration)

I'm thinking of entering the Breakthrough Junior Challenge. It is a global science video contest in which participants have to explain a hard science/math topic in a 3 min video. Right now I'm ...
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Archimedes Principle on other planet [closed]

How does the Archimedes Principle work on other planets where the gravity is different.? Does the wood block will float exactly same in water tub on different planets as on Earth.?
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1answer
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What does the Moon's gravity feel like? If you don't move, could you still tell you're on the Moon?

I am interested in descriptions and discussion from the Apollo astronauts. Almost all animals and many plants are sensitive to the earth's gravitational field. This is important for large mammals and ...
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What keeps galaxies together? [closed]

The super massive black hole at the centre of Milky Way has a mass of about 4 million times that of our sun. Is this enough to keep the entire galaxy together, is it this black hole which keeps the ...
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Would an astronaut experience a force during a gravity assist maneuver?

When an astronaut is inside of a ship accelerating (from engine burns), or decelerating (due to reentry) they experience a tug in a relative direction. Suppose an astronaut is in a space ship that is ...
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Can a satellite orbit the ISS?

Is stable orbit of a small satellite around the ISS theoratically possible with minimal station keeping?
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If I know the masses, positions, and velocities of two objects, how do I calculate their trajectories under gravity?

I was thinking about the effect of a near-miss with an asteroid upon the orbit of the earth around the Sun. My goal is to figure out a formula I could use for a visualization I'd like to build to get ...
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1answer
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My vector math seems to be off in this 2D simulation of a solar system

I intend to simulate gravitational acceleration on a 2D plane (simplified, no gravitational constant). My code is interpreted without any error in the console, but instead of having the two circles ...
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2answers
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Gravitational force of asteroid Bennu

How can the gravitational force of Bennu (being so weak) hold the spacecraft in orbit?
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2answers
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Two spaceships fly straight, parallel to each other, tied to each other by a rope, and pass a black hole between them. What happens to the rope? [closed]

To elaborate more on what I mean: Two spaceships are flying parallel to each other, both going completely straight relative to the observer. Their distances between each other do not change, as the ...
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Unix Epoch in International Space Station

The International Space Station is in a different gravitational field than us on the Earth's surface. Almost all computers / protocols depend on the Unix epoch being consistent everywhere. The Unix ...
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1answer
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Does gravity affect sweating?

I read this hot question. It's asked what is done with the sweat produced by astronauts in the ISS. This led me to question: does gravity affect the production of sweat? Is more, the same, or less ...
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1answer
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How does a rocket go from gravity turn to orbit?

A rocket launch normally begins with a roll to align with the orbital plane and a pitch to allow gravity to gradually torque the rocket down as it climbs. The combined roll and pitchover maneuver last ...
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Can Oberth bike? Is biking up and down a series of hills a good real-world analogy for understanding either the Oberth effect and/or gravity drag?

When faced with a series of ups and downs while riding a bicycle, I try to pedal like mad near the bottoms to gain as much speed as possible. I do this due to some vague, ill-formed notion that either ...
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Simple explanation for the 2nd “cosmic speed”

Many sources can explain about the first, second and third cosmic velocities, but the explanations contain difficult formulas and are not easy to understand. I can check with a powerful magnet and an ...
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1answer
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Is Earth's “pear shape” mostly J₃?

@OrganicMarble's answer to 1959 Peanuts cartoon about the Fischer ellipsoid (Earth is “pear-shaped”)? finally let me see the cartoon that Mathematician, Engineer and Geoscientist Irene Fischer wrote ...
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How does gravity vary in a gas giant's interior?

The Earth's gravitational pull in its interior looks like this: The pull remains about the same and increases even a bit till the outer core from where on it starts getting weaker till 0g in the core'...
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What is the context of this seemingly “zero-gravity” photo on Earth?

A man appears to be in zero gravity in a room which doesn't look like it could possibly be inside of an aircraft. If so, that's one gigantic aircraft, entirely unlike all the other photos of the "...
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4answers
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History of investigation of lunar and Martian surface gravity

I wonder when it was discovered that the Moon has about a sixth of the Earth's surface gravity and that Mars has 0.38 g. I think that until Newton, everyone assumed there was the same gravity on every ...
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1answer
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Why are all possibly habitable exoplanets higher mass than Earth?

I have been writing a scifi book in which I wanted to include real stars and planets as locations. It was simple enough to find a chart on Wikipedia that lists possibly habitable exoplanets, but I ...
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Escaping moons conflict with what I understand of gravity

I have known that the Earth's Moon, let's call it Luna (tip of the hat to The Expanse), has been slowly but surely increasing it's distance from the Earth by a small measure each year. This week I ...
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How does a planet's gravity push away smaller bodies that would otherwise intersect its orbit?

I was reading an article about dwarf planets online where I stumbled upon the following definition of a planet: The International Astronomical Union defines a planet as being in orbit around the ...
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If you fell into a crater on the moon in your spacesuit and no jetpack, is there a way to use low gravity to get out of the hole?

If you fell down a crater or hole on the moon, is there a way to exploit microfravity/low gravity to get to the top? Lets say your survived a fall into Aristarchus crater on the moon with a slow slide ...
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How much gravity could someone handle who lived his/her entire life in microgravity? [closed]

Let's say someone who was conceived and born in microgravity and spent his/her entire life on a space station in weightlessness until age 20 decides to land on a celestial body. How much surface ...
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How close would the Tesla Roadster with Starman have to get to Earth in order to become attracted and fall on Earth?

In 2091 the Tesla Roadster is said to maybe get closer to Earth than the Moon is. At Starman's current speed, would its location in 2091 be sufficient for the Earth to re-attract the Starman to let it ...
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What counts as “0 mGal” in these gravity maps?

In the following gravity map of Mars the changes in gravity are shown according to mass distribution: Map removed However, since no moon or planet other than the Earth with 9.80665 m/s² has a ...
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How much does it cost to land on a lunar mascon?

This answer to Delta-v for landing on the moon estimates that to go from a circular orbit at 110km to a landing on a spherical Moon would require an absolute minimum of 1736 m/s and the Apollo landers ...
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Did any spacecraft ever use the Sun's gravity for acceleration?

Space probes often use planets to accelerate onto a trajectory towards their goal(s) without having to consume too much fuel. But the fastest acceleration would be made through the Sun's gravity if ...
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Does lower gravity on Mars make it unsafe and unhealthy for humans?

I've been thinking about proposals to live on Mars. One idea is to create an artificial magnetic field to protect from solar radiation. Another idea is to warm the planet using solar mirrors. In the ...
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1answer
177 views

How low would gravity have to be for the balance system to fail?

This is a very critical question that is necessary to get answered for flights to distant celestial bodies. The inner ear liquid makes you perceive which way you're pulled onto a celestial body. This ...
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1answer
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If a spaceship were to lose all fuel, where does it go? [duplicate]

If a spaceship were to run out of fuel mid-flight, and it was between two solar systems, one with 2 suns and 6 planets, and one with 1 star and 10 planets, where does it go? I feel like I’m missing ...
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Why does Voyager 1 lose speed after the sudden gain in speed from gravity assist?

The Voyager 1 loses speed gradually after gaining speed from gravity assist. Is the external thrust is applied in the opposite direction to move closer to the planet, or does the spacecraft lose its ...
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1answer
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Would a space rocket launching from Ceres in a path to Jupiter be faster relatively to the sun than one launching from Earth?

Suppose you have a space rocket which when launching from Earth its speed relatively to Earth it's 11 km/s. For what I've read in another topic in Space SE, the orbital velocity of the planet where a ...
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What will happen to human body when affected by two opposing G forces?

(I am not quite sure whether I should be asking this question here or in Physics exchange or biology exchange, but i decided to place it here due to the context that this question came to my mind.) ...
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180 views

How to calculate slowing effect of a planets gravity on a projectile that is launched upwards

The acceleration a ballistic projectile would experience at a certain height above a planet (neglecting any atmosphere) is given by $$a = -\frac{GM}{(R + h)^2}$$ where $G$ is the gravitational ...
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86 views

Can an Asteriod be marshalled as a spacecraft providing sufficent earth like gravity for those on it [closed]

Can a sufficient massed and size asteroid in a safe area from earth have engines added and provide earthlike gravity for occupants to bring them reasonably close to planets and earth for supply and ...
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What does Earth's J₂₂ moment look like?

Wikipedia's Geopotential model give's the form of the potential component linked to $J_2$ as $$u = J_2\frac{P^0_2(\sin \theta)}{r^3} = J_2\frac{1}{r^3}\frac{1}{2} \left(3 \sin^2\theta-1 \right) = ...
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1answer
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Could you carry around with you a rocket pack to get off Mimas?

This question was inspired by the one here: Is there a self-rounding celestial body from which an Olympian could jump into space? regarding the, apparently shown infeasible, idea of jumping off what ...
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Is there a self-rounding celestial body from which an Olympian could jump into space?

Is there a self-rounding object in our solar system whose mass is insufficient to prevent the highest jumping human from escaping its gravity?
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How big are the tidal accelerations within the ISS?

This question asks about placing an object at rest in the International Space Station. But the ISS is a large object, large enough that gravity will vary across it and cause tidal forces that can ...
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1answer
108 views

Help with Vector format N-body state transition matrix

[Update] This is for an on-board autonomous navigation system (3-dimensions, interplanetary) using a Kalman Filter. There is no target trajectory. I have the position and velocity measurement models ...
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How much stronger does gravity have to be for space travel to be impossible? [duplicate]

I’ve heard that only a slightly stronger gravitational pull would make it impossible for rockets to launch. Is this true? I’ve heard this used as the reason why humanity is meant to be in space.
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How do stable equilibrium points work in GEO? If all geosynchronous spacecraft suddenly lost stationkeeping, would most “fall into” one or the other?

The (currently unanswered) question Quantitatively, how deep are the stable equilibrium points in GEO? How much delta-v to move from one to the other? (also see comments at Delta-v to move from GEO to ...
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1answer
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Gravity turn: How to reorient along zero angle of attack

I was doing some back-of-the-envelopish calculations on gravity turns. Now the basics are clear to me (I think), but this detail escapes me: After liftoff we perform pitchover manouvre at time T+x, ...
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1answer
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How big would a collection of asteroids near the Moon's L4 point need to be to aggregate naturally into a “stepping stone” for space exploration?

Wouldn't it be useful to catch few meter sized near-Earth asteroids whenever opportunity knocks and "lock them up" at the L4 Langrangian point of our Moon ? Although at the L4 and L5 Lagrangian ...
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1answer
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Is it possible to have a planet made entirely out of water? [closed]

Let's say we had a mechanism of adding unlimited amounts of water at a certain point in space. How much water could we add until the water molecules would turn into something else due to gravity? What ...
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6answers
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Is it possible for a moon to have a higher surface gravity than the planet it is attached to?

Is it possible that a moon has a higher surface gravity than its planet? I guess it would mean that the moon has a higher mass, but then it would be the planet gravitating around the moon and the ...
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Comparison of Titan to Europa

Why does Titan have an atmosphere denser than that of the Earth? And why does Europa not have even a fraction of Titans atmosphere given that it is not that small as compared to Titan?
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1answer
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Zonal vs Tesseral part of geopotential?

So I've only recent started to try to wrap my brain around geopotential models. I've done work with some special perturbations using $J_2$ before, however I've never dealt with a full spherical ...
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Does trajectory of an object orbiting a planet depend on the object's mass? (With hypothetical Apollo example)

For example (hypothetically), if an Apollo crew of one of the lunar missions went on EVA just after Trans Earth Injection burn and carefully released a small bolt, or a plastic package from their food,...

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