# 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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### Have gravitation multipoles of Jupiter and Saturn beyond J2 been measured or at least estimated? At least the zonal harmonics?

This excellent answer has me wondering if there are any measurements or estimates of gravitational multipole moments of Jupiter or Saturn beyond J2. Here is what I found for J2 (in unitless form) in ...
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### Time to fall into the Sun from Mars orbit

If a body starts to fall freely from Mars orbit towards the Sun, then how can we calculate the time to touch the Sun' surface? I have tried the third equation of motion that says R=(1/2 dg)*dt^2. ...
238 views

### Gravity mapping of grail mission

This I asked has answers about how gravity is mapped of earth using orbit data of the satellites as measured by ranging. Using ranging one can fit the model parameters to fit the orbit as it passes ...
251 views

### How quickly is the force of gravity exerted? Is a finite “speed of gravity” used in orbit calculations?

So I was reading a post of "What would happen if the sun disappeared". An excerpt: After eight minutes, the Earth would not only lose the sun's light and heat, but also its gravitational influence. ...
458 views

### Does Jupiter's high rotation speed affect its gravitational strength at the surface?

Jupiter's outer, equatorial atmosphere rotates at 12,517.12 meters/second, once every 9.5 hours, at a radius of 71,492 km. Geostationary orbital speeds for earth are around 3,000 meters/second, at a ...
590 views

### With what forces are Saturn's Rings cohesively held together? [closed]

With what sort of gravitation are Saturn's Rings held together? It is very spectacular and intriguing compared to the way Earth's gravitation acts. I do not have a basic or conceptual idea of what/...
94 views

### Could a Gravity Tractor be used for mining asteroids?

Recently, I came across the concept of the Gravity Tractor for the first time. And I was intrigued. https://en.wikipedia.org/wiki/Gravity_tractor A Gravity Tractor, as I understand it, is a concept ...
290 views

### why dose reentry speed need to be so fast [duplicate]

I have been wondering this since I was a kid. watching films of capsules and shuttles heating up and all that tile trouble and work that went into all. I would always wonder why they dont slow down ...
286 views

### Ceres gravity from spherical harmonics from Dawn, how to get the coefficients, definitions and potential?

update: I think I've found what I'm looking for. The file JGDWN_CER18C_SHA.TAB has what looks like spherical harmonics up to order 18, except I don't know the ...
152 views

### How heavy can a fuel tank get before making it heavier is a liability under any circumstances?

This Question may bend the boundaries of this community a little, since it's mostly about hypothetical rockets that would never be built. Considering a filled fuel tank has to withstand a lot of ...
600 views

### How do you calculate gravity loss (simplified)?

Assume a rocket with constant mass and thrust. To simplify things, we can ignore aerodynamic drag, and we'll also not perform a gravity turn, hence our flight plan is as follows: -Burn radially from ...
238 views

### Ballistic missile typical trajectory - along which path is it supposed to travel between Russia, China and US?

Today I was puzzled when my son was holding a school globe asking me to show with my finger a trajectory of a (nuclear) ballistic missile flying from US to China and Russia and vice versa (from Russia ...
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### Tesseral Part of the Geopotential

I am working on the design of a constellation for academic purposes. I try to describe a phenomenon that appears in the simulations by means of analytic expression and I can't really find a good ...
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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 ...
78 views

### 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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### why dark matter causes gravity as its property is different than ordinary matter? [closed]

For temperature, pressure, vacuum, electomegnetisum etc. there is only one physical phenomena responsible(it can not be created by other means). Is it true? If so, why dark matter causes gravity as ...
100 views

### Space model transfer to moon displacement [closed]

I'm having a problem with the insertion from a LEO orbit into a moon orbit/ moon flyby in my gravity simulator. I use the calculations listed below. I think it is due to the fact that the moon pulls ...
46 views

### How massive can a planet become before it is impossible to escape from using chemical rocket propulsion? [duplicate]

Assuming a vaguely Earth like world but with higher gravity, at what point is it no longer possible to launch a human being from the surface into orbit? Or anything into orbit?