## Interest

on Dec 28, 2009

# Stumblers Who Commented On This Page

## izzabell

### izzabell

http://xkcd.com/681/

## kv8r84

### kv8r84

I should gently point out that "Newton's Constant" (9.81m/s^2) only applies to our local (Earth's) gravitational acceleration. Planets like Jupiter would have higher rates of acceleration corresponding to their total mass. Now that I think about it, the larger the mass of the attracted object relative to earth, the higher that value would be, making it not really Newton's "Constant" at all. In physics classes I've taken, I've never heard it called "Newton's Constant," probably for that reason.

However, there IS a universal gravitational constant, which is 6.67*10^-11/kg of mass. You can plug that into the following formula to calculate aggregate gravitational attraction: F=G(mass1*mass2)/r^2; where F=the total force of mutual gravitational attraction, mass1 and mass2 are the masses of the bodies in kilograms, and r=is the radius, or distance between the centers of the mass.

Essentially, this means that a given object's "gravity well" is theoretically infinite, because one must also factor in the mass of whatever is being attracted (though technically both objects are mutually attracted.) The only reason we aren't affected by, say Jupiter's gravity well, to a noticeable degree is the interference of the gravity of the sun and other planets. Think of how ripples in a calm pond dissipate much less rapidly than on a tumultuous surface. If Earth and Jupiter were the only two objects in the Universe, they would inevitably collide, no matter how far apart they were placed initially. Sooo, the closest thing to a true "gravity well" is an object's "Hill Sphere," or the radius at which it dominates the attraction of satellites; but since even that sphere of influence is dependent on whatever else is nearby, there's no such thing as an objective "gravity well".

Anyway, sorry to bomb your post. I'm an astrophysics major, so this stuff matters to me, haha.

## deercircle

### deercircle

lol your mom

## ian-atkinson

### Ian

Representing gravity wells on a graph with the strength of gravity (space-time distortion) represented in the vertical and the width of the well (in space) represented by the horizontal, gives a real insight into how difficult it is to escape from various bodies in our Solar System; e. g. it took huge Saturn V rockets to get out of Earth's gravity well and land on the moon, but to get back only required the Lunar Module's comparatively tiny engine and the, only moderately larger, service module engine.

## Natural

### Natural

This gravity well graphic is worth a look.

## pirsquared

### pirsquared

An interesting representation of the Solar System's major gravity wells.

## ciperlone

## ciperlone

gravity wells