Just supposin'....

[Velocity517]

Imagine if you were to build an indestructible ring around the earth, say out of metal or carbon steel or whatever, and put it in orbit so that it circled the planet completely. I was just wondering how gravity, the rotation, the moon, etc. would effect the ring...would it be stable?

[insane_alien]

if its a ring, it can be spun so that its orbiting the earth and it'll sit there quite nicely. hollow spheres that size have all sorts of stresses on them when they are spun in a similar manner.

 

if its not spinning, it would need to be quite thick to support its own weight. we don't have the technology or materials yet to do this.

 

they wouldn't be stable due to outside forces and the non-uniformity of earth. and the moon ywould probably throw it off whack as well.

[Fremen2378]

wouldn't it also depend on the distance away from the planet? The ring itself would generate its own pull as well effecting the tides and moon alignment...

[insane_alien]

the ring wouldn't affect anything inside it. only the outside would be affected by the rings presence.

[YT2095]

why is the assumption that of a Hollow cross section?

it was never implied in the OP.

[insane_alien]

Imagine if you were to build an indestructible ring around the earth

 

i just mentioned spheres because i thought it would come up eventually.

[Velocity517]

the ring wouldn't affect anything inside it. only the outside would be affected by the rings presence.

 

Well, once the moon effected the ring's orbit (as it's bound to in some way) wouldn't the ring have some sort of effect on things inside it? I mean when it gets misaligned an' all...

[insane_alien]

nope, net force of gravity from the ring on the inside is zero, at all places. it all cancels out. its the same principle as why the electric field inside a charged conductor is zero.

[Sisyphus]

It would be unstable. There would be nothing pulling it out of place, but nothing holding it in place, either. You would need to be constantly nudging it back in place.

[swansont]

the ring wouldn't affect anything inside it. only the outside would be affected by the rings presence.

 

True of a sphere, but not of a ring.

[insane_alien]

oh yeah, i forgot about up and down, oops. i'm ever so slightly hungover today. not quite on the ball.

[Velocity517]

Well wait, isn't the constant gravitational pull of the moon "constantly nudging it" anyway?

[Sisyphus]

Well wait, isn't the constant gravitational pull of the moon "constantly nudging it" anyway?

 

I don't think so. The Earth and the ring would have the same center of mass, so they shouldn't change position relative to one another from outside gravitational influence like the moon.

 

However, since it's an unstable equilibrium, if anything does move it, it will just keep on moving and crash into the Earth...

[foodchain]

Some planets have rings:D Even Jupiter if memory serves, though I don’t know how it would relate as the ring in not a solid body on those planets, also if memory is correct on that.

 

I think you probably would have to have some sort of energy based mechanisms generating on earth to constantly make sure it was correctly in place, some sort of magnet system that can judge slight corrections, that is if such a system itself was at all possible without some serious side effects.

[Rocket Man]

the planetary rings are made of debris, each chunk follows a slighly eliptical orbit such that the collective boundaries are circular.

 

if the ring were solid and spinning, you'll still have unbalanced forces wouldn't you? the thing is a single satellite so if it moves out of equilibrium, the closer side experiences an attraction greater than the further side.

 

the ring would still spin on it's own axis but would behave (orbitally) as though it were stationary