Originally posted by jonamendallIts a very long bridge that doesnt have to support anything but its own weight. With super light materiels the compression forces neednt be that big (or are they? Any civil engineers fancy a challenge?)
olddog is correct I think. We are discussing a very long arch. Think how long the longest bridges are and then consider what sort of material would be able to withstand the forces involved. A non-starter I would say
IF the forces are too great lets spin our ring around the Earth a little to reduce the apparent weight.
Originally posted by wolfgang59I was thinking of that. If it's within the atmosphere it would probably take a massive amount of energy to sustain it. Outside, though, not such a problem. You basically put each part of it in orbit.
IF the forces are too great lets spin our ring around the Earth a little to reduce the apparent weight.
Originally posted by mtthwIn fact, you could put enough spin on the structure that it would effectively be in a suspension state (put it in an orbit slightly faster than is necessary for that altutude, effectively a form of pre-stressing), the fact that it's in vacuum means that friction between joins in the network would be the only source of drag. Nanotubes, being very prone to carrying electric charge, would allow the joins to be electrostatic in nature, meaning the system is virually frictionless.
I was thinking of that. If it's within the atmosphere it would probably take a massive amount of energy to sustain it. Outside, though, not such a problem. You basically put each part of it in orbit.
Equipment packages would be suspended in the same way. An important point to note is that the satellites out of an equatorial geosynchronous orbit WOULD have a weight which would bear down on the structure, thus an equivalent weight would need to be distributed around the ring to maintain a geocentric centre of gravity, as well as the ring supporting that weight needing a faster rotational velocity to bear the extra weight.
All of these definitely represent challenges to engineers, but the problems seem surmountable to me.
Perhaps if the ring is flexible (thus, parts at opposite sides of the earth does not exert force on each other in a vertical direction) and it's rotated around the earth, it will be able to stabilise in some sort of orbit (like individual satelites connected with a string)? Much like Saturn's rings I guess?
But if it is rigid, and close to earth's surface, which is the basic idea as I understand the question (thus cancelling the effect of gravity on the opposite sides of the earth), and it is not placed exactly symmetrical, without even the smallest variation, it will over time "fall" to one end. This is because the force of gravity becomes less further away from the earth. So, at the closer side, the force pulling towards the earth will increase, whilst at the other side the force will decrease, causing the ring to fall to the side closer to earth. A positive feedback cycle, which is not stable? Also, since the earth revolves around the sun, and rotates around it's own axis, it will have to be symmetrical with regards to those forces as well. That's what I think... Could be wrong?
Is the earths center of gravity always in the center? I know the magnetic poles shift but would the movement of rock under the earths crust continually alter the earths center of gravity slightly?
Also you'd have to take into account the moons gravity, I'm presuming if it can effect water it might be able to effect a giant planetary ring. Or would this effect be negligible?
Originally posted by FeastboyInteresting question: "Is the earths center of gravity always in the center?"
Is the earths center of gravity always in the center? I know the magnetic poles shift but would the movement of rock under the earths crust continually alter the earths center of gravity slightly?
Also you'd have to take into account the moons gravity, I'm presuming if it can effect water it might be able to effect a giant planetary ring. Or would this effect be negligible?
I think we have to define the "Center of the earth" as exactly somewhere at the rotational axis. But where exatly in the between?
This ring around the Earth, it hasn't to be equatorial, it can as easy be polar or any other alignment, as long that Earth center is exactly in the center of this ring.
The tidal forces of the Moon and the Sun, as well as other forces, has to be into account, mostly that of the Moon and the sun.
I still think this ring around the Earth is not stable. It ´has to be supported by continuus changes in its 'orbit'. And I still think that there are other reasons than the engineering ones that this ring never will be built. Finansial reasons.
I dunno about finical reasons, with sufficient advances in material science and engineering such that we could do it the volume of money you'd save on space exploration alone over 50 - 100 years could almost justify it.... Rocket fuel, and all the disposables along the way, isn't cheap...... Thats not to mention the possibility for satellite coverage, power generation etc.
Think solar panels on this ring would probably do pretty well, plus if its spinning that wouldn't be too hard to harness.
As to the center of gravity (COG). The Surface and mantle is heterogeneous, plus the mantle is a semi ductile solid, but it gets pretty homogeneous toward the core and most of our mass is located there. so I would Imagine that the COG would be pretty close to the center of the earth. Ideas?
Originally posted by MexicoAre we still talking about the ring proposed in the initial posting? Then I can't see anything justifiyng the enormous price for it.
I dunno about finical reasons, with sufficient advances in material science and engineering such that we could do it the volume of money you'd save on space exploration alone over 50 - 100 years could almost justify it.... Rocket fuel, and all the disposables along the way, isn't cheap...... Thats not to mention the possibility for satellite coverage, power g ...[text shortened]... ere. so I would Imagine that the COG would be pretty close to the center of the earth. Ideas?
If Earth was a perfect globe then the center of Earth would be easy definable. But it isn't. Therefore none can e exactly defined. Close to center of gravity is the best we can achive.
Originally posted by MexicoAssume earth as a perfectly homogenous sphere of mass M with the same force of gravity at any point belonging to a given concentric sphere above the surface.
Firstly I know the practicalities of this are ridiculous. But I asked my physics teacher in school and Never got a satisfactory answer. Then I forgot to ask one of my physics lecturers in college, and then dropped physics for geology anyway.
If one was to build a ring shaped object with a diameter 1 meter longer than the Earths Diameter (Taken as a consta ...[text shortened]... ure about the hovering in the first place, It seems like such a weird Idea in the first place.
Every point in a ring belonging to this sphere is subject to same force - the force of gravity, which is directed toward the same point: the center of earth. Assume no other forces act on the sphere.
Since the force is the same for every point and directed to a single point, by symmetry, (the sphere is concentric) the ring will hover above the surface. The diameter of the ring can assume any value.
Originally posted by smaiaBut what if you bump it?
Assume earth as a perfectly homogenous sphere of mass M with the same force of gravity at any point belonging to a given concentric sphere above the surface.
Every point in a ring belonging to this sphere is subject to same force - the force of gravity, which is directed toward the same point: the center of earth. Assume no other forces act on the sphere.
Si ...[text shortened]... ncentric) the ring will hover above the surface. The diameter of the ring can assume any value.
It has been suggested that gravity will naturally correct bumps.
Originally posted by FabianFnasNo sorry about the confusion. I was talking about a larger semi orbital ring. The Original ring would be pointless.
Are we still talking about the ring proposed in the initial posting? Then I can't see anything justifiyng the enormous price for it.
If Earth was a perfect globe then the center of Earth would be easy definable. But it isn't. Therefore none can e exactly defined. Close to center of gravity is the best we can achive.
The earths not a perfect globe, the density is heterogeneous in the extreme also. However because most of or density is concentrated in an almost perfect sphere in the very center (core) and the bulk of the rest is a ductile to semi ductile solid. It would be a reasonable assumption that the center of the earth and its center of gravity are going to be pretty close to one another is it not?
Originally posted by MexicoClose to some degree, yes.
No sorry about the confusion. I was talking about a larger semi orbital ring. The Original ring would be pointless.
The earths not a perfect globe, the density is heterogeneous in the extreme also. However because most of or density is concentrated in an almost perfect sphere in the very center (core) and the bulk of the rest is a ductile to semi ductile s ...[text shortened]... r of the earth and its center of gravity are going to be pretty close to one another is it not?