Biggest Constructs possible today.

If money were no object and we can use any technology reasonably available,any materials plus the plant that is actually in existance today, what would be the biggest Dome, highest tower and wall that we could build?

Usefullness and purpose are irrelevant.

A PBS documentary on supertall skyscrapers a few years ago asked exactly that question. If price is no object and if you’re not concerned about terrorist attack or economic usefulness, several civil engineers on the show said you can build just about as high as you want to go.

In this as in so many other things, Frank Lloyd Wright was a true visionary: The Illinois - Wikipedia

And consider this: Space elevator - Wikipedia

An elevator to space would be easy. I mean its just the carbon nano links are a bitch/expensive to make. I think with current tech a space elevator would cost more then the entire planets GDP, we justneed to work on getting the nanotubes cheaper

The X-seed 4000 was designed to be 4,000m high.

A slightly less extreme example would be building a skyscraper out of commercially available graphite fiber. In principle it could be ridiculously high- 40 or 50 kilometers- but at current prices would cost several trillion dollars.

I’ve posted before that I’m a little uncertain as to claims that tensegrity structures, such as geodesic domes, can be limitless in size. I don’t know how to reconcile that claim with limitations such as the square-cube law.

A building 1/2 mile high already exists.

Burj Khalifa - Wikipedia

I think I’ve read reports on the feasibility of space elevators that the weight-strength ratio of carbon nanotubes that concluded that even those would be unable to support their own weight over the distance needed for a space elevator, let alone lift any cargo. May have been an Asimov or Clarke essay. I’ll see if I can dig it up.

Remember that even if a straight cable couldn’t support its weight, you could still use a tapered cable, thicker at the geosynch point than the ends. You could build a space elevator out of the same steel cable used to build suspension bridges IF the cable was a thousand miles thick at geosynch and tapered down to a thread. So it’s more a question of how strong the cable needs to be practical. Proposals exist for the first version to be a ribbon only microns thick but capable of lifting a few hundred kilos at the Earth end. So you taper the ribbon by making it millimeters thick in orbit

Leave it to the Japanese to build a replica of Mount Fuji, only larger.

So far as I know, the biggest device ever planned to be built is the Laser Interferometer Space Antenna, an equilateral triangle with sides 5 million km long. It kind of stretches the definition of a single thing, since it’s composed of three separate spacecraft connected only by laser beams, but I would maintain that it should count, since a single LISA spacecraft, or even two of them, is completely useless-- You need all three for it to work. It’s expected to be about ten years away from launch, and has been for the past decade, so it’s an open question whether it ever actually will be, but it’s certainly possible.

Ref the Space Elevator,I don’t think that counts as technology thats reasonably available.

The pyramids of Egypt certainly count as buildings, even though they’re largely just piles of rock. There doesn’t seem to be any reason why you couldn’t build such a structure to the height of a large mountain, several miles in height. The ultimate limiting factor would be the ability of the earth’s crust to support the weight.

In that case, could we pick a large mountain that already exists, and carve it down until it’s a building? Kind of like NORAD’s bunker, but taken to its full conclusion.

I have a feeling that would be cheating, according to the OP.

Also, see post #4 :wink:

A space elevator IS currently available technology.

But, we’re looking for ways to make it cheaper before we do it. A steel cable is feasible but would be large and expensive. We’re hoping to get the carbon fiber tech to the point where we could make a small and less expensive cable.

Maybe someone in this thread can tell me how a space elevator can work. If you have a cable tethered to the ground, with another end in orbit, you’re supposed to attach wheels and drive the cargo into orbit, right? How does this not pull down the counterweight? Any force pulling up the cargo must try to pull down the cable. I think there’s something I’m missing.

The proposals I’ve seen have the cable have a net upward force, prevented from rising up by being anchored to the ground. So the payload simply reduces the upward force.

Teacher nerd: It has a tension upward. If it had a net force up it would be accelerating up.

Because the mass of your payload is insignificant when compared against the forces acting on the space elevator.

Realistically, I would say mile-high skyscrapers are about the maximum at current technology. Or about twice as tall as the Burj Dubai. Any bigger than that, you start getting into exotic materials or construction methods that I’m not sure are feasible.