Excavating a City/Moving tons of sand (Brainteaser: Lots of Math/Physics needed)

[Nifft]

"Whatever is put through one ring comes out the other, and up to 100 pounds of material can be transferred each day."

... and it's been like that since 3.0e. Silly penguin.

Oh well, a nice 20 ft. gate could do the job, given enough time. How much sand would go through a 20 ft. gate in 2 minutes? (Assume it's only 300 ft. down.)

Thanks, -- N

 

[Nail]

...depends on gravity on the other side of the gate, doesn't it?

 

[Nifft]

...depends on gravity on the other side of the gate, doesn't it?

Not sure if gravity waves penetrate the surface of the gate.

A thought struck me though: what if Mithardir is in its current state because of repetition of this tactic on buried desert cities across the many Primes?

Cheers, -- N

 

[geosapient]

Which settings are actually on planets? I was under the impression that the default DnD setting was a discworld, hence the term "plane."

I'm pretty sure that all planes are different in shape. Some would probably be discs, The astral(?) plane is more of a void type where movement is like flying and you propel yourself with thought and the elemental planes all have there own modes of movement in an infinite(?) volume of the native element.

 

[tomBitonti]

Only need gravity on this side

Not sure if gravity waves penetrate the surface of the gate.

Probably wouldn't matter ... as long as there wasn't reverse pressure on the other side of the gate, and somewhere for the sand to go. The column sand on this side should push down hard enough to force material through the gate. Or, freely falling sand would carry through the gate on momentum.

 

[Nifft]

Probably wouldn't matter ... as long as there wasn't reverse pressure on the other side of the gate, and somewhere for the sand to go. The column sand on this side should push down hard enough to force material through the gate. Or, freely falling sand would carry through the gate on momentum.

That was my thinking. You'd presumably position the other end of the gate high enough off the surface that it wouldn't become blocked.

So, assuming we're dumping the sand into an "unblocked" location, how much will make its way through a 20 ft. wide gate spell over the course of two minutes? Assume that every time we cast, we are casting it at level 20, and we are opening it 300 ft. (or more) straight down (from the current surface of the sand).

-- N

 

[Someone]

I'd ignore the Gate, or face the risk of opening an unpredictable can of worms. The DM can remember that and the next time you open a gate to the elemental plane of water you'll flood your location, or be violently sucked through it if the DM rules that both sides are not at the same pressure, or suffer any other environmental related danger ("The Solar comes out of the gate, after you spend 1000 xp calling him. Nitrogen bubbles form in his blood thanks to the sudden decompression and he dies. Painfully")

 

[Boondoggle]

Basically, I think this sort of thing is better handled with a discussion with your DM. If you want to raise the city, research/design some sort of ritual to do it for you. If you want to leave it where it is, research/design a method of bypassing the Mythal effect so you can teleport/d-door in. Both of these should be achievable by an epic level party given 3 months.

I tend to think trying to apply real-world physics to a magic heavy situation in search of a solution is rather futile. Then again, I am a physics student and tend not to like haphazardly applied physics.

 

[tomBitonti]

I'd ignore the Gate, or face the risk of opening an unpredictable can of worms. The DM can remember that and the next time you open a gate to the elemental plane of water you'll flood your location, or be violently sucked through it if the DM rules that both sides are not at the same pressure, or suffer any other environmental related danger ("The Solar comes out of the gate, after you spend 1000 xp calling him. Nitrogen bubbles form in his blood thanks to the sudden decompression and he dies. Painfully")

That brings up an interesting question ... what is the pressure on the elemental plane of water? (You could ask the same of the elemental plane of air.)

Brings up a second aside, which is whether there is gravity on either plane. If there is, and the planes are of any decent size (say, thousands of miles across), then you end up with pressures the same as at the center of Jupiter. (On a smaller scale, there would be real-world problems with an underdark that was miles deep, because of mounting pressures and temperatures.)

So ... let's suppose that ambient effects on either side of the gate do not travel through the gate. Nevertheless, I'd presume that a rock could be thrown through the gate. So, put a channel (say, 20-30 feet) above the near side of the gate, and create a flow of sand down that channel into the gate. By the time the freely falling sand reaches the gate, it should be moving fast enough to fall through.

 

[Ghostmoon]

I am not sure if this will meet your timelines and is a little on the expensive side on XP, but it should work. It assumes a 23rd level wizard:

Use xorn movement (from the Spell Compendium) or a similar spell to glide down through the sand until you reach an area near the entrance to the city.

Use wish to create a temporary air-filled chamber, a cube about 200 ft on each side. It should only need to last about a minute, so it would seem well within the limitations of the wish spell. There may be alternative methods of creating this chamber, but I could not find them.

Next, cast prismatic wall in the chamber and make it permanent via the permanency spell. If you have enough XP, I would cast a second prismatic wall and make that permanent too.

Once this is done, dimension door to the surface and wait for the chamber to collapse. Once this happens, the sand will be forced into the prismatic wall. Once it passes through the first 6 layers, the violet layer will destroy it utterly. The immense weight from the sand above should keep it flowing into the wall.

Over the next few months, use move earth to keep shoving sand over the area that has the prismatic wall to keep the pressure and flow as high as possible.

This method, assuming one prismatic wall, will cost 9000 XP. But it will create a area of 8464 ft² for the sand to interact with, as both side of the wall will come in contact with it. Once you have cleared the sand, you can dispel the wall.

For the walls of force, check out the ruby ray of reversal spell from the Spell Compendium. It can create a permanent 5-ft diameter hole in a wall of force without disrupting the rest of the wall.