Hello, Straightdopers; AMAPAC here with a question.
I’m writing a story in which a very, very large alien spacecraft makes a soft landing in north central Niger.
How large? It’s a box 45 miles square and 220 miles long, full of water.
It settles into the sand until it hits bedrock underneath, then it just sits there.
What are the effects on local weather? Gravity gradient?
So, it’s a 200-mile long, 45-mile thick wall, basically, that extends WAY out of the atmosphere.
The country’s only about 600 miles across, so this is going to make somebody’s commute a little more difficult.
That’s right! I drew the rough dimensions on the Nigerien plain in google earth. It’s going to develop that the…individuals…who drove it there landed there on purpose so as not to kill anyone in the landing.
It’s sparsely populated, but there still are people in Niger, and they are in no position to evacuate even with warning.
If that was their concern, why wouldn’t they land in water?
Check you geography/geology: Niger is almost entirely hamada, not erg, I doubt you will find 9000 square miles of sand dunes for your box to land in. The lion’s share of the Sahara is mostly like a big stone parking lot.
What sort of propulsion/lift systems does this ship have? In other words, what’s supporting it while it’s in the process of making its soft landing? Does it have a bunch of rocket nozzles pointing down from the bottom, or is it some sort of antigravity thing?
If it becomes a 200 mile long, 45 mile high wall it’s going to have pretty profound meteorological effects on the weather across a huge region.
It’s going to be a huge impediment to air and surface travel.
It may effect the stability of the subsurface tectonic geology in the area re earthquakes etc.
If it penetrates the crust far enough due to weight and the presumably hyper-strong material you may have vulcanism issues
The shade from the structure will impact regional flora and fauna
It will penetrate the crust, to a depth of perhaps a quarter of its total height, unless you leave the magic antigravity generators running (assuming it does use antigravity). On scales that large, you can pretty much treat rock as effectively a liquid, so you’re just using Archimedes’ Principle to see how high it floats.
Wouldn’t that have localized gravity?
1 mile^3 of water
5280 ft x 5280 ft x 5280 ft x 62.4 lbs per square ft = 9,185,152,204,800 lbs
45x45x220 = 445,500 miles^3
9,185,152,204,800 lbs x 445,500 miles^3 = 4.0919853072384e+18 lbs (or 2,045,992,653,619,200 tons or 1,856,093,313,515,444,224 kg).
For reference, taking the mass of Earth to be ~6x10^24kg, that’s a paltry 3.0935e-7% of the Earths mass, but still…pretty heavy.
Given that it’s full of water, probably not very high.
You misunderstood me. I’m not talking about it floating in water. I’m talking about it floating in rock. And since water is significantly less dense than rock, it’ll float pretty high. It’s just that, for an object this size, “floating pretty high” would still leave it penetrating about ten miles into the crust.
Another thing to take into account is the curvature of the earth over 200 miles - it might mean that the middle segment might sink into the earth quite far while the far ends still stick out (although given how heavy 4545200 mile^3 of water is going to be it might just sink below the surface of the earth across the entire length.
The biggest things that the crust can support are on the order of the structure that Mt Everest sits on, or perhaps the volcanoes of Hawaii. Your hypothetical ship is going to fuck up the local geology big style.
Niger’s gonna make a fortune leasing it’s new space launch facility that’s already A sixth of the way to the ISS.
Ignoring the sinkage into the Earth’s crust, what would be the most efficient way to reach the top of this new addition to the Earth’s surface? Balloon? Rocket? 45 mile-high elevator?
I doubt that Nigeria would be making any kinds of fortune any time soon, seeing as it will have just been visited the most catastrophic geological event since the last time the Caldera blew up.
And what if the space aliens don’t want us using their spaceship as a stepladder?
Niger and Nigeria are different countries, you know that, right?
… :smack:
Well, I do now.
Landing in north-central Niger makes a lot more sense now.
Okay, I’m curious… if people from Nigeria are Nigerians, what do people from Niger call themselves?
Nigerien.
Not quite as confusing as it could be since Nigeria and Niger pronounce the “niger” part differently (Nigeria being an English-speaking country and Niger being a French-speaking one) and that carries over into the pronunciation of “Nigerian” and “Nigerien”.
Nigeriens.