61
votes
Accepted
What would a 1.5 km wide, 20 km tall spire look like?
If you were at sea level (e.g. on a boat), the tower would disappear over the horizon at approximately 505km away.
Horizon calculations are generally dealt with as simple right-angle triangles; a ...
- 3,638
56
votes
Accepted
What does a solid, 1 mile diameter subterranean glass sphere look like?
If the glass is unflawed, the opening will look like a flat, nearly-black (but possibly also greenish) mirror .
When you look at glass, you see a combination of the light reflecting off the surface ...
- 3,768
49
votes
Hiding a subterranean alien megastructure
Consider the following:
The diameter of the Earth is 12,742 kilometers.
Our planet's crust thickness is anywhere from 30 kilometers on the continents, to 5 - 10 kilometers on the ocean floors (which ...
- 34.7k
43
votes
What would a 1.5 km wide, 20 km tall spire look like?
Interesting side effect:
Astronomers would kill for a tower like this.
Middle of the ocean is where you find lowest light pollution levels on Earth
20km up the atmosphere is rather thin further ...
- 23.8k
41
votes
Hiding a subterranean alien megastructure
The Earth is better surveyed than is generally realized. It is probable that geophysical survey techniques would have revealed the existence of an underground megastructure.
Geophysical surveys may ...
- 38.5k
37
votes
Are there any benefits to a large body of water in a space habitat?
Radiation shield
There is lots of radiation in space. There are few better shields than water. Due to its hydrogen bonds and large dipole (that is, the oxygen is negatively charged, the hydrogen ...
- 85.7k
33
votes
Accepted
What to do with all the heat in a Dyson Sphere?
I think the best solution would be a Matrioshka Brain. This is effectively a layered set of Dyson spheres. Once it reaches equilibrium, each shell has a particular temperature differential across it,...
- 133k
31
votes
What would a 1.5 km wide, 20 km tall spire look like?
There would be a lot of local climate effects caused by the tower. One of the most visually dramatic would be clouds. It would likely have a cloud wake, the most dramatic of which are Von Kármán ...
- 809
30
votes
Are there any benefits to a large body of water in a space habitat?
Depends on your definition of benefit. In the case of Rama the lake wasn't just a lake, it was also a machine reclamation (and presumably construction) yard where machines from anywhere in the habitat ...
- 66.4k
30
votes
Minimising the environmental effects of my dyson brain
Give your Dyson sphere an equatorial window
All of the inhabitable parts of the solar system lie along a single plane meaning that we don't need any of the sun light escaping above or below this ...
- 101k
26
votes
Accepted
Stable ringworld interactivity with other solar system objects
TL;DR: Yes, helical motion around a ringworld is possible. However, it is far from uniform at larger distances (≥ 0.04 AU).
Summary of results:
For a toroidal ringworld with mass
$M_R = 3 M_\text{...
- 1,076
26
votes
What does a solid, 1 mile diameter subterranean glass sphere look like?
Also worth touching on refractive and transparent colour - which can vary wildly depending upon specific trace elements in the glass... and which can also significantly impact reflectivity and ...
- 5,811
23
votes
Are planetary orbits absolutely necessary?
Could an arrangement of three or more proximal stars produce one or more points of balanced gravitation pull, each of which could hold a planet such that it would rest in a stationary position ...
- 33.3k
21
votes
Can Cloud Nine be built?
Feasible Only with a Decreased Internal Pressure and Great Difficulty
This is a very complicated problem with many variables that affect the final outcome of the design. I made a few assumptions ...
- 2,690
21
votes
Accepted
Can you protect a Space Elevator from Space Junk?
Lasers.
You don't need to destroy the debris, just push it out of the way by the slightest amount. The vast majority of space junk is tracked, as others have mentioned, so you'll know what's a threat ...
- 3,600
21
votes
Accepted
Would it be possible to build a powerless holographic projector?
Mirrors work fine
...as the Norwegian town of Rjukan has already demonstrated.
Read about it here.
The villages of Rjukan, Norway, and Viganella, Italy, are both situated in deep valleys where ...
- 43.9k
19
votes
Could you build a non-spherical structure that's >1000km long?
Whatever or not an artificial structure in space would be deformed to a sphere due to gravitational forces depends on the material. That tells us the gravitational force and the effort-deformation ...
- 6,380
18
votes
Accepted
Orbital Mechanics of a shell world
The thing you probably care about is the shell theorem. Newton proved that
A spherically symmetric body affects external objects gravitationally as though all of its mass were concentrated at a point ...
- 78.4k
17
votes
What to do with all the heat in a Dyson Sphere?
In order to keep your dyson sphere hidden, you don't really have to do anything.
There's two key things to keep in mind.
The whole point of a dyson sphere is to extract as much useful energy as ...
- 1,167
17
votes
If I knock down this building, how many other buildings do I knock down as well?
In your case, I think close packing of such buildings is actually a good thing and will prevent a disaster from happening.
Consider cutting down a tree in a meadow. What happens when you slice through ...
- 40.9k
17
votes
Accepted
Feasibility of a 5000km tall orbital tower using active support
Not possible
For every action, there is an opposite and equal reaction.
The surface of your planet could not endure the reaction force of your active support system. All of the force you exert ...
- 101k
16
votes
What happens at the hub/core of a rotating space station?
Docking and Storage
Rotating station designs almost always assume docking is at the core to make lining up with the station easier and to limit disruption to the station's spin. Also, since you ...
- 101k
15
votes
Accepted
How long would it take a civilization to see and understand a Dyson ring?
Anywhere from ancient times to the present.
Question 1: Is there anything there? (answered pretty quickly)
Sunspots, for instance, were first observed by the Chinese in 364 B.C., two millenia before ...
- 102k
15
votes
What would a 1.5 km wide, 20 km tall spire look like?
Clearly it's going to be visible from extreme distances. You can see the Shard in London, or the Burj Kalifa in Dubai long, long before you can see anything at ground level around them, and from some ...
- 11.9k
15
votes
Would a space elevator necessarily need to be situated on the equator?
The center of mass of your space elevator is going to need to be in the geostationary orbit, no matter where you put the base anchor. As a result, while you can put the foot elsewhere other than the ...
- 2,873
15
votes
Calculating Living Area on a Concentric Shellworld
1.183*10¹¹ square km
The total area is $4\pi \sum_0^{100}(3000+120n)^2$.
We ask Wolfram Alpha (leaving out the 4$\pi$):
Now we just have to multiply the result by 4$\pi$:
4$\pi$ * 9.417.240.000 = 1....
- 16.4k
14
votes
Are planetary orbits absolutely necessary?
You won’t find an arrangement of 3 or more stars in a stable configuration to begin with, other than those having vastly different sizes so the little ones orbit the big one like planets, or a ...
- 69.7k
14
votes
Accepted
How do 21st century C.E. submersibles enter an underwater dome swiftly and safely?
You can use the concept of a decompression chamber with two doors, one to the outer, one to the inner environment.
When it is open to the outer environment it is closed to the inner. Submersible can ...
- 296k
14
votes
Accepted
Life on the Broken Ring - an issue of size
If there is a gap between the sections of the ring, it would allow all the atmosphere to spill through the gap, like so:
The question really isn't one of how long of segments you need (the answer ...
- 1,560
14
votes
How to cool a planet's core to avoid inconvenient melting during deconstruction
The direct answer to your question: Same way we currently cool space ships: By using a heat exchange to capture and transport heat, and radiating that heat off as IR radiation. A solar shade to limit ...
- 44.3k
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