this post was submitted on 02 Dec 2023
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[–] [email protected] 108 points 11 months ago* (last edited 11 months ago) (5 children)

Turns out it'd be a dissapointingly small sphere:

US annual defence budget = $800 billion

2% = $16 billion

Obsidian cost per kg = $5

Total kg in budget = 3.2 billion kg

Density of obsidian = 2.6 g/cm3 = 2600 kg/m3

Total volume of sphere = 3.2b/2600 = 1230769 m3

Volume of sphere = 4/3 π r^3

Radius = (3V/4π)^(1/3) = 66.48 m

The sphere would only stand at 133m tall, I propose we instead utilise the entire defence budget for a much more skyscraper like 490m tall orb

[–] [email protected] 72 points 11 months ago

Nobody said it had to be a solid sphere, how else would you get it to emit the ominous hum without attuning its natural frequency by carefully designing the thickness of the obsidian layer?

[–] [email protected] 67 points 11 months ago (1 children)

ignores engineering and construction cost. but we can assume that all people involved would work for free, because its a massive honour

[–] [email protected] 7 points 11 months ago

Obsidian Orb is really Roko's Basilisk. Allowing you to live is your payment for building it.

[–] [email protected] 41 points 11 months ago (1 children)

Well that's assuming it's completely solid and not hollow. Hollow would probably be pretty huge, although the structural rigidity might not be great. Maybe we make a giant obsidian 3D printer and print it at like 10-15% infill.

[–] [email protected] 26 points 11 months ago (3 children)

An obsidian 3d print is less crazy than you might think. It's essentially rapidly cooled lava.

Need something to hold the lava, then pressurize it to squeeze it through a nozzle that that has attached cooling units.

[–] [email protected] 12 points 11 months ago (1 children)

I think you just described a volcano.

[–] [email protected] 10 points 11 months ago (1 children)

Simple: bucket of lava, bucket of water, repeat.

[–] [email protected] 3 points 11 months ago* (last edited 11 months ago)

Grabs a bucket. Quick, to the lava depository!

[–] [email protected] 3 points 11 months ago

less crazy than you might think

Using a planet for a 3d printer's nozzle still sounds pretty crazy.

[–] [email protected] 14 points 11 months ago

You're assuming one year of budget. I take it as 2% per year and something of that size would likely take 10+ years to build out.