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Three thoughts


We're living on a grain of sand, five meters away from a light bulb. Of all the solar energy falling onto our tiny grain of sand, we are currently able to utilize 0.01%. The total energy falling onto our tiny grain of sand is roughly 0.00000005% of the total output of the light bulb.


Gravity sorting. In a gravity well, denser particles end up below lighter particles given time. Here's a list of densities of common elements. It matches the distribution of elements on Earth: air above water, water above silicon, silicon above iron. Note that the rare elements tend to be at the bottom of the list. There are three reasons for that. 1) Heavy elements are rare in the Universe. You need supernovas to produce them. 2) Heavy elements get gravity sorted below iron and mostly reside in the middle of the planet. 3) Some elements - like gold - don't oxidize easily, so they don't bubble up as lighter oxides. For a counter-example, tungsten has a similar density as gold (19.3 g/cm3), but oxidizes as wolframite (Fe,Mn)WO4, which has a density of 7.5 g/cm3 (close to elemental iron). As a result, the annual global tungsten production is 75,000 tons, whereas the annual gold production is 3,100 tons.

Elemental abundances from Wikipedia

The Earth formed from dust in the protoplanetary disk, similarly to other planets and objects in the Solar System. As a result, asteroids should have similar overall composition as the Earth.

Gravity sorting acts slower on less massive objects. You should see relatively more heavy elements at the surface of less massive objects. The force of gravity is also weaker, making the grains of matter less densely packed. This should make mining asteroids less energy-intensive compared to mining on Earth. Asteroid ores should also be more abundant in metals compared to Earth ores. At the extreme end, you'd have iridium, which is 500x more common on asteroids compared to the Earth's crust. Couple that with - let's say - factor of two energy reduction compared to Earth mining, and an asteroid mine could generate 1000x the iridium per watt compared to an Earth-based operation.

Suppose you want to have reusable space launch vehicles to minimize launch costs. Rockets that land. Your customers pay you to launch their stuff to space, then you recover your rocket to save on costs. You don't want to recover the stage that gets to LEO because it'd be too expensive. But what if the returning LEO vehicle brought back a ton of gold. That'd be worth $40 million at today's prices. And the amount of gold brought back this way would be small enough (say, 25 tons per year) that it wouldn't put much dent into gold demand or affect the price of gold. If anything, you could sell it as Star Gold for jewelry at 10x the spot price. Even at spot price, it'd go a long way towards covering the cost of the entire launch.


In a few decades, it looks likely that we'll be able to simulate humans in real-time using a computer the size of a match box. Match box humans. If it takes half a square meter of solar panel to power one match box human, you could sustain a population of 2 trillion in the US alone. If you were to use fusion to convert all the cosmic dust that falls on Earth (let's say, 100 tons) to energy at 1% mass-to-energy ratio, it would generate around 1 PW of energy, which could sustain 10 trillion match box humans running at 100 watts per person.

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