Hello, SFIA audio listeners. In this month's Nebula exclusive, big alien theory,

we're asked at the reason alien civilizations might be rare is because most aliens are huge.

To hear it and every episode early and add-free, plus hours of bonus content,

check out go.nebula.tv slash Isaac Arthur and use my code, Isaac Arthur.

From the moon to the asteroids.

The race for space resources could spark the greatest economic boom in human history.

Why mine in space?

When we think about mining, our instinct is to picture hard hats and tunnels, but the truth is that Earth is a planet that we've

already dug deep. There's plenty more, though. Earth outmasses our moon, every other moon,

Mars, Mercury, and the entire asteroid belt combined. On Earth, the easy near-surface

veins of gold, silver, and copper, were tapped centuries ago, and every year we're

chasing ores that are lowering concentration, harder to reach, and more destructive to the

environment to extract. Mining remains one of the most polluting and energy-intensive industries

on the planet, and the cost, both economic and ecological, will only keep climbing.

Future technologies will likely help mitigate both concerns, as they already do to some degree,

but space offers a very different equation.

Out beyond Earth's crust, there are no delicate ecosystems to poison,

no communities displaced by strip mines, and no mountains ground down for a few ounces

of metal. Instead, we find an environment of abundance. Rocks and ice untouched for billions

of years, near them rich in the very elements that drive our technology and economies.

Some asteroids are more metal than stone, vast chunks of nickel-iron alloy laced with

platinum group metals.

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