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

we're asking 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.nebola.tv slash Isaac Arthur and use my code, Isaac Arthur.

This episode is brought to you by Brilliant.

The solar system is full of wonders we're only beginning to discover and explore, but what will we

do in the future when all that stuff is just getting in our way? Humanity mostly lives,

works, and plays on only a small fraction of Earth's surface,

and virtually all activity here is limited to maybe the first 10 meters of dirt, rock, water,

and air on that surface, but the ground goes down nearly a million times deeper than that.

Similarly, the Earth receives less than a billionth of the light the Sun puts off,

and even when we add in all light the Sun puts off, and

even when we add in all the other planets, moons and asteroids in our solar system, it's

still only a tiny fraction of the Sun's light that falls on these worlds and mostly

goes to waste there.

For scale context, as sunlight is essentially the ultimate fuel all life runs on, it is

as if we produce enough food for

a vast empire, but only had one single person eating. Indeed it is even worse than that as

Earth, the only place known to host life, is quite wasteful with the light it gets, especially

from an anthropocentric perspective. The Sun produces around 4 trillion trillion times the power a human

actually runs on. From the center of the sun, where fusion takes place and makes the power

that runs our life, to the final endpoint of running a human, only about one watt out of every

...