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.

We always imagine life needing water, but the universe may have stopped its oceans with methane

instead, and filled them with creatures beyond our strangest dreams.

In our recent episode on colonizing rogueets, we explored how civilizations might build

homes on worlds cast adrift in the dark.

That got me thinking more broadly about ecosystems that exist without sunlight leading to an

episode on dark biospheres, where we looked at a variety of exotic habitats.

Among those we touched on the intriguing possibility of life lurking beneath the icy

crusts of moons,

orbiting giant planets. I also noted there that while ammonia tends to be a top-tier candidate

for alternative biochemistry or solvents, methane and other hydrocarbons also have a lot going for them.

I also made me think of Titan, the only moon we know over with an actual atmosphere, and thus

where surface life using sunlight might be possible.

While we typically associate methane with dark, frigid places, like Titan's hydrocarbon

lakes, there's no rule saying you wouldn't pair methane chemistry with a bit of sunlight,

crafting alien biospheres every bit as rich and varied as Earths.

And so today, I thought methane deserved its very own spotlight.

We'll explore what life might look like on worlds with methane oceans, whether complex ecosystems

could evolve there, and what such discoveries would teach us about the breath of nature's

...