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 often wonder where all the ancient alien civilizations are, and if they might not exist,

but could the reason be something as simple as a vital element being scarce?

So we had a big new discovery recently that we found phosphine gas on Venus, a possible biosignature

for life, and while this episode was written before that and is focusedine gas on Venus, a possible biosignature for life, and while this episode

was written before that and is focused principally on what the scarcity of phosphorus might

mean for looking for alien life, it's a bit too important and relevant of a discovery not to

address, and so we'll begin to it at the end of the episode as an addition.

Our regular viewers know that one of our favorite topics, and indeed the topic that

inspired me to start the channel in the first place, is the Formy Paradox.

This is the great looming question in our so-far fruitless search for other life forms

in the galaxy.

Why, when the universe is so vast and old, and life can form spontaneously from

base molecules and involving dissension beings like we did, have we not detected any clear

signs of life anywhere, let alone galactic civilizations? The answer is that so far we don't

know why, but we have come up with a number of theories as to what might make it more rare

and difficult than we thought for life to form or for intelligence to arise, what forces

might just occasionally kill all life off and start the process over, and what errors in

judgment might lead civilizations to destroy themselves not very long after they start

...