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.nebola.tv slash Isaac Arthur and use my code, Isaac Arthur.

Isaac Asmos, the currents of space, set during the rise of the galactic empire from his

foundation series, featured a scientist called Spatianalysts, who studied the thin gases

drifting between the stars.

Their proud motto was, we analyze nothing.

But modern physics shows that the vacuum itself is anything but nothing.

It's a restless ocean of energy whose hidden depths may someday destroy not just a single star,

but the entire universe.

We often talk as if there's some otherworldly alternate reality waiting to leap out of us,

monsters, mind-bending geometry, that sort of thing.

And forget that we already live inside multiple overlapping realities.

They are less cinematic and more mundane, which is why we tend not to notice them.

They are invisible to the naked eye, discovered

by equations, experiments, rather than seances and fever dreams. Still, they are real. Different

layers governed by different physics and different organizing principles. Today we're

going to look at one of the most dramatic examples, vacuum decay. That's a fancy name for a process that in the worst case scenario could tear a hole in

the fabric of a reality and replaced with a different vacuum state.

Think for it as a bubble nucleating a pot of water, only here the bubble would contain

different lines of physics.

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